Diamond semiconductor element and process for producing the same

The present invention relates to a diamond semiconductor device, and more particularly to a semiconductor device structure in which the occurrence of crystal defects peculiar to a diamond semiconductor device is suppressed, and a method for manufacturing the same.

Diamond has the highest thermal conductivity among various materials and the highest dielectric breakdown electric field strength among semiconductors. Therefore, diamond is the most suitable semiconductor material for high-power semiconductor devices that require high-voltage, high-current operation. Furthermore, since the electrons and holes in diamond have high mobility and saturation rate, diamond is also suitable as a high frequency semiconductor device capable of operating at high frequencies. The high-frequency diamond semiconductor device is a semiconductor device that controls a large amount of electric power in the high-frequency band of the microwave band and the millimeter-wave band region.

5A to 5C are diagrams showing a manufacturing process of a conventional diamond semiconductor device. Hereinafter, the manufacturing process of the diamond semiconductor transistor according to the prior art disclosed in Non-Patent Document 1 will be described (see Non-Patent Document 2 for the plane orientation).

First, prepare a single crystal diamond substrate 1-31 as shown in FIG. 5A. Surface orientation of single crystal diamond substrate 1-31

<maths num="1"><img file="JP4908409B2_D0001.tif" /></maths>

Has a plane orientation exactly in the [001] direction.

Next, as shown in FIG. 5B, the single crystal diamond thin film 1-32 is crystal-grown on the single crystal diamond substrate 1-31. In the crystal growth step, two-dimensional hole channels 1-33 are formed so as to be parallel to the surface of the single crystal diamond thin film 1-32. Surface orientation of single crystal diamond thin film 1-32

<maths num="2"><img file="JP4908409B2_D0002.tif" /></maths>

And the plane orientation of the formation surface of hole channels 1-33 (channel)

<maths num="3"><img file="JP4908409B2_D0003.tif" /></maths>

Is equal to the plane orientation of the surface of the single crystal diamond substrate 1-31, so it has the plane orientation exactly in the [001] direction.

Further, as shown in FIG. 5C, a source electrode 1-34, a gate electrode 1-35, and a drain electrode 1-36 are formed on the surface of the single crystal diamond thin film 1-32, respectively. Longitudinal direction of gate electrode 35

<maths num="4"><img file="JP4908409B2_D0004.tif" /></maths>

Is in the [100] direction.

The characteristics of the transistor produced by the conventional method described above are disclosed in detail in Non-Patent Document 1. All transistor characteristic data are disclosed by unifying the characteristics of transistors with a gate length of 0.2 μm (normalized by the gate width). According to Non-Patent Document 1, the maximum transconductance gmmax of this transistor was at most 150 mS / mm.

However, the diamond single crystal has a problem that the crystal defect density is remarkably high as compared with other semiconductors such as silicon, gallium arsenide, indium phosphide, and gallium nitride. Therefore, the original physical properties of diamond such as high thermal conductivity, high dielectric breakdown electric field, and good high frequency characteristics cannot be reflected in the transistor characteristics. Transistors using diamond semiconductors have not yet been put into practical use. This problem is described in Non-Patent Document 1. Therefore, in order to realize a practical transistor using a diamond single crystal, the element must be manufactured by a method of suppressing the occurrence of crystal defects peculiar to diamond.

A first object of the present invention is to remarkably suppress the occurrence of crystal defects peculiar to diamond by slightly shifting the plane orientation of the diamond substrate from the [001] direction.

Since diamond has the highest thermal conductivity of the material and the highest dielectric breakdown electric field strength of the semiconductor, it is theoretically the most suitable semiconductor material for high-power semiconductor devices capable of operating at high voltage and high current. It has become clear. In addition, it is also known to be suitable as a high-frequency semiconductor device capable of operating at a high frequency because of its high electron and hole mobility and saturation rate.

In addition, FIGS. 13A to 13G show the process of manufacturing a conventional diamond semiconductor device. Gold (Au) is deposited on a diamond single crystal thin film 2-11 (Fig. 13A) having two-dimensional hole channels near the surface to form an Au thin film 2-12 (Fig. 13B). Resist 2-13 is applied on the Au thin film 2-12 (Fig. 13C). Next, photolithography or electron beam exposure and development is performed to remove a portion of the resist 2-13 to form an opening in the resist 2-13 on the region forming the gate electrode (Fig. 13D). Next, the sample is immersed in an Au etching solution to etch the Au thin film 2-12 near the opening of the resist 2-13 (Fig. 13E).

As shown in FIG. 13E, the Au thin film 2-12 is etched on the surface exposed from the opening of the resist 2-13, and at the same time in the depth direction (direction perpendicular to the diamond single crystal thin film 2-11). It is also etched in the lateral direction (horizontal to the diamond single crystal thin film 2-11). Therefore, in the Au thin film 2-12, the region under the resist 2-13 is also scraped. The part cut like this is called an undercut. When etched laterally by the etching solution in this way, the adhesive force between the Au thin film 2-12 and the resist 2-13 is stronger than the adhesive force between the Au thin film 12 and the diamond single crystal thin film 2-11. The etching rate in the direction is slower on the resist 2-13 side and faster on the diamond single crystal thin film 2-11 side. Therefore, the angle θ of the end face on the etched side of the Au thin film 2-12 is about 45 degrees. That is, the Au thin film 2-12 divided into two by etching has an inverted mesa shape that is wider on the upper side than on the lower side.

Next, Al (aluminum) is vapor-deposited (Fig. 13F). Al deposited directly on the surface of the diamond single crystal thin film 2-11 through the openings of the resist 2-13 and Au thin film 2-12, and Al deposited on the resist 2-13 are Al thin films 2 respectively. Form -15G, 2-15. Next, the sample is immersed in a lift-off solution to lift off the resist 2-13, and the resist 2-13 and the Al thin film 2-15 deposited on the resist 2-13 are removed (Fig. 13G). Here, one of the Au thin films 2-12 is used as the source electrode 2-16S, the other Au thin film 2-12 is used as the drain electrode 2-16D, and the Al thin film 2-15G remaining on the surface of the diamond single crystal thin film 2-11 is used. The gate electrode is 2-17G. At this time, the thickness t_S, T_DIs 0.6 μm, and the gate length d corresponds to the length from the source side end to the drain side end of the gate electrode 2-17G._GIs 0.2 μm.

Unlike other semiconductors such as silicon, gallium arsenide, indium phosphide, and gallium nitride, diamond semiconductors have a physical constraint that the channels through which the electrons and holes of the transistor travel must be within 0.1 μm from the surface. Yes (see Non-Patent Document 3).

Under this physical constraint, the transconductance g, which is the amplification degree of the diamond semiconductor device,_mMaximum oscillation frequency f, which is the upper limit of the operating frequency in high frequency characteristics_maxSource-gate electrode spacing between the edge of the surface of the source electrode 2-16S in contact with the diamond single crystal thin film 2-11 and the source-side edge of the gate electrode 2-17G. d_SG, And the gate-drain electrode spacing d between the drain side end of the gate electrode 2-17G and the end of the surface of the drain electrode 2-16D in contact with the diamond single crystal thin film 2-11._GDNeed to be narrowed. This is not so much a problem for other semiconductors, but it is an important problem to be solved due to its physical properties in diamond semiconductor devices. Furthermore, the maximum oscillation frequency f_maxTo increase, the gate length d in Figure 13G_GIt is also necessary to narrow as much as possible.

In Non-Patent Document 4, the distance between the source electrode 2-16S and the drain electrode 2-16D is 2.6 μm or 2.7 μm, and the gate length d._GIs 0.2 μm, so the source-gate electrode spacing d_SG, Gate / drain electrode spacing d_GDDisclose that each is 1.3 to 1.4 μm.

On the other hand, the source electrode resistance and the drain electrode resistance must be reduced as much as possible in order not to cause an unnecessary voltage drop during transistor operation. To reduce the source electrode resistance and drain electrode resistance, the thickness of the source electrode 2-16S t_S, Drain electrode 2-16D thickness t_DShould be as thick as possible.

However, in the process of etching the Au thin film 2-12, the end face of the source electrode 2-16S and the drain electrode 2-16D on the gate electrode 2-17G side has an inverted mesa structure with an angle θ of about 45 degrees as shown in FIG. 13E. Therefore, the source / gate electrode spacing d_SG, Gate / drain electrode spacing d_GDIs the thickness of the source electrode 2-16S t_S, Drain electrode 2-16D thickness t_DThere was a problem that it could not be made narrower. In other words, the conventional technology simultaneously satisfies the two requirements of "narrowing the source-gate electrode spacing and gate-drain electrode spacing" and "increasing the source electrode thickness and drain electrode thickness". I couldn't get it.

Figures 14A to 14C show the characteristics of diamond transistors manufactured by the conventional method. This is the result disclosed in Non-Patent Document 3, and all the characteristics of the transistor having a gate length of 0.2 μm are unified. In the drain current-voltage characteristics shown in Fig. 14A, the gate length d_GThe maximum drain current standardized in is 0.35 A / mm at most. In addition, the transconductance g shown in FIG. 14B_mGate voltage V_GIn the dependency (transmission characteristic), the gate length d_GMaximum transconductance standardized in_mmaxIs at most 150 mS / mm. Furthermore, in the frequency f dependence of the power gain U shown in FIG. 14C, the maximum oscillation frequency f at the upper limit of the operating frequency_maxIs at most 81 GHz. Although not shown in the figure, the drain breakdown voltage is at most 45V.

Therefore, the second object of the present invention is "source-gate electrode spacing d._SG, Gate / drain electrode spacing d_GDNarrowing "and" Source electrode thickness t_S, Drain electrode thickness t_DBy achieving both "thickening" and "thickening", the maximum oscillation frequency f_maxIt is intended to reach a practical level by increasing the value to greatly improve the characteristics of the diamond field effect transistor and suppressing the voltage drop to a small value.

Further, a conventional method for producing a diamond single crystal thin film will be described with reference to FIGS. 22A and 22B. Prepare a diamond single crystal substrate 3-1 having a plane orientation of (100) (Fig. 22A). Next, using a microwave plasma CVD apparatus, a diamond single crystal thin film 3-2 is laminated on a diamond single crystal substrate 3-1 using methane as a reaction gas at a substrate temperature of 700 ° C for about 1-5 μm (Fig. 22B). The surface of the diamond thin film obtained by the CVD method is hydrogen-terminated in an as-grown state, has surface conductivity, and functions as a P-type semiconductor.

In Non-Patent Document 5, in order to improve the crystallinity of the diamond thin film formed on the silicon substrate, 1 × 10^‐6It is described that the diamond thin film is placed in a vacuumed ceramic tube of Torr and high temperature annealing of 1000 ° C. or higher is performed in vacuum.

By the way, the diamond single crystal thin film produced by the conventional method for producing a diamond single crystal thin film described with reference to FIGS. 22A and 22B has an average mobility of 800 cm at room temperature.²It is about / Vs, and a high-quality thin film is obtained with good reproducibility. However, a large number of crystal defects and impurities such as growth hills and abnormal growth particles are present in the diamond single crystal thin film.

Further, in Non-Patent Document 5, when the temperature at which annealing is performed becomes 1200 ° C. or higher, band-A emission (emission derived from defects) due to deterioration of the diamond thin film increases. That is, in Patent Document 2, the deterioration of crystallinity increases at 1200 ° C. or higher.

The higher the temperature of the annealing, the better the crystallinity, so it is desirable to perform the annealing at a higher temperature. However, in Non-Patent Document 5, when the temperature is raised to improve the crystallinity, when the temperature rises above a certain temperature (1200 ° C), the diamond thin film is graphitized and the deterioration of the crystallinity increases.

Therefore, a third object of the present invention is to provide a diamond thin film manufacturing method capable of manufacturing a high quality diamond thin film by reducing crystal defects, impurities and the like existing in the diamond thin film.

Further, diamond is known to be superior in physical characteristics as a semiconductor to silicon (Si). It has been theoretically confirmed that a diamond element has 5 times the characteristics of a Si element at high temperature operation, 30 times at high voltage performance, and 3 times at high speed. Therefore, diamond is expected to realize a high output device having high thermal conductivity and dielectric breakdown electric field strength, a high frequency device having high carrier mobility and saturation drift speed, and the like. In other words, field effect transistors (FETs) and bipolar transistors using diamond semiconductors make electronic devices that can be driven at high frequencies and can operate at high power, far exceeding conventional semiconductors. Further, it has been theoretically clarified that when a semiconductor laser and a light emitting diode using a diamond semiconductor are realized, a high-intensity light emitting element having a wavelength of 225 nanometers in the ultraviolet region is realized (see Non-Patent Document 6).

Diamond has a bandgap of 5.5 eV and is originally an insulator, but as in the case of Si, when it is doped with B, which is a group III element, it forms an acceptor position, and in theory it becomes a p-type semiconductor. ing.

The p-type semiconductor layer in the transistor or optical device structure has a hole concentration of 1.0 × 10.¹⁵cm^‐3If it is less than, it has a high resistance like an insulator, so that it does not function sufficiently as a p-type semiconductor and is useless. In addition, the density of the dopant element of the p-type semiconductor layer in this transistor or optical device structure is 1.0 × 10.²¹cm^‐3If it exceeds, it will show metallic electrical conduction, so even in this case, it does not function sufficiently as a p-type semiconductor and is useless. Therefore, the p-type semiconductor layer has a hole concentration of 1.0 × 10.¹⁵cm^‐3With the above, and the dopant atom concentration is 1.0 × 10²¹cm^‐3Must be:

Further, since the hole concentration and the dopant atom concentration in the semiconductor depend on the temperature, it is important to satisfy the above requirements at an operating temperature near room temperature (300K) in order to guarantee the practicality of the device. Furthermore, when used in high power such as home appliances, electric power equipment, and industrial equipment, operation in a high temperature state is particularly required, so that the above requirements must be satisfied even at a temperature higher than room temperature, for example, around 500K. ..

However, as shown in FIG. 38, in the conventional technique of doping diamond with boron (B), the B atom concentration is 1.0 × 10.²¹cm^‐36 × 10 at room temperature (300K)¹⁴cm^‐3There was a problem that only the hole concentration of was obtained. In Fig. 38, the horizontal axis is the measured temperature (K), and the vertical axis is the hole concentration in the conventional p-type diamond semiconductor (cm).^-3), And the measured values are plotted for each B atom concentration in the conventional p-type diamond semiconductor. This value is 1.0 x 10 which is practically required at 300K.¹⁵cm^‐3As a result, there is a problem that the diamond semiconductor cannot be put into practical use as a transistor or an optical device.

In addition, as a means to increase the hole concentration near 300K of the diamond semiconductor, the B atom concentration is set to 1.0 × 10.²¹cm^‐3It is possible to make it even higher, but the B atom concentration is 1.0 × 10.²¹cm^‐3If the value is higher, the crystal quality of diamond becomes poor, and the properties of diamond as a semiconductor are lost, so that there is a problem that it cannot be put into practical use.

Therefore, the fourth object of the present invention is to have a hole concentration of 1.0 × 10 at room temperature (300 K) or higher.¹⁵cm^‐3With the above, and the dopant atom concentration is 1.0 × 10²¹cm^‐3It is an object of the present invention to provide the following practical p-type diamond semiconductor and its manufacturing method.

As mentioned above, diamond has the highest thermal conductivity (22W / cmK), dielectric breakdown electric field (&gt; 10MV / cm), and high carrier mobility (electrons: 4500cm).²/ Vs, Hall: 3800cm²It is a semiconductor that also has / Vs), and if high-efficiency doping is realized, a transistor that operates at high frequency and high output that surpasses Si, GaAs, and GaN will be realized.

Ion implantation is one of the methods for doping diamond. This ion implantation method is a method of accelerating impurities at a high voltage, giving energy of several kV to several MV, and introducing impurity ions into the crystal. Since it involves a high energy process, it is in the crystal in proportion to the acceleration voltage. Damage (crystal defects, amorphous layer, etc.) occurs. This damage can be removed by performing an appropriate high temperature annealing treatment, which electrically activates the dopant and reveals semiconductor properties due to the injected impurities. However, since diamond is a metastable layer thermodynamically under normal pressure (1 atm), high-quality diamond semiconductors cannot be obtained by annealing under normal pressure or vacuum, which is usually used. Therefore, in Patent Document 1, high-temperature annealing is performed under high pressure as shown below.

Figures 43A-43E show the manufacturing process of diamond semiconductors using the conventional ion implantation method. Dopant (boron) is added to a diamond single crystal (Fig. 43A) by an ion implanter at an acceleration voltage of 150 kV and a dose of 1 × 10.¹⁶cm^-2(Fig. 43B-43C), firing (annealing) at a pressure and temperature of 5GPa and 1700K for 1 hour (Fig. 43D).

However, the diamond thin film thus annealed has a problem that it has a high resistance and does not exhibit semiconductor characteristics. This is because the diamond surface is etched during the high-temperature and high-pressure annealing process, and the ion-implanted layer is scraped (Fig. 43D). As described above, in the conventional method, there is a problem that the diamond layer formed by ion implantation is etched during high-temperature and high-pressure annealing, and a diamond semiconductor cannot be obtained.

Therefore, a fifth object of the present invention is a method for producing a diamond semiconductor, which prevents etching of the diamond surface caused by high-temperature and high-pressure annealing of ion-implanted diamond and obtains high-quality P-type and N-type diamond semiconductors which cannot be obtained by conventional methods. Is to provide.

<patcit num="1"><text>Special Fair 8-15162 Gazette</text></patcit><nplcit num="1"><text>Makoto Kazu et al., "High Frequency Characteristics of Diamond MESFET", Journal of Japan Society of Applied Physics "Applied Physics", Vol. 73, No. 3 (March 2004), Page363-367</text></nplcit><nplcit num="2"><text>C, Kittel, "Introduction to Solid State Physics", Maruzen Publishing, 5th Edition, Volume 1, Page 11-22</text></nplcit><nplcit num="3"><text>Makoto Kazu, 6 outsiders, "High Frequency Characteristics of Diamond MESFET" Applied Physics, Japan Society of Applied Physics, 2004, Vol. 73, No. 3, P.0363-0367</text></nplcit><nplcit num="4"><text>M. Kasu, Influence of epitaxy on hydrogen-passivated diamond Diamond and Related Materials, 2004, No.13, P.226-232</text></nplcit><nplcit num="5"><text>J. Ruan et al. Cathodoluminescence and annealing study of plasma-deposited physically diamond films J. Appl. Phys. 69 (9), 1 May 1991</text></nplcit><nplcit num="6"><text>Kakazu, et al., "High Frequency Characteristics of Diamond MESFET", Applied Physics, 2004, Vol. 73, No. 3, P.363-367</text></nplcit><nplcit num="7"><text>FP Bundy, HP Bovenkerk, HM Strong, and RH Wentorf, "Diamond-Graphite Equilibrium Line from Growth and Graphitization of Diamond", The Journal of Chemical Physics, August, 1961, Vol. 35, Number 2, pp.383</text></nplcit>

In order to achieve the above-mentioned first object, the present invention of the present invention<u style="single">First</u>Aspects are a single crystal diamond thin film, holes or electron channels formed inside the single crystal diamond thin film, and a drain electrode, a gate electrode, and a source electrode formed on the single crystal diamond thin film.<u style="single">With</u>In the electric field effect transistor, the single crystal diamond thin film has the crystal axis [001] direction of the single crystal diamond thin film with respect to the surface orientation of the surface of the single crystal diamond thin film, or the plane orientation of the formation surface of the channel. The crystal axis [001] direction of<u style="single">The angle β formed by the longitudinal direction of the gate electrode and the crystal axis [110] direction of the single crystal diamond thin film is in the range of -30 degrees to +30 degrees.</u>It is characterized by that.

The angle αd formed by the surface orientation of the surface of the single crystal diamond thin film and the crystal axis [001] direction of the single crystal diamond thin film, or the surface orientation of the formation surface of the channel and the crystal axis [001] of the single crystal diamond thin film. The angle αc formed by the direction can be in the range of 0.05 degrees to 1.1 degrees.

<u style="single">The single crystal diamond thin film</u>On the board<u style="single">What was formed</u>It is characterized by.

<u style="single">The substrate is</u>Single crystal diamond<u style="single">It is a substrate, and the single crystal diamond substrate</u>And the single crystal diamond thin film<u style="single">World with</u>Plane orientation of the surface and the single crystal diamond<u style="single">substrate</u>Angle with respect to the crystal axis [001] direction of<u style="single">αs</u>Can be in the range of 0.05 to 1.1 degrees.

Of the present invention<u style="single">No. 2</u>Aspects of<u style="single">Single crystal diamond thin film</u>And the hole or electron channel formed on the single crystal diamond thin film, and the drain electrode, gate electrode, and source electrode formed on the channel.<u style="single">With</u>In the field effect transistor, the crystal axis [001] direction of the single crystal diamond thin film is inclined with respect to the plane orientation of the surface of the channel.<u style="single">The angle β formed by the longitudinal direction of the gate electrode and the crystal axis [110] direction of the single crystal diamond thin film is in the range of -30 degrees to +30 degrees.</u>It is characterized by that.

The angle αc formed by the plane orientation of the surface of the channel and the crystal axis [001] direction of the single crystal diamond thin film can be in the range of 0.05 degrees to 1.1 degrees.

Also, these<u style="single">The single crystal diamond thin film is formed on the substrate.</u>be able to.

Also, these<u style="single">The substrate is a single crystal diamond substrate, and the angle αs formed by the plane orientation of the interface between the single crystal diamond substrate and the single crystal diamond thin film and the crystal axis [001] direction of the single crystal diamond substrate is 0.05 degrees. Range from 1.1 degrees</u>Can be.

Of the present invention<u style="single">number 3</u>Aspects of<u style="single">Of the first aspect</u>In the method of manufacturing field effect transistors,<u style="single">substrate</u>above,<u style="single">Single crystal diamond thin film</u>And the steps to form<u style="single">Formed</u>A step of forming the channel on the single crystal diamond thin film, a step of further forming the single crystal diamond thin film on the formed channel, and a step of further forming the single crystal diamond thin film.<u style="single">On the channel</u>The plane orientation of the surface of the single crystal diamond thin film is the surface orientation of the single crystal diamond thin film.<u style="single">Crystal axis</u>A step of polishing the surface of the single crystal diamond thin film so as to be inclined with respect to the [001] direction.<u style="single">The single crystal diamond polished so that the angle β formed by the longitudinal direction of the gate electrode and the crystal axis [110] direction of the single crystal diamond thin film is in the range of -30 degrees to +30 degrees. With the steps to form on the thin film</u>It is characterized by having.

In addition, the present invention<u style="single">the 4th</u>Aspects of<u style="single">Of the first aspect</u>In the method of manufacturing field effect transistors,<u style="single">substrate</u>above,<u style="single">Single crystal diamond thin film</u>And the surface of the formed single crystal diamond thin film of the single crystal diamond thin film<u style="single">Crystal axis</u>A step of polishing the surface of the single crystal diamond thin film so as to be inclined with respect to the [001] direction, and a step of forming the channel on the polished single crystal diamond thin film.<u style="single">The angle β formed by the step of further forming the single crystal diamond thin film on the formed channel and the gate electrode in the longitudinal direction of the gate electrode and the crystal axis [110] direction of the single crystal diamond thin film is formed. With the step of forming on the single crystal diamond thin film formed on the channel so as to be in the range of -30 degrees to +30 degrees.</u>It is characterized by having.

Of the present invention<u style="single">Fifth aspect</u>Is<u style="single">Of the first aspect</u>In the method of manufacturing field effect transistors,<u style="single">Single crystal diamond substrate</u>The plane orientation of the single crystal diamond substrate<u style="single">Crystal axis</u>The step of polishing the surface of the single crystal diamond substrate so as to be inclined with respect to the [001] direction, and on the polished single crystal diamond substrate,<u style="single">Single crystal diamond thin film</u>And on the single crystal diamond thin film<u style="single">Channel</u>And the steps to form<u style="single">The angle β formed by the step of further forming the single crystal diamond thin film on the formed channel and the gate electrode in the longitudinal direction of the gate electrode and the crystal axis [110] direction of the single crystal diamond thin film is formed. With the step of forming on the single crystal diamond thin film formed on the channel so as to be in the range of -30 degrees to +30 degrees.</u>It is characterized by having.

The plane orientation of the conventional single crystal diamond substrate is exactly in the [001] direction. However, the plane orientation of [001] is a plane orientation in which defects are generated very easily. Therefore, by slightly shifting the plane orientation of the diamond substrate from the [001] direction, the occurrence of crystal defects peculiar to diamond can be remarkably suppressed. High field effect transistor transconductance is obtained.

<figref num="1A">It is a figure which shows the structure of the diamond semiconductor element which concerns on 1st Embodiment of this invention.</figref><figref num="1B">It is a figure which shows the structure of the diamond semiconductor element which concerns on 1st Embodiment of this invention.</figref><figref num="2">It is a figure which shows the structure of the diamond semiconductor element which concerns on 2nd Embodiment of this invention.</figref><figref num="3A">It is a figure explaining the manufacturing process of the diamond semiconductor element of 1st Embodiment.</figref><figref num="3B">It is a figure explaining the manufacturing process of the diamond semiconductor element of 1st Embodiment.</figref><figref num="3C">It is a figure explaining the manufacturing process of the diamond semiconductor element of 1st Embodiment.</figref><figref num="3D">It is a figure explaining the manufacturing process of the diamond semiconductor element of 1st Embodiment.</figref><figref num="4A">This is a characteristic of the transistor of the diamond semiconductor device according to the first embodiment of the present invention.</figref><figref num="4B">This is a characteristic of the transistor of the diamond semiconductor device according to the first embodiment of the present invention.</figref><figref num="5A">It is a figure explaining the manufacturing process of the diamond semiconductor element by the prior art.</figref><figref num="5B">It is a figure explaining the manufacturing process of the diamond semiconductor element by the prior art.</figref><figref num="5C">It is a figure explaining the manufacturing process of the diamond semiconductor element by the prior art.</figref><figref num="6">It is a figure which shows the structure of the diamond semiconductor element which concerns on this invention of the structure which removed the diamond substrate.</figref><figref num="7A">It is a figure which shows the manufacturing process of the diamond semiconductor element which concerns on one Embodiment of this invention.</figref><figref num="7B">It is a figure which shows the manufacturing process of the diamond semiconductor element which concerns on one Embodiment of this invention.</figref><figref num="7C">It is a figure which shows the manufacturing process of the diamond semiconductor element which concerns on one Embodiment of this invention.</figref><figref num="7D">It is a figure which shows the manufacturing process of the diamond semiconductor element which concerns on one Embodiment of this invention.</figref><figref num="7E">It is a figure which shows the manufacturing process of the diamond semiconductor element which concerns on one Embodiment of this invention.</figref><figref num="7F">It is a figure which shows the manufacturing process of the diamond semiconductor element which concerns on one Embodiment of this invention.</figref><figref num="7G">It is a figure which shows the manufacturing process of the diamond semiconductor element which concerns on one Embodiment of this invention.</figref><figref num="7H">It is a figure which shows the manufacturing process of the diamond semiconductor element which concerns on one Embodiment of this invention.</figref><figref num="7I">It is a figure which shows the manufacturing process of the diamond semiconductor element which concerns on one Embodiment of this invention.</figref><figref num="7J">It is a figure which shows the manufacturing process of the diamond semiconductor element which concerns on one Embodiment of this invention.</figref><figref num="8A">It is a figure which shows the characteristic of the diamond field effect transistor of the gate length 0.2 μm using the diamond semiconductor element which concerns on one Embodiment of this invention, and is the figure which shows the drain current-voltage characteristic.</figref><figref num="8B">It is a figure which shows the characteristic of the diamond field effect transistor of the gate length 0.2 μm using the diamond semiconductor element which concerns on one Embodiment of this invention, and is the transconductance g._mGate voltage V_GIt is a figure which shows the dependence (transmission characteristic).</figref><figref num="8C">It is a figure which shows the characteristic of the diamond field effect transistor of the gate length 0.2 μm using the diamond semiconductor element which concerns on one Embodiment of this invention, and is the figure which shows the frequency f dependence of the power gain U.</figref><figref num="9A">Lower source gate spacing d_SGBAnd maximum oscillation frequency f_maxIt is a figure which shows the relationship with.</figref><figref num="9B">Upper source gate spacing d_SGTAnd maximum oscillation frequency f_maxIt is a figure which shows the relationship with.</figref><figref num="10A">Gate / lower drain distance d_GDBAnd drain breakdown voltage V_BRIt is a figure which shows the relationship with.</figref><figref num="10B">Gate / upper drain distance d_GDTAnd maximum oscillation frequency f_maxIt is a figure which shows the relationship with.</figref><figref num="11A">Bottom source electrode 2-6SB thickness t_SBAnd maximum oscillation frequency f_maxIt is a figure which shows the relationship with.</figref><figref num="11B">Upper source electrode 2-6ST thickness t_STAnd maximum oscillation frequency f_maxIt is a figure which shows the relationship with.</figref><figref num="12A">Lower drain electrode 2DB thickness t_DBAnd maximum oscillation frequency f_maxIt is a figure which shows the relationship with.</figref><figref num="12B">Upper drain electrode 2DB thickness t_DTAnd maximum oscillation frequency f_maxIt is a figure which shows the relationship with.</figref><figref num="13A">It is a figure which shows the manufacturing process of the diamond semiconductor element by the prior art.</figref><figref num="13B">It is a figure which shows the manufacturing process of the diamond semiconductor element by the prior art.</figref><figref num="13C">It is a figure which shows the manufacturing process of the diamond semiconductor element by the prior art.</figref><figref num="13D">It is a figure which shows the manufacturing process of the diamond semiconductor element by the prior art.</figref><figref num="13E">It is a figure which shows the manufacturing process of the diamond semiconductor element by the prior art.</figref><figref num="13F">It is a figure which shows the manufacturing process of the diamond semiconductor element by the prior art.</figref><figref num="13G">It is a figure which shows the manufacturing process of the diamond semiconductor element by the prior art.</figref><figref num="14A">It is a characteristic of the transistor using the diamond semiconductor element by the prior art, and is the figure which shows the drain current-voltage characteristic.</figref><figref num="14B">Transconductance g, which is a characteristic of a transistor using a diamond semiconductor element according to the prior art._mGate voltage V_GIt is a figure which shows the dependence (transmission characteristic).</figref><figref num="14C">It is a characteristic of the transistor using the diamond semiconductor element by the prior art, and is the figure which shows the frequency f dependence of the power gain U.</figref><figref num="15A">It is a figure for demonstrating the manufacturing method of the diamond thin film by Example 1 of this invention.</figref><figref num="15B">It is a figure for demonstrating the manufacturing method of the diamond thin film by Example 1 of this invention.</figref><figref num="15C">It is a figure for demonstrating the manufacturing method of the diamond thin film by Example 1 of this invention.</figref><figref num="15D">It is a figure for demonstrating the manufacturing method of the diamond thin film by Example 1 of this invention.</figref><figref num="16A">It is a figure for demonstrating the manufacturing method of the diamond thin film by Example 2 of this invention.</figref><figref num="16B">It is a figure for demonstrating the manufacturing method of the diamond thin film by Example 2 of this invention.</figref><figref num="16C">It is a figure for demonstrating the manufacturing method of the diamond thin film by Example 2 of this invention.</figref><figref num="16D">It is a figure for demonstrating the manufacturing method of the diamond thin film by Example 2 of this invention.</figref><figref num="17A">It is a figure for demonstrating the manufacturing method of the diamond thin film according to Example 3 of this invention.</figref><figref num="17B">It is a figure for demonstrating the manufacturing method of the diamond thin film according to Example 3 of this invention.</figref><figref num="17C">It is a figure for demonstrating the manufacturing method of the diamond thin film according to Example 3 of this invention.</figref><figref num="17D">It is a figure for demonstrating the manufacturing method of the diamond thin film according to Example 3 of this invention.</figref><figref num="17E">It is a figure for demonstrating the manufacturing method of the diamond thin film according to Example 3 of this invention.</figref><figref num="17F">It is a figure for demonstrating the manufacturing method of the diamond thin film according to Example 3 of this invention.</figref><figref num="18A">It is a figure for demonstrating the manufacturing method of the diamond thin film according to Example 4 of this invention.</figref><figref num="18B">It is a figure for demonstrating the manufacturing method of the diamond thin film according to Example 4 of this invention.</figref><figref num="18C">It is a figure for demonstrating the manufacturing method of the diamond thin film according to Example 4 of this invention.</figref><figref num="18D">It is a figure for demonstrating the manufacturing method of the diamond thin film according to Example 4 of this invention.</figref><figref num="18E">It is a figure for demonstrating the manufacturing method of the diamond thin film according to Example 4 of this invention.</figref><figref num="18F">It is a figure for demonstrating the manufacturing method of the diamond thin film according to Example 4 of this invention.</figref><figref num="19A">It is a figure for demonstrating the manufacturing method of the diamond thin film according to Example 5 of this invention.</figref><figref num="19B">It is a figure for demonstrating the manufacturing method of the diamond thin film according to Example 5 of this invention.</figref><figref num="19C">It is a figure for demonstrating the manufacturing method of the diamond thin film according to Example 5 of this invention.</figref><figref num="19D">It is a figure for demonstrating the manufacturing method of the diamond thin film according to Example 5 of this invention.</figref><figref num="20A">It is a figure for demonstrating the manufacturing method of the diamond thin film according to Example 6 of this invention.</figref><figref num="20B">It is a figure for demonstrating the manufacturing method of the diamond thin film according to Example 6 of this invention.</figref><figref num="20C">It is a figure for demonstrating the manufacturing method of the diamond thin film according to Example 6 of this invention.</figref><figref num="20D">It is a figure for demonstrating the manufacturing method of the diamond thin film according to Example 6 of this invention.</figref><figref num="21">It is a figure which shows the stable region of diamond and graphite which concerns on one Embodiment of this invention.</figref><figref num="22A">It is a figure for demonstrating the manufacturing method of the diamond thin film by the conventional method.</figref><figref num="22B">It is a figure for demonstrating the manufacturing method of the diamond thin film by the conventional method.</figref><figref num="23A">It is a figure for comparing the current-voltage characteristic of the field effect transistor made on the diamond single crystal thin film before and after the high-voltage high-temperature annealing according to Example 1 of this invention.</figref><figref num="23B">It is a figure for comparing the current-voltage characteristic of the field effect transistor made on the diamond single crystal thin film before and after the high-voltage high-temperature annealing according to Example 1 of this invention.</figref><figref num="24">It is a figure which shows the relationship between the concentration in the raw material gas, and the concentration in a p-type diamond semiconductor of the dopant atom which concerns on embodiment of this invention.</figref><figref num="25">It is a figure which shows the temperature dependence of the hole concentration with respect to each Al atom concentration in the p-type diamond semiconductor which concerns on Embodiment 4 of this invention.</figref><figref num="26">It is a figure which shows the temperature dependence of the hole concentration with respect to each Be atom concentration in the p-type diamond semiconductor which concerns on Embodiment 5 of this invention.</figref><figref num="27">It is a figure which shows the temperature dependence of the hole concentration with respect to each Ca atom concentration in the p-type diamond semiconductor which concerns on Embodiment 6 of this invention.</figref><figref num="28">It is a figure which shows the temperature dependence of the hole concentration with respect to each Cd atom concentration in the p-type diamond semiconductor which concerns on Embodiment 7 of this invention.</figref><figref num="29">It is a figure which shows the temperature dependence of the hole concentration with respect to each Ga atom concentration in the p-type diamond semiconductor which concerns on Embodiment 8 of this invention.</figref><figref num="30">It is a figure which shows the temperature dependence of the hole concentration with respect to each In atom concentration in the p-type diamond semiconductor which concerns on Embodiment 9 of this invention.</figref><figref num="31">It is a figure which shows the temperature dependence of the hole concentration with respect to each Mg atom concentration in the p-type diamond semiconductor which concerns on Embodiment 11 of this invention.</figref><figref num="32">It is a figure which shows the temperature dependence of the hole concentration with respect to each Zn atom concentration in the p-type diamond semiconductor which concerns on Embodiment 12 of this invention.</figref><figref num="33">It is a figure which shows the cross-sectional block diagram of the MESFET (metal-semiconductor field effect transistor) which concerns on Embodiment 15 of this invention.</figref><figref num="34">It is a figure which shows the cross-sectional block diagram of the MISFET (metal-insulating film-semiconductor field effect transistor) which concerns on Embodiment 16 of this invention.</figref><figref num="35">It is a figure which shows the cross-sectional block diagram of the npn type bipolar transistor which concerns on Embodiment 17 of this invention.</figref><figref num="36">It is a figure which shows the cross-sectional block diagram of the pnp type bipolar transistor which concerns on Embodiment 18 of this invention.</figref><figref num="37">It is a figure which shows the cross-sectional block diagram of the light emitting diode (LED) which concerns on Embodiment 19 of this invention.</figref><figref num="38">It is a figure which shows the temperature dependence of the hole concentration with respect to each B atom concentration in the conventional p-type diamond semiconductor.</figref><figref num="39">It is a figure which shows the temperature dependence of the hole concentration with respect to each Li atom concentration in the p-type diamond semiconductor which concerns on Embodiment 10 of this invention.</figref><figref num="40A">It is a figure which shows the manufacturing process of the diamond semiconductor which concerns on Embodiment 1 of this invention.</figref><figref num="40B">It is a figure which shows the manufacturing process of the diamond semiconductor which concerns on Embodiment 1 of this invention.</figref><figref num="40C">It is a figure which shows the manufacturing process of the diamond semiconductor which concerns on Embodiment 1 of this invention.</figref><figref num="40D">It is a figure which shows the manufacturing process of the diamond semiconductor which concerns on Embodiment 1 of this invention.</figref><figref num="40E">It is a figure which shows the manufacturing process of the diamond semiconductor which concerns on Embodiment 1 of this invention.</figref><figref num="40F">It is a figure which shows the manufacturing process of the diamond semiconductor which concerns on Embodiment 1 of this invention.</figref><figref num="40G">It is a figure which shows the manufacturing process of the diamond semiconductor which concerns on Embodiment 1 of this invention.</figref><figref num="41A">It is a figure which shows the manufacturing process of the diamond semiconductor which concerns on Embodiment 2 of this invention.</figref><figref num="41B">It is a figure which shows the manufacturing process of the diamond semiconductor which concerns on Embodiment 2 of this invention.</figref><figref num="41C">It is a figure which shows the manufacturing process of the diamond semiconductor which concerns on Embodiment 2 of this invention.</figref><figref num="41D">It is a figure which shows the manufacturing process of the diamond semiconductor which concerns on Embodiment 2 of this invention.</figref><figref num="41E">It is a figure which shows the manufacturing process of the diamond semiconductor which concerns on Embodiment 2 of this invention.</figref><figref num="41F">It is a figure which shows the manufacturing process of the diamond semiconductor which concerns on Embodiment 2 of this invention.</figref><figref num="42">It is a figure which shows the cathode luminescence (CL) spectrum (measurement temperature: 10K) before and after high temperature and high pressure annealing of the diamond thin film which ion-implanted with boron (B) as a dopant.</figref><figref num="43A">It is a figure which shows the manufacturing process of the diamond semiconductor by using the ion implantation method by the prior art.</figref><figref num="43B">It is a figure which shows the manufacturing process of the diamond semiconductor by using the ion implantation method by the prior art.</figref><figref num="43C">It is a figure which shows the manufacturing process of the diamond semiconductor by using the ion implantation method by the prior art.</figref><figref num="43D">It is a figure which shows the manufacturing process of the diamond semiconductor by using the ion implantation method by the prior art.</figref><figref num="43E">It is a figure which shows the manufacturing process of the diamond semiconductor by using the ion implantation method by the prior art.</figref>

In order to achieve the first object, the diamond semiconductor device according to the present invention is unique to the present invention in that the plane orientations of the single crystal diamond substrate, the single crystal diamond thin film, the holes or electron channels, and the formation direction of the gate electrode are set. It is characterized by the direction of. Hereinafter, the structure and manufacturing method of the diamond semiconductor device according to the present invention for achieving the first object will be described in detail. (Embodiment 1) 1A and 1B are structural diagrams of the diamond semiconductor device according to the first embodiment of the present invention. As shown in the cross-sectional view of FIG. 1B, the single crystal diamond thin film 1-2 is formed on the single crystal diamond substrate 1-1. Two-dimensional holes or electron channels 1-3 are formed in the single crystal diamond thin film 1-2. Then, the angle formed by the plane orientation of the single crystal diamond substrate 1-1 and the crystal axis [001] direction of the single crystal diamond substrate 1-1 is αs, and the plane orientation of the single crystal diamond thin film 1-2 and the single crystal diamond thin film 1 Let αd be the angle formed by the crystal axis [001] direction of -2, and αc be the angle formed by the plane orientation of channels 1-3 and the crystal axis [001] direction of the single crystal diamond thin film 1-2. As shown in the top view of FIG. 1A, a source electrode 1-4, a gate electrode 1-5, and a drain electrode 1-6 are formed on the surface of the single crystal diamond thin film 1-2, respectively. Channels 1-3 formed inside the single crystal diamond thin film 1-2 are shown by dotted lines. Longitudinal direction of gate electrodes 1-5

<maths num="5"><img file="JP4908409B2_D0005.tif" /></maths>

Let β be the angle between and the crystal axis [110] of the single crystal diamond thin film. αs, αd, αc and β will be described later. Next, the process of manufacturing the diamond semiconductor device will be described.

3A to 3D are diagrams illustrating a process for producing a diamond semiconductor device according to the present invention. As shown in FIG. 3A, first, a single crystal diamond substrate 1-1 whose plane orientation is mainly oriented in the [001] direction of the crystal axis is prepared.

Next, as shown in FIG. 3B, the plane direction of the surface of the single crystal diamond substrate 1-1

<maths num="6"><img file="JP4908409B2_D0006.tif" /></maths>

However, the surface is polished so that the crystal axis of the single crystal diamond substrate 1-1 is tilted by αs (°) from the [001] direction. This surface polishing can be performed, for example, by the following procedure. First, the inclination angle of the substrate surface from the [001] plane direction is measured in advance by X-ray diffraction measurement. Then, the single crystal diamond substrate 1-1 is adhered to the sample table with wax. Then, diamond abrasive grains (particle size 0.3 μm to 1 μm) are applied together with oil on an iron flat plate. This sample table to which the single crystal diamond substrate 1-1 is adhered is placed on an iron flat surface, and with the sample table fixed, the iron flat plate is rotated for polishing. After polishing for a certain period of time, the inclination angle is measured by X-ray diffraction measurement, and the above-mentioned polishing and X-ray diffraction measurement are repeated until a desired angle αs is obtained. That is, as shown in FIG. 3B, the substrate is scraped off by polishing so that the plane orientation of the single crystal diamond substrate becomes a predetermined αs. The surface tilted by αs (°) may be only the surface on which the single crystal diamond thin film is grown in the next step described later.

Next, as shown in FIG. 3C, the single crystal diamond thin film 1-2 is crystal-grown on the single crystal diamond substrate 1-1 having the plane azimuth of αs formed. Crystal growth of this thin film can be carried out by, for example, a microwave plasma CVD method. More specifically, methane gas and hydrogen gas (flow rate ratio of methane gas is 1%) are supplied as raw material gases into the reaction tube in which the single crystal diamond substrate 1-1 is placed. The degree of vacuum in the reaction tube is set to 50 Torr, and microwaves of 2.45 GHz and 1.3 kW are irradiated to generate plasma in the reaction tube. The temperature of the single crystal diamond substrate 1-1 is set to 700 degrees (above, condition 1). Surface orientation of single crystal diamond thin film 1-2

<maths num="7"><img file="JP4908409B2_D0007.tif" /></maths>

Can be formed at an angle of αd (°) from the [001] direction of the crystal axis of the single crystal diamond thin film 1-2, similarly to the 1-1 surface of the single crystal diamond substrate.

Further, inside the single crystal diamond thin film 1-2, two-dimensional holes or electron channels 1-3 are formed along the surface of the single crystal diamond thin film 1-2. Channels 1-3 are formed by, for example, a microwave plasma CVD method, as in the case of the single crystal diamond thin film 1-2 described above. That is, the conditions of the temperature, the degree of vacuum, and the microwave in the reaction tube are the same, and the conditions of the raw material gas are changed to hydrogen gas only (condition 2). Under this condition 2, channels 1-3 are formed by irradiating the surface of the single crystal diamond thin film 1-2 in the process of preparation with plasma for 15 minutes. Then, by returning to the original condition (condition 1) and forming the single crystal diamond thin film 1-2 again, channels 1-3 can be formed inside the single crystal diamond thin film 1-2.

The above-mentioned conditions 1 and 2 are examples when a hole channel is used. When a diamond semiconductor device is constructed using an electronic channel, hydrogen, methane gas, or phosphine (PH3) gas can be used as a raw material gas (condition 3). In this case, first, the single crystal diamond thin film 1-2 is formed under the condition 1, the condition 3 is changed to form the electron channel 1-3, the condition 1 is returned, and the single crystal diamond thin film 1-2 is formed again. To do. Plane orientation of the formation plane of two-dimensional channels 1-3

<maths num="8"><img file="JP4908409B2_D0008.tif" /></maths>

Can be formed by tilting αc (°) from the [001] direction of the crystal axis of the single crystal diamond thin film 1-2.

Next, as shown in FIG. 3D, a source electrode 1-4, a gate electrode 1-5, and a drain electrode 1-6 are formed on the surface of the single crystal diamond thin film 1-2. When viewed from above the surface of the single crystal diamond thin film 1-2, channels 1-3 exist directly below the source electrode 1-4 and directly below the drain electrode 1-6 (channels 1-3 are dotted in the top view of Fig. 3D). Shown). The gate electrode 1-5 is arranged between the source electrode 1-4 and the drain electrode 1-6. When viewed from above the surface of the single crystal diamond thin film 1-2, the gate electrodes 1-5 are arranged so as to intersect the channels 1-3. Longitudinal direction of gate electrodes 1-5 above channels 1-3

<maths num="9"><img file="JP4908409B2_D0009.tif" /></maths>

As shown in FIG. 3D, gate electrodes 1-5 are prepared so as to be oriented in the [110] direction of the single crystal diamond thin film crystal axis or in the direction inclined by β (degrees) from the [110] direction of the crystal axis. .. By each of the above steps, the field effect transistor having the diamond semiconductor device structure according to the present invention is completed.

Here, the relationship between αs, αd, and αc will be further described. First, after determining αs by the polishing step of the single crystal diamond substrate 1-1 described above, if the single crystal diamond thin film layer 1-2 and the channels 1-3 are formed as they are, αs = αd = αc. However, this condition is not limited, and each angle can be controlled independently. For example, after forming the single crystal diamond thin film 1-2 and before forming the electrode, the surface of the single crystal diamond thin film 1-2 can be polished and tilted so that αd and αs have different angles. .. Immediately before the formation of channels 1-3, the surface of the single crystal diamond thin film formed so far is once taken out from the reaction tube and tilted, and then channels 1-3 are formed to form αs and αc. Can also be controlled independently.

FIGS. 4A and 4B are diagrams showing the characteristics of the field effect transistor manufactured by the above-described step according to the present invention. FIG. 4A is a diagram showing the relationship between the maximum transconductance gmmax and the inclination angles (αs, αc, αd) of each plane direction from the [001] direction. Here, αs, αd, and αc are changed at the same time with the same angle. Transconductance is the most basic parameter that describes the performance of a field effect transistor. In general, the presence of crystal defects can be evaluated by a typical device performance gm. If gm is high, it can be evaluated that there are few crystal defects. In FIG. 4B, the value of β described later is 0 °.

In the transistor manufactured by the prior art, the plane orientation of the single crystal diamond substrate or the like is accurately oriented in the [001] direction. That is, αs = 0 °, αc = 0 °, and αd = 0 °. In this case, gmmax was about 40 to 80 mS / mm.

As can be seen from Fig. 4A, gmmax increases sharply as αs, αc, and αd are increased, and under the conditions of αs = 0.05 °, αc = 0.05 °, and αd = 0.05 °, gmmax = 310 to 390 mS / mm. Become. When αs, αc, and αd are in the range of 0.05 ° to 1.1 °, gmmax is 300 mS / mm or more. On the other hand, when αs, αc and αd exceed 1.1 °, gmmax decreases sharply. By setting αs, αc, and αd in the range of 0.05 ° to 1.1 ° in this way, it is possible to obtain a gmmax that is significantly larger than that of the prior art. As described above, by slightly shifting the plane orientation of the single crystal diamond substrate or the like from the [001] direction, the occurrence of crystal defects peculiar to diamond can be remarkably suppressed, and high field effect transistor transconductance can be obtained.

FIG. 4B is a diagram showing the relationship between the maximum transconductance gmmax and the inclination angle β from the [110] direction in the longitudinal direction of the gate electrode. In this case, αs = αc = αd = 0.05 °.

In the prior art, the [100] direction has been used as the longitudinal direction of the gate electrode. That is, when the longitudinal direction of the gate electrode is directed to the [100] direction, it corresponds to the state where β = ± 45 ° in FIG. 4B. Under this condition of β = ± 45 °, which is the conventional technique, gmmax was at most 25 mS / mm.

In the diamond semiconductor device according to the present invention, when β is in the range of -30 ° to 30 °, gmmax is 100 mS / mm or more, and when β = 0 ° (corresponding to g = [110]), gmmax is 200 mS / mm. To reach. By optimizing the direction in which the gate electrodes 1-5 are formed in the above range in this way, it is possible to manufacture a field effect transistor using a diamond semiconductor having a practical level of transconductance for the first time.

In the above description, the case where channels 1-3 are configured inside the single crystal diamond thin film 1-2 has been described. However, after the step of forming channels 1-3, the source electrode 1-4, the gate electrode 1-5, and the drain electrode 1 are directly formed on the surface of the channel 1-3 without forming two single crystal diamond thin films again. The structure forming -6 can also be operated as a semiconductor element. That is, a configuration without the 1-2 layers of the single crystal diamond thin film formed above the channels 1-3 in FIG. 1B is also possible. In this case, the angle αc formed by the plane orientation of the surface of channels 1-3 and the crystal axis [001] direction of the single crystal diamond thin film 1-2, and the plane orientation of the single crystal diamond substrate 1-1 and the single crystal diamond substrate 1 By setting the angle αs formed by the crystal axis [001] direction of -1 within the above-mentioned ranges, the effect of suppressing the occurrence of similar crystal defects can be obtained with a simpler configuration. Therefore, as shown in FIG. 1B, it goes without saying that channels 1-3 are not limited to the structure located exactly in the middle of the single crystal diamond thin film layer 1-2 in the thickness direction.

Further, the single crystal diamond substrate 1-1 in FIG. 1 was removed before forming the source electrode 1-4, the gate electrode 1-5, and the drain electrode 1-6, and as a result, the single crystal diamond substrate 1- A structure without 1 is also possible. That is, as shown in FIG. 6, the single crystal diamond substrate 1-1 is removed from FIG. 1, and the single crystal diamond thin film 1-2, the channel 1-3, the source electrode 1-4, the gate electrode 1-5, and the drain electrode are removed. The effect peculiar to the present invention can also be obtained by the structure consisting of 1-6. In this case, the single crystal diamond thin film 1-2 has a relatively thick film thickness so that the film itself can be structurally self-supporting. The removal of the single crystal diamond substrate 1-1 can be performed by, for example, polishing.

Next, the definition of the plane orientation used in the present specification will be described. The [110] direction and the [100] direction are the main directions of the 1-1 surface of the single crystal diamond substrate or the main direction of the 1-2 surface of the single crystal diamond thin film 1-2 when the main direction is designated as the [001] direction. Needless to say, it is a definition. Diamond crystallographically has a cubic lattice system. In general, a crystal plane has the property that the smaller the number of bonds between atoms that must be broken when the plane is formed, the more likely it is to appear. Therefore, in the case of diamond, the plane orientations that are likely to appear are [001], [111], and [011]. As mentioned above, since diamond is a cubic system, [001], [100], [010], etc. are physically equivalent. Mathematically, there are also [100], [-100], [010], [0-10], and [00-1]. However, due to the symmetry of the crystals, these are all equivalent to [001] (see Non-Patent Document 2 for details). In this specification, the main direction of the 1-1 surface of the single crystal diamond substrate or the main direction of the 1-2 surface of the single crystal diamond thin film is described as the [001] direction. The "main direction" indicates the above-mentioned most likely plane orientation.

When the main direction of the 1-1 surface of the single crystal diamond substrate or the main direction of the 1-2 surface of the single crystal diamond thin film 1-2 is defined as the [001] direction, it is the preferred direction in the longitudinal direction of the gate electrodes 1-5 [ The 100] direction is crystallographically equivalent to the [010] direction. Therefore, the description herein of the [100] direction naturally includes the [010] direction as well. As mentioned earlier, [100], [-100], [010], [0-10], and [00-1] are equivalent, and these are collectively referred to as gate electrode 1-5. It is set to the [100] direction, which is a preferable direction in the longitudinal direction of. It should be noted that the [110] direction is also a generic term.

In the steps shown in FIGS. 3A to 3D, the single crystal diamond substrate 1-1 was used. However, even when the single crystal diamond substrate 1-1 is not used, the plane orientation of the single crystal diamond thin film 1-2 or the plane orientation of the channels 1-3 is the αd and αc described in FIG. Needless to say, if they are in each angle range, they have the same effect of increasing the transconductance. When the single crystal diamond substrate 1-1 is not used, for example, Ir (iridium metal), MgO, and Si can be used as the substrate. Any substrate may be used as long as it can form a single crystal diamond thin film. (Embodiment 2) FIG. 2 is a diagram showing a structure of a diamond semiconductor device according to a second embodiment of the present invention. The structure of this embodiment is a structure suitable for high power operation. In this embodiment, the gate electrodes are arranged in the shape of a track in a stadium. On the single crystal diamond substrate 1-11, the single crystal diamond thin film 1-12 and the two-dimensional hole or electron channel 1-13 are formed inside the single crystal diamond thin film. As shown in FIG. 2, the channel has an oval shape. A source electrode 1-14, a gate electrode 1-15, and a drain electrode 1-16 are formed above the channels 1-13 on the surface of the single crystal diamond thin film 1-12. The gate electrode 1-15 and the source electrode 1-14 are sequentially formed toward the outer circumference so as to surround the innermost oval-shaped drain electrode 1-16.

Although not explicitly shown in FIG. 2, in the present embodiment as well, the plane orientations of the single crystal diamond substrate 1-11, the single crystal diamond thin film 1-12, and the channel 1-13 are the cases of the first embodiment, respectively. Make sure that αs, αd, and αc are in the same range as. In the linear region except for the two arcs at both ends of the oval shape, each electrode is arranged so that the longitudinal direction of the gate electrodes 1-15 is inclined by β degrees from the crystal axis [110] direction. Has been done. Needless to say, it has the effect of increasing the transconductance as in the case shown in FIG.

As described in detail above, the book that the occurrence of crystal defects peculiar to diamond is remarkably suppressed by slightly shifting the plane orientation of the single crystal diamond thin film, the single crystal diamond substrate, or the channel forming surface from the [001] direction. The effect peculiar to the invention can be obtained. Remarkably high mutual conductance of field effect transistors can be obtained, and a diamond semiconductor device that can be put into practical use can be realized.

Next, a diamond semiconductor device according to the present invention and a method for manufacturing the diamond semiconductor device for achieving the second object will be described in detail. (Embodiment 3) 7A to 7J show the manufacturing process of the diamond semiconductor device according to the embodiment of the present invention. A thin film 2-1 (hereinafter referred to as a diamond single crystal thin film 2-1) which is a diamond single crystal and has two-dimensional hole channels parallel to the surface thereof is prepared (Fig. 7A). Au is vapor-deposited on the entire surface of the diamond single crystal thin film 2-1 so as to have a thickness of 0.1 μm to form the Au thin film 2-2B (Fig. 7B). Next, resist 2-3 is applied with a width of 20 μm to the area where the gate electrode is provided on Au thin film 2-2B (Fig. 7C), and Au thin film 2-2T is deposited on the entire surface of the sample from above (Fig. 7D). .. At this time, the thickness of Au thin film 2-2T is 0.4 μm.

Next, the resist 2-3 is lifted off, and the resist 2-3 and a part of the Au thin film 2-2T deposited on the resist 2-3 are removed to form an opening 2-7 in the Au thin film 2-2T. (Fig. 7E). In order to lift off the resist 2-3 successfully, the distance in the direction perpendicular to the longitudinal direction of the resist 2-3 and horizontal to the surface of the diamond single crystal thin film 2-1 is Au thin film 2-2T diamond single crystal thin film 2 Must be longer than the thickness perpendicular to the plane of -1. Next, resist 2-4 is applied to the entire surface of the sample (Fig. 7F). The region forming the gate electrode in the region where Au thin film 2-2B and resist 2-4 are in contact is exposed and developed with a width of 0.05 μm, and a part of resist 2-4 is removed to remove Au thin film 2-. An opening 2-8 is formed in 2B (Fig. 7G).

Next, a part of the Au thin film 2-2B exposed from the opening 2-8 is etched with an etching solution (Fig. 7H). Since the etching occurs isotropically, the Au thin film 2-2B in the region under the resist 2-4 is also etched, resulting in undercut. Etching is stopped before reaching Au thin film 2-2T.

Next, Al is deposited on the entire surface of the sample (Fig. 7I). A part of Al is deposited on the diamond single crystal thin film 2-1 from the opening 2-8 of the Au thin film 2-2B to form the Al thin film 2-5G. On the other hand, most of the others are deposited on the resist 2-4 to form the Al thin film 2-5. After that, the resist 2-4 is lifted off to remove the resist 2-4 and the Al thin film 2-5 on the resist 2-4 (Fig. 7J).

Here, one of the Au thin films 2-2B is used as the lower source electrode 2-6SB, and the other is used as the lower drain electrode 2-6DB. Further, the Au thin film 2-2T on the lower source electrode 2-6SB is referred to as the upper source electrode 2-6ST, and the Au thin film 2-2T on the lower drain electrode 2-6DB is referred to as the upper drain electrode 2-6DT. However, although the lower source electrode and the upper source electrode are described separately in this specification, the lower source electrode 2-6SB and the upper source electrode 2-6ST together function as one source electrode. Therefore, the lower source electrode 2-6SB and the upper source electrode 2-6ST can be regarded as one source electrode. The lower drain electrode and the upper drain electrode can also be regarded as one drain electrode. The Al thin film 2-5G is used as the gate electrode 2-7G.

In the diamond semiconductor device according to the embodiment of the present invention, the diamond single crystal thin film 2-1 may be either single crystal or polycrystalline, and the channels in the diamond single crystal thin film 2-1 are electrons and holes. It may be either.

Where the gate length is d_GThe lower source / gate spacing between the end of the lower source electrode 2-6SB in contact with the surface of the diamond single crystal thin film 2-1 and the source side end of the gate electrode 2-7G is d._SGBThe gate / lower drain distance between the end of the lower drain electrode 2-6DB in contact with the surface of the diamond single crystal thin film 2-1 and the drain side end of the gate electrode 2-7G is d._GDBAnd. Also, the upper source-gate spacing between the end of the upper source electrode 2-6ST and the source side end of the gate electrode 2-7G is d._SGTThe gate / upper drain distance between the end of the upper drain electrode 2-6DT and the drain side end of the gate electrode 2-7G is d._GDTAnd.

T the total thickness of the source electrode_SAnd, among them, the thickness of the lower source electrode 2-6SB is t_SBAnd the thickness of the upper source electrode 2-6ST is t_STAnd. T the total thickness of the drain electrode_DAnd, among them, the thickness of the lower drain electrode 2-6DB is t_DBAnd the thickness of the upper drain electrode 2-6DB is t_DTAnd.

In this way, the source electrode and the drain electrode are formed separately as a layer to be etched with an etching solution and a layer to be lifted off with a resist. As a result, the reverse mesa portion of the electrode can be reduced, so the distance between the source electrode and the gate electrode can be reduced to reduce the maximum oscillation frequency f._maxAnd the thickness of the source electrode and the drain electrode can be increased to suppress the voltage drop.

Further, in the present embodiment, the source electrode and the drain electrode are each formed of two metal films, an Au thin film 2-2T which is an upper metal film and an Au thin film 2-2B which is a lower metal film. The source electrode and drain electrode may have any number of layers as long as the thickness of the metal film in contact with the diamond single crystal thin film 2-1 can be reduced.

Further, in the present embodiment, the end faces of the lower source electrode 2-6SB and the lower drain electrode 2-6DB on the gate electrode 2-7G side have an inverted mesa shape. However, what is important in the present invention is a layer for "narrowing the source / gate electrode spacing and the gate / drain electrode spacing" and a layer for "thickening the source electrode thickness and the drain electrode thickness". The structure of the end faces of the lower source electrode 2-6SB and the lower drain electrode 2-6DB on the gate electrode 2-7G side is not limited to the inverted mesa structure.

8A to 8C show the characteristics of the diamond field effect transistor using the diamond semiconductor element according to the embodiment of the present invention. Each dimension of the diamond semiconductor element used here is d._G= 0.2 μm, d_SGB= d_GDB= 0.1 μm, d_SGT= d_GDT= 1 μm, t_SB= t_DB= 0.05 μm, t_ST= t_DT= 10 μm.

FIG. 8A shows the drain current-voltage characteristics of the diamond field-effect transistor according to this embodiment. Maximum drain current I_DmaxWas 0.35 A / mm in the conventional type, but reaches 1 A / mm in this embodiment. FIG. 8B shows the transconductance g of the diamond field effect transistors according to this embodiment._mGate voltage V_GShows dependence (transmission characteristics). Maximum transconductance g_mmaxIn the present embodiment, the value of is 520 mS / mm, while the value in the conventional type is 150 mS / mm. FIG. 8C shows the frequency f dependence of the power gain U of the diamond field effect transistor according to the present embodiment. Maximum oscillation frequency f as shown in Fig. 8C_maxIs 81 GHz in the conventional type, but reaches 310 GHz in this embodiment.

As described above, the diamond semiconductor device according to the embodiment of the present invention greatly improves the field effect transistor characteristics as compared with the conventional diamond semiconductor device, and enables a practical level diamond transistor.

The change in characteristics of the diamond transistor according to the embodiment of the present invention due to the dimensions will be described in detail with reference to FIG. 7J. When the shape of the gate electrode 2-7G is a so-called T-shaped gate (also called a mushroom-type gate), the distance at the part of the gate electrode 2-7G in contact with the surface of the diamond single crystal thin film is the gate length d._GAnd. In such a case, the lower source gate interval d_SGB, Upper source gate spacing d_SGTIs the distance from the source side end of the gate electrode 2-7G of the part in contact with the surface of the diamond single crystal thin film 2-1 to the lower source electrode 2-6SB and the upper source electrode 2-6ST, respectively. Drain interval d_GDB, Gate / upper drain spacing d_GDTIs the distance from the drain side end of the gate electrode 2-7G at the portion in contact with the surface of the diamond single crystal thin film 2-1 to the lower drain electrode 2-6DB and the upper drain electrode 2-6DT, respectively. The diamond semiconductor elements used in FIGS. 9A, 9B to 12A, and 12B are d except for the dimensions of the parts used as variables._G= 0.2 μm, d_SGB= d_GDB= 0.1 μm, d_SGT= 10 μm, d_GDT= 50 μm, t_SB= t_DB= 0.05 μm, t_ST= t_DTIt shall have a size of = 10 μm.

Figure 9A shows the lower source gate spacing d_SGBAnd maximum oscillation frequency f_maxShow the relationship with. d_SGBWhen increases, f_maxDecreases, but d_SGBWhen increases from 0.1 μm to 10 μm, f_maxOnly decreased from 250GHz to 100GHz, f in the conventional configuration_maxGood characteristics can be obtained compared to 81GHz.

Figure 9B shows the top source gate spacing d_SGTAnd maximum oscillation frequency f_maxShow the relationship with. d_SGTWhen increases, f_maxDecreases, but d_SGBWhen increases from 0.07 μm to 30 μm, f_maxOnly decreased from 250GHz to 120GHz, f in the conventional configuration_maxGood characteristics can be obtained compared to 81GHz.

Figure 10A shows the gate-lower drain spacing d_GDBAnd drain breakdown voltage V_BRShow the relationship with. d_GDBWhen increases, V_BRIncreases, but d_GDBIncreases sharply from 0.05 μm to around 0.1 μm, and in the range of 0.1 μm or more, V_BRWill be over 100V. V in conventional configuration_BRGood characteristics can be obtained compared to 45V. However, d_GDBWhen exceeds 50 μm, f_maxDecreases.

Figure 10B shows the gate-upper drain spacing d_GDTAnd maximum oscillation frequency f_maxShow the relationship with. d_GDTIncreases, f up to 3 μm_maxIncreases, but above that, f_maxDecreases. Here d_GDTWhen is 30 μm, f_maxIndicates 140 GHz, f in the conventional configuration_maxIt was able to show better characteristics than 81GHz.

Figure 11A shows the thickness t of the lower source electrode 2-6SB._SBAnd maximum oscillation frequency f_maxShow the relationship with. t_SBWhen increases f_maxDecreases, but t_SBWhen increases from 0.01 μm to 0.2 μm, f_maxOnly decreased from 260GHz to 130GHz, f in the conventional configuration_maxIt is possible to obtain better characteristics than the 81 GHz.

Figure 11B shows the thickness t of the upper source electrode 2-6ST._STAnd maximum oscillation frequency f_maxShow the relationship with. t_STWhen increases, f_maxWill also increase, but t_STWhen is 0.2 μm, f_maxIs 100GHz, t_STWhen is 100 μm, f_maxReach 270GHz. This allows f in the conventional configuration_maxIt is possible to obtain better characteristics than the 81 GHz.

Figure 12A shows the thickness t of the lower drain electrode 2-6DB._DBAnd maximum oscillation frequency f_maxShow the relationship with. t_DBWhen increases, f_maxDecreases, but t_DBWhen increases from 0.01 μm to 0.2 μm, f_maxOnly decreased from 300GHz to 100GHz, f in the conventional configuration_maxIt is possible to obtain better characteristics than the 81 GHz.

Figure 12B shows the thickness t of the upper drain electrode 2-6DB._DTAnd maximum oscillation frequency f_maxShow the relationship with. t_DTWhen increases, f_maxIncreases, but t_DTWhen is 0.2 μm, f_maxIs 100GHz, t_DTWhen is 100 μm, f_maxReaches 280GHz. This allows f in the conventional configuration_maxIt is possible to obtain better characteristics than the 81 GHz.

Table 1 relates to a conventional diamond semiconductor device in which the material of the source electrode and the drain electrode is Au, and an embodiment of the present invention in which the material of the lower source electrode 2-6SB and the lower drain electrode 2-6DB is an AuPt alloy. Maximum oscillation frequency with diamond semiconductor device f_maxIs shown. At this time, the material of the upper source electrode 2-6ST and the upper drain electrode 2-6DT is Au. Au is used as the electrode material of the diamond semiconductor device described above, but when an AuPt alloy having a composition ratio of Au: Pt = 8: 2 is used as the electrode material of the diamond semiconductor device according to the embodiment of the present invention, f_maxWill increase dramatically to 220GHz.

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Table 2 shows the composition ratio of the conventional diamond semiconductor device in which the material of the source electrode and the drain electrode is Au, and the material of the upper source electrode 2-6ST and the upper drain electrode 2-6DT in Au: Pt = 8: 2. Maximum oscillation frequency f with a diamond semiconductor device according to an embodiment of the present invention, which is an AuPt alloy, Pt, Pd, Ti, Mo, W._maxIs shown. At this time, the material of the lower source electrode 2-6SB and the lower drain electrode 2-6DB is Au. Au is used as the electrode material of the diamond semiconductor element described above, but when the electrode material shown in Table 2 is used as the electrode material of the diamond semiconductor element according to the embodiment of the present invention, f_maxWill increase dramatically.

<tables num="2"><img file="JP4908409B2_D0011.tif" /></tables>

As described above, the lower source electrode 2-6SB and the lower drain electrode 2-6DB and the upper source electrode 2-6ST and the upper drain electrode 2-6DT can be formed of different materials.

Next, a method for producing a diamond thin film according to the present invention for achieving the third object will be described in detail. One embodiment of the present invention is characterized in that a diamond crystal thin film is calcined (annealed) by giving a sufficient temperature to the diamond under a stable high pressure. Attempts to improve the crystallinity of the diamond crystal thin film have been made using high-temperature annealing at 1000 ° C or higher in vacuum (see Non-Patent Document 5), but diamond is originally an ultrahigh pressure of 1.5 Gpa or higher. Since it is stable due to crystallization, deterioration occurs in high temperature vacuum annealing. Therefore, in one embodiment of the present invention, diamond is annealed under a stable high pressure. As a result, lattice defects and the like contained in the crystal are recovered and removed, and the quality of the diamond crystal thin film can be improved.

As used herein, "(diamond) is stable and stable" refers to a state in which a diamond remains in a diamond state without being graphitized. That is, a stable diamond is a state in which the state of diamond is maintained without graphitization even when annealing is performed at high temperature and high pressure. For example, in the case of a single crystal diamond, the diamond single crystal is in a state of maintaining a single crystal state without being graphitized. Therefore, by annealing the diamond crystal thin film under a high pressure so that the diamond is in a stable state, graphitization of the diamond crystal thin film can be prevented or reduced.

Further, the temperature (also referred to as annealing temperature) T for annealing and the pressure (also referred to as annealing pressure) P for annealing within the region where diamond can be stably annealed are determined. This region satisfies P&gt; 0.71 + 0.0027T or P = 0.71 + 0.0027T and is a region of P 1.5 GPa shown in FIG. Such an area is a shaded area in FIG. The relational expression of P 0.71 + 0.0027T is a well-known relation to those skilled in the art. And the temperature T is more optimal at 550 ° C.

In FIG. 21, the symbols Yes and × indicate the conditions under which the diamond crystal thin film was annealed at high pressure and high temperature. The symbol Yes represents a condition in which the diamond structure was stable even after annealing, and the symbol × represents a condition in which the diamond substrate was graphitized after annealing.

In one embodiment of the present invention, deterioration of the diamond crystal thin film can be reduced by setting the annealing temperature and annealing pressure within the above region, that is, by setting the annealing temperature and annealing pressure at which diamond is stable. .. Further, even if the annealing temperature is increased, if the annealing pressure is increased, the annealing temperature is within the above region, so that the annealing temperature can be set high. Therefore, it is possible to reduce crystal defects. Therefore, according to one embodiment of the present invention, it is possible to improve the quality of the diamond crystal thin film.

The annealing can be performed by forming a diamond crystal thin film on a diamond single crystal substrate by a microwave plasma CVD apparatus or the like, and placing the diamond single crystal substrate on which the diamond crystal thin film is formed in an ultrahigh pressure high temperature firing furnace. ..

In addition, two diamond single crystal substrates on which the above diamond crystal thin film is formed are prepared, and the surface of each diamond crystal thin film (the interface between the diamond single crystal substrate and the diamond crystal thin film formed on the diamond single crystal substrate in the diamond crystal thin film). The two substrates may be overlapped and annealed so as to be in contact with each other. It should be noted that this superposition may be performed so that at least a part of the surfaces of the two diamond crystal thin films are in contact with each other. By superimposing in this way, the surface of the diamond crystal thin film is exposed to the air during annealing, or the surface is reduced, so that the influence of oxygen, nitrogen, and water vapor in the air can be reduced. Further, during annealing, the sample is surrounded by NaCl or the like in order to apply pressure, but the above superposition can reduce the adhesion of NaCl or the like to the surface of the diamond crystal thin film during annealing. it can.

By superimposing the two diamond crystal thin films so that their surfaces are on the inside in this way, each of the two diamond crystal thin films can function as a protective member against the opposite diamond crystal thin films. That is, by contacting at least a part of the surface of one diamond crystal thin film with at least a part of the surface of the other diamond crystal thin film, the contact region of the other is covered. By overlaying and annealing in this way, it is possible to anneal at almost the same position at the same time while protecting the surfaces of each of the two diamond crystal substrates, or it is necessary to anneal the two substrates separately. Annealing can be performed in a space smaller than the space. Therefore, since the space for annealing can be reduced, the number of substrates that can be annealed at one time can be increased, and a high-quality diamond crystal thin film can be produced more efficiently.

Further, a protective member such as an insulator thin film, a metal thin film, or an alloy may be formed on at least a part of the surface of the diamond crystal thin film to perform annealing. Since at least a part of the surface of the diamond crystal thin film is covered with a protective member to perform annealing in this way, the influence of oxygen, nitrogen, and water vapor in the air during annealing can be reduced as in the above superposition. it can. Further, it is possible to reduce the adhesion of a diamond crystal thin film such as NaCl to the surface during annealing.

In the present specification, the "protective member" is a member for reducing the influence of each component in the air or a material such as NaCl used for applying pressure on the surface of the diamond crystal thin film. The protective member functions by covering or forming at least a portion of the surface of the diamond crystal thin film. That is, due to the presence of the protective member on the surface of the diamond crystal thin film, each component such as oxygen, nitrogen, and water vapor in the air and materials such as NaCl used for applying pressure reach and adhere to the surface of the diamond crystal thin film. It is possible to prevent or reduce the problem.

In one embodiment of the present invention, the substrate on which the diamond crystal thin film is formed is not limited to the diamond single crystal substrate, and other substrates such as a diamond polycrystalline substrate and a silicon substrate may be used. Further, the diamond crystal thin film formed on the substrate may be a diamond single crystal thin film or a diamond polycrystalline thin film.

Hereinafter, the method for producing a diamond thin film according to an embodiment of the present invention will be described in detail based on Examples, but the present invention is not limited to the following Examples, and is various as long as it does not deviate from the gist thereof. It goes without saying that it can be changed. For example, the diamond single crystal thin film may have an arbitrary thickness and is not limited to the values of the following examples.

(Example 1) The method for producing the diamond thin film according to Example 1 of the present invention will be described with reference to FIGS. 15A to 15D. Prepare a diamond single crystal substrate 3-11 having a plane orientation of (100) (Fig. 15A). Next, using a microwave plasma CVD device on the diamond single crystal substrate 3-11, methane is used as a reaction gas, and the diamond single crystal thin film 3-12 is laminated by about 1-5 μm at a substrate temperature of 700 ° C (Fig. 15B). The diamond single crystal thin film thus formed may contain defects and impurities. In this embodiment, the microwave plasma CVD method is used, but the growth method does not matter as long as it is a method capable of forming a diamond thin film.

After that, the diamond single crystal substrate 3-11 on which the diamond single crystal thin film 3-12 was formed was placed in an ultrahigh pressure high temperature firing furnace, and the diamond single crystal thin film 3-12 was annealed under the conditions of 1200 ° C. and 6 GPa. (Fig. 15C). The annealing results in a high quality diamond crystal thin film with reduced defects and impurities (Fig. 15D).

By the way, as a preliminary experiment, as shown in FIG. 21, a diamond single crystal substrate on which a diamond crystal thin film is formed is annealed under various temperature and pressure conditions, but the diamond is stably annealed under the conditions of 1200 ° C and 6 GPa. It is located in the area where it can be done.

Holes of the diamond crystal thin film were measured before and after high-pressure and high-temperature annealing, and the characteristics were compared. Incidentally, the mobility of the semiconductor obtained from the hole measurement is closely related to the crystallinity, and the better the crystallinity, the higher the mobility. In this embodiment, several samples are prepared under the same conditions in order to suppress variations among the samples, and hole measurement is performed to obtain the average value (average mobility) of the mobility.

As can be seen from Table 3, the sample before annealing (Fig. 15B), that is, the sample prepared by the conventional method, has an average mobility of 800 cm at room temperature.²It became about / Vs. On the other hand, the sample after high-pressure and high-temperature annealing (Fig. 15D) has an average mobility of 1000 cm.²It becomes / Vs and the average mobility is increasing.

In addition, field effect transistors (FETs) were made using diamond crystal thin films before and after high-temperature and high-voltage annealing, and current-voltage (Ids-Vds) measurements were performed to compare their characteristics (Fig. 23). In the above FET, gold is used for the source and drain electrodes, and aluminum is used for the gate electrode. The gate length is 5 μm and the gate width is 100 μm. The gate voltage is measured at 0-3.5V in 0.5V increments.

As can be seen from FIG. 23, the current leak observed before annealing was almost eliminated after annealing, and the characteristics were improved. From these results, it can be seen that by performing high-pressure and high-temperature annealing on the diamond crystal thin film formed on the substrate, defects in the diamond crystal thin film are reduced and the quality of the diamond crystal thin film is improved. At this time, since the annealing temperature and the annealing pressure are set so that the diamond is stable, deterioration of the diamond crystal thin film can be suppressed. Further, as long as the diamond can be stably annealed, the annealing temperature can be increased, so that defects can be further reduced.

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(Example 2) The method for producing the diamond thin film according to Example 2 of the present invention will be described with reference to FIGS. 16A to 16D. Prepare a diamond single crystal substrate 3-21 having a plane orientation of (100) (Fig. 16A). Next, using a microwave plasma CVD device on the diamond single crystal substrate 3-21, methane is used as a reaction gas, and the diamond single crystal thin film 3-22 is laminated by about 1-5 μm at a substrate temperature of 700 ° C (Fig. 16B). The diamond single crystal thin film thus formed may contain defects and impurities. Further, in this embodiment, two diamond single crystal substrates 3-21 on which the diamond single crystal thin film 3-22 produced as described above is formed are prepared.

After that, as shown in FIG. 16C, the two diamond single crystal thin films 3-22 are overlapped so that the surfaces are on the inside, that is, the surfaces of the two diamond single crystal thin films 3-22 are in contact with each other. The superposed substrate is placed in an ultra-high pressure high temperature firing furnace and annealed under the conditions of 1200 ° C. and 6 GPa.

The superposition may be performed manually, or by means of sandwiching the substrate and arranging the sandwiched substrate at a predetermined position and an arranging means having a driving means for driving the means. You may go. When such an arrangement means is used, by driving a driving means such as a motor, one of the diamond single crystal substrates 3-21 is sandwiched, and the other diamond single crystal substrate 3-21 is 2 The sandwiched diamond single crystal substrate 3-21 is arranged so that the surfaces of the single diamond single crystal thin films 3-22 meet. As described above, in this embodiment, any means may be used as long as the surfaces of the two diamond single crystal thin films 3-22 can be overlapped so as to be in contact with each other.

When the annealing is completed, the two overlapping substrates are separated from each other, and the annealing gives a high-quality diamond crystal thin film with reduced defects and impurities (Fig. 16D).

Holes of the diamond crystal thin film were measured before and after high-pressure and high-temperature annealing, and the characteristics were compared. As can be seen from Table 3, the sample before annealing (Fig. 16B), that is, the sample prepared by the conventional method, has an average mobility of 800 cm at room temperature.²It became about / Vs. On the other hand, the sample after high-pressure high-temperature annealing (Fig. 16D) is 1300 cm.²It became / Vs and the average mobility increased. From these results, it is understood that the high-pressure and high-temperature annealing reduces the defects in the diamond crystal thin film and improves the quality of the diamond thin film. Further, in this embodiment, since the surfaces of the diamond crystal thin films are brought into contact with each other during annealing, the influence of nitrogen, oxygen, water vapor, etc. in the air on the diamond crystal thin films can be reduced. Further, by the above-mentioned superposition, it is possible to reduce the adhesion of NaCl arranged around the substrate for applying pressure to the surface of the diamond crystal thin film during annealing.

In this embodiment, the surfaces of the two diamond single crystal thin films 3-22 are overlapped so that the entire surfaces of the two diamond single crystal thin films 3-22 are in contact with each other, but the present invention is not limited to this. In this embodiment, it is important to reduce the influence of each component in the air and NaCl used for applying pressure on the surface of the diamond single crystal thin film 3-22 during annealing. Therefore, during annealing, It is important not to expose the surface as much as possible. Therefore, in one embodiment of the present invention, the above influence can be reduced by superimposing the two substrates so that at least a part of the surfaces of the two diamond crystal thin films are in contact with each other.

As described above, in this embodiment, the exposure of the surface of the diamond crystal thin film is reduced in order to reduce the influence of each component in the air and NaCl used for applying pressure on the surface of the diamond crystal thin film during annealing. If possible, it is not limited to overlapping the two diamond crystal thin films so that the surfaces are on the inside. For example, at least a part of the diamond crystal thin film is protected by arranging a diamond crystal substrate or an oxide, a nitride, a metal, an alloy, etc., which will be described later in Examples 3 and 4, as a protective member. Annealing may be performed by covering with a member.

(Example 3) The method for producing the diamond thin film according to Example 3 of the present invention will be described with reference to FIGS. 17A to 17F. Prepare a diamond single crystal substrate 3-31 having a plane orientation of (100) (Fig. 17A). Next, using a microwave plasma CVD apparatus on the diamond single crystal substrate 3-31, methane is used as a reaction gas, and the diamond single crystal thin film 3-32 is laminated by about 1-5 μm at a substrate temperature of 700 ° C (Fig. 17B). The diamond single crystal thin film thus formed may contain defects and impurities.

Then, as shown in FIG. 17C, a protective film 3-33 as a protective member is formed on the diamond single crystal thin film 3-32. The protective film 3-33 can be made of various metal compounds having a film thickness of about 0.5 μm. The material of such protective film 3-33 is not limited to, for example, silicon oxide (SiO)._x), Silicon nitride (SiN)_x), Aluminum oxide (AlO_x) Etc. These silicon oxide, silicon nitride, and aluminum oxide may be formed by the ECR sputtering method.

Next, the diamond single crystal substrate 3-31 on which the protective film 3-33 and the diamond single crystal thin film 3-32 were formed was placed in an ultrahigh pressure high temperature firing furnace, and the diamond single crystal was placed under the conditions of 1200 ° C. and 6 GPa. Anneal the thin film 3-32 (Fig. 17D). The annealing results in a high quality diamond crystal thin film with reduced defects and impurities (Fig. 17E). Next, etching is performed to remove the protective film 3-33 (Fig. 17F).

Holes of the diamond crystal thin film were measured before and after high-pressure and high-temperature annealing, and the characteristics of the samples were compared. As can be seen from Table 3, the sample before annealing (Fig. 17B), that is, the sample prepared by the conventional method, has an average mobility of 800 cm at room temperature.²It became about / Vs. On the other hand, the average mobility of the sample (Fig. 17F) after high-pressure and high-temperature annealing is 1300 cm regardless of the type of protective film.²It became / Vs, which was higher than the conventional method. From these results, it is understood that the defects in the diamond crystal thin film are reduced by the high pressure and high temperature annealing, and the quality of the diamond crystal thin film is improved. Further, in this embodiment, since the protective film is formed on the surface of the diamond crystal thin film during annealing, the influence of nitrogen, oxygen, water vapor, etc. in the air on the surface of the diamond crystal thin film can be reduced. .. In addition, the protective film can reduce the amount of NaCl placed around the substrate for applying pressure to adhere to the surface of the diamond crystal thin film during annealing.

In this embodiment, the protective film 3-33 is formed on the entire surface of the diamond single crystal thin film 3-32, but the present invention is not limited to this. In this embodiment, it is important to reduce the influence of each component in the air and NaCl used for applying pressure on the surface of the diamond single crystal thin film 3-32 during annealing. Therefore, during annealing, It is important not to expose the surface as much as possible. Therefore, in one embodiment of the present invention, the above influence can be reduced by forming the protective film on at least a part of the diamond single crystal thin film.

(Example 4) The method for producing the diamond thin film according to Example 4 of the present invention will be described with reference to FIGS. 18A to 18F. Prepare a diamond single crystal substrate 3-41 having a plane orientation of (100) (Fig. 18A). Next, using a microwave plasma CVD device on the diamond single crystal substrate 3-41, methane is used as a reaction gas, and the diamond single crystal thin film 3-42 is laminated by about 1-5 μm at a substrate temperature of 700 ° C (Fig. 18B). The diamond single crystal thin film thus formed may contain defects and impurities.

Then, as shown in FIG. 18C, a protective film 3-43 as a protective member is formed on the diamond single crystal thin film 3-42. The protective film 3-43 can be various metal films or alloy films having a film thickness of about 0.5 μm. The material of such a protective film 3-43 is not limited to, for example, platinum (Pt), titanium (Ti), tungsten (W), palladium (Pd), molybdenum (Mo), titanium-aluminum alloy ( Ti65% -Al35%) etc. These platinum, titanium, tungsten, palladium, molybdenum, titanium-aluminum alloy and the like may be formed by a vacuum vapor deposition method. Further, in this embodiment, a titanium-aluminum alloy is used as the alloy, but any alloy containing at least one metal among Pt, Ti, W, Pd and Mo may be used.

Next, the diamond single crystal substrate 3-41 on which the protective film 3-43 and the diamond single crystal thin film 3-42 were formed was placed in an ultrahigh pressure high temperature firing furnace, and the diamond single crystal was placed under the conditions of 1200 ° C. and 6 GPa. Anneal the thin film 3-42 (Fig. 18D). The annealing results in a high quality diamond crystal thin film with reduced defects and impurities (Fig. 18E). Next, etching is performed to remove the protective film 3-43 (Fig. 18F).

Holes of the diamond crystal thin film were measured before and after high-pressure and high-temperature annealing, and the characteristics of the samples were compared. As can be seen from Table 3, the sample before annealing (Fig. 18B), that is, the sample prepared by the conventional method, has an average mobility of 800 cm at room temperature.²It became about / Vs. On the other hand, the average mobility of the sample (Fig. 18F) after high-pressure and high-temperature annealing is 1300 cm regardless of the type of protective film.²It became / Vs, which was higher than the conventional method. From these results, it is understood that the defects in the diamond crystal thin film are reduced by the high pressure and high temperature annealing, and the quality of the diamond crystal thin film is improved. Further, in this embodiment, since the protective film is formed on the surface of the diamond crystal thin film during annealing, the influence of nitrogen, oxygen, water vapor, etc. in the air on the surface of the diamond crystal thin film can be reduced. .. In addition, the protective film can reduce the amount of NaCl placed around the substrate for applying pressure to adhere to the surface of the diamond crystal thin film during annealing.

(Example 5) The method for producing the diamond thin film according to Example 5 of the present invention will be described with reference to FIGS. 19A to 19D. Prepare a diamond single crystal substrate 3-51 having a plane orientation of (111) (Fig. 19A). Next, using a microwave plasma CVD device on the diamond single crystal substrate 3-51, methane was used as the reaction gas, and the diamond single crystal thin film 3-52 having a substrate temperature of 700 ° C and a plane orientation of (111) was 1-. Laminate about 5 μm (Fig. 19B). The diamond single crystal thin film thus formed may contain defects and impurities.

Then, the diamond single crystal substrate 3-51 on which the diamond single crystal thin film 3-52 was formed was placed in an ultrahigh pressure high temperature firing furnace, and the diamond single crystal thin film 3-52 was annealed under the conditions of 1200 ° C. and 6 GPa. (Fig. 19C). The annealing results in a high quality diamond crystal thin film with reduced defects and impurities (Fig. 19D).

Holes of the diamond crystal thin film were measured before and after high-pressure and high-temperature annealing, and the characteristics were compared. As can be seen from Table 3, the sample before annealing (Fig. 19B), that is, the sample prepared by the conventional method, has an average mobility of 800 cm at room temperature.²It became about / Vs. On the other hand, the sample after high-pressure high-temperature annealing (Fig. 19D) is 1200 cm.²It becomes / Vs and the average mobility is increasing. From these results, it can be seen that the high-pressure and high-temperature annealing reduces the defects in the diamond crystal thin film and improves the quality of the diamond crystal thin film.

(Example 6) The method for producing the diamond thin film according to Example 6 of the present invention will be described with reference to FIGS. 20A to 20D. Prepare a diamond single crystal substrate 3-61 having a plane orientation of (100) (Fig. 20A). Using a microwave plasma CVD device on a diamond single crystal substrate 3-61, methane is used as a reaction gas (gas concentration 0.5%), and a diamond single crystal thin film 3-62 is laminated about 1-5 μm at a substrate temperature of 650-700 ° C. (Fig. 20B). In this embodiment, the substrate temperature during the growth of the diamond crystal thin film (the temperature for heating the substrate when forming the diamond crystal thin film), the methane flow rate, etc. are controlled, so that the average self-squared roughness is 1 μm.²A diamond crystal thin film having a surface flatness of 30 nm or less can be obtained in the range of 30 nm or less.

The control conditions for the substrate temperature and the methane flow rate are shown below. That is, the substrate temperature is controlled to 650 ° C or higher and 700 ° C or lower. That is, the substrate temperature is controlled at a temperature equal to or higher than the growth temperature at which the diamond crystal thin film is formed and lower than 700 ° C. The methane flow rate is controlled so that the methane flow rate / hydrogen flow rate, which is the ratio of the methane flow rate to the hydrogen flow rate (ratio of the flow rate (sccm)), is larger than 0% and 0.5% or less. When the reaction gas is only hydrogen (the above ratio is 0%), the diamond crystal thin film does not grow, so the above ratio needs to be set to be larger than 0%. However, if the above ratio is greater than 0% and less than 0.1%, the growth rate will be slower than when the above ratio is 0.1% or more and 0.5% or less. It is preferably% or less.

That is, in this embodiment, the surface flatness of the diamond crystal thin film can be improved by controlling at least one of the control of the substrate temperature and the control of the methane flow rate.

The diamond single crystal thin film thus formed may contain defects and impurities. Further, in this embodiment, two diamond single crystal substrates 3-61 on which the diamond single crystal thin film 3-62 produced as described above is formed are prepared.

Then, as shown in FIG. 20C, the two diamond single crystal thin films 3-62 were superposed so that the surfaces were on the inside, and then the superposed substrates were placed in an ultrahigh pressure high temperature firing furnace at 1200 ° C. , Perform annealing under the conditions of 6 GPa. When the annealing is completed, the two overlapping substrates are separated from each other, and the annealing gives a high-quality diamond crystal thin film with reduced defects and impurities (Fig. 20D).

Holes of the diamond crystal thin film were measured before and after high-pressure and high-temperature annealing, and the characteristics were compared. As can be seen from Table 3, the sample before annealing (Fig. 20B), that is, the sample prepared by the conventional method, has an average mobility of 800 cm at room temperature.²It became about / Vs. On the other hand, the sample after high-pressure high-temperature annealing (Fig. 20D) is 1500 cm.²It became / Vs and the average mobility increased. From these results, it can be seen that the high-pressure and high-temperature annealing reduces the defects in the diamond crystal thin film and improves the quality of the diamond thin film.

Next, the p-type diamond semiconductor according to the present invention and the manufacturing method thereof for achieving the fourth object will be described in detail.

In the present invention, in order to simultaneously improve the hole concentration and the dopant atom concentration in the p-type diamond semiconductor, aluminum (Al) and berylium (Be), which have lower activation energies than B as the p-type dopant element of diamond, are used. , Calcium (Ca), Cadmium (Cd), Gallium (Ga), Indium (In), Magnesium (Mg) or Zinc (Zn). As a result, by further using these p-type diamonds as part of the structure, MES-type, MIS-type field effect transistors (FETs), PNP-type, NPN-type bipolar transistors, semiconductor lasers, and light emitting that also function at 300K. A diode semiconductor element can be realized. (Embodiment 4) Methane gas (CH) with a flow rate ratio of 1% by microwave plasma chemical vapor deposition method₄), Dopant gas, balance H₂The diamond semiconductor film of the present invention having a thickness of 1.0 μm is grown on the diamond single crystal (001) plane orientation using a mixed gas having a total flow rate of 300 ccm, which is composed of the reaction gas. The pressure in the reaction tube is 50 Torr, and the frequency of the microwave source is 2.45 GHz and the output is 1.3 kW. Here, the dopant gas is trimethylaluminum ((CH), which is an organic metal raw material containing Al.₃)₃Al: TMAl) and triethylaluminum ((C)₂H₅)₃Use one of Al: TEAl). Alternatively, instead of using this dopant gas, solid Al can be inserted into the plasma and the vaporized Al can be used as the dopant gas.

When the holes of the obtained diamond semiconductor film are measured and the hole coefficients are determined, it can be confirmed that they are p-type semiconductors.

FIG. 24 shows the relationship between the concentration of the dopant atom according to the embodiment of the present invention in the raw material gas and the concentration in the p-type diamond semiconductor. The Al atom concentration in the diamond semiconductor film is measured by SIMS (secondary ion mass analysis) measurement, and the ratio of the number of Al atoms to the number of carbon (C) atoms in the raw material gas (Al / C) x (ppm) is calculated. Al atom concentration y (cm) in the semiconductor film on the horizontal axis^‐3) Is taken on the vertical axis, and the relationship is as shown in FIG. x (ppm) x 10¹⁷= y (cm)^‐3) ......... (1) Will be.

FIG. 25 shows the temperature dependence of the hole concentration with respect to each Al atom concentration in the p-type diamond semiconductor according to the fourth embodiment of the present invention. In Fig. 25, the horizontal axis is the measured temperature (K), and the vertical axis is the hole concentration in the p-type diamond semiconductor (cm).^-3), And the Al atom concentration (cm) in the p-type diamond semiconductor.^-3) Is a plot of the measured values.

Hole concentration 1.0 × 10 near practical level 300K¹⁵cm^‐3To get 2.0x10¹⁷cm^‐3The above Al atom concentration is required. Also, 1.0 x 10²¹cm^‐3It is known that the quality of diamond crystals deteriorates when the Al atom concentration exceeds. Therefore, the dopant atom concentration of the Al-doped p-type diamond semiconductor device at the practical level of around 300 K is 2.0 × 10.¹⁷cm^‐3More than 1.0 × 10²¹cm^‐3Must be:

From this, using equation (1), the ratio of the number of A atoms to the number of C atoms in the raw material gas (Al / C) is 2 ppm or more and 10⁴It can be seen that it should be in the range of ppm or less.

In addition, using FIG. 25 in which the hole concentration values in the p-type diamond semiconductor at each temperature are plotted for each dopant atom concentration, the hole concentration in the p-type diamond semiconductor at each temperature is 1.0 × 10.¹⁵cm^‐3It is possible to obtain the dopant atom concentration to be. For example, at 500K, the hole concentration in a p-type diamond semiconductor is 1.0 × 10.¹⁵cm^‐3The Al atom concentration is 2.6 × 10 from Fig. 25.¹⁶cm^‐3Is derived. In this case, the ratio (Al / C) of the number of atoms of Al to the number of atoms of C in the raw material gas is 0.26 ppm or more from Eq. (1).⁴It can be seen that it should be in the range of ppm or less.

Al atom concentration in p-type diamond semiconductor film is 1.0 × 10²¹cm^‐3Needless to say, within the following range, the higher the hole concentration, the higher the hole concentration, which is more suitable for practical use.

In addition, the hole concentration is 1.0 x 10 in order to function as a p-type semiconductor.¹⁵cm^‐3With the above, and the dopant atom concentration is 1.0 × 10²¹cm^‐3It may be as follows. Therefore, the p-type diamond semiconductor according to the fourth embodiment has a hole concentration of 1.0 × 10.¹⁵cm^‐3Line and Al atom concentration 1.0 × 10²¹cm^‐3It functions as a p-type semiconductor under the conditions in the region surrounded by the line. For example, Embodiment 4 can function as a p-type semiconductor even at temperatures other than 300 K. The region that functions as a p-type semiconductor according to the fourth embodiment is much wider than that of a conventional p-type diamond semiconductor doped with B, and is excellent in that it functions as a p-type semiconductor under various conditions.

Further, as a dopant gas, the trimethylaluminum of the present invention ((CH)₃)₃Al: TMAl), triethylaluminum ((C)₂H₅)₃Al: TEAl) or aluminum chloride (AlCl)₃) Is used, and the mobility of holes in each p-type diamond semiconductor film at 300 K is shown in Table 4.

<tables num="4"><img file="JP4908409B2_D0013.tif" /></tables>

As shown in Table 4, trimethylaluminum ((CH)₃)₃Al: TMAl), triethylaluminum ((C)₂H₅)₃Aluminum chloride (AlCl) when using Al: TEAl)₃) Is about 7 times higher in room temperature hole mobility than the case of using), and has very excellent characteristics.

(Embodiment 5) The dopant is Be, and the acceleration voltage is 150 kV and the implantation amount is 10 by the ion implantation method.¹⁵cm^‐2A Be impurity-doped diamond can be produced by injecting a Be dopant into a diamond single crystal under the above conditions. This Be impurity-doped diamond can be produced by using a microwave plasma chemical vapor deposition method in which a solid Be is inserted into a plasma and the vaporized Be is used as a dopant gas, in addition to the ion implantation method. By the microwave plasma chemical vapor deposition method, methane gas (CH) with a flow rate ratio of 1%₄), Solid Be, Remaining H₂The diamond semiconductor film of the present invention having a thickness of 1.0 μm is grown on the diamond single crystal (001) plane orientation using the reaction gas having a total flow rate of 300 ccm as a raw material. Here, the pressure in the reaction tube is 50 Torr, and the frequency of the microwave source is 2.45 GHz and the output is 1.3 kW.

Next, the obtained Be impurity-doped diamond is annealed. When the hole of the obtained Be-doped diamond semiconductor film of the present invention is measured and the hole coefficient is determined, it can be confirmed that the semiconductor is a p-type semiconductor.

The Be atom concentration y in the dialed semiconductor film is measured by SIMS measurement, and the ratio of the number of Be atoms to the number of C atoms in the raw material gas (Be / C) x (ppm) is taken as the horizontal axis, and the Be in the semiconductor film is taken as the horizontal axis. Atomic concentration y (cm^‐3) Is taken on the vertical axis, and the relationship is as shown in Fig. 24. x (ppm) x 10¹⁷= y (cm)^‐3) ......... (1) become.

1.0×10¹⁶cm^-3~1.0×10²¹cm^-3The temperature dependence of the hole concentration in each Be dopant atom concentration sample was measured by Hall measurement. From the results, FIG. 26 shows the temperature dependence of the hole concentration with respect to each Be atom concentration in the p-type diamond semiconductor according to the fifth embodiment of the present invention. In Fig. 26, the horizontal axis is the measured temperature (K), and the vertical axis is the hole concentration in the p-type diamond semiconductor (cm).^-3), And the Be atomic concentration (cm) in the p-type diamond semiconductor.^-3) Is a plot of the measured values.

Hole concentration 1.0 × 10 near practical level 300K¹⁵cm^-3To get 7.0x10¹⁶cm^-3The above Be atom concentration is required. Also 1.0 x 10²¹cm^-3If the Be atom concentration exceeds, the quality of diamond crystals deteriorates. Therefore, the dopant atom concentration of the Be-doped p-type diamond semiconductor device at the practical level of around 300 K is 7.0 × 10.¹⁶cm^-3More than 1.0 × 10²¹cm^‐3Must be:

From this, using equation (1), the ratio of the number of Be atoms to the number of C atoms in the raw material gas (Be / C) is 0.7 ppm or more and 10⁴It can be seen that it should be in the range of ppm or less.

Further, using FIG. 26 in which the hole concentration values in the p-type diamond semiconductor at each temperature are plotted for each dopant atom concentration, the hole concentration in the p-type diamond semiconductor at each temperature is 1.0 × 10.¹⁵cm^‐3It is possible to obtain the dopant atom concentration to be. For example, at 500K, the hole concentration in a p-type diamond semiconductor is 1.0 × 10.¹⁵cm^‐3The Be atom concentration is 1.3 × 10 from Fig. 26.¹⁶cm^‐3Is derived.

Be atomic concentration is 1.0 × 10²¹cm^-3Needless to say, within the following range, the higher the hole concentration, the higher the hole concentration, which is more suitable for practical use.

Further, the p-type diamond semiconductor according to the present embodiment can obtain a room temperature hole concentration about 25,000 times that of a conventional p-type diamond semiconductor doped with B at the same dopant atom concentration.

In addition, the hole concentration is 1.0 x 10 in order to function as a p-type semiconductor.¹⁵cm^‐3With the above, and the dopant atom concentration is 1.0 × 10²¹cm^‐3It may be as follows. Therefore, the p-type diamond semiconductor according to the fifth embodiment has a hole concentration of 1.0 × 10.¹⁵cm^‐3Line and Be atomic concentration 1.0 × 10²¹cm^‐3It functions as a p-type semiconductor under the conditions in the region surrounded by the line. For example, Embodiment 5 can function as a p-type semiconductor even at temperatures other than 300 K. The region that functions as a p-type semiconductor according to the fifth embodiment is much wider than that of a conventional p-type diamond semiconductor doped with B, and is excellent in that it functions as a p-type semiconductor under various conditions.

(Embodiment 6) The dopant is Ca, and the acceleration voltage is 150 kV and the implantation amount is 10 by the ion implantation method.¹⁵cm^‐2It is possible to prepare a Ca impurity-doped diamond by injecting a Ca dopant into a diamond single crystal under the above conditions. This Ca impurity-doped diamond can be produced by using a microwave plasma chemical vapor deposition method in addition to the ion implantation method. Methane gas (CH) with a flow rate ratio of 1% by microwave plasma chemical vapor deposition method₄), Dopant gas, balance H₂The diamond semiconductor film of the present invention having a thickness of 1.0 μm is grown on the diamond single crystal (001) plane orientation using a mixed gas having a total flow rate of 300 ccm, which is composed of the reaction gas. The pressure in the reaction tube is 50 Torr, and the frequency of the microwave source is 2.45 GHz and the output is 1.3 kW. Here, the dopant gas is calcium chloride CaCl.₂Is used. Alternatively, instead of using this dopant gas, solid Ca can be inserted into the plasma and vaporized Ca can be used as the dopant gas.

The Ca atom concentration y in the diamond semiconductor film is measured by SIMS measurement, and the ratio of the number of Ca atoms to the number of C atoms in the raw material gas (Ca / C) x (ppm) is taken on the horizontal axis, and Ca in the semiconductor film is taken. Atomic concentration y (cm^‐3) Is taken on the vertical axis, and the relationship is as shown in Fig. 24. x (ppm) x 10¹⁷= y (cm)^‐3) ......... (1) become.

1.0×10¹⁶cm^-3~1.0×10²¹cm^-3The temperature dependence of the hole concentration in the sample of each Ca dopant atom concentration was measured by Hall measurement. From the results, FIG. 27 shows the temperature dependence of the hole concentration with respect to each Ca atom concentration in the p-type diamond semiconductor according to the sixth embodiment of the present invention. In Fig. 27, the horizontal axis is the measured temperature (K), and the vertical axis is the hole concentration in the p-type diamond semiconductor (cm).^-3), Ca atom concentration (cm) in the p-type diamond semiconductor^-3) Is a plot of the measured values.

Hole concentration 1.0 × 10 near practical level 300K¹⁵cm^-3To get 3.0x10¹⁷cm^-3The above Ca atom concentration is required. Also, 1.0 x 10²¹cm^-3At Ca atom concentrations above, the quality of diamond crystals deteriorates. Therefore, the dopant atom concentration of the Ca-doped p-type diamond semiconductor device at the practical level of around 300 K is 3.0 × 10.¹⁷cm^-3More than 1.0 × 10²¹cm^‐3Must be:

From this, using equation (1), the ratio of the number of Ca atoms to the number of C atoms in the raw material gas (Ca / C) is 3.0 ppm or more and 10⁴It can be seen that it should be in the range of ppm or less.

Further, using FIG. 27 in which the hole concentration values in the p-type diamond semiconductor at each temperature are plotted for each dopant atom concentration, the hole concentration in the p-type diamond semiconductor at each temperature is 1.0 × 10.¹⁵cm^‐3It is possible to obtain the dopant atom concentration to be. For example, at 500K, the hole concentration in a p-type diamond semiconductor is 1.0 × 10.¹⁵cm^‐3The Ca atom concentration is 3.2 × 10 from Fig. 27.¹⁶cm^‐3Is derived. In this case, the ratio of the number of Ca atoms (Ca / C) to the number of C atoms in the raw material gas is 0.32 ppm or more from Eq. (1).⁴It can be seen that it should be in the range of ppm or less.

Ca atom concentration is 1.0 × 10²¹cm^-3Needless to say, within the following range, the higher the hole concentration, the higher the hole concentration, which is more suitable for practical use.

Further, the p-type diamond semiconductor according to the present embodiment has about 5.7 × 10 as compared with the conventional p-type diamond semiconductor doped with B at the same dopant atom concentration.³Double the room temperature hole concentration can be obtained.

In addition, the hole concentration is 1.0 x 10 in order to function as a p-type semiconductor.¹⁵cm^‐3With the above, and the dopant atom concentration is 1.0 × 10²¹cm^‐3It may be as follows. Therefore, the p-type diamond semiconductor according to the sixth embodiment has a hole concentration of 1.0 × 10.¹⁵cm^‐3Line and Ca atom concentration 1.0 × 10²¹cm^‐3It functions as a p-type semiconductor under the conditions in the region surrounded by the line. For example, Embodiment 6 can function as a p-type semiconductor even at temperatures other than 300 K. The region that functions as a p-type semiconductor according to the sixth embodiment is much wider than that of a conventional p-type diamond semiconductor doped with B, and is excellent in that it functions as a p-type semiconductor under various conditions.

The mobility of holes in the p-type diamond semiconductor film obtained in the present embodiment at room temperature has a Ca atom concentration of 1.0 × 10.¹⁹cm^-3200 cm under the conditions²/ Vs.

(Embodiment 7) Methane gas (CH) with a flow rate ratio of 1% by microwave plasma chemical vapor deposition method₄), Dopant gas, balance H₂The diamond semiconductor film of the present invention having a thickness of 1.0 μm is grown on the diamond single crystal (001) plane orientation using a mixed gas having a total flow rate of 300 ccm, which is composed of the reaction gas. The pressure in the reaction tube is 50 Torr, and the frequency of the microwave source is 2.45 GHz and the output is 1.3 kW. Here, the dopant gas is dimethyl cadmium ((CH), which is an organometallic raw material containing Cd.₃)₂Cd: DMCd) and diethyl cadmium ((C)₂H₅)₂Use one of Cd: DECd).

When the holes of the obtained diamond semiconductor film are measured and the hole coefficients are determined, it can be confirmed that they are p-type semiconductors.

In addition, the Cd atom concentration in the diamond semiconductor film is measured by SIMS measurement, and the ratio of the number of Cd atoms to the number of C atoms in the raw material gas (Cd / C) x (ppm) is taken as the horizontal axis, and the Cd atom concentration is taken in the semiconductor film. Cd atomic concentration y (cm^‐3) Is taken on the vertical axis, and the relationship is as shown in Fig. 24. x (ppm) x 10¹⁷= y (cm)^‐3) ......... (1) become.

FIG. 28 shows the temperature dependence of the hole concentration with respect to each Cd atom concentration in the p-type diamond semiconductor according to the seventh embodiment of the present invention. In Fig. 28, the horizontal axis is the measured temperature (K), and the vertical axis is the hole concentration in the p-type diamond semiconductor (cm).^-3), Cd atomic concentration in p-type diamond semiconductor (cm)^-3) Is a plot of the measured values.

Hole concentration 1.0 × 10 near practical level 300K¹⁵cm^‐3To get 2.0x10¹⁶cm^‐3It can be seen that the above Cd atom concentration is required. Also 1.0 x 10²¹cm^‐3It is known that the quality of diamond crystals deteriorates when the Cd atom concentration exceeds. Therefore, the practical level dopant atom concentration of the Cd-doped p-type diamond semiconductor device is 2.0 × 10.¹⁶cm^‐3More than 1.0 × 10²¹cm^‐3Must be:

From this, using Eq. (1), the ratio of the number of Cd atoms to the number of C atoms in the raw material gas (Cd / C) is 0.2 ppm or more and 10⁴It can be seen that it should be in the range of ppm or less.

Further, using FIG. 28 in which the hole concentration values in the p-type diamond semiconductor at each temperature are plotted for each dopant atom concentration, the hole concentration in the p-type diamond semiconductor at each temperature is 1.0 × 10.¹⁵cm^‐3It is possible to obtain the dopant atom concentration to be. For example, at 500K, the hole concentration in a p-type diamond semiconductor is 1.0 × 10.¹⁵cm^‐3The Cd atomic concentration is 6.4 × 10 from Fig. 28.¹⁵cm^‐3Is derived. In this case, the ratio of the number of Cd atoms to the number of C atoms in the raw material gas (Cd / C) is 0.064 ppm or more from Eq. (1).⁴It can be seen that it should be in the range of ppm or less.

The Cd atom concentration in the p-type diamond semiconductor film is 1.0 × 10.²¹cm^‐3Needless to say, within the following range, the higher the hole concentration, the higher the hole concentration, which is more suitable for practical use.

In addition, the hole concentration is 1.0 x 10 in order to function as a p-type semiconductor.¹⁵cm^‐3With the above, and the dopant atom concentration is 1.0 × 10²¹cm^‐3It may be as follows. Therefore, the p-type diamond semiconductor according to the seventh embodiment has a hole concentration of 1.0 × 10.¹⁵cm^‐3Line and Cd atomic concentration 1.0 × 10²¹cm^‐3It functions as a p-type semiconductor under the conditions in the region surrounded by the line. For example, Embodiment 7 can function as a p-type semiconductor even at temperatures other than 300 K. The region that functions as a p-type semiconductor according to the seventh embodiment is much wider than that of a conventional p-type diamond semiconductor doped with B, and is excellent in that it functions as a p-type semiconductor under various conditions.

Further, as a dopant gas, the dimethyl cadmium of the present invention ((CH)₃)₂Cd: DMCd), diethyl cadmium ((C)₂H₅)₂Cd: DECd) or cadmium chloride (CdCl)₂) Is used, and the results of comparing the mobilities of holes in each p-type diamond semiconductor film at 300 K are shown in Table 5.

<tables num="5"><img file="JP4908409B2_D0014.tif" /></tables>

Cadmium chloride (CdCl) as shown in Table 5₂) Compared to the case of using dimethyl cadmium ((CH)₃)₂Cd: DMCd), diethyl cadmium ((C)₂H₅)₂When Cd: DECd) is used, the room temperature hole mobility is more than 8 times higher, and it has very excellent characteristics.

(Embodiment 8) Methane gas (CH) with a flow rate ratio of 1% by microwave plasma chemical vapor deposition method₄), Dopant gas, balance H₂The diamond semiconductor film of the present invention having a thickness of 1.0 μm is grown on the diamond single crystal (001) plane orientation using a mixed gas having a total flow rate of 300 ccm, which is composed of the reaction gas. The pressure in the reaction tube is 50 Torr, and the frequency of the microwave source is 2.45 GHz and the output is 1.3 kW. Here, the dopant gas is trimethylgallium ((CH), which is an organometallic raw material containing Ga.₃)₃Ga: TMGa) or triethyl gallium ((C)₂H₅)₃Ga: TEGa) is used.

When the holes of the obtained diamond semiconductor film are measured and the hole coefficients are determined, it can be confirmed that they are p-type semiconductors.

Furthermore, the Ga atom concentration in the diamond semiconductor film is measured by SIMS measurement, and the ratio of the number of Ga atoms to the number of C atoms in the raw material gas (Ga / C) x (ppm) is taken on the horizontal axis, and the ratio in the semiconductor film is taken. Ga atomic concentration y (cm^‐3) Is taken on the vertical axis, and the relationship is as shown in Fig. 24. x (ppm) x 10¹⁷= y (cm)^‐3) ......... (1) become.

FIG. 29 shows the temperature dependence of the hole concentration with respect to each Ga atom concentration in the p-type diamond semiconductor according to the eighth embodiment of the present invention. In Fig. 29, the horizontal axis is the measured temperature (K), and the vertical axis is the hole concentration in the p-type diamond semiconductor (cm).^-3), Ga atomic concentration in p-type diamond semiconductor (cm)^-3) Is a plot of the measured values.

Hole concentration 1.0 × 10 near practical level 300K¹⁵cm^‐3To get 3.0x10¹⁶cm^‐3It can be seen that the above Ga atom concentration is required. Also 1.0 x 10²¹cm^‐3It is known that the quality of diamond crystals deteriorates when the Ga atom concentration exceeds. Therefore, the practical level dopant atom concentration of the Ga-doped p-type diamond semiconductor device is 3.0 × 10.¹⁶cm^‐3More than 1.0 × 10²¹cm^‐3Must be:

From this, using Eq. (1), the ratio of the number of Ga atoms to the number of C atoms in the raw material gas (Ga / C) is 0.3 ppm or more and 10⁴It can be seen that it should be in the range of ppm or less.

Further, using FIG. 29 in which the hole concentration values in the p-type diamond semiconductor at each temperature are plotted for each dopant atom concentration, the hole concentration in the p-type diamond semiconductor at each temperature is 1.0 × 10.¹⁵cm^‐3It is possible to obtain the dopant atom concentration to be. For example, at 500K, the hole concentration in a p-type diamond semiconductor is 1.0 × 10.¹⁵cm^‐3The Ga atom concentration is 8.1 × 10 from Fig. 29.¹⁵cm^‐3Is derived. In this case, the ratio (Ga / C) of the number of atoms of Ga to the number of atoms of C in the raw material gas is 0.081 ppm or more from Eq. (1).⁴It can be seen that it should be in the range of ppm or less.

Ga atom concentration in p-type diamond semiconductor film is 1.0 × 10²¹cm^‐3Needless to say, within the following range, the higher the hole concentration, the higher the hole concentration, which is more suitable for practical use.

In addition, the hole concentration is 1.0 x 10 in order to function as a p-type semiconductor.¹⁵cm^‐3With the above, and the dopant atom concentration is 1.0 × 10²¹cm^‐3It may be as follows. Therefore, the p-type diamond semiconductor according to the eighth embodiment has a hole concentration of 1.0 × 10.¹⁵cm^‐3Line and Ga atom concentration 1.0 × 10²¹cm^‐3It functions as a p-type semiconductor under the conditions contained in the region surrounded by the line. For example, Embodiment 8 can function as a p-type semiconductor even at temperatures other than 300 K. The region that functions as a p-type semiconductor according to the eighth embodiment is much wider than that of a conventional p-type diamond semiconductor doped with B, and is excellent in that it functions as a p-type semiconductor under various conditions.

As the dopant gas, the trimethylaluminum of the present invention ((CH)₃)₃Al: TMAl), triethyl gallium ((C)₂H₅)₃Ga: TEGa) or gallium chloride (GaCl)₃) Is used, and the mobility of holes in each p-type diamond semiconductor film at 300 K is shown in Table 6.

<tables num="6"><img file="JP4908409B2_D0015.tif" /></tables>

As shown in Table 6, gallium chloride (GaCl)₃) Is more than trimethylaluminum ((CH)₃)₃Ga, TMGa), triethylaluminum ((C)₂H₅)₃When Ga, TEGa) is used, the room temperature hole mobility is more than 7 times higher, and it has very excellent characteristics.

(Embodiment 9) Methane gas (CH) with a flow rate ratio of 1% by microwave plasma chemical vapor deposition method₄), Dopant gas, balance H₂The diamond semiconductor film of the present invention having a thickness of 1.0 μm is grown on the diamond single crystal (001) plane orientation using a mixed gas having a total flow rate of 300 ccm, which is composed of the reaction gas. The pressure in the reaction tube is 50 Torr, and the frequency of the microwave source is 2.45 GHz and the output is 1.3 kW. Here, the dopant gas is trimethylindium ((CH), which is an organometallic raw material containing In.₃)₃In: TMIn) or triethylindium ((C)₂H₅)₃In: TEIn) is used.

When the holes of the obtained diamond semiconductor film are measured and the hole coefficients are determined, it can be confirmed that they are p-type semiconductors.

Furthermore, the In atom concentration in the diamond semiconductor film is measured by SIMS measurement, and the ratio of the number of In atoms to the number of C atoms in the raw material gas (In / C) x (ppm) is taken on the horizontal axis, and the ratio in the semiconductor film is taken. In atomic concentration y (cm^‐3) Is taken on the vertical axis, and the relationship is as shown in Fig. 24. x (ppm) x 10¹⁷= y (cm)^‐3) ......... (1) become.

FIG. 30 shows the temperature dependence of the hole concentration with respect to each In atom concentration in the p-type diamond semiconductor according to the ninth embodiment of the present invention. In Fig. 30, the horizontal axis is the measured temperature (K), and the vertical axis is the hole concentration in the p-type diamond semiconductor (cm).^-3), And the In atomic concentration (cm) in the p-type diamond semiconductor^-3) Is a plot of the measured values.

Hole concentration 1.0 × 10 near practical level 300K¹⁵cm^‐3To get 1.5x10¹⁶cm^‐3It can be seen that the above In atom concentration is required. Also 1.0 x 10²¹cm^‐3It is known that the quality of diamond crystals deteriorates when the In atom concentration exceeds. Therefore, the practical level dopant atom concentration of the In-doped p-type diamond semiconductor device is 1.5 × 10.¹⁶cm^‐3More than 1.0 × 10²¹cm^‐3It is as follows.

From this, using Eq. (1), the ratio (In / C) of the number of In atoms to the number of C atoms in the raw material gas is 0.15 ppm or more and 10⁴It can be seen that it should be in the range of ppm or less.

Further, using FIG. 30 in which the hole concentration values in the p-type diamond semiconductor at each temperature are plotted for each dopant atom concentration, the hole concentration in the p-type diamond semiconductor at each temperature is 1.0 × 10.¹⁵cm^‐3It is possible to obtain the dopant atom concentration to be. For example, at 500K, the hole concentration in a p-type diamond semiconductor is 1.0 × 10.¹⁵cm^‐3The In atomic concentration is 5.1 × 10 from Fig. 30.¹⁵cm^‐3Is derived. In this case, the ratio (In / C) of the number of atoms of In to the number of atoms of C in the raw material gas is 0.051 ppm or more from Eq. (1).⁴It can be seen that it should be in the range of ppm or less.

The In atom concentration in the p-type diamond semiconductor film is 1.0 × 10.²¹cm^‐3Needless to say, within the following range, the higher the hole concentration, the higher the hole concentration, which is more suitable for practical use.

In addition, the hole concentration is 1.0 x 10 in order to function as a p-type semiconductor.¹⁵cm^‐3With the above, and the dopant atom concentration is 1.0 × 10²¹cm^‐3It may be as follows. Therefore, the p-type diamond semiconductor according to the ninth embodiment has a hole concentration of 1.0 × 10.¹⁵cm^‐3Line and In atomic concentration 1.0 × 10²¹cm^‐3It functions as a p-type semiconductor under the conditions contained in the region surrounded by the line. For example, Embodiment 9 can function as a p-type semiconductor even at temperatures other than 300 K. The region that functions as a p-type semiconductor according to the ninth embodiment is much wider than that of a conventional p-type diamond semiconductor doped with B, and is excellent in that it functions as a p-type semiconductor under various conditions.

Further, as the dopant gas, the trimethylindium of the present invention ((CH)₃)₃In: TMIn), Triethyl Indium ((C)₂H₅)₃In: TEIn) or indium chloride (InCl)₃) Is used, and the mobility of holes in each p-type semiconductor film at 300 K is shown in Table 7.

<tables num="7"><img file="JP4908409B2_D0016.tif" /></tables>

As shown in Table 7, indium chloride (InCl)₃) Than when using trimethylindium ((CH)₃)₃In: TMIn) or triethylindium ((C)₂H₅)₃When In: TEIn) is used, the room temperature hole mobility is more than 7 times higher, and it has very excellent characteristics.

(Embodiment 10) The dopant is Li, and the acceleration voltage is 150 kV and the implantation amount is 10 by the ion implantation method.¹⁵cm^‐2A Li impurity-doped diamond can be produced by injecting a Li dopant into a diamond single crystal under the above conditions. This Li impurity-doped diamond can be produced by using a microwave plasma chemical vapor deposition method by inserting solid Li into plasma in addition to the ion implantation method. Methane gas with a flow rate ratio of 1% (CH)₄), Dopant gas, balance H₂The diamond semiconductor film of the present invention having a thickness of 1.0 μm is grown on the diamond single crystal (001) plane orientation using the reaction gas having a total flow rate of 300 ccm as a raw material. Here, the pressure in the reaction tube is 50 Torr, and the frequency of the microwave source is 2.45 GHz and the output is 1.3 kW. Here, the dopant gas is methyllithium (CH).₃Li), ethyllithium (C)₂H₅Li), propyl lithium (C)₃H₇Any of Li) can be used.

Next, the obtained Li impurity-doped diamond is annealed. When the hole of the obtained Li-doped diamond semiconductor film of the present invention is measured and the hole coefficient is determined, it can be confirmed that the semiconductor is a p-type semiconductor. Furthermore, the concentration of Li dopant atoms in the dialed semiconductor film was measured by SIMS measurement.

1.0×10¹⁶cm^-3~1.0×10²¹cm^-3The temperature dependence of the hole concentration in the sample of each Li dopant atom concentration was measured by Hall measurement. From the results, FIG. 39 shows the temperature dependence of the hole concentration with respect to each Li atom concentration in the p-type diamond semiconductor according to the tenth embodiment of the present invention. In Fig. 39, the horizontal axis is the measured temperature (K), and the vertical axis is the hole concentration in the p-type diamond semiconductor (cm).^-3), Li atom concentration (cm) in p-type diamond semiconductor^-3) Is a plot of the measured values.

Hole concentration 1.0 × 10 near practical level 300K¹⁵cm^-3To get 3.0x10¹⁷cm^-3The above Li atom concentration is required. Also 1.0 x 10²¹cm^-3If the Li atom concentration exceeds, the quality of diamond crystals deteriorates. Therefore, the dopant atom concentration of the Li-doped p-type diamond semiconductor device at the practical level of around 300 K is 3.0 × 10.¹⁶cm^-3More than 1.0 × 10²¹cm^‐3Must be:

Further, using FIG. 39 in which the hole concentration values in the p-type diamond semiconductor at each temperature are plotted for each dopant atom concentration, the hole concentration in the p-type diamond semiconductor at each temperature is 1.0 × 10.¹⁵cm^‐3It is possible to obtain the dopant atom concentration to be. For example, at 500K, the hole concentration in a p-type diamond semiconductor is 1.0 × 10.¹⁵cm^‐3The Li atom concentration is 3.2 × 10 from Fig. 39.¹⁶cm^‐3Is derived.

Li atom concentration is 1.0 × 10²¹cm^-3Needless to say, within the following range, the higher the hole concentration, the higher the hole concentration, which is more suitable for practical use.

Further, the p-type diamond semiconductor according to the present embodiment can obtain a room temperature hole concentration about 5700 times that of a conventional p-type diamond semiconductor doped with B at the same dopant atom concentration.

In addition, the hole concentration is 1.0 x 10 in order to function as a p-type semiconductor.¹⁵cm^‐3With the above, and the dopant atom concentration is 1.0 × 10²¹cm^‐3It may be as follows. Therefore, the p-type diamond semiconductor according to the tenth embodiment has a hole concentration of 1.0 × 10.¹⁵cm^‐3Line and Li atom concentration 1.0 × 10²¹cm^‐3It functions as a p-type semiconductor under the conditions in the region surrounded by the line. For example, embodiment 10 can function as a p-type semiconductor even at temperatures other than 300 K. The region that functions as a p-type semiconductor according to the tenth embodiment is much wider than that of a conventional p-type diamond semiconductor doped with B, and is excellent in that it functions as a p-type semiconductor under various conditions.

<tables num="8"><img file="JP4908409B2_D0017.tif" /></tables>

(Embodiment 11) Methane gas (CH) with a flow rate ratio of 1% by microwave plasma chemical vapor deposition method₄), Dopant gas, balance H₂The diamond semiconductor film of the present invention having a thickness of 1.0 μm is grown on the diamond single crystal (001) plane orientation using a mixed gas having a total flow rate of 300 ccm, which is composed of the reaction gas. The pressure in the reaction tube is 50 Torr, and the frequency of the microwave source is 2.45 GHz and the output is 1.3 kW. Here, the dopant gas is biscyclopentadeeneyl magnesium ((C), which is an organometallic raw material containing Mg.₅H₅)₂Mg: Cp₂Mg) or bismethylcyclopentadeeneyl magnesium ((CH)₃C₅H₄)₂Mg: MCp₂Mg) is used.

When the holes of the obtained diamond semiconductor film are measured and the hole coefficients are determined, it can be confirmed that they are P-type semiconductors.

Furthermore, the Mg atomic concentration in the diamond semiconductor film is measured by SIMS measurement, and the ratio of the number of Mg atoms to the number of C atoms in the raw material gas (Mg / C) x (ppm) is taken on the horizontal axis, and Mg in the semiconductor film is taken. Atomic concentration y (cm^‐3) Is taken on the vertical axis, and the relationship is as shown in Fig. 24. x (ppm) x 10¹⁷= y (cm)^‐3) ......... (1) become.

FIG. 31 shows the temperature dependence of the hole concentration with respect to each Mg atom concentration in the p-type diamond semiconductor according to the eleventh embodiment of the present invention. In Fig. 31, the horizontal axis is the measured temperature (K), and the vertical axis is the hole concentration in the p-type diamond semiconductor (cm).^-3), And the Mg atomic concentration (cm) in the p-type diamond semiconductor.^-3) Is a plot of the measured values.

Hole concentration 1.0 × 10 near practical level 300K¹⁵cm^‐3To get 2.0x10¹⁸cm^‐3It can be seen that the above Mg atom concentration is required. Also 1.0 x 10²¹cm^‐3It is known that the quality of diamond crystals deteriorates at Mg atomic concentrations exceeding. Therefore, the practical level dopant atom concentration of Mg-doped p-type diamond semiconductor devices is 2.0 × 10.¹⁸cm^‐3More than 1.0 × 10²¹cm^‐3It is as follows.

From this, using equation (1), the ratio of the number of Mg atoms to the number of C atoms in the raw material gas (Mg / C) is 20 ppm or more and 10⁴It can be seen that it should be in the range of ppm or less.

In addition, using FIG. 31, which plots the hole concentration values in the p-type diamond semiconductor at each temperature for each dopant atom concentration, the hole concentration in the p-type diamond semiconductor at each temperature is 1.0 × 10.¹⁵cm^‐3It is possible to obtain the dopant atom concentration to be. For example, at 500K, the hole concentration in a p-type diamond semiconductor is 1.0 × 10.¹⁵cm^‐3The Mg atomic concentration is 1.0 × 10 from Fig. 31.¹⁷cm^‐3Is derived. In this case, the ratio of the number of Mg atoms (Mg / C) to the number of C atoms in the raw material gas is 1.0 ppm or more from Eq. (1).⁴It can be seen that it should be in the range of ppm or less.

The Mg atom concentration in the p-type diamond semiconductor film is 1.0 × 10.²¹cm^‐3Needless to say, within the following range, the higher the hole concentration, the higher the hole concentration, which is more suitable for practical use.

In addition, the hole concentration is 1.0 x 10 in order to function as a p-type semiconductor.¹⁵cm^‐3With the above, and the dopant atom concentration is 1.0 × 10²¹cm^‐3It may be as follows. Therefore, the p-type diamond semiconductor according to the eleventh embodiment has a hole concentration of 1.0 × 10.¹⁵cm^‐3Line and Mg atomic concentration 1.0 × 10²¹cm^‐3It functions as a p-type semiconductor under the conditions contained in the region surrounded by the line. For example, Embodiment 11 can function as a p-type semiconductor even at temperatures other than 300 K. The region that functions as a p-type semiconductor according to the eleventh embodiment is much wider than that of a conventional p-type diamond semiconductor doped with B, and is excellent in that it functions as a p-type semiconductor under various conditions.

Further, as a dopant gas, the biscyclopentadeeneyl magnesium (C) of the present invention₅H₅)₂Mg: Cp₂Mg), bismethylcyclopentadeeneyl magnesium ((CH)₃C₅H₄)₂Mg: MCp₂Mg) or magnesium chloride (MgCl)₂) Is used, and the mobility of holes in each p-type diamond semiconductor film at 300 K is shown in Table 9.

<tables num="9"><img file="JP4908409B2_D0018.tif" /></tables>

Magnesium chloride (MgCl) as shown in Table 9₂) Than when using biscyclopentadeeneyl magnesium (C)₅H₅)₂Mg: Cp₂Mg), or bismethylcyclooenta de eneil magnesium ((CH)₃C₅H₄)₂Mg: MCp₂When Mg) is used, the room temperature hole mobility is 12 times or more higher, and it has very excellent characteristics.

(Embodiment 12) Methane gas (CH) with a flow rate ratio of 1% by microwave plasma chemical vapor deposition method₄), Dopant gas, balance H₂The diamond semiconductor film of the present invention having a thickness of 1.0 μm is grown on the diamond single crystal (001) plane orientation using a mixed gas having a total flow rate of 300 ccm, which is composed of the reaction gas. The pressure in the reaction tube is 50 Torr, and the frequency of the microwave source is 2.45 GHz and the output is 1.3 kW. Here, the dopant gas is dimethylzinc ((CH), which is an organometallic raw material containing Zn.₃)₂Zn: DMZn) or diethylzinc ((C)₂H₅)₂Zn: DEZn) is used.

When the holes of the obtained diamond semiconductor film are measured and the hole coefficients are determined, it can be confirmed that they are p-type semiconductors.

Furthermore, the Zn atom concentration in the diamond semiconductor film is measured by SIMS measurement, and the ratio of the number of Zn atoms to the number of C atoms in the raw material gas (Zn / C) x (ppm) is taken as the horizontal axis, and the ratio in the semiconductor film is taken. Zn atomic concentration y (cm)^‐3) Is taken on the vertical axis, and the relationship is as shown in Fig. 24. x (ppm) x 10¹⁷= y (cm)^‐3) ......... (1) become.

FIG. 32 shows the temperature dependence of the hole concentration with respect to each Zn atom concentration in the p-type diamond semiconductor according to the twelfth embodiment of the present invention. In Fig. 32, the horizontal axis is the measured temperature (K), and the vertical axis is the hole concentration in the p-type diamond semiconductor (cm).^-3), Zn atomic concentration in p-type diamond semiconductor (cm)^-3) Is a plot of the measured values.

Hole concentration 1.0 × 10 near practical level 300K¹⁵cm^‐3To get 1.0x10¹⁷cm^‐3It can be seen that the above Zn atom concentration is required. Also 1.0 x 10²¹cm^‐3It is known that the quality of diamond crystals deteriorates when the Zn atom concentration exceeds. Therefore, the practical level dopant atom concentration of Zn-doped p-type diamond semiconductor devices is 1.0 × 10.¹⁷cm^‐3More than 1.0 × 10²¹cm^‐3It is as follows.

From this, using equation (1), the ratio of the number of Zn atoms to the number of C atoms in the raw material gas (Zn / C) is 1.0 ppm or more and 10⁴It can be seen that it should be in the range of ppm or less.

Further, using FIG. 32 in which the hole concentration values in the p-type diamond semiconductor at each temperature are plotted for each dopant atom concentration, the hole concentration in the p-type diamond semiconductor at each temperature is 1.0 × 10.¹⁵cm^‐3It is possible to obtain the dopant atom concentration to be. For example, at 500K, the hole concentration in a p-type diamond semiconductor is 1.0 × 10.¹⁵cm^‐3The Zn atomic concentration is 1.6 × 10 from Fig. 32.¹⁶cm^‐3Is derived. In this case, the ratio of the number of Zn atoms (Zn / C) to the number of C atoms in the raw material gas is 0.16 ppm or more from Eq. (1).⁴It can be seen that it should be in the range of ppm or less.

Zn atom concentration is 1.0 × 10²¹cm^‐3Needless to say, within the following range, the higher the hole concentration, the higher the hole concentration, which is more suitable for practical use.

In addition, the hole concentration is 1.0 x 10 in order to function as a p-type semiconductor.¹⁵cm^‐3With the above, and the dopant atom concentration is 1.0 × 10²¹cm^‐3It may be as follows. Therefore, the p-type diamond semiconductor according to the twelfth embodiment has a hole concentration of 1.0 × 10.¹⁵cm^‐3Line and Zn atomic concentration 1.0 × 10²¹cm^‐3It functions as a p-type semiconductor under the conditions contained in the region surrounded by the line. For example, Embodiment 12 can function as a p-type semiconductor even at temperatures other than 300 K. The region that functions as a p-type semiconductor according to the twelfth embodiment is much wider than that of a conventional p-type diamond semiconductor doped with B, and is excellent in that it functions as a p-type semiconductor under various conditions.

Further, as the dopant gas, dimethylzinc ((CH) used in the present invention₃)₂Zn: DMZn), diethylzinc ((C)₂H₅)₂Zn, DEZn), or zinc chloride (ZnCl)₂Table 10 shows the mobility of holes in each p-type semiconductor film at 300 K obtained by using) and.

<tables num="10"><img file="JP4908409B2_D0019.tif" /></tables>

Zinc chloride (ZnCl), as shown in Table 10.₂) Is compared with dimethylzinc ((CH)₃)₂Zn: DMZn), diethylzinc ((C)₂H₅)₂When Zn: DEZn) is used, the room temperature hole mobility is 23 times or more higher, and it has very excellent characteristics.

(Embodiment 13) A diamond powder mixed with Al, Be, Ca, Cd, Ga, In, Li, Mg or Zn as a dopant is dissolved in a Fe-Ni solvent. 5.0GPa, about 1.4x10³The p-type diamond semiconductor film of the present invention can be obtained by the ultra-high temperature and high pressure method by leaving it under the condition of ° C for 7 hours. When the holes of the obtained p-type diamond semiconductor film of the present invention are measured and the hole coefficients are determined, it can be confirmed that they are P-type semiconductors.

Further, in Table 11, when the dopant atom concentration in the diamond semiconductor film was measured by SIMS measurement and the atomic concentration ratio (dopant atom / C) was kept constant at 0.01%, the p-type diamond semiconductor film was positive at 300 K. Indicates hole concentration and hole mobility.

<tables num="11"><img file="JP4908409B2_D0020.tif" /></tables>

Room temperature hole concentration is when doping B, which is a conventional technique (6.2 × 10).¹²cm^‐3), Al, Be, Ca, Cd, Ga, In, Li, Mg or Zn is 4.8 × 10²~7.3.0×10⁵It is twice as expensive and very good. Regarding room temperature hole mobility, when B is doped, which is a conventional technique (200 cm).²Compared to / (Vs)), Al, Be, Ca, Cd, Ga, In, Li, Mg or Zn are 4.7 to 5.7 times, which is very excellent.

(Embodiment 14) Dopants are Al, Be, Ca, Cd, Ga, In, Li, Mg or Zn, and the acceleration voltage is 150 kV and the implantation amount is 10 by the ion implantation method.¹⁵cm^‐2A dopant was injected into a diamond single crystal under the above conditions to prepare an impurity-doped diamond. Next, the obtained diamond was annealed. When the hole measurement of the obtained impurity-doped diamond semiconductor film of the present invention is performed to determine the hole coefficient, it can be confirmed that they are p-type semiconductors.

Furthermore, in Table 12, the dopant atom concentration in the diamond semiconductor film was measured by SIMS measurement, and the dopant atom concentration was 1.0 × 10.¹⁹cm^‐3The hole concentration and hole mobility of the p-type diamond semiconductor film at 300 K are shown.

<tables num="12"><img file="JP4908409B2_D0021.tif" /></tables>

Regarding the room temperature hole concentration, when doping B, which is a conventional technique, is performed (3.0 × 10).¹²cm^‐3), Al, Be, Ca, Cd, Ga, In, Li, Mg or Zn is 1.0 × 10³~6.7×10⁵It is twice as good and very good. On the other hand, regarding the room temperature hole mobility, when B is doped, which is a conventional technique (50 cm).²Compared to / (Vs)), Al, Be, Ca, Cd, Ga, In, Li, Mg or Zn are 18 to 21 times more, which is very excellent.

(Embodiment 15) FIG. 33 shows a cross-sectional configuration diagram of the MESFET (metal-semiconductor field effect transistor) according to the fifteenth embodiment of the present invention. Methane gas (CH) with a flow rate ratio of 1% on a diamond substrate 4-11 by microwave plasma chemical vapor deposition.₄), Dopant gas, balance H₂A p-type diamond semiconductor film 4-12 having a thickness of 1.0 μm is grown from a mixed gas having a total flow rate of 300 ccm, which is composed of the reaction gas. In this embodiment, the pressure in the reaction tube is 50 Torr, the frequency of the microwave source is 2.45 GHz, and the output is 1.3 kW. At this time, Al, Ca, Cd, Ga, In, Li, Mg or Zn is used as the dopant.

When Be is used as the dopant, the acceleration voltage is 150 kV and the implantation amount is 10 by the ion implantation method.¹⁵cm^‐2A p-type diamond semiconductor film 4-12 is produced by injecting a Be dopant into a diamond single crystal under the above conditions.

In order to provide electrical insulation between the transistors, the p-type diamond semiconductor film 4-12 is etched in the region outside the transistors until the diamond substrate 4-11 is exposed. That is, etching is performed so that the area of the surface of the p-type diamond semiconductor film 4-12 perpendicular to the stacking direction is smaller than that of the diamond substrate 4-11, and a portion located near the center of the diamond substrate 4-11 remains. ..

Gold (Au) is deposited as a source electrode 4-13, Al is deposited as a gate electrode 4-14, and Au is deposited as a drain electrode 4-15 on a p-type diamond semiconductor film 4-12 to fabricate a FET.

Table 13 shows that the dopant atom concentration of the p-type diamond semiconductor film 4-12 is 1.0 × 10.¹⁸cm^‐3The transconductance (gm) (amplification rate) of the conventional MESFET and the MESFET according to the fifteenth embodiment of the present invention at 300K is shown.

<tables num="13"><img file="JP4908409B2_D0022.tif" /></tables>

Whereas conventional MESFETs with B-doped diamond semiconductor films have gm = 0.0001mS / mm, p-type diamond semiconductors doped with Al, Be, Ca, Cd, Ga, In, Li, Mg or Zn. MESFET with a membrane has a gm of 8.0 x 10⁵~1.5×10⁶It doubles and is very good.

The gm value of the MESFET according to the 15th embodiment shown in Table 13 is the result obtained by providing the p-type diamond semiconductor film 4-12 manufactured by the microwave plasma chemical vapor deposition method. Even when the method for producing the p-type diamond semiconductor film 4-12 is the ion implantation method or the high-temperature high-pressure synthesis method, the transconductance (gm) is reduced to about half that of the fifth embodiment, but it is still compared with the conventional MESFET. Is very good.

(Embodiment 16) FIG. 34 shows a cross-sectional configuration diagram of a MISFET (metal-insulating film-semiconductor field effect transistor) according to the 16th embodiment of the present invention. Methane gas (CH) with a flow rate ratio of 1% on a diamond substrate 4-21 by microwave plasma chemical vapor deposition method₄), Dopant gas, balance H₂A diamond semiconductor film 4-22 having a thickness of 1.0 μm is grown from a mixed gas having a total flow rate of 300 ccm, which is composed of the reaction gas. In this embodiment, the pressure in the reaction tube is 50 Torr, the frequency of the microwave source is 2.45 GHz, and the output is 1.3 kW. At this time, Al, Ca, Cd, Ga, In, Li, Mg or Zn is used as the dopant in the p-type diamond semiconductor film 4-22.

When Be is used as the dopant, the acceleration voltage is 150 kV and the implantation amount is 10 by the ion implantation method.¹⁵cm^‐2A p-type diamond semiconductor film 4-22 is produced by injecting a Be dopant into a diamond single crystal under the above conditions.

For electrical insulation between the transistors, the outer periphery of the diamond semiconductor film 4-22 is etched until the diamond substrate 4-21 is exposed. That is, etching is performed so that the area of the surface of the diamond semiconductor film 4-22 perpendicular to the stacking direction is smaller than that of the diamond substrate 4-21, and a portion located near the center of the diamond substrate 4-21 remains.

Au is vapor-deposited on the diamond semiconductor film 4-22 as the source electrode 4-23 and Au as the drain electrode 4-24, and SiO is deposited as the insulating film 4-25 in the gate region.₂, Al is vapor-deposited as a gate electrode 4-26 to manufacture a FET.

Table 14 shows that the dopant atom concentration of the diamond semiconductor film 4-22 is 1.0 × 10.¹⁸cm^‐3The transconductance (gm) (amplification rate) of the conventional MESFET and the MISFET according to the 16th embodiment of the present invention at 300K is shown.

<tables num="14"><img file="JP4908409B2_D0023.tif" /></tables>

Conventional MISFETs with B-doped p-type diamond semiconductor films have gm = 1.0 × 10^-5MISFETs with diamond semiconductor films doped with Al, Be, Ca, Cd, Ga, In, Li, Mg or Zn, while mS / mm, have a gm of 7.5 × 10.⁶~1.3×10⁷It doubles and is very good.

The gm value of the MISFET according to the 12th embodiment shown in Table 14 is the result obtained by providing the diamond semiconductor film 4-22 manufactured by the microwave plasma chemical vapor deposition method. Even when the ion implantation method or the high-temperature and high-pressure synthesis method is used as the method for producing the diamond semiconductor film 4-22, the transconductance (gm) is reduced to about half that of Embodiment 12, but the device characteristics are still the same as those of the conventional MISFET. Very good in comparison.

(Embodiment 17) FIG. 35 shows a cross-sectional configuration diagram of the npn type bipolar transistor according to the 17th embodiment of the present invention. Methane gas (CH) with a flow rate ratio of 1% on a diamond substrate 4-31 by microwave plasma chemical vapor deposition.₄), Dopant gas, balance H₂A 5.0 μm-thick n-type diamond semiconductor film 4-32, a 0.5 μm-thick p-type diamond semiconductor film 4-33, and an n-type diamond semiconductor film made from a mixed gas having a total flow rate of 300 ccm. Grow 4-34 in order. In this embodiment, the pressure in the reaction tube is 50 Torr, and the microwave source has a frequency of 2.45 GHz and an output of 1.3 kW. At this time, Al, Ca, Cd, Ga, In, Li, Mg or Zn is used as the dopant in the p-type semiconductor film 4-33.

When Be is used as the dopant, the acceleration voltage is 150 kV and the implantation amount is 10 by the ion implantation method.¹⁵cm^‐2A p-type diamond semiconductor film 4-33 is produced by injecting a Be dopant into a diamond single crystal under the above conditions.

For electrical insulation between the transistors, the outer periphery of the n-type diamond semiconductor film 4-32 is etched until the diamond substrate 4-31 is exposed. Further, in order to form the electrodes, the p-type diamond semiconductor film 4-33 and the n-type diamond semiconductor film 4-34 are etched as shown in FIG. Ti collector electrode 4-35 on n-type diamond semiconductor film 4-32, Ni base electrode 4-36 on p-type diamond semiconductor film 4-33, Ti on n-type diamond semiconductor film 4-34 The emitter electrode 4-37 is vapor-deposited.

Table 15 shows that the dopant atom concentration of the p-type diamond semiconductor film 4-33 is 1.0 × 10.¹⁸cm^‐3The current amplification factor β at 300 K of the conventional npn-type bipolar transistor and the npn-type bipolar transistor according to the 17th embodiment of the present invention is shown.

<tables num="15"><img file="JP4908409B2_D0024.tif" /></tables>

A conventional npn-type bipolar transistor having a B-doped p-type diamond semiconductor film has β = 1.0 × 10^-2On the other hand, the npn-type bipolar transistor having a p-type diamond semiconductor film doped with Al, Be, Ca, Cd, Ga, In, Li, Mg or Zn has a current amplification factor β of 5.0 × 10.⁴~2.0×10⁵It doubles and is very good.

The current amplification factor β of the npn-type bipolar transistor according to the 17th embodiment shown in Table 15 is obtained by providing the p-type diamond semiconductor film 4-33 produced by the microwave plasma chemical vapor deposition method. This is the result. Even when the ion implantation method or the high-temperature high-pressure synthesis method is used as the method for producing the p-type diamond semiconductor film 4-33, the current amplification factor β is reduced to about half that of the 17th embodiment, but it is still the conventional npn type. Very good compared to bipolar transistors.

(Embodiment 18) FIG. 36 shows a cross-sectional configuration diagram of the pnp type bipolar transistor according to the 18th embodiment of the present invention. Methane gas (CH) with a flow rate ratio of 1% on a diamond substrate 4-41 by microwave plasma chemical vapor deposition.₄), Dopant gas, balance H₂A 5.0 μm-thick p-type diamond semiconductor film 4-42, a 0.5 μm-thick n-type diamond semiconductor film 4-43, and a p-type diamond semiconductor film made from a mixed gas having a total flow rate of 300 ccm. Grow 4-44 in sequence. In this embodiment, the pressure in the reaction tube is 50 Torr, the frequency of the microwave source is 2.45 GHz, and the output is 1.3 kW. At this time, Al, Ca, Cd, Ga, In, Li, Mg or Zn are used as the dopant in the p-type diamond semiconductor films 4-42 and 4-44.

When Be is used as the dopant, the acceleration voltage is 150 kV and the implantation amount is 10 by the ion implantation method.¹⁵cm^‐2Be dopants are injected into a diamond single crystal under the above conditions to prepare p-type diamond semiconductor films 4-42 and 4-44.

For electrical insulation between the transistors, the outer periphery of the p-type diamond semiconductor film 4-42 is etched until the diamond substrate 4-41 is exposed. Further, in order to form the electrodes, the n-type diamond semiconductor film 4-43 and the p-type diamond semiconductor film 4-44 are etched as shown in FIG. Ni collector electrode 4-45 on p-type diamond semiconductor film 4-42, Ti base electrode 4-46 on n-type diamond semiconductor film 4-43, Ni on p-type diamond semiconductor film 4-44 The emitter electrode 4-47 is vapor-deposited.

Table 16 shows that the dopant atom concentrations of the p-type diamond semiconductor films 4-42 and 4-44 are 1.0 × 10.¹⁸cm^‐3The current amplification factor β at 300 K of the conventional pnp type bipolar transistor and the pnp type bipolar transistor according to the eighteenth embodiment of the present invention is shown.

<tables num="16"><img file="JP4908409B2_D0025.tif" /></tables>

A conventional pnp-type bipolar transistor having a B-doped p-type diamond semiconductor film has a current amplification factor β = 1.0 × 10.³On the other hand, the pnp-type bipolar transistor having a p-type diamond semiconductor film doped with Al, Be, Ca, Cd, Ga, In, Li, Mg or Zn has a current amplification factor β of 4.0 × 10.⁵~1.8×10⁶It doubles and is very good.

The current amplification factor β of the pnp-type bipolar transistor according to the 18th embodiment shown in Table 16 includes p-type diamond semiconductor films 4-42 and 4-44 manufactured by the microwave plasma chemical vapor deposition method. This is the result obtained by doing so. However, even when the ion implantation method or the high-temperature high-pressure synthesis method is used as the method for producing the p-type diamond semiconductor films 4-42 and 4-44, the current amplification factor β is reduced to about half of that of the 18th embodiment. It still has very good characteristics compared to conventional pnp type bipolar transistors.

(Embodiment 19) FIG. 37 shows a cross-sectional configuration diagram of the light emitting diode (LED) according to the nineteenth embodiment of the present invention. Methane gas (CH) with a flow rate ratio of 1% on a diamond substrate 4-51 by microwave plasma chemical vapor deposition.₄), Dopant gas, balance H₂A 5.0 μm-thick p-type diamond semiconductor film 4-52 and a 0.5 μm-thick n-type diamond semiconductor film 4-53 are grown in order using a mixed gas having a total flow rate of 300 ccm. In this embodiment, the pressure in the reaction tube is 50 Torr, the frequency of the microwave source is 2.45 GHz, and the output is 1.3 kW. At this time, Al, Ca, Cd, Ga, In, Li, Mg or Zn is used as the dopant in the p-type semiconductor film 4-52.

When Be is used as the dopant, the acceleration voltage is 150 kV and the implantation amount is 10 by the ion implantation method.¹⁵cm^‐2A p-type diamond semiconductor film 4-52 is produced by injecting a Be dopant into a diamond single crystal under the above conditions.

Etching is performed on the p-type diamond semiconductor film 4-52 and the n-type diamond semiconductor film 4-53 as shown in FIG. 37 for electrical insulation between LEDs and electrode formation. Then, the Ni anode electrode 4-54 is deposited on the p-type diamond semiconductor film 4-52, and the Ti cathode electrode 4-55 is deposited on the n-type diamond semiconductor film 4-53.

Table 17 shows the applied voltage of 7 V and the current density of 10 A / mm of the conventional light emitting diode (LED) and the LED according to the 19th embodiment of the present invention.²Indicates the emission brightness (output power density) at a wavelength of 235 nm.

<tables num="17"><img file="JP4908409B2_D0026.tif" /></tables>

In the case of B, which is the conventional technology, 1.0 x 10^-4mW / mm²However, when Al, Be, Ca, Cd, Ga, In, Li, Mg or Zn were used, the output power density was 2.8 × 10.⁷~7.1×10⁷It doubled and turned out to be very good.

In FIG. 37, the p-type diamond semiconductor film 4-52 and the n-type diamond semiconductor film 4-53 are laminated in this order, but the characteristics did not change even if the order was reversed. That is, the same result as in Table 17 can be obtained even when the n-type diamond semiconductor film and the p-type diamond semiconductor film are laminated in this order on the diamond substrate 4-51.

The emission brightness (output power density) of the LED according to the 19th embodiment shown in Table 17 at a wavelength of 235 nm is obtained by providing the p-type diamond semiconductor film 4-52 produced by the microwave plasma chemical vapor deposition method. This is the result obtained. However, even when the ion implantation method and the high-temperature and high-pressure synthesis method are used to fabricate the p-type diamond semiconductor film 4-52, the emission brightness (output power density) at a wavelength of 235 nm is reduced by about half, but it is still It has very good characteristics compared to conventional LEDs.

It is important that the present invention is a p-type diamond semiconductor using any of Al, Be, Ca, Cd, Ga, In, Li, Mg or Zn as a dopant, and the p-type diamond semiconductor used in each embodiment is important. It is not limited to the method for producing the film.

Next, a method for manufacturing a diamond semiconductor according to the present invention in order to achieve the fifth object will be described in detail.

The present invention makes it possible to remove the damage formed by ion implantation while protecting the surface ion-implanted diamond thin film with a protective layer and then performing high-temperature and high-pressure annealing to prevent surface etching due to high-temperature and high-pressure annealing. , Enables the production of high quality diamond semiconductors. (Embodiment 20) FIG. 40A-40G shows a manufacturing process of the diamond semiconductor according to the 20th embodiment of the present invention. A diamond substrate 5-11 is prepared (Fig. 40A), and a 1 μm diamond thin film 5-12 is laminated on the diamond substrate 5-11 at a substrate temperature of 700 ° C using methane as a reaction gas using a microwave plasma CVD device (Fig. 40A). Figure 40B). In this embodiment, the microwave plasma CVD method is used, but any method can be used as long as the diamond thin film 5-12 can be formed. Further, a diamond single crystal produced by high-temperature and high-pressure synthesis may be used.

Using an ion implanter for the diamond thin film 5-12, the acceleration voltage is 60 kV and the dose amount is 1 x 10.¹⁴cm^-2Drive the dopant with (Fig. 40C, 40D). Dopants to be driven here include B, Al, Ga, In, Zn, Cd, Be, Mg, Ca, P, As, Sb, O, S, Se, Li, Na, and K.

Then, a protective layer (platinum) 5-14 is formed on the ion-implanted diamond thin film 5-13 (Fig. 40E). In this embodiment, platinum is used for the protective layer 5-14, but the protective layer 5-14 is made of various metals, alloys, oxides, nitrides and multilayer films thereof having a thin film of 0.01 to 10 μm. be able to. In particular, metals containing at least one of titanium, tungsten, platinum, palladium, molybdenum, or Al._1-xSi_xO_1-yN_yIt is desirable that (0 x 1, 0 y 1), or two or more of these layers be multi-layered. The protective layer 5-14 can be produced by a vapor deposition method, a sputtering method, a CVD method, or a laser ablation method.

An ion-implanted diamond thin film 5-13 having a protective layer 5-14 formed on its surface is placed in an ultra-high temperature and high-pressure firing furnace and annealed at a pressure and temperature of 3.5 GPa or higher and 600 ° C or higher (Fig. 40F). .. That is, the pressure P (kbar) and the temperature T (K) are annealed under the condition that the pressure is 35 kbar or more and the temperature is 873 K or more satisfying the relationship of the equation P&gt; 7.1 + 0.027T (see Non-Patent Document 7). To do.

When the protective layer 5-14 is removed with an acid, a semiconductor diamond thin film 5-15 is obtained (Fig. 40G).

As an example, an electrode is formed on a semiconductor diamond thin film 5-15 prepared by annealing under the conditions of 1400 ° C and 7 GPa for 1 hour to perform hole measurement, and polarity, carrier concentration at room temperature, and mobility at room temperature are performed. I asked for the degree. Table 18 shows the polarity, carrier concentration at room temperature, and mobility of the semiconductor diamond thin films 5-15 for each dopant in this case.

<tables num="18"><img file="JP4908409B2_D0027.tif" /></tables>

As shown in Table 18, the semiconductor diamond thin film 5-15 has a protective layer 5-14 formed on the ion-implanted diamond thin film 5-13 and then annealed at high temperature and high pressure to obtain high quality that cannot be obtained by the conventional manufacturing method. It has the characteristics of P-type and N-type semiconductors.

Further, FIG. 42 shows the cathodoluminescence (CL) spectrum (measurement temperature: 10K) before and after high-temperature and high-pressure annealing of a diamond thin film ion-implanted using boron (B) as a dopant as an example. Ion-implanted diamond thin film 5-13 before high-temperature and high-pressure annealing did not show free exciton (FE) -related emission peculiar to diamond, but semiconductor diamond thin film after high-temperature and high-pressure annealing under the conditions of 1400 ° C and 7 GPa 5 At -15, FE-related luminescence appeared. This FE emission is emitted from excitons, and the emission intensity increases as the crystal quality increases. Therefore, the crystal quality can be evaluated based on the emission intensity. In addition, bound exciton emission (BE) derived from boron is also observed, indicating that boron functions as a dopant in the diamond thin film.

These facts indicate that the crystal quality of the produced semiconductor diamond thin film 5-15 is better than that of the ion-implanted diamond thin film 5-13 before high-temperature and high-pressure annealing, and boron is present in the semiconductor diamond thin film 5-15. It shows that it is doing. That is, crystal defects and amorphous layers are introduced into the ion-implanted diamond thin film 5-13 by ion implantation of boron, and deterioration of diamond crystals occurs. However, these crystal defects and amorphous layers are removed by high-temperature and high-pressure annealing, and boron is removed. Is activated as a dopant.

As described above, the result of CL also indicates that the semiconductor diamond thin film 5-15 obtained by the method for producing a diamond semiconductor according to the present embodiment is a high-quality P-type or N-type diamond semiconductor that cannot be obtained by the conventional method. Suggests. (Embodiment 21) FIGS. 41A-41F show the manufacturing process of the diamond semiconductor according to the 21st embodiment of the present invention. A diamond substrate 5-21 is prepared (Fig. 41A), and a 1 μm diamond thin film is laminated on the diamond substrate 5-21 at a substrate temperature of 700 ° C using methane as a reaction gas using a microwave plasma CVD device (Fig. 41B). ..

After that, an ion implanter was used for the produced diamond thin film 5-22, and the acceleration voltage was 60 kV and the dose amount was 1 × 10.¹⁴cm^-2Drive in the dopant with (Fig. 41C-41D). As in the case of the 20th embodiment, the dopants to be driven here include B, Al, Ga, In, Zn, Cd, Be, Mg, Ca, P, As, Sb, O, S, Se, Li, Na and K. is there.

The two substrates on which the ion-implanted diamond thin film is formed are placed on top of each other so that the surface of the ion-implanted diamond thin film is on the inside and placed in an ultra-high temperature and high-pressure firing furnace. That is, the diamond thin film 5-23A formed on the diamond substrate 5-21A and the diamond thin film 5-23B formed on the diamond substrate 5-21B are in contact with each other, and the diamond thin films 5-21A and 5-21B are in contact with each other. Overlay 5-23A and 5-23B so that they are sandwiched between them. Then, the laminated substrates are annealed in an ultra-high temperature and high pressure firing furnace at a pressure and temperature of 3.5 GPa or higher and 600 ° C or higher (Fig. 41E). That is, the pressure P (kbar) and the temperature T (K) are annealed under the condition that the pressure is 35 kbar or more and the temperature is 873 K or more satisfying the relationship of the equation P&gt; 7.1 + 0.027T (see Non-Patent Document 7). To do.

After the high-temperature and high-pressure annealing is completed, the superposed diamond substrates 5-21A and 5-21B are separated to obtain a high-quality semiconductor diamond thin film 5-24 (Fig. 41F). Since the diamond thin films 5-23A and 5-23B hardly adhere to each other, the diamond substrates 5-21A and 5-21B can be easily separated naturally or by applying a light impact.

As an example, a diamond (100) substrate is used as the diamond substrate 5-21, and electrodes are formed on a semiconductor diamond thin film 5-24 prepared by high-temperature and high-pressure annealing for 1 hour under the conditions of 1400 ° C and 7 GPa. Hall measurement was performed to determine the polarity, carrier concentration, and room temperature mobility. Table 19 shows the polarity, carrier concentration at room temperature, and mobility of the semiconductor diamond thin film 5-24 for each dopant in this case.

<tables num="19"><img file="JP4908409B2_D0028.tif" /></tables>

As shown in Table 19, it can be seen that the semiconductor diamond thin films 5-24 produced in this embodiment have high room temperature mobility. These results show that the surface of the ion-implanted diamond thin film 5-23 is protected and then high-temperature and high-pressure annealed to prevent surface etching, resulting in high-quality P-type and N-type diamond semiconductors that cannot be obtained by conventional methods. It shows that it can be obtained.