Semiconductor device and method for manufacturing the same

The present invention relates to a semiconductor device having a semiconductor element using an oxide semiconductor and a method for manufacturing the same. To.

A thin film transition using a semiconductor thin film formed at a relatively low temperature on a substrate having an insulating surface. Attention is being paid to the technologies that make up TFTs. Thin film transistors are represented by LCD TVs It is used in display devices that can be used. As a semiconductor thin film applicable to thin film transistors Silicon-based semiconductor materials are known, but oxide semiconductors are attracting attention as other materials. To.

As a material for an oxide semiconductor, a material containing zinc oxide or zinc oxide as a component is known. .. And the electron carrier density is 10¹⁸cm^-3Amorphous oxides that are less than (oxide semiconductors) ) Is disclosed (Patent Documents 1 to 3).

<p><patcit num="1"><text>Japanese Unexamined Patent Publication No. 2006-165527</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 2006-165528</text></patcit><patcit num="3"><text>Japanese Unexamined Patent Publication No. 2006-165529</text></patcit></p>

<p>By the way, transistors used in semiconductor devices for high power applications have high withstand voltage, high conversion efficiency, and high speed. Characteristics such as switching are required. Sirico is a semiconductor material for these semiconductor devices. However, from the above viewpoint, a new semiconductor material whose characteristics can be further improved. Is required.</p><p>Examples of semiconductor materials that may improve the above-mentioned properties include silicon carbide. You can get rid of it. Silicon carbide has a short Si-C bond interatomic distance of about 0.18 nm. It has a high binding energy and a large bandgap of about 3 times that of silicon. Therefore, it is known to be advantageous for improving the withstand voltage of semiconductor devices and reducing power loss.</p><p>However, since silicon carbide is difficult to melt due to its nature, silicon carbide is used. Use a highly productive method such as the Czochralski method (CZ method) used when manufacturing c There is a problem that it cannot be manufactured. Also, for silicon carbide, micro pie There is a problem of defects called pu. Due to these problems, semiconductor packaging using silicon carbide The practical application of the device has been delayed.</p><p>In view of the above, in one aspect of the disclosed invention, high power using a new semiconductor material with high productivity One of the purposes is to provide a semiconductor device for Alternatively, a new semiconductor material was used. One of the purposes is to provide a semiconductor device having a new structure.</p>

<p>In one aspect of the present invention, a first oxide semiconductor film is formed on a first electrode formed on a substrate. , 450 ° C or higher and 850 ° C or lower, preferably 550 ° C or higher and 750 ° C or lower. A first crystalline oxide half that grows crystallized from the surface to the inside and is in contact with the first electrode. An oxide having a second crystallinity on an oxide semiconductor film that forms a conductor film and has a first crystallinity. It is characterized by laminating semiconductor films. The oxide semiconductor film having the first crystallinity and The oxide semiconductor film having the second crystallinity has a flat plate-like polycrystalline region having the same crystal orientation on its surface. Has a region. The flat polycrystalline region includes the oxide semiconductor film having the first crystallinity and the second bond. The c-axis orientation is perpendicular to the surface of the crystalline oxide semiconductor film. In addition, a- The elements of adjacent planes on plane b are the same. Also, an oxide having the first crystallinity The c-axis direction of the semiconductor film and the oxide semiconductor film having the second crystallinity is the direction perpendicular to the surface. Matches.</p><p>The oxide semiconductor film having the second crystallinity is a second on the oxide semiconductor film having the first crystallinity. After forming the oxide semiconductor film of, 450 ° C or more and 850 ° C or less, preferably 550 ° C or more 7 After heat treatment at 50 ° C or less, the surface above the surface of the oxide semiconductor film having the first crystallinity It can be formed by crystal growth toward the surface of the second oxide semiconductor film. sand That is, the oxide semiconductor film having the first crystallinity is a seed crystal for the second oxide semiconductor film. Corresponds to.</p><p>Further, the oxide semiconductor film having the second crystallinity is on the oxide semiconductor film having the first crystallinity. In addition, it is deposited while heating at 200 ° C or higher and 550 ° C or lower. Typically, the sputtering method is used. Epitaxy from the surface of the oxide semiconductor film having the first crystallinity by depositing using To form an oxide semiconductor film having a second crystallinity by growing or axially growing. Can be done. That is, the oxide semiconductor film having the first crystallinity becomes the second oxide semiconductor film. It corresponds to a seed crystal.</p><p>The oxide semiconductor film having the second crystallinity is a seed crystal of the oxide semiconductor film having the first crystallinity. Since the crystal grows as a crystal, it is substantially the same crystal as the oxide semiconductor film having the first crystallinity. Has an orientation.</p><p>After that, the first oxide semiconductor film and the second oxide semiconductor film are etched to form islands, and the first A second electrode is formed on the oxide semiconductor film of 2, and functions as a gate insulating film and a gate electrode. By forming a third electrode, a vertical transistor and a vertical die can be used as a semiconductor element. Aude and the like can be produced. The first electrode is the source electrode and the drain electrode. It functions as one, and the second electrode functions as the other of the source electrode and the drain electrode.</p><p>Heat treatment for forming the oxide semiconductor film having the first crystallinity (first heat treatment), and And the heat treatment (second heat treatment) for forming the oxide semiconductor film having the second crystallinity , Hydrogen and moisture-free atmosphere (nitrogen atmosphere, oxygen atmosphere, dry air atmosphere) It is preferable to do it. By this first heat treatment and the second heat treatment, the first oxidation H, OH, H from the semiconductor film₂Dehydration or dehydrogenation is performed to desorb O etc. High-purity oxide semiconductor film with crystallinity 1 and oxide semiconductor film with second crystallinity Can be transformed into. In addition, the heat treatment raises the temperature in an inert atmosphere and switches the acid in the middle. It is also possible to perform heat treatment to create an atmosphere containing elements, and a place where heat treatment is performed in an oxygen atmosphere. In that case, since the oxide semiconductor film is oxidized, oxygen defects can be repaired. The heat treatment The first crystalline oxide semiconductor film obtained from the above is TDS (Thermal Desor). Even if the measurement is performed up to 450 ° C with ption Spectroscopy), two pees of water Of these, one peak that appears at least around 300 ° C is not detected.</p><p>The oxide semiconductor film having the first crystallinity and the oxide semiconductor film having the second crystallinity When In is contained, in the flat polycrystalline region, the electron clouds of In overlap each other and are continuous. By touching, mobility increases. Therefore, an oxide semiconductor film having a polycrystalline region is used. The transistor provided in the channel can realize high field effect mobility.</p><p>The oxide semiconductor film having the first crystallinity and the oxide semiconductor film having the second crystallinity If a polycrystalline region that is c-axis oriented perpendicular to the surface can be obtained, the material of The material is not particularly limited, and different materials may be used, or materials having the same composition may be used. In addition, it should be noted. When different materials are used, heteroepitaxial growth is carried out. It is a structure.</p><p>The oxide semiconductor film having the first crystallinity and the oxide semiconductor film having the second crystallinity are used. When formed from an oxide semiconductor material having the same principal component, the oxide semiconductor film having the first crystallinity and The boundary of the oxide semiconductor film having the second crystallinity becomes unclear, resulting in a substantially single-layer structure. Sometimes. When materials of the same composition are used, homoepitaxial growth is performed. It has a homoepitaxial structure.</p><p>In the case of an amorphous oxide semiconductor film immediately after film formation, the oxide semiconductor film having the first crystallinity The polycrystalline region with the same crystal orientation formed on the surface of the crystal grows from the surface in the depth direction. Therefore, it is formed without being affected by the underlying member of the oxide semiconductor film having the first crystallinity. Can be done.</p><p>A vertical transistor and a vertical diode according to an embodiment of the present invention are acids having a first crystallinity. An oxide semiconductor laminate in which a compound semiconductor film and an oxide semiconductor film having a second crystallinity are laminated. Have. In the process of crystal growth, the electron donor (d) contained in the oxide semiconductor laminate Since the impurities that become ner) are removed, the oxide semiconductor laminate is highly purified and carriers are used. A low density, true or substantially true semiconductor. Also, vans rather than silicon semiconductors The gap is large.</p><p>The hydrogen concentration contained in the highly purified oxide semiconductor laminate is 1 × 10.¹⁸cm^-3Below, 1 × 10¹⁶cm^-3Below, it is set to 0 in substance, and the carrier density is 1 × 10.¹²cm^-31.45 × 10 less than, more preferably less than the lower limit of measurement¹⁰cm^-3Is less than The end gap is 2 eV or more, preferably 2.5 eV or more, more preferably 3 eV or more. To.</p><p>The oxide semiconductor laminate thus purified in this way is used for the channel formation region of the transistor. Therefore, not only the surface of the oxide semiconductor laminate in contact with the gate insulating film but also the oxide semiconductor It is possible to form channels inside the laminate (the entire oxide semiconductor laminate). Therefore, a large current can be passed when it is on. In the off state, the depletion layer is acid. Since it extends to a deeper area inside the compound semiconductor laminate, the off current flowing in the off state is low. Can be reduced. Furthermore, the withstand voltage is increased and hot carrier deterioration is less likely to occur. Therefore, it is possible to manufacture a semiconductor device for high power to which a high voltage is applied.</p><p>Further, by using the oxide semiconductor laminate having such high purity for the diode, it can be adjusted. It becomes a diode with high flowability.</p><p>The transistor of one embodiment of the present invention is an insulated gate field effect transistor (Insul). ated-Gate Field-Effect Transistor (IGFET) ), Includes power MOSFETs.</p>

<p>According to one embodiment of the present invention, an acid having a reduced hydrogen concentration, high purity, and a polycrystalline region. By using a compound semiconductor film, the operation of transistors and diodes should be improved. Can be done. Especially in transistors, the withstand voltage is increased and the short channel effect is reduced. It can be reduced and the on / off ratio can be increased. Therefore, by using the transistor, A semiconductor device for high power can be manufactured.</p>

<figref num="1">It is the top view and sectional drawing explaining the transistor.</figref><figref num="2">It is a vertical cross-sectional view of a vertical transistor using an oxide semiconductor.</figref><figref num="3">It is an energy band diagram (schematic diagram) in the A-A'cross section shown in FIG.</figref><figref num="4">It is a figure which shows the relationship between the vacuum level, the work function (φM) of a metal, and the electron affinity (χ) of an oxide semiconductor.</figref><figref num="5">It is an energy band diagram (schematic diagram) in the cross section of B-B'in FIG.</figref><figref num="6">It is a figure which shows the state which (A) the positive potential (+ VG) is applied to the gate (GE1), and shows the state which the negative potential (-VG) is applied to (B) the gate (GE1).</figref><figref num="7">It is the top view and sectional drawing explaining the transistor.</figref><figref num="8">It is sectional drawing explaining the diode.</figref><figref num="9">It is sectional drawing explaining the manufacturing method of a transistor.</figref><figref num="10">It is sectional drawing explaining the manufacturing method of a transistor.</figref><figref num="11">It is sectional drawing explaining the manufacturing method of a transistor.</figref><figref num="12">It is sectional drawing explaining the manufacturing method of a transistor.</figref><figref num="13">It is sectional drawing explaining the manufacturing method of a transistor.</figref><figref num="14">It is sectional drawing explaining the manufacturing method of a transistor.</figref><figref num="15">It is sectional drawing explaining the manufacturing method of a transistor.</figref><figref num="16">It is sectional drawing explaining the manufacturing method of a transistor.</figref><figref num="17">It is sectional drawing explaining the manufacturing method of a transistor.</figref><figref num="18">It is a figure explaining an example of a photovoltaic power generation system.</figref><figref num="19">It is a cross-sectional TEM photograph of an oxide semiconductor film and a schematic view of a cross section of an oxide semiconductor film.</figref><figref num="20">It is a cross-sectional TEM photograph of an oxide semiconductor film and a schematic view of a cross section of an oxide semiconductor film.</figref>

Embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is described below. Various forms and details without departing from the spirit and scope of the present invention. It is easily understood by those skilled in the art that it can be changed to. Therefore, the present invention is carried out as shown below. It is not construed as being limited to the description in the form of. The structure of the present invention described below. In the process, the same reference numerals are used for the same parts or parts having similar functions between different drawings. It will be used throughout, and the description of its repetition will be omitted.

In addition, in each figure described in this specification, the size of each structure, the thickness of a layer, or a region is clarified. May be exaggerated for clarity. Therefore, it is not necessarily limited to that scale. ..

In addition, terms such as 1, 2, and 3 used in this specification are used to avoid confusion of components. It is attached to, and is not limited in number. Therefore, for example, "first" is changed to "" It can be explained by replacing it with "second" or "third" as appropriate.

The voltage is the potential difference between two points, and the potential is the electrostatic field at one point. It refers to the electrostatic energy (electrical potential energy) of the unit charge inside. However However, in general, the potential difference between the potential at a certain point and the reference potential (for example, the ground potential) This is simply called electric potential or voltage, and electric potential and voltage are often used as synonyms. .. Therefore, in the present specification, the potential may be read as a voltage unless otherwise specified. Voltage may be read as electric potential.

(Embodiment 1) In this embodiment, FIG. 1 is used for the structure of a transistor, which is a form of a semiconductor element. I will explain.

FIG. 1 (A) is a top view of the transistor 145, and FIG. 1 (B) is the alternate long and short dash line A of FIG. 1 (A). -Corresponds to the cross-sectional view of B.

As shown in FIG. 1 (B), the first electrode 10 is placed on the insulating film 103 formed on the substrate 101. 5. The oxide semiconductor film 107 having a polycrystalline region and the second electrode 109 are laminated. Na The second electrode 109 is laminated in contact with the entire upper surface of the oxide semiconductor film 107. Also, the first The gate is closed so as to cover the electrode 105 of 1, the oxide semiconductor film 107, and the second electrode 109. A marginal membrane 111 is provided. On the gate insulating film 111, at least an oxide semiconductor film A third electrode 113 facing the side surface is provided. Gate insulating film 111 and third electrode An insulating film 117 that functions as an interlayer insulating film is provided on the 113. On the insulating film 117 An opening is formed in the wiring 131 that connects to the first electrode 105 in the opening. (See Fig. 1 (A)), Wiring 129 to connect to the second electrode 109, Connect to the third electrode 113 Wiring 125 is formed. In this specification, the upper surface of the film is referred to as the substrate 101. A pair of parallel surfaces that are provided on the opposite side of the substrate 101.

The first electrode 105 serves as one of the source electrode and the drain electrode of the transistor 145. It works. The second electrode 109 is the other of the source electrode and the drain electrode of the transistor 145. Functions as. The third electrode 113 functions as the gate electrode of the transistor 145. ..

In the present embodiment, the oxide semiconductor film 107 has crystallinity and is flat with the same crystal orientation on the surface. It has a plate-shaped polycrystalline region. That is, the polycrystalline region of the oxide semiconductor film 107 is relative to the surface. It has a c-axis orientation in the vertical direction. That is, the c-axis direction of the oxide semiconductor film 107 is relative to the surface. Matches vertically. The elements of adjacent planes on the ab plane are the same. The flat plate-shaped polycrystalline region has a plurality of single crystal regions having a c-axis in the direction perpendicular to the surface. Area.

In the polycrystalline region, the electron clouds of In are overlapped and connected to each other, so that the electrical conductivity σ is increased. Rise. Therefore, a transistor having an oxide semiconductor film having a polycrystalline region has a high electric power. The field effect mobility can be realized.

The oxide semiconductor film 107 is a metal oxide and is a quaternary metal oxide In-Sn-Ga-. Zn-O film, In-Ga-Zn-O film, which is a ternary metal oxide, In-Sn-Zn-O Membrane, In-Al-Zn-O Membrane, Sn-Ga-Zn-O Membrane, Al-Ga-Zn-O Membrane, Sn -Al-Zn-O film, In-Zn-O film, which is a binary metal oxide, Sn-Zn-O film, Al-Zn-O film, Zn-Mg-O film, Sn-Mg-O film, In-Mg-O film, In- Metal oxide films such as O film, Sn-O film, and Zn-O film can be used.

The oxide semiconductor film 107 is an InMO.₃(ZnO)_mUse the material represented by (m&gt; 0) be able to. Where M is one or more selected from Ga, Al, Mn and Co. Indicates a metal element. For example, as M, Ga, Ga and Al, Ga and Mn, or Ga and There is Co and so on.

Further, the oxide semiconductor film 107 uses an oxide semiconductor material represented by In-ABO. You may. Here, A is a Group 13 element such as gallium (Ga) or aluminum (Al). One selected from Group 14 elements such as silicon (Si) and germanium (Ge) Or it represents multiple kinds of elements. In addition, B is selected from Group 12 elements represented by zinc (Zn). Represents one or more selected elements. The contents of In, A, and B are arbitrary, and A Including the case where the content of is zero. On the other hand, the contents of In and B are not zero. That is, The above notation includes In-Ga-Zn-O, In-Zn-O and the like.

Oxide semiconductor film 107 is In₂Ga₂ZnO₇Crystal structure and InGaZnO₄Crystal structure In the case of construction, it contains any of In, Ga, Zn, and a-axis and b-axis (b). It can be regarded as a layered structure of layers parallel to -axis). InGaZnO₄Crystals and In₂Ga₂ZnO₇The electrical conduction of the crystals in the crystal is mainly controlled by In. Therefore, the layer containing In has good electrical characteristics in the direction parallel to the a-axis and b-axis. is there. InGaZnO₄Crystals and In₂Ga₂ZnO₇Crystals of In electron clouds with each other They overlap and connect to form a career path.

That is, the direction of the ab plane is likely to crystallize between the direction of the ab plane and the direction of the c axis. Also, a flat plate In the shape of the polycrystalline region, the ab plane of each single crystal region is parallel to the surface. Ma In addition, there is a free space above the surface of the oxide semiconductor film 107, and the crystal grows upward here. There is no. These things are the oxide semiconductor when the TDS is measured up to 450 ° C. When the film 107 is an In-Ga-Zn-O film, In and Ga are not detected, but zinc is evacuated. It is inferred from the fact that it has been confirmed that peaks are detected under thermal conditions, especially near 300 ° C. To. The TDS was measured in vacuum, and zinc detachment was detected from around 200 ° C. It has been confirmed that

Conventional oxide semiconductors are generally n-type, and transistors using oxide semiconductors are gates. Even if the voltage is 0V, a current flows between the source electrode and the drain electrode, which is a so-called normal-on. Easy to use. Even if the field effect mobility is high, if the transistor is normally on, it will be a circuit. Is difficult to control. In the oxide semiconductor, a part of hydrogen becomes a donor and n It is known to be one factor in typing. In addition, some of the oxygen defects also become donors. It is known to be one factor in typing.

Therefore, in order to make the oxide semiconductor film i-type, hydrogen, which is an n-type impurity, is removed from the oxide semiconductor film. Purification is performed so that impurities other than the main components of the oxide semiconductor film are not contained as much as possible, and By removing oxygen defects, it becomes true (type i) or substantially true. That's right Therefore, instead of adding impurities to form i-type, impurities such as hydrogen and water and oxygen defects are removed as much as possible. As a result, it is characterized by being a highly purified i-type (intrinsic) semiconductor or close to it. ing. By purifying the oxide semiconductor film, the threshold voltage value of the transistor can be increased. It can be a lath, and a so-called normally-off switching element can be realized.

The hydrogen concentration of the oxide semiconductor film 107 at this time is 1 × 10.¹⁸cm^-3Below, 1 x 10¹⁶cm^-3Hereinafter, further, substantially 0 is preferable. In addition, the oxide semiconductor film 107 can be used. Rear density is 1x10¹²cm^-31.45 × 10 less than, more preferably less than the lower limit of measurement¹⁰cm^-3Is less than. That is, the carrier density of the oxide semiconductor film is as close to zero as possible. .. The bandgap is 2eV or more, preferably 2.5eV or more, more preferably 3e. V or higher. The hydrogen concentration in the oxide semiconductor film is measured by secondary ion mass spectrometry (SI). What to do with MS: Secondary Ion Mass Spectroscopy) Can be done. The carrier density can be measured by Hall effect measurement. Also lower Measurement of carrier density is CV measurement (Capacitance-Voltage-Mea) It can be obtained by the measurement result of surement) and the formula 1.

<maths num="1"><img file="JP5116896B2_D0001.tif" /></maths>

The thickness of the oxide semiconductor film 107 is 1 μm or more, preferably 3 μm or more, more preferably 1 By setting the thickness to 0 μm or more, a semiconductor device for high power can be manufactured.

Further, in the present embodiment, the third electrode 113 that functions as a gate electrode is annular. Ge By making the third electrode 113, which functions as a transistor electrode, annular, the channel of the transistor The width can be increased. In the transistor of this embodiment, the channel length L is an acid. It is the thickness of the compound semiconductor film, and the channel width W is the oxide in contact with the first electrode or the second electrode. It is the length of the edge of the semiconductor film. Here, in the first electrode or the second electrode, Let W be the length of the end of the oxide semiconductor film where the larger area is in contact with the oxide semiconductor film. This implementation In the form of, the top surface shape of the oxide semiconductor film of the transistor is W.₁And W₂With a rectangle whose sides are Therefore, the channel width W is 2W.₁And 2W₂Is the sum of. Half the oxide of the transistor When the upper surface shape of the conductor film is circular, the channel width W is 2πr when the radius of the circle is r. To.

Further, the transistor of the present embodiment is turned on because the oxide semiconductor film has a polycrystalline region. In the state, the entire oxide semiconductor film functions as a channel and more carriers move. Therefore, the on-current is high. Further, the transistor of the present embodiment has an intrinsic carrier density. Because it is extremely low, the maximum depletion layer width becomes extremely wide, and in the off state, the depletion layer is oxide semiconducting. It spreads inside the body membrane and reduces off-current. That is, it is a transistor with a high on / off ratio. To.

The transistor has at least three terminals including a gate, a drain, and a source. It is an element that has a channel formation region between the drain region and the source region. Current can flow through the rain region, the channel formation region, and the source region. here , Source and drain change depending on the transistor structure and operating conditions, so It is difficult to limit whether this is a source or drain. So the sauce and de The area that functions as a rain may not be called a source or drain. In that case, As an example, they may be referred to as a first terminal and a second terminal, respectively. Or that Each may be referred to as a first electrode and a second electrode. Alternatively, the first area, the second It may be referred to as an area.

The substrate 101 must have at least enough heat resistance to withstand the subsequent heat treatment. It will be important. The substrate 101 includes barium borosilicate glass and aluminoborosilicate glass. A glass substrate such as the above can be used.

In addition, as a glass substrate, when the temperature of the subsequent heat treatment is high, the strain point is 730 ° C or higher. It is good to use the one. Further, on the glass substrate, for example, aluminosilicate glass, a. Glass materials such as luminoborosilicate glass and barium borosilicate glass are used. .. In addition, B₂O₃It is preferable to use a glass substrate containing a larger amount of BaO.

Instead of the above glass substrate, ceramic substrate, quartz substrate, sapphire substrate, etc. A substrate made of an edge body may be used. In addition, crystallized glass or the like can be used.

The insulating film 103 is an oxide insulating film such as a silicon oxide film or a silicon oxynitride film, or nitriding. Silicon film, silicon nitride film, aluminum nitride film, or aluminum nitride Which nitride insulating film is used to form the film. Further, the insulating film 103 may have a laminated structure, for example, the substrate 1 One or more of the above-mentioned nitride insulating films from the 01 side and either of the above-mentioned oxide insulating films It can be a laminated structure with one or more. The thickness of the insulating film 103 is 100 nm or more 2 It is preferably μm or less.

The first electrode 105 and the second electrode 109 are made of aluminum, chromium, copper, tantalum, and chita. Metal elements selected from molybdenum, tungsten, yttrium, or gold mentioned above It is formed of an alloy containing a genus element as a component, an alloy combining the above-mentioned metal elements, or the like. Also, One or more of manganese, magnesium, zirconium, beryllium, thorium A metal element selected from the above can be used. The first electrode 105 has a single-layer structure. Alternatively, it can have a laminated structure of two or more layers. For example, an aluminum film containing silicon Single-layer structure, two-layer structure in which a titanium film is laminated on an aluminum film, and chita on a tungsten film A two-layer structure in which a titanium film is laminated, a titanium film, and an aluminum film laminated on the titanium film. Further, a three-layer structure in which a titanium film is formed on the titanium film and the like can be mentioned. Also on aluminum , Titanium, tantalum, tungsten, molybdenum, chromium, neodymium, scandium A film, an alloy film, or a nitride film in which a single element or a combination of a plurality of selected elements may be used may be used. I.

Further, as the first electrode 105 and the second electrode 109, indium tin oxide and tongue oxide are used. Indium oxide containing stainless steel, indium zinc oxide containing tungsten oxide, titanium oxide Indium oxide containing tongue, indium tin oxide containing titanium oxide, indium zinc acid Applying a conductive material with translucency such as indium tin oxide to which a compound or silicon oxide is added You can also do it. Further, the above-mentioned conductive material having translucency and the above-mentioned laminated structure of metal elements You can also do it.

The gate insulating film 111 includes a silicon oxide film, a silicon nitride film, a silicon oxide nitride film, and an acid nitride. A siliconized silicon film or an aluminum oxide film can be formed as a single layer or laminated. .. It is preferable that the portion of the gate insulating film 111 in contact with the oxide semiconductor film 107 contains oxygen. It is particularly preferably formed of a silicon oxide film. By using a silicon oxide film, acid Oxygen can be supplied to the compound semiconductor film 107, and the characteristics can be improved.

Also, as the gate insulating film 111, hafnium silicate (HfSiO)_x), Nitrogen added Hafnium silicate (HfSi)_xO_yN_z), Hafnium al with nitrogen added Minate (HfAl_xO_yN_z), Hafnium oxide, yttrium oxide, etc. high- Gate leak can be reduced by using k material. Furthermore, high-k materials and oxidation Silicon film, silicon nitride film, silicon oxide film, silicon oxide film, or oxide It can have a laminated structure with any one or more of the luminium films. Gate insulating film 111 The thickness should be 50 nm or more and 500 nm or less. Increase the thickness of the gate insulating film 111 Therefore, the gate leak current can be reduced.

The third electrode 113, which functions as a gate electrode, is made of aluminum, chromium, copper, tantalum, etc. Form a metal element selected from titanium, molybdenum, tungsten, or the above-mentioned metal element It can be formed by using an alloy to be separated or an alloy film in which the above-mentioned metal elements are combined. Wear. Also, one or more of manganese, magnesium, zirconium, and beryllium. A metal element selected from the numbers may be used. Further, the third electrode 113 may have a single-layer structure. It may have a laminated structure of two or more layers. For example, a single-layer structure of an aluminum film containing silicon, A two-layer structure in which a titanium film is laminated on an aluminum film, and a titanium film is laminated on a titanium nitride film. Two-layer structure, two-layer structure in which a tungsten film is laminated on a titanium nitride film, on a tantalum nitride film A two-layer structure in which a gusten film is laminated, a titanium film, and an aluminum film laminated on the titanium film. In addition, there is a three-layer structure that forms a titanium film on it. Also, on aluminum Choose from tongue, tantalum, tungsten, molybdenum, chromium, neodymium, scandium A film of the above-mentioned elements, an alloy film in which a plurality of the elements are combined, or a nitride film may be used.

The third electrode 113, which functions as a gate electrode, includes indium tin oxide and tongue oxide. Indium oxide containing stainless steel, indium zinc oxide containing tungsten oxide, titanium oxide Indium oxide containing tongue, indium tin oxide containing titanium oxide, indium zinc acid Applying a conductive material with translucency such as indium tin oxide to which a compound or silicon oxide is added You can also do it. Further, the above-mentioned conductive material having translucency and the above-mentioned laminated structure of metal elements You can also do it.

Next, an energy band diagram is shown for the operation of the transistor having the oxide semiconductor film 107. It will be described using.

FIG. 2 shows a vertical cross-sectional view of a vertical transistor using an oxide semiconductor. Drain electrode (D ) Is provided with an oxide semiconductor film (OS), and a source electrode (S) is provided on the oxide semiconductor film (OS). ) Is provided, and a gate insulating film (GI) is provided on the drain electrode, the oxide semiconductor film, and the source electrode. ) Is provided, and a gate electrode (GE1) is provided on the gate electrode (GE1).

FIG. 3 shows an energy band diagram (schematic diagram) in the AA'cross section shown in FIG. Figure 3 ( A) shows the case where the voltage between the source and the drain is equipotential (VD = 0V), and Fig. 3 (B) ) Applyes a positive potential (VD&gt; 0) to the drain with respect to the source and a positive voltage (VG) to the gate electrode. Shows the case where&gt; 0) is added.

FIG. 5 shows an energy band diagram (schematic diagram) in the cross section of B-B'in FIG. The state when the voltage is 0V is shown. Figure 6 (A) shows the positive potential (+ VG) at the gate (GE1). ) Is applied, and carriers (electrons) flow between the source and drain. Is shown. In Fig. 6 (B), a negative potential (-VG) is applied to the gate (GE1). Indicates a case where the state is off and the state is off.

Figure 4 shows the vacuum level and the work function of the metal (φ)._M), The relationship between the electron affinity (χ) of oxide semiconductors Shown.

Since the metal is degenerate, the Fermi level is located in the conduction band. On the other hand, conventional oxide semiconducting The body is generally n-type, in which case the Fermi level (E)_F) Is located in the center of the bandgap It is located closer to the conduction band, away from the true Fermi level (Ei). Half of the oxide It is known that a part of hydrogen in a conductor becomes a donor and is one of the factors for n-type formation. ..

On the other hand, the oxide semiconductor according to the present invention removes hydrogen, which is an n-type impurity, from the oxide semiconductor. By removing it and purifying it so that impurities other than the main component of the oxide semiconductor are not contained as much as possible. It is considered to be genuine (type i), or it is considered to be genuine. That is, add impurities It was made highly pure by removing impurities such as hydrogen and water as much as possible instead of making it i-shaped. It is characterized by being i-type or close to it. By doing so, the Fermi level ( Ef) can be as high as the true Fermi level (Ei).

Oxide semiconductor bandgap (E_g) Is 3.15 eV, the electron affinity (χ) is It is said to be 4.3eV. Titanium (Ti) that constitutes the source electrode and drain electrode The function is almost equal to the electron affinity (χ) of the oxide semiconductor. In this case, metal-oxide semiconduct No Schottky barrier is formed against electrons at the body interface.

That is, the work function of metal (φ_M) And the electron affinity (χ) of the oxide semiconductor are equal, both When a person comes into contact, an energy band diagram (schematic diagram) as shown in FIG. 3 (A) is shown.

In Fig. 3 (B), black circles () indicate electrons, and when a positive potential is applied to the drain, the electrons Is injected into the oxide semiconductor beyond the barrier (h) and flows toward the drain. in this case , The height of the barrier (h) varies depending on the gate voltage and drain voltage, but it is a positive dray. Barrier height or band in Figure 3 (A) without voltage applied when voltage is applied Gap (E_gThe barrier height (h) is smaller than 1/2 of).

The thickness of the oxide semiconductor film is 1 μm or more, preferably 3 μm or more, more preferably 10 μm or more. It is above and has a low carrier density. Therefore, the positive potential (+ VG) at the gate (GE1) ) Is applied, as shown in FIG. 6 (A), a van on the surface of the oxide semiconductor film. There is little bending, the lower end of the conduction band approaches the Fermi level, and the entire oxide semiconductor film smells. It becomes energetically stable. Therefore, not only in the vicinity of the gate insulating film, but also in the oxide semiconductor. Electrons can easily flow as a whole, channels are formed throughout the oxide semiconductor, and more Can carry a large amount of current. On the other hand, the off-current, that is, the negative potential (-) at the gate (GE1). The current flowing with VG) applied is holes and electrons due to direct or indirect recombination. Oxide semiconductors have a wide bandgap and are excited by electrons, although they flow by recombination. Therefore, a large amount of thermal energy is required, so that direct recombination and indirect recombination are unlikely to occur. Therefore, when a negative potential (-VG) is applied to the gate (GE1), a small number of carriers Since the number of holes is virtually zero, direct recombination and indirect recombination are unlikely to occur, and the current Is infinitely low, with a current per unit area of the channel of 100 aA / μm or less, preferably It is 10 aA / μm or less, more preferably 1 aA / μm or less, which is close to zero.

Here, the intrinsic carrier density of the oxide semiconductor will be described.

Intrinsic carrier density contained in semiconductor n_iIs Fermi by Fermi Dirac statistics It can be obtained by approximating the Dirac distribution with the Boltzmann distribution formula (see Equation 2).

<maths num="2"><img file="JP5116896B2_D0002.tif" /></maths>

Intrinsic carrier density obtained by an approximate expression n_iIs the effective density of states N in the conduction band_C, Price Effective density of states N in the electron band_V, And bandgap E_gIt is a relational expression of Intrinsic carrier density of silicon n_iIs 1.45 × 10¹⁰cm^-3, Oxide semiconductors (here Is the intrinsic carrier density of In-Ga-Zn-O membrane) n_iIs 1.2 × 10^-7cm^-3Tona The former has a carrier density of 10 more than the latter.¹⁷Twice as big. That is, oxidation compared to silicon It can be seen that the intrinsic carrier density of the physical semiconductor is extremely low.

Next, the depletion layer width and Debye length when a negative potential (-VG) is applied to the gate (GE1) This will be described below.

Donor density N_dVoltage is applied to a MOS transistor composed of semiconductors, insulators, and metals. Maximum depletion layer width T formed in the semiconductor when applied_{D MAX}Is calculated by formula 3 ..

<maths num="3"><img file="JP5116896B2_D0003.tif" /></maths>

The maximum depletion layer width is expressed as a function of donor density and fermi potential, and is fermi potency. Jar φ_FIs calculated by Equation 4.

<maths num="4"><img file="JP5116896B2_D0004.tif" /></maths>

Also, the Debye length L of the MOS transistor_DIs calculated by Equation 5.

<maths num="5"><img file="JP5116896B2_D0005.tif" /></maths>

In addition, ε_sIs the relative permittivity of oxide semiconductors, ε₀Is the permittivity of vacuum, N_dIs donor density, q is prime Charge, k is Boltzmann's constant, and T is temperature.

Silicon n_i(Intrinsic carrier density) 1.45 × 10¹⁰cm^-3, Ε_S11.9 and And n of oxide semiconductors_i1.2 × 10^-7cm^-3, Ε_SWith 10 as silicon and The maximum depletion layer width and Debye length of MOS transistors using oxide semiconductors were calculated. here Transistors are horizontal MOS transistors with channels formed parallel to the substrate surface. It was calculated using the structure of the data. Further, the maximum depletion layer width here is wide in the direction perpendicular to the substrate. It corresponds to the width of the depletion layer. The spread of the depletion layer of the horizontal MOS transistor is vertical M. It is said that the same tendency can be seen in OS transistors.

In the case of silicon, the donor density depends on the density of impurities (P). Field of oxide semiconductor In that case, oxygen defects and hydrogen contribute as donors.

The maximum depletion layer width obtained from Equation 4 and the Debye length obtained from Equation 5 have low donor densities. As the maximum depletion layer expands, the Debye length increases. Also, the maximum depletion layer width T_{D MAX}Is true Sex carrier density n_iDepends on n_iOxide semiconductors with less depletion layer have more depletion layer than silicon You can see that it spreads. Also, donor density (N_d) Decreases, the Debye length increases and the sky The poor layer spreads throughout the oxide semiconductor. Typically, the donor density is 1x10¹²~1×10¹⁸cm^-3Is the maximum depletion layer width of oxide semiconductors and silicon on the submicron order? The debye length of oxide semiconductors and silicon is several nm to several μm. Ma Also, the donor concentration is 1 × 10^-5~1×10¹cm^-3In the range of, the maximum sky of oxide semiconductors The depletion layer has a significantly increased width from several tens of μm to several thousand μm and a Debye length from several μm to several hundred μm. Can be seen to spread over the entire oxide semiconductor.

From the above, oxide semiconductors have a wide bandgap and a low intrinsic carrier density. , The maximum depletion layer and Debye length increase, and the depletion layer spreads throughout the oxide semiconductor in the off state. Therefore, the off-current can be reduced and it becomes as close to zero as possible.

In this way, the purity is refined so that impurities other than the main components of the oxide semiconductor are not contained as much as possible. By making it true (i type), or making it substantially true, the boundary with the gate insulating film Surface characteristics become apparent. Therefore, the gate insulating film can form a good interface with the oxide semiconductor. Those are preferable. For example, high-density plastic generated at power frequencies from the VHF band to the microwave band. A dense insulating film produced by the CVD method using a Zuma, or produced by the sputtering method. It is preferable to use an insulating film. Furthermore, the interface between the gate insulating film and the gate electrode is good. Therefore, the high frequency generated in the VHF band to microwave band on the surface of the gate insulating film. A dense insulating film produced by a CVD method using a density plasma may be formed.

In this way, purification should be performed so that impurities other than the main components of the oxide semiconductor are not contained as much as possible. As a result, the on-current is high, the off-current is low, the on-off ratio is high, and it has good operating characteristics. It becomes a transistor. In addition, on-current, field-effect mobility, and threshold voltage due to temperature changes Fluctuation is extremely low.

Here, the drain resistance of a transistor using an oxide semiconductor will be described.

When the electric field in the semiconductor reaches a certain threshold, collision ionization occurs due to the high electric field in the depletion layer. The accelerated carriers collide with the crystal lattice and generate electron-hole pairs. Further high electric field Then, the pair of electrons and holes generated by collision ionization is further accelerated by the electric field. Repeated collision ionization results in an avalanche breakdown in which the current increases exponentially. collision In ionization, carriers (electrons, holes) generate kinetic energy that exceeds the band gap of the semiconductor. It is generated by having. Collision ionization coefficient and van indicating the likelihood of collision ionization There is a correlation between the gaps, and the larger the bandgap, the smaller the collision ionization coefficient. The tendency is known.

The bandgap of oxide semiconductors is 3.15 eV, which is one of the bandgap of silicon. Compared to .12eV, it is larger, so it is expected that avalanche breakdown will not occur easily. Therefore, a transistor using an oxide semiconductor has a high drain withstand voltage, and a high electric field is applied. Even if it is done, it is expected that the exponential surge of the on-current is unlikely to occur.

Next, hot carrier deterioration of a transistor using an oxide semiconductor will be described.

Hot carrier degradation is a game near the drain in a channel due to high-speed accelerated electrons. A fixed charge is generated in the oxide film, and a trap level is formed at the interface of the gate insulating film. This causes deterioration of transistor characteristics such as threshold voltage fluctuation and gate leak. As a cause of hot carrier deterioration, channel hot electron injection (CHE injection) ) And drain avalanche hot carrier injection (DAHC injection).

Since silicon has a narrow bandgap, avalanche breakdown causes avalanche electrons. It is easy, and the number of electrons accelerated at high speed increases so that the barrier to the gate insulating film can be overcome. Shi However, since the oxide semiconductor shown in this embodiment has a wide bandgap, it is avalanche. Shear yield is less likely to occur and is more resistant to hot carrier deterioration than silicon. High resistance Silicon carbide bandgap and oxide semiconductor bandgap, which are one of the pressure materials Oxide semiconductors have the same mobility, but the mobility is about two orders of magnitude smaller, so electrons are accelerated. Silicon carbide and gallium nitride are barriers to the oxide film, which is the gate insulating film. Since it is larger than silicon, very few electrons are injected into the oxide film, so silicon power -Hot carrier deterioration is less likely to occur than bide, gallium nitride, and silicon, and drain pressure resistance Can be said to be high. Therefore, the oxide semiconductor that functions as a channel, the source electrode, and the dowel There is no need to form a low-concentration impurity region with the rain electrode, and the transistor structure is extremely high. It becomes simple and the number of manufacturing processes can be reduced.

From the above, the transistor using the oxide semiconductor has a high drain withstand voltage, specifically. Has a drain withstand voltage of 100V or higher, preferably 500V or higher, more preferably 1kV or higher It is possible to do.

Here, about the comparison between silicon carbide, which is a typical example of a transistor, and an oxide semiconductor. It is shown below. Here, 4H-SiC is used as the silicon carbide.

Oxide semiconductors and 4H-SiC have some things in common. Intrinsic carrier density is that This is an example. Intrinsic power of oxide semiconductor using Fermi-Dirac distribution at room temperature Rear density is 10^-7cm^-3It is estimated to be a degree, but this is 6. in 4H-SiC. 7 × 10^-11cm^-3Similar to, it is an extremely low value.

The energy band gap of oxide semiconductors is 3.0 to 3.5 eV, which is 4H-S. Since the energy bandgap of iC is 3.26eV, it is called a wide-gap semiconductor. In this respect as well, oxide semiconductors and silicon carbide are common.

However, the production temperatures of oxide semiconductors and silicon carbide differ greatly. .. Silicon carbide requires, for example, an activation heat treatment of 1500 ° C to 2000 ° C. one On the other hand, oxide semiconductors are 450 ° C or higher and 850 ° C or lower, preferably 550 ° C or higher and 750 ° C or lower. It is possible to produce crystalline oxide semiconductors by the heat treatment of Langista can be made. In addition, the throughput can be increased.

Impure potential donor or acceptor in the fabrication process of SiC-MOSFETs It includes a step of doping a substance (phosphorus, boron, etc.) and a step of high temperature heat treatment for activation. When By the way, oxide semiconductors have a relatively large electron affinity. Therefore, it has a proper work function By selecting a metal as the electrode, no impurities are added in the transistor manufacturing process. Ohmic contact with the electrode can be formed with n⁺Forming an area The process can be simplified at the point.

In oxide semiconductors, DOS (density of st) within the bandgap Many physical properties studies such as ate) have been done, but these studies are sufficient for DOS itself. It does not include the idea of reducing. In this embodiment, the cause of DOS in the energy gap By removing possible water and hydrogen from the oxide semiconductor, a highly purified oxide semiconductor is created. To make. This is based on the idea of reducing DOS itself sufficiently. And This makes it possible to manufacture extremely excellent industrial products.

Furthermore, oxygen is supplied to the unpaired bond of the metal generated by oxygen deficiency, due to oxygen deficiency. By reducing the amount of DOS, it becomes a more purified (i-type) oxide semiconductor. It is also possible. For example, it forms an oxygen-rich oxide film in close contact with the channel formation region. , It is possible to supply oxygen from the oxide film to reduce DOS due to oxygen defects. ..

Oxide semiconductor defects are shallow levels of 0.1-0.2 eV below the conduction band due to excess hydrogen. It is also attributed to deep levels due to lack of oxygen. Eliminate these defects Therefore, the technical idea of thoroughly removing hydrogen and supplying sufficient oxygen is correct. Will.

Further, the oxide semiconductor is generally considered to be n-type, but in the present embodiment, impurities such as water and water are used. I-type is realized by removing hydrogen. In this regard, impurities such as silicon are added. It can be said that it includes an unprecedented technical idea rather than the i-type. Also, oxide semiconductors The density of impurities such as heavy elements that do not constitute iron, nickel, etc. is also 1 × 10.¹⁵cm^-3Less than Is preferable.

In addition, by converting the oxide semiconductor into an i-type, the temperature characteristics of the transistor are good, and the cost is increased. Tablewise, the current-voltage characteristics of the transistor in the temperature range from -25 ° C to 150 ° C. On current, off current, field effect mobility, S value, and threshold voltage fluctuations There is almost no deterioration of current-voltage characteristics due to temperature.

The transistor using the oxide semiconductor shown in the present embodiment uses silicon carbide. The channel mobility is slightly lower than that of the transistor used, but the drain voltage is increased. By increasing the channel width (W), the current value of the transistor is increased and the device characteristics are improved. Can be improved.

On the contrary, the technical idea of the present embodiment is unwillingly added without further addition to the oxide semiconductor. By intentionally removing impurities such as existing water and hydrogen, the oxide semiconductor itself is highly pure. It is to be a degree. That is, the water or hydrogen that constitutes the donor level is removed, and the acid is further removed. By reducing elementary defects and supplying sufficient oxygen as the main component material that constitutes the oxide semiconductor. , Purifying oxide semiconductors.

1 × 10 for oxide semiconductors at the time of film formation²⁰cm^-3~9×10²⁰cm^-3Of the range Hydrogen is measured by SIMS (Secondary Ion Mass Spectrometry). The water that causes this donor level Or oxygen that intentionally removes hydrogen and at the same time decreases with the removal of water or hydrogen By adding (one of the components of the oxide semiconductor) to the oxide semiconductor, the oxide semiconductor is highly purified. It is converted into an i-type (intrinsic) semiconductor.

Further, in the present embodiment, the smaller the amount of water and hydrogen in the oxide semiconductor, the smaller the amount. Preferably, the fewer carriers, the better. That is, the carrier density is 1 × 10.¹²cm^-31.45 × 10 less than, more preferably less than the lower limit of measurement¹⁰cm^-3Less than required It can be found. Furthermore, in terms of the technical idea of the present embodiment, it is ideal that it is close to zero or zero. .. In particular, use oxide semiconductors with oxygen, nitrogen, or ultra-dry air (water content of 20 ppm or less). Air) atmosphere, preferably 1 ppm or less, more preferably 10 ppb or less, 450 ° C. By heat treatment of 850 ° C or higher, preferably 550 ° C or higher and 750 ° C or lower, Water or hydrogen, which is an n-type impurity, can be removed to purify the product. Also water, again By removing impurities such as hydrogen to purify oxide semiconductors, carriers Density 1x10¹²cm^-31.45 × 10 less than, more preferably less than the lower limit of measurement¹⁰cm^-3Can be less than.

Further, heat treatment is performed at a high temperature of 450 ° C or more and 850 ° C or less, preferably 600 ° C or more and 700 ° C or less. Then, it is possible to purify the oxide semiconductor and crystallize it, and the oxide Oxide half with crystal growth c-axis oriented polycrystalline region from the surface of the semiconductor toward the inside Become a conductor. A c-axis oriented polycrystalline region is a single crystal region that has a c-axis perpendicular to the surface. It is a region having a plurality of regions.

In the present invention, an oxide semiconductor film having the c-axis oriented polycrystalline region is used as a seed crystal, and the present invention is formed on the oxide semiconductor film. A second oxide semiconductor film is provided on the surface of 450 ° C or higher and 850 ° C or lower, preferably 550 ° C or higher 7 By heat treatment at 50 ° C or less, the second oxide semiconductor film is oriented in the c-axis like the seed crystal. It can have a polycrystalline region. That is, the c-axis of the seed crystal and the c of the second oxide semiconductor film. Ideal axial growth or epitaxial growth with coaxial axes Wear.

In addition, the second oxide semiconductor film coaxial with the seed crystal only grows in solid phase by heat treatment after film formation. Instead, do not heat at 200 ° C or higher and 600 ° C or lower, preferably 200 ° C or higher and 550 ° C or lower. A second oxide semiconductor is formed by forming a film, typically by sputtering, to crystallize while depositing. Can grow.

Furthermore, by reducing the carriers of oxide semiconductors and preferably eliminating them, tran In the gista, the oxide semiconductor functions as a path through which carriers pass. So As a result, oxide semiconductors are highly purified i-type (intrinsic) semiconductors, have no carriers, and By making it extremely low, the off-current is extremely low when the transistor is off. It is the technical idea of this embodiment that it can be done.

In addition, the oxide semiconductor functions as a path, and the oxide semiconductor itself does not have a carrier. If the i-type (intrinsic) is purified to be extremely low, the carrier is the electrode. It is supplied by the boot and drain. Electron affinity χ and Fermi level of oxide semiconductor, theory Fermi level, which is conceptually consistent with the true Fermi level, and the work relationship between the source and drain electrodes. Carriers can be injected from the source electrode and drain electrode by appropriately selecting the number. This makes it possible to appropriately manufacture n-type transistors and p-type transistors.

By the way, in a horizontal transistor in which a channel is formed substantially parallel to a substrate, a channel is used. It is necessary to provide a source and a drain in addition to the transistor, and the occupied surface of the transistor on the board. The product becomes large, which hinders miniaturization. However, it smells like a vertical transistor. Because the source, channel, and drain are laminated, the area occupied on the substrate surface is low. Can be reduced. As a result, the transistor can be miniaturized.

Thus, impurities other than the main components of the oxide semiconductor film, typically hydrogen, water, hydroxyl groups or By purifying the product so that it does not contain hydrides as much as possible, and by providing a polycrystalline region. Therefore, the operation of the transistor can be improved. In particular, increase the pressure resistance and short The channel effect can be suppressed and the on / off ratio can be increased. Also, before and after the BT test It is possible to suppress the amount of change in the threshold voltage of the transistor and realize high reliability. Can be done. Moreover, the temperature dependence of the electrical characteristics can be suppressed. Also reported so far The resulting metal oxide is in an amorphous state, a polycrystalline state, or 1 Only those obtained single crystals by treatment at a high temperature of about 400 ° C, as shown above. After forming a flat plate-shaped polycrystalline region on the oxide semiconductor film, the crystallite region is used as a seed for crystallization. By the growing method, it is possible to thicken the oxide semiconductor film having a polycrystalline region at a relatively low temperature. It opens up a wider range of industrial applications.

(Embodiment 2) In the present embodiment, a transistor having a structure different from that of the first embodiment will be described using FIG. 7. I will reveal.

FIG. 7 (A) is a top view of the transistor 147, and FIG. 7 (B) is the alternate long and short dash line A of FIG. 7 (A). -Corresponds to the cross-sectional view of B.

As shown in FIG. 7B, the first electrode 10 is placed on the insulating film 103 formed on the substrate 101. 5. The oxide semiconductor film 107 and the second electrode 109 are laminated. The second electrode 10 The difference from the first embodiment is that the end portion of 9 is located inside the end portion of the oxide semiconductor film 107. Further, the first electrode 105, the oxide semiconductor film 107, and the second electrode 109 are covered so as to cover the first electrode 105, the oxide semiconductor film 107, and the second electrode 109. A gate insulating film 111 is provided. At least half an oxide on the gate insulating film 111 A third electrode 113 is provided so as to face the conductor film and the side surface of the second electrode. Ge An insulating film 117 that functions as an interlayer insulating film is formed on the insulating film 111 and the third electrode 113. It is provided. An opening is formed on the insulating film 117, and the first opening is formed. Wiring 131 to connect to electrode 105 (see Fig. 7 (A)), wiring to connect to second electrode 109 129, wiring 125 connected to the third electrode 113 is formed.

In the present embodiment, as in the first embodiment, the oxide semiconductor film 107 has crystallinity and is represented by a table. It is oriented in the c-axis direction perpendicular to the surface. That is, the c-axis direction of the oxide semiconductor film 107 is Aligns perpendicular to the surface. The elements of adjacent planes on the ab plane are the same. It is a thing.

The oxide semiconductor film 107 is highly purified, and the hydrogen concentration is 1 × 10.¹⁸cm^-³Below, 1 x 10¹⁶cm^-3Hereinafter, further, substantially 0 is preferable. Also, half an oxide The carrier density of the conductor film 107 is 1 × 10.¹²cm^-3Less than, more preferably not the lower limit of measurement Full 1.45 × 10¹⁰cm^-3Is less than. That is, the carrier density of the oxide semiconductor film is It is as close to zero as possible. The bandgap is 2 eV or more, preferably 2.5 eV or more. More preferably, it is 3 eV or more.

In the transistor of the present embodiment, the channel length L has an oxide semiconducting structure in the cross-sectional structure. Distance between the first electrode 105 and the second electrode 109 in the region where the body film is in contact with the gate insulating film. It is separated. Further, the channel width W is the oxide semiconductor film in contact with the first electrode or the second electrode. The length of the end. Here, the area of the first electrode or the second electrode is large. Let W be the length of the edge of the oxide semiconductor film where the one is in contact with the oxide semiconductor film. In this embodiment Since the upper surface shape of the oxide semiconductor film of the transistor is rectangular, the channel width W is 2W.₁And 2W₂Is the sum of. If the top surface of the oxide semiconductor film of the transistor is circular, , When the radius of the circle is r, the channel width W is 2πr.

In the present embodiment, the channel length L is longer than that in the first embodiment. Also, oxide semiconductors Not only on the side surface of the film 107, but also on the upper surface side of the oxide semiconductor film 107, as a gate electrode. It is affected by the voltage applied to the functioning third electrode 113. Therefore, the first embodiment Compared with, it becomes easier to control the channel.

Thus, impurities other than the main components of the oxide semiconductor film, typically hydrogen, water, hydroxyl groups or By purifying the product so that it does not contain hydrides as much as possible, and by providing a polycrystalline region. Therefore, the operation of the transistor can be improved. Especially, the pressure resistance is increased and the show The channel effect can be reduced and the on / off ratio can be increased. Also, before and after the BT test It is possible to suppress the amount of change in the threshold voltage of the transistor and realize high reliability. Can be done. In addition, the temperature dependence of electrical characteristics can be suppressed.

(Embodiment 3) In the present embodiment, the transistors shown in the first embodiment or the second embodiment are used. The form of the 3-terminal diode will be described with reference to FIG.

FIG. 8 corresponds to a cross-sectional view of a 3-terminal diode.

The three-terminal diode 149a shown in FIG. 8 (A) has an insulating film 10 formed on the substrate 101. The first electrode 105, the oxide semiconductor film 107, and the second electrode 109 are laminated on the three. .. Also, so as to cover the first electrode 105, the oxide semiconductor film 107, and the second electrode 109. , The gate insulating film 111 is provided. On the gate insulating film 111, a third electrode 113 Is provided. Further, an opening is formed in the gate insulating film 111, and the opening has an opening. The second electrode 109 and the third electrode 113 are connected to each other.

The three-terminal diode 149b shown in FIG. 8 (B) has an insulating film 10 formed on the substrate 101. The first electrode 105, the oxide semiconductor film 107, and the second electrode 109 are laminated on the three. .. Also, so as to cover the first electrode 105, the oxide semiconductor film 107, and the second electrode 109. , The gate insulating film 111 is provided. On the gate insulating film 111, a third electrode 113 Is provided. Further, an opening is formed in the gate insulating film 111, and the opening has an opening. The first electrode 105 and the third electrode 113 are connected to each other.

The three-terminal diode shown in the present embodiment includes a third electrode that functions as a gate electrode and a diode. It is characterized in that one of the boot electrode and the drain electrode is electrically connected. example For example, a first electrode that functions as a drain electrode and a third electrode that functions as a gate electrode For electrically connected structures, the drain electrode has a higher voltage (positive voltage) than the source electrode. Is applied, a positive voltage is also applied to the gate electrode, so the transistor is in the on state. Therefore, the forward current becomes easier to flow. On the other hand, the drain electrode has a lower electricity than the source electrode. When pressure (negative voltage) is applied, the transistor is turned off and more reverse current flows. Since it becomes difficult, the rectifying characteristics of the diode can be further improved.

Although the 3-terminal diode has been described in this embodiment, it does not have a third electrode. It is possible to manufacture a 2-terminal diode.

(Embodiment 4) In the present embodiment, a transistor having high heat resistance will be described with reference to FIG.

In the substrate 101 shown in FIG. 1, a transistor having high heat resistance is used by using a substrate having high heat dissipation. Gista can be made. Substrates with high heat dissipation include semiconductor substrates, metal substrates, and substrates. There are rustic, etc., and typical examples of semiconductor substrates are single connection of silicon, silicon carbide, etc. Crystal semiconductor substrates, polycrystalline semiconductor substrates, compound semiconductor substrates such as silicon germanium, etc. To. Typical examples of the metal substrate include an aluminum substrate, a copper substrate, a stainless steel substrate, and the like. As a typical example of a plastic substrate, a plus having carbon fiber, metal fiber, metal piece, etc. There is a tick board. The semiconductor substrate, metal substrate, and plastic substrate are limited to these. If it is not defined and has high heat dissipation, it can be used as appropriate.

Further, as the insulating film 103 shown in FIG. 1, heat resistance is obtained by forming an insulating film having high thermal conductivity. It is possible to manufacture a transistor having a high value. As an insulating film with high thermal conductivity, Al nitride There are a mium film, an aluminum oxide film, a silicon nitride film, and the like.

Further, a semiconductor film may be provided between the first electrode 105 and the insulating film 103 shown in FIG. Semi-leading Typical examples of body membranes are silicon membranes, germanium membranes, silicon carbide membranes, and DLC (DLC). Diamond Like Carbon) There are membranes and the like.

By using one or more of the above configurations, a transistor with high heat resistance can be manufactured. can do.

(Embodiment 5) In the present embodiment, the first electrode 105 and the second electrode 109 have different work functions. A transistor characterized by being formed using a material will be described.

In the present embodiment, one of the first electrode 105 and the second electrode 109 is an oxide semiconductor electric current. Formed of a conductive material with a work function of less than or equal to the child affinity, the first electrode 105 and the second electrode 109 The other is formed of a conductive material with a work function greater than the electron affinity of the oxide semiconductor.

For example, when the electron affinity (χ) of an oxide semiconductor is 4.3 eV, the electrons of the oxide semiconductor Tungsten (W), molybdenum, as examples of conductive materials with a work function greater than affinity Use (Mo), chromium (Cr), iron (Fe), indium tin oxide (ITO), etc. Can be done. Also, as an example of a conductive material whose work function is less than or equal to the electron affinity of an oxide semiconductor. , Titanium (Ti), Yttrium (Y), Aluminum (Al), Magnesium (Mg) , Silver (Ag), Zirconium (Zr), etc. can be used.

First, the electrode that functions as a drain has a larger work function than the electron affinity of the oxide semiconductor. The electrode, which is made of a conductive material and functions as a source, has an electron affinity or less of that of an oxide semiconductor. The case of forming with a conductive material having a function will be described.

Let φmd be the work function of the conductive material that forms the electrode that functions as the drain, and use it as the source. The work function φms of the conductive material that forms the functioning electrode, the work function φms, and the electron affinity Make the relationship between the force χ and the work function φmd the relationship shown in Equation 6.

<maths num="6"><img file="JP5116896B2_D0006.tif" /></maths>

In this way, the work function of the electrode that functions as a source is less than the electron affinity of the oxide semiconductor. Therefore, the barrier when the transistor is on (for example, h in Fig. 3 (B)) can be reduced. It can be turned on at a low gate voltage and a large current can flow.

On the other hand, the relationship between the work function φmd, the electron affinity χ, and the work function φms is the relationship shown by Equation 7. To be.

<maths num="7"><img file="JP5116896B2_D0007.tif" /></maths>

In this way, the work function of the electrode that functions as a source is greater than the electron affinity of the oxide semiconductor. Therefore, the barrier of the transistor becomes high. Therefore, the current in the off state is reduced. be able to.

The electrode that functions as a source is one of the first electrode 105 and the second electrode 109. The electrode that functions as a drain is the other of the first electrode 105 and the second electrode 109. Can be done.

From the above, one of the first electrode 105 and the second electrode 109 is an oxide semiconductor electron. Formed of a conductive material with a work function of less than or equal to affinity, of the first electrode 105 and the second electrode 109 The other is formed of a conductive material with a work function greater than the electron affinity of the oxide semiconductor. The on-character or off-characteristics of the transistor can be improved.

Further, also in the diode shown in the third embodiment, by satisfying the relationship of the equation 6 or the equation 7. , It becomes a diode with high rectification characteristics.

(Embodiment 6) In the present embodiment, the manufacturing process of the transistor shown in FIG. 1 or 7 is shown in FIGS. 9 to 7. This will be described using 12.

As shown in FIG. 9 (A), the insulating film 103 is formed on the substrate 101, and the first is formed on the insulating film 103. Electrode 105 is formed. The first electrode 105 is the source electrode and drain of the transistor. Functions as one of the electrodes.

The insulating film 103 can be formed by a sputtering method, a CVD method, a coating method, or the like.

When the insulating film 103 is formed by the sputtering method, hydrogen, water, etc. remaining in the treatment chamber are used. It is preferable to form the insulating film 103 while removing hydroxyl groups, hydrides, and the like. is this , To prevent hydrogen, water, hydroxyl groups, hydrides, etc. from being contained in the insulating film 103. To. Adsorption to remove hydrogen, water, hydroxyl groups or hydrides remaining in the treatment chamber It is preferable to use a type vacuum pump. As a suction type vacuum pump, for example, a cry It is preferable to use an oppump, an ion pump, or a titanium sublimation pump. Also As the exhaust means, a turbo pump with a cold trap may be added. Ku Hydrogen, water, hydroxyl groups or hydrides are exhausted in the treatment room exhausted using the Rio pump. Therefore, when the insulating film 103 is formed in the processing chamber, the impurities contained in the insulating film 103 The concentration can be reduced.

The sputtering gas used to form the insulating film 103 is hydrogen, water, a hydroxyl group, or hydrogen. Use a high-purity gas from which impurities such as compounds have been removed to a concentration of about ppm and a concentration of about ppb. Is preferable.

The sputtering method includes the RF sputtering method, which uses a high-frequency power supply as the sputtering power supply, and D. There is a C sputtering method, and pulsed DC sputtering that gives a pulse bias. There is also a method. The RF sputtering method is mainly used for forming an insulating film, and is a DC sputter. The taling method is mainly used when forming a metal film.

There is also a multi-dimensional sputtering device that can install a plurality of targets made of different materials. Multiple spatter The device can be laminated with films of different materials in the same chamber, or multiple films in the same chamber. It can also be formed by simultaneously discharging different types of materials.

In addition, a spat using the magnetron sputtering method equipped with a magnet mechanism inside the chamber. ECRs that use a data device or plasma generated using microwaves without using glow discharge There are sputtering devices that use the putting method.

In addition, as a sputtering method, the target substance and the sputter gas component are chemically reacted during film formation. Reactive sputtering method to form thin films of these compounds in response, and substrates during film formation A bias sputtering method in which a voltage is also applied can also be used.

In the sputtering of the present specification, the above-mentioned sputtering apparatus and sputtering The method can be used as appropriate.

In the present embodiment, the substrate 101 is transported to the processing chamber, and hydrogen, water, hydroxyl groups, hydrides, etc. Introduce a sputter gas containing high-purity oxygen from which has been removed, and use a silicon target to base the group. A silicon oxide film is formed on the plate 101 as an insulating film 103. The insulating film 103 is formed. When doing so, the substrate 101 may be heated.

For example, using a quartz (preferably synthetic quartz) target, substrate temperature 108 ° C, substrate and tar Distance between get (distance between TS) is 60mm, pressure 0.4Pa, high frequency power supply 1.5k W, oxygen and argon (oxygen flow rate 25sccm: argon flow rate 25sccm = 1: 1) atmosphere A silicon oxide film is formed in the surrounding air by the RF sputtering method. The film thickness is 100 nm It is good. A silicon target is used instead of the quartz (preferably synthetic quartz) target. Can be The sputter gas is oxygen or a mixed gas of oxygen and argon. This is done using a computer.

When the insulating film 103 is formed in a laminated structure, for example, between the silicon oxide film and the substrate. Spatter gas and syrup containing high-purity nitrogen from which hydrogen, water, hydroxyl groups or hydrides have been removed A silicon nitride film is formed using a recon target. Even in this case, silico oxide Nitrogen while removing hydrogen, water, hydroxyl groups or hydrides remaining in the treatment chamber, similar to the film It is preferable to form a siliconized silicon film. In the process, the substrate 101 is heated. It may be.

When the silicon nitride film and the silicon oxide film are laminated as the insulating film 103, the silicon nitride film And silicon oxide film in the same processing room using a common silicon target Can be done. Silicon installed in the processing chamber by first introducing an etching gas containing nitrogen A silicon nitride film is formed using the target, and then switched to an etching gas containing oxygen. The same silicon target is used to form a silicon oxide film. Silicon nitride film and oxidation Since the silicon film can be continuously formed without being exposed to the atmosphere, the surface of the silicon nitride film It is possible to prevent impurities such as hydrogen, water, hydroxyl groups or hydrides from being adsorbed on the surface. ..

The first electrode 105 is a conductive film formed on a substrate 101 by a sputtering method, a CVD method, or a vacuum. It is formed by a vapor deposition method, and a resist mask is formed on the conductive film by a photolithography process. The conductive film can be formed by etching the conductive film using the resist mask. Or The first electrode 105 is formed by the printing method and the inkjet method without using the photolithography process. By doing so, the number of processes can be reduced. The end of the first electrode 105 is tapered. The shape is preferable because the covering property of the gate insulating film formed later is improved. First electrode The angle between the end of 105 and the insulating film 103 is 30 ° or more and 60 ° or less, preferably 40 °. By setting the temperature to 50 ° or more, the coverage of the gate insulating film formed later can be improved. it can.

In the present embodiment, as the conductive film to be the first electrode 105, the film thickness is increased by the sputtering method. A titanium film of 50 nm is formed, an aluminum film of 100 nm thickness is formed, and a thickness of 50 nm is formed. Titanium film is formed. Next, the resist mask formed by the photolithography process is Etching using to form the first electrode 105.

Next, as shown in FIG. 9 (B), the thickness is 2 nm or more on the insulating film 103 and the first electrode 105. A first oxide semiconductor film 102a having an upper portion of 15 nm or less is formed.

Here, a method for producing the first oxide semiconductor film 102a will be described.

Thickness on the insulating film 103 and the first electrode 105 by sputtering, coating, printing, etc. A first oxide semiconductor film 102a having a size of 2 nm or more and 15 nm or less is formed.

The first oxide semiconductor film 102a has a rare gas (typically argon) atmosphere, an oxygen atmosphere, and the like. Alternatively, it is formed by sputtering in a rare gas (typically argon) and oxygen atmosphere. Can be done.

Further, before, during, or after the film formation of the first oxide semiconductor film 102a is performed. It is preferable to remove the water remaining in the sputtering apparatus. Residue in sputtering equipment In order to remove retained water, it is preferable to use an adsorption type vacuum pump. For example, Kura It is preferable to use an io pump, an ion pump, and a titanium sublimation pump. Ma Further, as the exhaust means, a turbo pump to which a cold trap is added may be used. The film forming chamber of the sputtering apparatus exhausted using the cryopump is, for example, hydrogen atoms or water (H).₂Oxide semiconducting film formed in the film forming chamber because compounds containing hydrogen atoms such as O) are exhausted. The concentration of impurities contained in the body membrane can be reduced.

The first oxide semiconductor film 102a is In-Sn-Ga-Z, which is a quaternary metal oxide. nO film, In-Ga-Zn-O film, which is a ternary metal oxide, In-Sn-Zn-O film , In-Al-Zn-O Membrane, Sn-Ga-Zn-O Membrane, Al-Ga-Zn-O Membrane, Sn- Al-Zn-O film, In-Zn-O film, which is a binary metal oxide, Sn-Zn-O film, A l-Zn-O film, Zn-Mg-O film, Sn-Mg-O film, In-Mg-O film, In-O Oxide semiconductor membranes such as membranes, Sn-O membranes, and Zn-O membranes can be used.

The first oxide semiconductor film 102a is an InMO.₃(ZnO)_mNotated by (m&gt; 0) Materials can be used. Here, M was selected from Ga, Al, Mn and Co. Indicates one or more metal elements. For example, as M, Ga, Ga and Al, Ga and Mn, Or there are Ga and Co.

The first oxide semiconductor film 102a is an oxide semiconductor material represented by In-ABO. You may use a fee. Where A is 13 such as gallium (Ga) and aluminum (Al). Select from group elements, group 14 elements such as silicon (Si) and germanium (Ge) Represents one or more kinds of elements to be made. In addition, B is a group 12 element represented by zinc (Zn). Represents one or more elements selected from the elements. The contents of In, A, and B are optional. Yes, including the case where the content of A is zero. On the other hand, the contents of In and B are not zero. Su That is, the above-mentioned notation includes In-Ga-Zn-O, In-Zn-O, and the like.

When forming the first oxide semiconductor film, In: Ga: Zn = 1: 0 or more and 2 or less: 1 or more 5 It is characterized by using a metal oxide target having the following composition ratio. In this embodiment Is an oxide semiconductor target (In-Ga-Zn-O based oxide semiconductor target (In)₂O₃: Ga₂O₃: ZnO = 1: 1: 2 [mol number ratio], In: Ga: Zn = 1: 1: 1 [Atomic ratio])), the distance between the substrate and the target is 170 mm, and the pressure is 0.4 Pa. , Direct current (DC) power supply 0.5kW, oxygen only, argon only, or argon and oxygen atmosphere A first oxide semiconductor film having a film thickness of 5 nm is formed by air. Also, as an oxide semiconductor target In: Ga: Zn = 1: 1: 0.5 [atomic ratio] target, In: G A target with a composition ratio of a: Zn = 1: 1: 1 [atomic ratio], or In: Ga: Zn Target with composition ratio of = 1: 1: 2 [atomic ratio], In: Ga: Zn = 1: 0.5: A target having a composition ratio of 2 [atomic ratio] can also be used. Also, it does not contain Ga A target with In: Zn = 1: 1 [atomic ratio] may be used. In-Ga-Zn-O film The field effect mobility can be increased by using an In-Zn-O film rather than using it. In the present embodiment, since heat treatment is performed later to intentionally crystallize, crystallization is likely to occur. It is preferable to use an oxide semiconductor target.

The relative density of the oxide semiconductor in the oxide semiconductor target is 80% or more, preferably 9. It is preferably 5% or more, more preferably 99.9% or more. Relative density target It is possible to reduce the concentration of impurities in the oxide semiconductor film formed by using electricity. Transistors with high characteristics or reliability can be obtained.

Further, before forming the first oxide semiconductor film 102a, the inner wall of the sputtering apparatus and the target Preheat treatment to remove residual water or hydrogen on the surface or target material It is good to do. As a preheat treatment, the inside of the film formation chamber is reduced to 200 ° C to 600 ° C. There is a method of heating to the air, a method of repeatedly introducing nitrogen and an inert gas and exhausting while heating, etc. .. After preheating, cool the substrate or sputtering equipment and do not expose it to the atmosphere. A oxide semiconductor film is formed. Even if nitrogen is introduced and exhausted repeatedly without heating, there is a certain effect. However, it is better to do it while heating.

Next, the first heat treatment of the first oxide semiconductor film 102a is performed to crystallize at least a part of the first oxide semiconductor film 102a. Let me. The temperature of the first heat treatment is 450 ° C or higher and 850 ° C or lower, preferably 550 ° C or higher. The temperature should be 750 ° C or less. The heating time shall be 1 minute or more and 24 hours or less. For the first heat treatment Therefore, the first oxide semiconductor film 102b (first) having a polycrystalline region crystal-grown from the surface. It is also called an oxide semiconductor film having crystallinity. ) Is formed (see Fig. 9 (C)). Polycrystalline territory The region crystal grows from the surface to the inside and has an average thickness of 2 nm or more and 15 nm or less. It is a plate-like crystal. In addition, the polycrystalline region formed on the surface is c in the direction perpendicular to the surface. It is axially oriented. In the present embodiment, the first oxide semiconductor film is subjected to the first heat treatment. An example in which most of them are polycrystalline is shown. Relatively crystals formed on the surface of the first oxide semiconductor film The well-oriented polycrystalline region is affected by the underlying member because the crystal grows vertically from the surface. It can be formed without squeezing.

Of the first oxide semiconductor film 102b, the region overlapping the unevenness of the first electrode 105 is formed. It has a grain boundary and becomes a polycrystal. In addition, among the first oxide semiconductor film 102b, the polycrystalline The ab plane, a axis, and b axis may shift.

When the first oxide semiconductor film is, for example, an In-Ga-Zn-O film, the first oxide semiconducting film is used. An example of the mechanism by which crystal regions having uniform crystal orientations are formed on the surface of the body membrane will be described. Addition By heat treatment, zinc contained in the In-Ga-Zn-O film diffuses and gathers near the surface. It becomes a seed for crystal growth. The crystal growth at this time is better in the direction parallel to the surface. Since it is stronger than the crystal growth in the direction perpendicular to the surface, a flat polycrystalline region is formed. That is, the direction of the ab plane and the direction of the c axis are likely to crystallize. Also, flat plate In the polycrystalline region of, the ab plane of each single crystal region is parallel to the surface. Also , In-Ga-Zn-O film is free space on the surface, and there is no upward crystal growth here. I. These things detect In and Ga when measuring up to 450 ° C when measuring TDS. Although not, it was confirmed that zinc peaks are detected under vacuum heating conditions, especially around 300 ° C. coming. The TDS measurement was performed in vacuum, and zinc was detected from around 200 ° C. It has been confirmed that

In the first heat treatment, nitrogen, oxygen, helium, neon, argon, etc. It is preferable that the rare gas does not contain water, hydrogen, or the like. Alternatively, it is introduced into a heat treatment device. Purity of nitrogen, oxygen, or rare gas such as helium, neon, argon, 6N (99.99) 99%) or higher, preferably 7N (99.99999%) or higher (ie, impurity concentration 1pp It is preferably m or less, preferably 0.1 ppm or less). Also, the water content is 20 In ultra-dry air of ppm or less, preferably 1 ppm or less, more preferably 10 ppb or less The first heat treatment may be performed.

In the present embodiment, as the first heat treatment, a heating treatment at 700 ° C. for 1 hour in a dry air atmosphere is performed. Do the reason.

In addition, when the temperature of the first heat treatment is raised, the inside of the furnace is made into a nitrogen atmosphere, and when it is cooled, the inside of the furnace is acid The atmosphere may be switched as a raw atmosphere, after dehydration or dehydration in a nitrogen atmosphere. , Oxygen is replenished inside the first oxide semiconductor film by switching the atmosphere to an oxygen atmosphere. Can be i-type.

The heat treatment device used for the first heat treatment is not particularly limited, and is a heating element such as a resistance heating element. A device for heating the object to be processed by heat conduction or heat radiation may be provided. For example , Electric furnace, GRTA (Gas Rapid Thermal Anneal) equipment, L RTA (Ra) such as RTA (Lamp Rapid Thermal Anneal) equipment pid Thermal Anneal) equipment can be used. LRTA device Halogen lamps, metal halide lamps, xenon arc lamps, carbon arc lamps For radiation of light (electromagnetic waves) emitted from lamps such as high-pressure sodium lamps and high-pressure mercury lamps. This is a device that heats the object to be treated. GRTA equipment uses hot gas for heat treatment It is a device to perform.

Next, on the first oxide semiconductor film 102b having at least a flat polycrystalline region on the surface. , Forming a second oxide semiconductor film 104a, which is thicker than the first oxide semiconductor film 102b. (See Figure 9 (D)). The film thickness of the second oxide semiconductor film 104a is 1 μm or more, and further. Is preferably 3 μm or more, more preferably 10 μm or more. The second oxide semiconductor film 104a is rare. Gas (typically argon) atmosphere, oxygen atmosphere, or rare gas (typically argon) And can be formed by the sputtering method in an oxygen atmosphere.

The second oxide semiconductor film 104a is In-Sn-Ga-Z, which is a quaternary metal oxide. nO film, In-Ga-Zn-O film, which is a ternary metal oxide, In-Sn-Zn-O film , In-Al-Zn-O Membrane, Sn-Ga-Zn-O Membrane, Al-Ga-Zn-O Membrane, Sn- Al-Zn-O film, In-Zn-O film, which is a binary metal oxide, Sn-Zn-O film, A l-Zn-O film, Zn-Mg-O film, Sn-Mg-O film, In-Mg-O film, In-O Oxide semiconductor membranes such as membranes, Sn-O membranes, and Zn-O membranes can be used.

Further, the same component material is used for the first oxide semiconductor film and the second oxide semiconductor film 104a. Is preferable. When the same component material is used, the first oxide is used in the subsequent crystallization. Crystal growth can be easily performed using the polycrystalline region of the semiconductor film as a seed for crystal growth. Also, the same ingredient In the case of a material containing, the interfacial physical characteristics such as adhesion and electrical properties are also good.

Next, a second heat treatment is performed, and the crystal region of the first oxide semiconductor film 102b is used as a seed for crystal growth. Crystal growth is performed as. The temperature of the second heat treatment is preferably 450 ° C or higher and 850 ° C or lower, preferably Is 600 ° C or more and 700 ° C or less. The heating time shall be 1 minute or more and 24 hours or less. No. The second oxide semiconductor film 104a is crystallized by the heat treatment of 2. Thus the polycrystalline territory Oxide semiconductor film 108 having a region (also referred to as an oxide semiconductor film having a second crystallinity) It can be obtained (see Figure 9 (E)). At this time, the same crystal structure and close lattice determination It is preferable to have a number (mismatch is 1% or less). The oxide semiconductor film 108 is Includes a first oxide semiconductor film and a second oxide semiconductor film. The temperature of the second heat treatment, 45 Second oxidation by setting 0 ° C or higher and 850 ° C or lower, preferably 600 ° C or higher and 700 ° C or lower. The crystal axis in the crystal growth of the material semiconductor film 104a and the crystal of the first oxide semiconductor film 102b Crystal growth (epitaxial) of the second oxide semiconductor film 104a so that the axes are substantially the same. Also called growth or axial growth. ) Can be made. Also, the second oxide semiconduct Body membrane 104a can be epitaxially or axially grown by solid phase growth. ..

Further, in order to specifically explain the steps of FIGS. 9 (C) to 9 (E), FIGS. 12 (A) to 12 (E) are shown. This will be explained using 12 (C).

FIG. 12 (A) shows the first oxide semiconductor film 1 after the first heat treatment for crystallization was performed. It shows 02b. FIG. 12 (A) corresponds to FIG. 9 (C). In addition, Fig. 12 (B) shows It corresponds to FIG. 9D and is a cross-sectional view immediately after the film formation of the second oxide semiconductor film 104a. Further, FIG. 12 (C) corresponds to FIG. 9 (E) and is a cross-sectional view after the second heat treatment. By the second heat treatment, an oxide semiconductor film having a polycrystalline region with higher orientation It becomes 108. In addition, oxidation of the same principal component on the first oxide semiconductor film and the second oxide semiconductor film When a physical semiconductor material is used, as shown in FIG. 12 (C), the first oxide semiconductor film 102b Crystallized upward toward the surface of the second oxide semiconductor film 104b using the crystal region of The second oxide semiconductor film 104b is formed long, and the oxide semiconductor films have the same crystal structure. Have. Therefore, as shown by the dotted line in Fig. 12 (C), the first oxide semiconductor film and the second acid The boundaries of the compound semiconductor film may be obscured. In addition, by the second heat treatment, the film is formed directly. The inside of the second oxide semiconductor film 104b after that is highly purified.

The second heat treatment is for nitrogen, oxygen, or a rare gas such as helium, neon, or argon. Do it in an atmosphere. At this time, nitrogen, oxygen, or a rare gas such as helium, neon, or argon. It is preferable that water, hydrogen, etc. are not contained in the water. Alternatively, nitrogen to be introduced into the heat treatment equipment, Purity of oxygen or rare gas such as helium, neon, argon, 6N or more, preferably 7 It should be N or more (that is, the impurity concentration should be 1 ppm or less, preferably 0.1 ppm or less). preferable. In ultra-dry air with a water content of 20 ppm or less, preferably 1 ppm or less. The second heat treatment may be performed in. In addition, when the temperature rises in the second heat treatment, the inside of the furnace has a nitrogen atmosphere. The atmosphere may be switched by using the surrounding air and the oxygen atmosphere inside the furnace during cooling.

The heat treatment device used for the second heat treatment is not particularly limited, and is it a heating element such as a resistance heating element? A device for heating the object to be processed by heat conduction or heat radiation may be provided. For example , Electric furnaces and RTA devices such as GRTA devices and LRTA devices can be used.

Next, on the oxide semiconductor film 108 composed of the first oxide semiconductor film and the second oxide semiconductor film. After forming a resist mask by a photolithography process, use the resist mask. The oxide semiconductor film 108 is etched to form an island-shaped oxide semiconductor film 107. Further, the resist mask for forming the island-shaped oxide semiconductor film 107 is subjected to an inkjet method. May be formed with. A photomask is used when the resist mask is formed by the inkjet method. Therefore, the manufacturing cost can be reduced. By the etching, the second electrode 109 and the acid The angle between the end of the compound semiconductor film 107 and the first electrode 105 is 30 ° or more and 60 ° or less. By setting the temperature to 40 ° or more and 50 ° or less, the covering property of the gate insulating film formed later is preferable. Is preferable because it can improve.

The etching of the oxide semiconductor film here is wet etching even with dry etching. You may use both. To form an oxide semiconductor film 107 having a desired shape , Etching conditions (etching liquid, etching time, temperature, etc.) are adjusted appropriately according to the material. Clause.

Here, the case where the etching rates of the oxide semiconductor film and the first electrode 105 are different. In that case, the etching rate of the first electrode 105 is low, and the etching rate of the oxide semiconductor film is low. Select a high condition.

Phosphoric acid, acetic acid, and nitric acid are mixed as an etching solution for wet etching the oxide semiconductor film. Freeze solution, overwater ammonia (31 wt% hydrogen peroxide solution: 28 wt% ammonia water: water = 5 : 2: 2) etc. can be used. Also, even if ITO07N (manufactured by Kanto Chemical Co., Inc.) is used. Good.

In addition, the etching solution after wet etching is washed together with the etched material. Is removed. Purify the waste liquid of the etching solution containing the removed material, and use the contained material. It may be reused. Indium contained in the oxide semiconductor film from the waste liquid after etching. By collecting and reusing which materials, resources can be effectively used and costs can be reduced. To.

Further, the etching gas used for the dry etching of the oxide semiconductor film contains chlorine. Gas (chlorine-based gas, for example chlorine (Cl)₂), Boron chloride (BCl)₃), Silicon chloride (SiCl)₄), Carbon tetrachloride (CCl₄) Etc.) are preferable.

In addition, a gas containing fluorine (fluorine-based gas, for example, carbon tetrafluoride (CF)₄), Sulfur hexafluoride (S) F₆), Nitrogen trifluoride (NF₃), Trifluoromethane (CHF)₃) Etc.), hydrogen bromide (H Br), oxygen (O₂), These gases are rare gases such as helium (He) and argon (Ar). Gas with added gas, etc. can be used.

As a dry etching method, parallel plate type RIE (Reactive Ion Etch) ing) method and ICP (Inductively Coupled Plasma: induction A coupled plasma) etching method can be used. Can be etched to the desired processing shape Etching conditions (the amount of power applied to the coil type electrode, applied to the electrode on the substrate side) Adjust the amount of power generated, the electrode temperature on the substrate side, etc.) as appropriate.

Next, on the insulating film, the first electrode 105, and the island-shaped oxide semiconductor film 107, and later on the second electric current. A conductive film 110 that becomes a pole 109 is formed (see FIG. 10 (A)). The conductive film 110 was later added to the second It becomes the electrode 109 of 2. The conductive film 110 appropriately uses the material and method of the first electrode 105. However, by using a material with a faster etching rate than the first electrode 105, later The etching process becomes easy.

Next, after forming a resist mask on the conductive film 110 by a photolithography process, the present The conductive film 110 is etched with the resist mask to form the second electrode 109. (See Figure 10 (B).).

In the present embodiment, superwater ammonia water (ammonia, water, hydrogen peroxide) is used as an etchant. The conductive film to be the second electrode 109 is etched with a mixed solution of water), and the second electrode 1 Form 09.

The etching of the conductive film 110 here is wet etching even if it is dry etching. However, both may be used. A material to form a second electrode 109 of the desired shape Etching conditions (etching liquid, etching time, temperature, etc.) are adjusted appropriately according to ..

Next, as shown in FIG. 10 (C), the first electrode 105, the oxide semiconductor film 107, and the second electric current are used. A gate insulating film 111 is formed on the pole 109.

Oxide semiconductor film i-shaped or substantially i-shaped by removing impurities (hydrogen concentration) Oxide semiconductor film with reduced degree and high purity) is extremely sensitive to interface states and interfacial charges. Therefore, the interface with the gate insulating film 111 is important. Therefore, highly purified oxides The gate insulating film 111 in contact with the semiconductor film is required to have high quality.

For example, dense plasma withstand voltage by high-density plasma CVD using μ wave (2.45GHz) It is preferable because it can form a high-quality insulating film with high quality. Acid with reduced hydrogen concentration and high purity The interface state is reduced and the interface characteristics are reduced by the close contact between the compound semiconductor film and the high-quality gate insulating film. This is because the sex can be made good. Also obtained by high-density plasma CVD Since the resulting insulating film can form a film having a constant thickness, it is excellent in step covering property. Also high The insulating film obtained by density plasma CVD can precisely control the thickness of the thin film. To.

Of course, if a good quality insulating film can be formed as a gate insulating film, sputtering Other film forming methods such as the method and the plasma CVD method can be applied. Also, of the gate insulation film The heat treatment after formation modifies the film quality of the gate insulating film and the interface characteristics with the oxide semiconductor film. It may be an insulating film. In any case, the film quality as a gate insulating film is good. Of course, those that can reduce the interface level density with the oxide semiconductor film and form a good interface. If it is good.

In addition, 85 ° C, 2 × 10⁶V / cm, 12 hour gate bias / thermal stress test (B) In the T test), if impurities are added to the oxide semiconductor film, the impurities and oxide semiconducting The bond with the main component of the body membrane is broken by a strong electric field (B: bias) and high temperature (T: temperature). The generated unpaired coupling will induce a drift of the threshold voltage (Vth).

On the other hand, impurities of the oxide semiconductor film, especially hydrogen and water, are removed as much as possible, as described above. Stable transition even for BT test by improving the interface characteristics with the gate insulating film It is possible to get a star.

By forming the gate insulating film 111 by the sputtering method, the hydrogen concentration in the gate insulating film 111 The degree can be reduced. When forming a silicon oxide film by the sputtering method , Use a silicon target or quartz target as the target, and use it as a sputter gas. Oxygen or a mixed gas of oxygen and argon is used.

A halogen element (for example, fluorine or Gas atmosphere containing halogen elements with chlorine) impregnated or the oxide semiconductor film exposed Halogen element is impregnated in the oxide semiconductor film by plasma treatment in the air, and the oxide semiconductor film Alternatively, hydrogen, water, or water that may exist at the interface with the insulating film provided in contact with the oxide semiconductor film. Impurities such as acid groups or hydrides (also referred to as hydrogen compounds) may be eliminated. C on the insulating film When a logen element is included, the halogen element concentration in the insulating film is 5 × 10.¹⁸cm^-3~1×10²⁰cm^-3It should be about.

Further, as described above, the oxide semiconductor film or the oxide semiconductor film and the insulating film in contact with the oxide semiconductor film An insulating film that contains a halogen element at the interface and is provided in contact with the oxide semiconductor film is an oxide insulating film. If this is the case, cover the oxide insulating film on the side that does not come into contact with the oxide semiconductor film with a nitrogen insulating film. Is preferable. That is, silicon nitride is in contact with the oxide insulating film in contact with the oxide semiconductor film. A film or the like may be provided. With such a structure, hydrogen, water, hydroxyl groups or hydrogenation It is possible to reduce the invasion of impurities such as substances into the oxide insulating film.

The gate insulating film 111 includes a first electrode 105, an oxide semiconductor film 107, and a second electrode 10. It is also possible to have a structure in which a silicon oxide film and a silicon nitride film are laminated from the 9 side. For example Silicon oxide film (SiO) with a film thickness of 5 nm or more and 300 nm or less as the first gate insulating film_x( x&gt; 0)) is formed and sputtered as a second gate insulating film on the first gate insulating film. Silicon nitride film (SiN) with a thickness of 50 nm or more and 200 nm or less by the method_yProduct (y&gt; 0)) It may be layered to form a gate insulating film having a film thickness of 100 nm. In this embodiment, the pressure is 0.4P a, high frequency power supply 1.5kW, oxygen and argon (oxygen flow rate 25sccm: argon flow rate 2) 5sccm = 1: 1) Sirico oxide with a film thickness of 100 nm by RF sputtering in an atmosphere Form a film.

Further, before forming the gate insulating film 111, the inner wall of the sputtering apparatus, the target surface, and the like. Preheat to remove residual water or hydrogen in the target material Is preferable. After preheating, cool the substrate or sputtering equipment and then the atmosphere. The gate insulating film 111 is formed without touching. Nitrogen is introduced and exhausted without heating A certain effect can be obtained even if it is returned, but it is better to perform it while heating.

Next, a third heat treatment (preferably 200 ° C.) is performed in an inert gas atmosphere or an oxygen gas atmosphere. More than 400 ° C or less, for example, 250 ° C or more and 350 ° C or less) may be performed. For the heat treatment By supplying oxygen to the oxygen defects generated in the first heat treatment and the second, it becomes a donor. Oxygen defects can be further reduced, and the composition can satisfy the stoichiometric ratio, and the oxide semiconducting can be achieved. The body membrane 107 can be more i-shaped or substantially i-shaped. In addition, the third addition The heat treatment is performed on the third electrode 113, the insulating film 117, or the wiring 125, 12 which is formed later. It may be done after forming any of 9. By the heat treatment, it is contained in the oxide semiconductor film. The hydrogen or water contained in it can be diffused into the gate insulating film.

Next, a third electrode 113 that functions as a gate electrode is formed on the gate insulating film 111.

The third electrode 113 sputters a conductive film to be the third electrode 113 on the gate insulating film 111. Formed by ring method, CVD method, or vacuum deposition method, and photolithography is performed on the conductive film. A resist mask is formed according to the procedure, and the conductive film is etched using the resist mask. Can be formed.

In the above steps, a tran having an oxide semiconductor film 107 having a reduced hydrogen concentration and high purity. Gista 145 can be made.

Next, as shown in FIG. 11 (A), an insulating film is formed on the gate insulating film 111 and the third electrode 113. After forming 117, contact holes 119 and 123 are formed.

The insulating film 117 is a silicon oxide film, a silicon nitride film, an aluminum oxide film, or an acid. Oxide insulating film such as aluminum nitride film, silicon nitride film, silicon nitride film, nitride A nitride insulating film such as an aluminum film or an aluminum nitride oxide film is used. Or It is also possible to laminate an oxide insulating film and a nitride insulating film.

The insulating film 117 is formed by a sputtering method, a CVD method, or the like. The sputtering method When forming the insulating film 117 with hydrogen, the substrate 101 is heated to a temperature of 100 ° C to 400 ° C and hydrogen is used. , Water, hydroxyl group, hydride, etc. are removed, and sputter gas containing high-purity nitrogen is introduced. An insulating film may be formed by using a target of a recon semiconductor. Even in this case, processing Forming an insulating film while removing hydrogen, water, hydroxyl groups, hydrides, etc. remaining in the room. Is preferable.

After the insulating film 117 is formed, the temperature is 100 ° C or higher and 200 ° C or lower for 1 hour or longer in the atmosphere. The heat treatment may be carried out for 30 hours or less. This heat treatment turns off the normal Transistors can be obtained. Therefore, the reliability of display devices and semiconductor devices can be improved. ..

Contact holes 119 and 123 form a resist mask by a photolithography process. Then, selectively etching is performed to remove a part of the gate insulating film 111 and the insulating film 117. The contact lens reaches the first electrode 105, the second electrode 109, and the third electrode 113. Form 119 and 123.

Next, a conductive film was formed on the gate insulating film 111 and the contact holes 119 and 123. After that, it is etched using a resist mask formed by the photolithography process and arranged. It forms lines 125, 129, 131 (see Figure 11 (B)). In addition, the resist mask is a It may be formed by the ink jet method. When the resist mask is formed by the inkjet method, Since no tomask is used, manufacturing costs can be reduced.

Wiring 125, 129, 131 can be formed in the same manner as the first electrode 105.

It should be noted that flattening is cut off between the third electrode 113 and the wirings 125, 129, 131 for flattening. A marginal membrane may be provided. Typical examples of flattening insulating film are polyimide, acrylic, and benzosi. Heat resistant organic materials such as clobutene, polyamide and epoxy can be used. To. In addition to the above organic materials, low dielectric constant materials (low-k materials), siloxane-based resins, and P There are SG (phosphorus glass), BPSG (phosphorus glass), etc. In addition, with these materials A flattening insulating film may be formed by laminating a plurality of formed insulating films.

The siloxane-based resin is Si-OS formed from a siloxane-based material as a starting material. Corresponds to a resin containing an i-bond. Siloxane resins have organic groups (for example, Archi) as substituents. Lu group or aryl group) or fluoro group may be used. In addition, the organic group has a fluoro group. You may.

The method for forming the flattening insulating film is not particularly limited, and depending on the material, a sputtering method or SO G method, spin coating, dip, spray coating, droplet ejection method (injection method, screen) Printing, offset printing, etc.), doctor knife, roll coater, curtain coater , Knife coater and the like can be used.

As described above, the concentration of hydrogen in the oxide semiconductor film is reduced, the purity is increased, and the crystallinity is enhanced. be able to. Thereby, the oxide semiconductor film can be stabilized. Also, glass rolling Oxide semiconduct with extremely low carrier density and wide bandgap by heat treatment below the transfer temperature It can form a body membrane. Therefore, a transistor can be manufactured using a large area substrate. Therefore, mass productivity can be improved. In addition, the hydrogen concentration is reduced and the purity is increased. By using the oxide semiconductor film, the pressure resistance is high, the short channel effect is low, and so on. A transistor with a high on-off ratio can be manufactured.

This embodiment can be implemented in combination with the configurations described in other embodiments as appropriate. Is.

(Embodiment 7) In the present embodiment, FIGS. 9 and 9 show a method for manufacturing a transistor different from that in the sixth embodiment. This will be described using 13. In the present embodiment, the step of forming the conductive film to be the second electrode 109 is Different from embodiment 6.

Insulation on the substrate 101 through the steps of FIGS. 9 (A) to 9 (D) as in the sixth embodiment. The film 103, the first electrode 105, and the first heat treatment have at least a polycrystalline region on the surface. The first oxide semiconductor film 102b and the second oxide semiconductor film 104a are formed.

Next, as shown in FIG. 13 (A), the second electrode 10 is placed on the second oxide semiconductor film 104a. The conductive film 110 which becomes 9 is formed. Here, the conductive film 110 has a melting point of 1000 ° C or higher. Use the above metal elements. Typical examples of the conductive film 110 are molybdenum, tungsten, and chi. Tan, tantalum, niobium, iridium, vanadium, chromium, zirconium, platinum, para There are gium, scandium, iron, yttrium, cobalt, nickel, manganese and gold.

Next, a second heat treatment is performed to grow crystals in the polycrystalline region of the first oxide semiconductor film 102b. Crystal growth is performed as a seed. The temperature of the second heat treatment is 450 ° C or higher and 850 ° C or lower, which is preferable. Or 600 ° C or more and 700 ° C or less. Second oxide semiconductor film by the second heat treatment 1 04a can be crystallized to obtain an oxide semiconductor film 108.

Next, after forming a resist mask on the conductive film 110 by a photolithography process, the present The conductive film 110 is etched with the resist mask to form an island-shaped oxide semiconductor film 107. And the second electrode 109 and are formed (see FIG. 13 (C)).

After that, the transistor 145 goes through the steps of FIGS. 10 (C) to 11 shown in the sixth embodiment. Can be produced.

This embodiment can be implemented in combination with the configurations described in other embodiments as appropriate. Is.

(Embodiment 8) In the present embodiment, a method for manufacturing a transistor different from that of the sixth and seventh embodiments is adopted. This will be described with reference to FIGS. 9 and 14. In the present embodiment, the second oxide semiconductor film The forming process is different from the sixth embodiment and the seventh embodiment.

Similar to the sixth embodiment, it is shown in FIG. 14 (A) through the steps of FIGS. 9 (A) to 9 (C). Thus, on the substrate 101, the insulating film 103, the first electrode 105, and the first heat treatment reduce the amount. Both form a first oxide semiconductor film 102b having a polycrystalline region on the surface.

Next, as shown in FIG. 14 (B), 200 ° C or more and 600 ° C or less, preferably 200 ° C or more. The first oxide semiconductor film 102b by the sputtering method while heating at 550 ° C or lower. A second oxide semiconductor film 112 is deposited on the film. Here, the first oxide semiconductor film 102b The direction of the first oxide semiconductor film 102b and the crystal axis, using the polycrystalline region on the surface as the seed for crystal growth. Crystal growth (epitaxial growth) so that they are the same, especially so that the directions of the c-axis are the same. Also known as axial growth. ), The second oxide semiconductor film 112 is deposited. This As a result, the direction of the c-axis is the same as that of the first oxide semiconductor film 102b without performing the second heat treatment. It is possible to form the crystallized oxide semiconductor film 108 which is one. Oxide semiconductor The film includes a first oxide semiconductor film 102b and a second oxide semiconductor film 112.

After that, the transistor 145 is manufactured through the steps of the sixth embodiment or the seventh embodiment. be able to.

In the present embodiment, the number of heat treatments can be reduced, so that the throughput is improved. Can be made.

This embodiment can be implemented in combination with the configurations described in other embodiments as appropriate. Is.

(Embodiment 9) In the present embodiment, the forms different from the sixth to eighth embodiments are shown below using FIG. explain.

In this embodiment, an example in which the first oxide semiconductor film 102a has a film thickness of 15 nm is shown.

When the first oxide semiconductor film 102a has a film thickness of 15 nm, the first oxide semiconductor film 10 It depends on the material of 2a and the first electrode 105, which is the base member, and the conditions such as heating temperature and heating time. However, even if crystals grow from the surface of the first oxide semiconductor film 102b by the first heat treatment, there are many cases. The tip of the crystal region 151 does not reach the interface of the first electrode 105, and the amorphous region 153 remains. (See Figure 15 (A)).

Next, FIG. 15 (B) shows the second oxide semiconductor film 10 on the first oxide semiconductor film 102b. It is sectional drawing immediately after forming 4a.

Then, after forming the second oxide semiconductor film 104a, the second heat treatment is performed. Second addition By heat treatment, in the first oxide semiconductor film 102b, at the interface with the first electrode 105. The first oxide semiconductor film 10 in which crystal growth progresses downward and reaches the first electrode 105 It becomes 2c. The same applies to the first oxide semiconductor film 102c and the second oxide semiconductor film 104b. When a one-main component oxide semiconductor material is used, as shown in FIG. 15 (C), the first oxide half The surface of the second oxide semiconductor film 104b using the polycrystalline region of the conductor film 102b as a seed for crystal growth. A second oxide semiconductor film 104b is formed by crystal growth upward toward the same crystal structure. The oxide semiconductor film 108 having the above is formed. Therefore, it is shown by the dotted line in Fig. 15 (C). However, the boundary between the first oxide semiconductor film 102c and the second oxide semiconductor film 104b is unclear. May become.

In the present embodiment, the first oxide semiconductor film 102b and the second oxide semiconductor film 104 Crystal growth in the upward direction and at the same time in the downward direction with reference to the interface of a. Can be done.

Further, the first heat treatment condition and the second heat treatment condition are the same as the condition range described in the sixth embodiment. To do. When the heating temperature of the second heat treatment is higher than that of the first heat treatment, or the heating time is longer. In such cases, the surface of the second oxide semiconductor film 104a is simply exposed to the surface during the second heat treatment. Crystalline regions may be formed. A single crystal region is formed on the surface of the second oxide semiconductor film 104a. If the formation affects the transistor characteristics, etc., the second oxide semiconductor film 10 The practitioner may appropriately select the conditions under which the single crystal region is not formed on the surface of 4b.

Further, in the above description, an example in which the first oxide semiconductor film has a film thickness of 15 nm is shown, but in particular, Not limited, even when the first oxide semiconductor film 102b has a film thickness of 10 nm or less. If the temperature of the first heat treatment is lowered or the heating time is shortened, the first oxide semiconductor Amorphous region 153 remains between the polycrystalline region 151 of the film 102b and the first electrode 105. be able to. After that, the single crystal region reaching the first electrode 105 by the second heat treatment is formed. Once formed, the state shown in Fig. 15 (C) can be obtained. Therefore, the steps shown in this embodiment are , It is also possible to lower the temperature of the first heat treatment and shorten the heating time.

Moreover, this embodiment can be freely combined with other embodiments.

(Embodiment 10) Embodiments 6 to 9 are the same as the first oxide semiconductor film and the second oxide semiconductor film. The case where an oxide semiconductor material as a main component is used has been shown, but in the present embodiment, oxidation of different components is shown. The case where a semiconductor material is used is shown. Since FIG. 16 (A) is the same as FIG. 9 (A), The same parts will be described using the same reference numerals.

In this embodiment, a metal oxide target of In: Zn = 1: 1 [atomic ratio] containing no Ga. An example is shown in which the first oxide semiconductor film has a film thickness of 5 nm.

Similar to Embodiment 6, the first addition for crystallization on the insulating film 103 and the first electrode 105. The first oxide semiconductor film 102b after the heat treatment is shown in FIG. 16 (A). In addition, Fig. 1 Since 6 (A) is the same as FIG. 9 (A), the same parts will be described using the same reference numerals.

Then, the first heat treatment is performed. Material and heating of the first oxide semiconductor film and the first electrode 105 Although it depends on conditions such as temperature and heating time, crystals are grown from the surface by the first heat treatment. A first oxide semiconductor film 102b, which is polycrystalline, is formed up to the interface of the first electrode 105 ( See Figure 16 (A). ).

The first oxide semiconductor film 102b having a polycrystalline region having a relatively uniform crystal orientation on the surface is shown in the table. Crystals grow vertically from the plane. Further, the first oxide semiconductor film 102b is applied to the surface. It is vertically oriented on the c-axis.

Next, FIG. 16 (B) shows the second oxide semiconductor film 16 on the first oxide semiconductor film 102b. It is sectional drawing immediately after film formation of 1a. A second oxide semiconductor film is placed on the first oxide semiconductor film. When forming, a metal having a composition ratio of In: Ga: Zn = 0 or more and 2 or less: 1 or more and 5 or less It is characterized by using an oxide target. In this embodiment, the second oxide semiconducting In-Ga-Zn-O oxide semiconductor target (In: Ga: Z) as body membrane 161a Using n = 1: 1: 1 [atomic ratio])), form an In-Ga-Zn-O film with a film thickness of 1 μm. ..

Then, after forming the second oxide semiconductor film 161a, the second heat treatment is performed. Second addition Crystal growth is carried out by heat treatment as shown in FIG. 16 (C). As shown in Fig. 16 (C) , Using the polycrystalline region of the first oxide semiconductor film 102b as a seed on the surface of the second oxide semiconductor film A second oxide semiconductor film 161b can be formed by crystal growth toward the upper side.

Further, the first oxide semiconductor film 102b obtained by the first heat treatment is again subjected to the second heat treatment. Since it is heated, it becomes the first oxide semiconductor film 102c having further improved crystallinity.

Oxidation of components different from the first oxide semiconductor film 102b as the second oxide semiconductor film 161a Since a material semiconductor material is used, as shown in FIG. 16 (C), the first oxide semiconductor film 102c The boundary between the second oxide semiconductor film 161b and the second oxide semiconductor film 161b is formed. Also by the second heat treatment , Most of the first oxide semiconductor film including the vicinity of the interface of the first electrode 105 is a polycrystalline region. ..

The structure of FIG. 16 (C) is such that the first oxide semiconductor film 102c, which is in contact with the first electrode 105, It can be said that it is a two-layer structure in which the oxide semiconductor films 161b of 2 are laminated in this order. In-Ga-Zn-O By using an In-Zn-O film, which is easier to crystallize than a film, and using it as a seed for crystal growth, it can be done efficiently. Crystal growth can be carried out in the upward direction to make the In-Ga-Zn-O film a polycrystalline region. Further, a band gear between the first oxide semiconductor film 102c and the second oxide semiconductor film 161b You can change the output.

Further, the first heat treatment condition and the second heat treatment condition are the same as the condition range described in the sixth embodiment. To do.

Moreover, this embodiment can be freely combined with other embodiments.

(Embodiment 11) In the present embodiment, a method of manufacturing a semiconductor device having a high yield will be described with reference to FIG. To do.

As shown in FIG. 17 (A), the insulating film 103 is formed on the substrate 101, and the insulating film 103 is formed on the insulating film 103. Form the electrode 105 of 1. Next, a protective film 165 is formed on the first electrode 105. protection The film 165 is used to improve the adhesion between the first electrode 105 and the oxide semiconductor film to be formed later. Provided in. Also, in the process of forming the oxide semiconductor film, it is installed to prevent oxidation of the first electrode 105. Kake.

The protective film 165 is preferably formed of a metal nitride film having a thickness of 1 nm or more and 100 nm or less. It is typically formed of a titanium nitride film or a tantalum nitride film.

Next, by forming the first oxide semiconductor film 102a, the first oxide semiconductor film 102a It is possible to reduce the peeling of the film. In addition, oxidation of the first electrode 105 can be prevented. To.

After that, by performing any of the steps of the sixth embodiment to the tenth embodiment, the semiconductor device Can be produced.

(Embodiment 12) A description of a mode using a circuit having a semiconductor element shown in the first to eleventh embodiments. I will reveal.

A transistor and a capacitor, which are one form of the semiconductor element shown in the first to eleventh embodiments. Iode has a high on / off ratio, high pressure resistance, and little deterioration, so it can be used in air conditioners, refrigerators, and cooking. Home appliances that apply inverter technology such as rice bowls and solar power generation systems, notebook computers Battery-powered personal digital assistants such as data, power amplifiers such as strobes, and electric power Ki car, DC / DC (direct current / direct current) converter circuit, motor control circuit, audio amplification It can be used for instruments, logic circuits, switch circuits, high-frequency linear amplifiers, and the like.

Here, an Invar configured by using the semiconductor elements shown in the first to eleventh embodiments. An example of a photovoltaic power generation system equipped with a solar power generation system will be described with reference to FIG. In addition, here Then, an example of the configuration of the photovoltaic power generation system installed in a house or the like will be shown.

The residential photovoltaic power generation system shown in Fig. 18 is a method of supplying electricity according to the status of photovoltaic power generation. It is a system that changes expressions. For example, in situations where solar power is generated, such as in fine weather. , The electricity generated by solar power generation is consumed in the home, and the surplus electricity is distributed from the electric power company. Supply to line 414. On the other hand, distribution lines at night or in the rain when the power generated by solar power is insufficient. It receives electricity from 414 and consumes it at home.

The residential photovoltaic power generation system shown in Fig. 18 is a solar cell that converts sunlight into electric power (direct current). It includes a panel 400 and an inverter 404 that converts its power from direct current to alternating current. Inn The AC power output from the Verta 404 is used as the power to operate various electric appliances 410. used.

The extra power is supplied to the outside of the home through the distribution line 414. That is, the system is used. It is possible to sell electricity using it. The DC switch 402 is a solar panel 400 and an Invar. It is provided to select the connection or disconnection with the 404. Also, AC switch 408 Selects the connection or disconnection between the transformer 412 connected to the distribution line 414 and the distribution board 406. It is provided for selection.

By applying the semiconductor device of the disclosed invention to the above inverter, it is highly reliable and inexpensive. It is possible to realize a solar power generation system.

The configurations, methods, etc. shown in this embodiment may be used in combination with other embodiments as appropriate. it can.

<p>In this example, the result of photographing the cross section of the oxide semiconductor film crystallized by heat treatment with TEM is taken. This will be described with reference to FIGS. 19 and 20.</p><p>First, a method for producing sample A will be described below.</p><p>A silicon oxide nitride film (SiON) was formed on a glass substrate by a CVD method. Next, acid An In-Ga-Zn-O film (OS) having a thickness of 5 nm was formed on the silicon nitriding film. With this Oxide semiconductor target (In-Ga-Zn-O based oxide semiconductor target (In)₂O₃: Ga₂O₃: ZnO = 1: 1: 2 [mol number ratio], In: Ga: Zn = 1: 1: 1 [Atomic ratio])), the substrate temperature is 200 ° C, the film formation rate is 4 nm / min, and the tar The get was sputtered to form an In-Ga-Zn-O film. The above oxide half InGaZnO when using a conductor target₄Crystals are easy to obtain. Next, In-Ga A protective film was formed on the -Zn-O film. Next, In-Ga-Zn formed on the glass substrate Sample A was a -O film that had been heat-treated at 700 ° C for 1 hour in a dry air atmosphere.</p><p>A TEM photograph of a cross section of sample A is shown in FIG. 19 (A), and a schematic diagram of FIG. 19 (A) is shown in FIG. Shown in 9 (B). The TEM photograph shows a high-resolution transmission electron microscope with an acceleration voltage of 300 kV. High-magnification photograph (8 million times) observed with a microscope (Hitachi "H9000-NAR": TEM) ). The In-Ga-Zn-O film should be c-axis oriented perpendicular to the surface. , The vicinity of the interface between the silicon oxide nitriding film and the In-Ga-Zn-O film is also crystallized, and the surface is It can be confirmed that the c-axis is oriented in the vertical direction. That is, an acid having a flat polycrystalline region A compound semiconductor film is formed. The elements of adjacent planes on the ab plane are the same. To. Further, the c-axis direction of the flat plate-shaped polycrystalline region coincides with the direction perpendicular to the surface.</p><p>Next, a method for producing sample B, which is a comparative example, will be described below.</p><p>A silicon oxide nitride film (SiON) was formed on a glass substrate by a CVD method. Next, acid In-Ga-Zn-O with a thickness of 50 nm on the silicon nitriding film under the same conditions as sample A. A film was formed. Next, a protective film was formed on the In-Ga-Zn-O film. Next, the dry air atmosphere Sample B was obtained by heating at 700 ° C. for 1 hour in the surrounding air.</p><p>A TEM photograph of a cross section of sample B is shown in FIG. 20 (A), and a schematic diagram of FIG. 20 (A) is shown in FIG. Shown in 0 (B). The TEM photograph shows a high-resolution transmission electron microscope with an acceleration voltage of 300 kV. High-magnification photograph (2 million times) observed with Hitachi "H9000-NAR": TEM) To. About 5 nm crystallizes from the surface of the In-Ga-Zn-O film, and In-Ga-Zn-O Many amorphous parts and multiple crystals with non-alignment are randomly present inside the film. You can see how it is. Therefore, it is higher than 650 ° C after forming a thick film with a thickness of 50 nm. High orientation across thick film thicknesses, even with a single 1-hour heat treatment at 700 ° C, longer than 6 minutes It can be said that it is difficult to make a single crystal region having.</p><p>Based on the results of these experiments, the oxide semiconductor film is formed in two steps, which serves as a seed for crystal growth. After forming a polycrystalline region, the crystal is grown again after forming a film again to form a thick polycrystalline region. It can be said that the method disclosed herein is extremely useful. To. Polycrystals with high orientation can only be formed by forming a film in two steps and then performing two heat treatments. A polycrystalline region that is c-axis oriented perpendicular to the surface of the region, that is, the flat polycrystalline region. The area can be obtained thickly.</p>

101 board 102a First oxide semiconductor film 102b First oxide semiconductor film 102c First oxide semiconductor film 103 Insulating film 104a Second oxide semiconductor film 104b Second oxide semiconductor film 105 1st electrode 107 Oxide semiconductor film 108 Oxide semiconductor film 109 Second electrode 110 Conductive film 111 Gate insulation film 112 Second oxide semiconductor film 113 Third electrode 117 Insulation film 119 Contact hole 125 wiring 129 Wiring 131 Wiring 145 transistor 147 transistor 149a 3-terminal diode 149b 3-terminal diode 151 Polycrystalline region 153 Amorphous region 161a Second oxide semiconductor film 161b Second oxide semiconductor film 165 Protective film 400 solar panel 402 DC switch 404 inverter 406 Distribution board 408 AC switch 410 Electric appliances 412 transformer 414 Distribution line