Semiconductor film, semiconductor device and method of forming it

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a method for producing a semiconductor film having an amorphous structure by a sputtering method, a semiconductor device having a circuit composed of a thin film transistor (hereinafter referred to as TFT) using the semiconductor film, and a method for producing the same. For example, the present invention relates to an electro-optical device typified by a liquid crystal display panel and an electronic device equipped with such an electro-optic device as a component.

【0002】

In the present specification, the semiconductor device refers to all devices that can function by utilizing the semiconductor characteristics, and the electro-optical device, the semiconductor circuit, and the electronic device are all semiconductor devices.

【0003】

[Conventional technology]

A thin film transistor (hereinafter referred to as TFT) is known as a typical semiconductor element using a semiconductor film having a crystal structure. TFTs are attracting attention as a technology for forming integrated circuits on an insulating substrate such as glass, and liquid crystal display devices with integrated drive circuits are being put into practical use. In the conventional technique, the semiconductor film having a crystal structure is an amorphous semiconductor film deposited by a plasma CVD method or a reduced pressure CVD method, which is heat-treated or laser annealed (a technique for crystallizing a semiconductor film by irradiating a laser beam). Is made by.

【0004】

The semiconductor film having a crystal structure thus produced is an aggregate of a large number of crystal grains, and its crystal orientation is oriented in an arbitrary direction and cannot be controlled, which is a factor that limits the characteristics of the TFT. In response to such problems, the technique disclosed in Japanese Patent Application Laid-Open No. 7-183540 is to add a metal element such as nickel that promotes crystallization of a semiconductor film to prepare a semiconductor film having a crystal structure. In addition to the effect of lowering the heating temperature required for crystallization, it is possible to increase the orientation of the crystal orientation in a single direction. Forming a TFT with a semiconductor film having such a crystal structure not only improves the mobility of the electric field effect, but also reduces the subthreshold coefficient (S value), which makes it possible to dramatically improve the electrical characteristics. ing.

【0005】

However, since the metal element that promotes crystallization is added, there is a problem that the metal element remains in the film or the surface of the semiconductor film having a crystal structure, and the characteristics of the obtained element are dispersed. .. One example is the problem that the off-current increases in TFT and varies among individual elements. That is, the metal element that promotes crystallization becomes unnecessary once a semiconductor film having a crystal structure is formed.

【0006】

Gettering using phosphorus is effectively utilized as a method for removing a metal element that promotes crystallization from a specific region of a semiconductor film having a crystal structure. For example, by adding phosphorus to the source / drain region of the TFT and performing a heat treatment at 450 to 700 ° C., the metal element can be easily removed from the channel formation region.

【0007】

[Problems to be Solved by the Invention]

Phosphorus is ion-doped (PH)₃It is a method of dissociating with plasma and accelerating ions with an electric field to inject them into a semiconductor. Basically, it refers to a method of not performing mass separation of ions) to inject into a semiconductor film having a crystal structure. The phosphorus concentration required for gettering is 1 x 10²⁰/cm³That is all. Addition of phosphorus by the ion doping method causes amorphization of the semiconductor film having a crystal structure, but an increase in phosphorus concentration hinders recrystallization by subsequent annealing, which is a problem. In addition, the addition of a high concentration of phosphorus causes an increase in the treatment time required for doping and reduces the throughput in the doping process, which is a problem.

【0008】

Furthermore, the concentration of boron required to invert the conductive type of phosphorus added to the source / drain region of the p-channel type TFT needs to be 1.5 to 3 times, which is associated with the difficulty of recrystallization. , It causes a high resistance in the source / drain region, which is a problem.

【0009】

The present invention is a means for solving such a problem, and after obtaining a semiconductor film having a crystal structure by using a metal element that promotes crystallization of the semiconductor film, the metal element remaining in the film is used. The purpose is to provide a technique for effective removal.

【0010】

[Means for solving problems]

Gettering technology is positioned as a major technology in the manufacturing technology of integrated circuits using single crystal silicon wafers. Gettering is known as a technique for reducing the concentration of impurities in the active region of an element by segregating metal impurities incorporated in a semiconductor into gettering sites with some energy. It is roughly divided into two types: Extrinsic Gettering and Intrinsic Gettering. Extrinsic gettering gives a strain field or chemical action from the outside to bring about a gettering effect. Gettering that diffuses high-concentration phosphorus from the back surface of a single crystal silicon wafer corresponds to this, and the above-mentioned gettering using phosphorus can also be regarded as a kind of extralinthic gettering.

【0011】

On the other hand, intrinsic gettering is known to utilize the strain field of lattice defects in which oxygen generated inside a single crystal silicon wafer is involved. The present invention focuses on intrinsic gettering utilizing such lattice defects or lattice strain, and employs the following means for application to a semiconductor film having a crystal structure having a thickness of about 10 to 100 nm. Is what you do.

【0012】

The present invention comprises a step of forming a first semiconductor film having a crystal structure on an insulating surface using a metal element, a step of forming a film (barrier layer) serving as an etching stopper, and a second step containing a rare gas element. It has a step of forming a semiconductor film (gettering site), a step of getting a metal element at the gettering site, and a step of removing the second semiconductor film.

【0013】

In the present invention, as a step of forming the gettering site, a target made of a semiconductor is used, a film is formed by a sputtering method by glow discharge in an atmosphere containing a rare gas element, and the rare gas element is contained in a high concentration. A semiconductor film having an amorphous structure, typically an amorphous silicon film. Further, a semiconductor target (specific resistance value of 0.01 to 1000 Ω · cm) containing an impurity element (phosphorus, arsenic, boron, etc.) that imparts a monoconductive type to the semiconductor may be used. Further, a target made of silicon, silicon germanium, or silicon carbide is used corresponding to the semiconductor film having an amorphous structure to be formed. Of course, when forming a silicon compound, a silicon target and a target of the element may be placed side by side and formed by co-sputtering, or a reactive gas containing the element may be introduced and reactive sputtering may be performed. good.

【0014】

In addition, the concentration of rare gas elements in the film is higher when the film is formed by the RF sputtering device than when the film is formed by the DC sputtering device, specifically, 1 × 10.²⁰/cm³It can be included in the above.

【0015】

The configuration of the invention relating to the method for producing a semiconductor film disclosed in the present specification is a sputtering method in which a rare gas is introduced into a film forming chamber at a film forming pressure of 0.1 Pa to 5 Pa and a glow discharge is generated by applying an AC electric field. , Rare gas element 1 × 10¹⁹/cm³~1×10²²/cm³This is a method for producing a semiconductor film having an amorphous structure, which comprises forming a semiconductor film having an amorphous structure on a surface to be coated with. The lower the film forming pressure in the film forming chamber, the higher the concentration of the rare gas element in the film.

【0016】

Further, in the above configuration, the RF power density for generating the glow discharge is 0.137 W / cm.²~ 6.847W / cm²(When an electrode with a diameter of 30.5 cm is used, the RF power is 0.1 kW to 5 kW). The smaller the RF power density, the higher the concentration of the rare gas element in the film.

【0017】

In the above configuration, it is preferable that the film forming chamber performs film forming at a film forming pressure of 1.5 Pa or less. Further, high frequency power of 1 kHz to 30 MHz, preferably 10 to 20 MHz is applied to excite the glow discharge. Further, the temperature of the substrate may be room temperature, and there is no problem if the temperature is 300 ° C or less.

【0018】

Atoms sputtered by a rare gas element obtain kinetic energy and scatter, and a part of the atoms adhere to the substrate to form a film. By lowering the film formation pressure, the probability that the atoms sputtered in the gas phase collide with the rare gas element is reduced, and high-energy atoms are incident on the substrate and deposited. It is considered that the high-frequency discharge increases the electron energy, increases the number of excited rare gas atoms and ionized rare gas elements, and increases the interaction on the growth surface of the film. As a result, the probability that the rare gas element is incorporated into the film increases, and it becomes possible to form a semiconductor film containing the rare gas element at the above concentration and having an amorphous structure.

【0019】

Further, in the above configuration, the rare gas is characterized in that it is one or more kinds selected from He, Ne, Ar, Kr, and Xe. In particular, a rare gas element having an atomic radius larger than that of silicon, typically Ar, is desirable.

【0020】

The semiconductor film obtained by the above manufacturing method is 1 × 10 in the film.¹⁹/cm³~1×10²¹/cm³It is a semiconductor film having an amorphous structure, which contains a rare gas element at the concentration of the above, and the internal stress of the film is compressive stress. The lower the film forming pressure in the film forming chamber in the film formation, the larger the internal stress of the film, and the smaller the RF power density, the smaller the internal stress of the film.

【0021】

By adding a rare gas element to the amorphous semiconductor film at the above concentration, strain can be imparted to the semiconductor film. The density of the amorphous silicon film is about 5 × 10²²/cm³Therefore, a strain field is formed by adding 0.25 atomic% or more of argon. Rare gas elements such as argon distort the atomic position of silicon by being inserted into the lattice without binding to silicon, and generate internal stress. Since the stress is in the direction in which the atoms repel each other, it becomes a compressive stress.

【0022】

Generally, internal stress includes tensile stress and compressive stress. When the thin film tries to shrink with respect to the substrate, the substrate is deformed with the thin film inside in order to pull in a direction that hinders it, and this is called tensile stress. On the other hand, when the thin film tries to stretch, the substrate is compressed to form the thin film on the outside, which is called compressive stress. In the present specification, the compressive stress is represented by minus (-) and the tensile stress is represented by plus (+).

【0023】

If a semiconductor film having a strain and an amorphous structure thus obtained is applied as a gettering site, a high gettering ability can be obtained. Alternatively, if it is used as an active region (active layer) of the device, the mobility of electrons and holes can be improved.

【0024】

The configuration of the invention relating to the method for manufacturing a semiconductor device disclosed in the present specification includes a first step of forming a first semiconductor film having an amorphous structure on an insulating surface and a first step having the amorphous structure. A second step of adding a metal element to the semiconductor film, a third step of crystallizing the first semiconductor film to form a first semiconductor film having a crystal structure, and a first semiconductor having the crystal structure. A fourth step of forming a barrier layer on the surface of the film, a fifth step of forming a second semiconductor film containing a rare gas element on the barrier layer by a sputtering method, and the metal on the second semiconductor film. It is characterized by having a sixth step of removing or reducing the metal element in the first semiconductor film having a crystal structure by gettering the elements, and a seventh step of removing the second semiconductor film. This is a method for manufacturing a semiconductor device.

【0025】

In the above configuration, in the second semiconductor film, a rare gas is introduced into the film forming chamber at a film forming pressure of 0.1 Pa to 5 Pa, and 0.137 W / cm.²~ 6.847W / cm²It is characterized by being formed by a sputtering method that generates glow discharge at the RF power density of.

【0026】

Further, in the above configuration, the metal element is a metal element that promotes crystallization of silicon, and is a kind selected from Fe, Ni, Co, Ru, Rh, Pd, Os, Ir, Pt, Cu, and Au. There are multiple species.

【0027】

Further, in each of the above configurations, the rare gas is one or more kinds selected from He, Ne, Ar, Kr, and Xe, and by containing these ions in the semiconductor film, a dangling bond or a lattice is formed. Strains can be formed to form gettering sites.

【0028】

Further, after obtaining a second semiconductor film containing a rare gas element at the film forming stage by using a sputtering method, the rare gas element, H, H, is further applied to the second semiconductor film.₂, O, O₂, One or more selected from P may be added. By adding a plurality of elements in this way, a gettering effect can be synergistically obtained.

【0029】

As described above, the semiconductor film obtained by the above-mentioned manufacturing method is suitable as a semiconductor film having a strain field for forming a gettering site. Applications of semiconductors with such distortion are not necessarily limited to gettering sites. For example, although the technical fields are different, a strain crystal technology in which stress strain is added has been proposed as a new technology for improving the performance of a transistor. By giving strain to the silicon crystal, it has been confirmed that the mobility of electrons and holes due to the change in the band structure is improved, and it is expected as a new generation technology (Applied Physics, 69 [11] (2000-11)). p.1315-1319). It is conceivable that such technology will be further applied to devices using thin films such as TFTs in the future.

【0030】

The semiconductor device of the present invention is a semiconductor device having an amorphous silicon film, and the concentration of Ar in the amorphous silicon film is 1 × 10.²⁰/cm³Above, preferably 1 × 10²⁰/cm³~6×10²⁰/cm³It is a semiconductor device characterized by being in the range of. The impurity concentration of oxygen, carbon and nitrogen is 5 × 10.¹⁵It is less than / cm3. In the semiconductor device of the present invention, the concentration of Ar in the semiconductor film having an amorphous structure is 1 × 10.²⁰/cm³Since the above is included, a semiconductor device having a distorted amorphous silicon (amorphous silicon) film can be manufactured. In addition, the concentration of Ar in the amorphous silicon film is 1 × 10.²⁰/cm³~6×10²⁰/cm³Therefore, it is possible to manufacture a semiconductor device in which film peeling is unlikely to occur.

【0031】

Further, the semiconductor device of the present invention is a semiconductor device having an amorphous silicon film, and the compressive stress in the amorphous silicon film is -10.0 × 10.¹⁰dynes / cm²~-5.0×10⁹dynes / cm²It is a semiconductor device characterized by being in the range of. In the semiconductor device of the present invention, the compressive stress of the amorphous silicon film is -10.0 × 10.¹⁰dynes / cm²~-5.0×10⁹dynes / cm²Therefore, it is possible to manufacture a semiconductor device having a distorted amorphous silicon (amorphous silicon) film and less likely to cause film peeling.

【0032】

The method for manufacturing a semiconductor device of the present invention is a method for manufacturing a semiconductor device for forming an amorphous silicon film, in which RF (1 kHz to 30 MHz, preferably 10) is used at room temperature (22 to 28 ° C, preferably 25 ° C). This is a method for manufacturing a semiconductor device in which the film forming pressure is maintained in the range of 0.2 to 1.0 Pa by discharging with (~ 20 MHz) and the amorphous silicon film is formed by a sputtering method using a silicon target in an Ar atmosphere. In the method for manufacturing a semiconductor device of the present invention, the discharge and film formation pressure due to RF (1 kHz to 30 MHz, preferably 10 to 20 MHz) are maintained in the range of 0.2 to 1.0 Pa, so that the semiconductor device of the present invention is not present. Ar concentration in the crystalline silicon layer is 1 × 10²⁰/cm²~6×10²⁰/cm²And the compressive stress in the amorphous silicon layer is -10.0 × 10.¹⁰dynes / cm²~-5.0×10⁹dynes / cm²Therefore, it is possible to manufacture a semiconductor device having a distorted amorphous silicon (amorphous silicon) film and less likely to cause film peeling.

【0033】

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described below.

【0034】

In this embodiment, the relationship between the concentration of the rare gas element (Ar) and the film forming pressure in the amorphous silicon film formed by the sputtering method was obtained. The experimental procedure is shown below.

【0035】

An amorphous silicon film containing a rare gas element was formed on a glass substrate by a sputtering apparatus using an RF power source. Using a silicon target, set the frequency to 1kHz to 30MHz, preferably 10 to 20MHz, pass Ar through the film formation chamber, set the RF power (electrode size: 30.5cm in diameter) to 0.1kW to 5kW, here 1.2kW, and set the substrate temperature. Was set to room temperature (22 to 28 ° C, here 25 ° C), and the film was laminated by sequentially changing the film forming pressure every time a film was formed with a thickness of 0.2 μm. The film formation pressure is adjusted by the conductance valve on the exhaust side. The film forming pressure was set to 0.2Pa, 0.4Pa, 0.6Pa, 0.8Pa, 1.0Pa, 1.2Pa on the glass substrate, and the film was formed in order with a thickness of 0.2 μm under each condition, and the film was formed in the film. The atomic concentration of Ar was measured by secondary ion mass spectrometry (SIMS).

【0036】

The results obtained are shown in Fig. 2. In FIG. 2, the vertical axis shows the atomic concentration of Ar, and the horizontal axis shows the depth from the sample surface. In addition, Fig. 2 also shows the ionic strength of silicon, where the vertical axis is the secondary ionic strength and the horizontal axis is the depth from the sample surface.

【0037】

From FIG. 2, it can be seen that the lower the film forming pressure, the higher the atomic concentration of Ar in the film, and the more suitable the film can be formed as a gettering site. The reason why the lower the film formation pressure is, the higher the Ar atom concentration in the film is, the lower the sputter film formation pressure is, the Ar gas in the reaction chamber and the rebounding atoms (Ar atoms reflected on the target surface). ) Is reduced, so that the rebounding atom is likely to be incident on the substrate.

【0038】

Next, the internal stress in the amorphous silicon film was measured using the same sample used in FIG. The results obtained are shown in FIGS. 3 and 4.

【0039】

FIG. 3 shows the relationship between the internal stress in the film and the film forming pressure, and the smaller the film forming pressure, the larger the compressive stress.

【0040】

Further, FIG. 4 shows the relationship between the internal stress in the film and the Ar concentration, and the higher the Ar concentration in the film, the larger the compressive stress. For example, an amorphous silicon film formed at a sputtering pressure of 1.0 Pa has an atomic concentration of 1 × 10.²⁰/cm³Contains Ar and compressive stress (approx. -4.7 × 10)⁹(dynes / cm²)) Is shown. In addition, the amorphous silicon film formed at a film formation pressure of 0.2 Pa has an atomic concentration of 6 × 10.²⁰/cm³Contains Ar and compressive stress (approx. -9.47 × 10)⁹(dynes / cm²))) Is shown. In addition, the inventors set the lower limit of the compressive stress at which the amorphous silicon film does not peel off to -10.0 × 10.¹⁰(dynes / cm²). Therefore, in order to produce a distorted amorphous silicon (amorphous silicon) film within the range where the film does not peel off due to the subsequent heat treatment, the sputter film formation pressure should be set to 0.2 Pa to 1.0 Pa. Good. The concentration of Ar in the amorphous silicon film at the film formation pressure of this sputtering is 1 × 10.²⁰/cm³~6×10²⁰/cm³, The internal stress of the amorphous silicon film is -10.0 × 10¹⁰(dynes / cm²)~-5.0×10⁹(dynes / cm²))become.

【0041】

From these experimental results, when a strained amorphous silicon film is used as the active layer of the TFT, it is possible to form it by appropriately setting the film forming pressure and the internal stress using FIG. 2, FIG. 3, or FIG. Good.

【0042】

Next, the relationship between the concentration of the rare gas element (Ar) in the amorphous silicon film formed by the sputtering method and the RF power (or RF power density) was obtained. The experimental procedure is shown below.

【0043】

An amorphous silicon film containing a rare gas element was formed on a glass substrate by a sputtering apparatus using an RF power source. Using a silicon target (resistivity 10Ωcm), the frequency is 1kHz to 30MHz, preferably 10 to 20MHz, Ar is passed 50sccm in the film formation chamber, the film formation pressure is 0.1Pa to 5Pa, here 0.4Pa, and the substrate temperature is 300. The temperature was set to ° C or lower, here 150 ° C, and the RF power was sequentially changed for each time a film was formed with a thickness of 0.2 μm. The electrode size is 30.5 cm in diameter. The RF power density refers to the value obtained by dividing the RF power by the electrode area. RF power is set to 0.4kW, 0.5kW, 1kW, and 3kW on a glass substrate, and a film is formed in order with a thickness of 0.2 μm under each condition, and the atomic concentration of Ar in the film is the secondary ion mass. It was measured by the analytical method (SIMS).

【0044】

The results obtained are shown in Fig. 5. In FIG. 5, the vertical axis shows the atomic concentration of Ar, and the horizontal axis shows the depth from the sample surface. In addition, FIG. 5 also shows the ionic strength of silicon with the vertical axis representing the secondary ionic strength and the horizontal axis representing the depth from the sample surface.

【0045】

From FIG. 5, it can be seen that the lower the RF power (or RF power density), the higher the atomic concentration of Ar in the film, and the more suitable the film can be formed as a gettering site. Further, when the RF power (or RF power density) is lowered, the internal stress can be reduced, so that the film peeling can be less likely to occur.

【0046】

From these experimental results, for a suitable gettering site (amorphous silicon film containing a rare gas element), the film formation pressure and RF power (or RF power density) are appropriately set using FIGS. 2 to 5. It may be formed.

【0047】

Further, as a comparative example, the relationship between the concentration of the rare gas element (Ar) and the film forming pressure in the amorphous silicon film formed by the DC sputtering method was obtained. The experimental procedure is shown below.

【0048】

An amorphous silicon film containing a rare gas element was formed on a glass substrate with a sputtering apparatus using a DC power source. Using a silicon target (resistivity 0.2Ωcm), Ar is passed 80sccm in the film formation chamber, and DC power is 3kW (DC power density 2.5W / cm).²), The substrate temperature was set to 150 ° C, and the film formation pressure was changed for each thickness of 0.2 μm. The film formation pressure is adjusted by the conductance valve on the exhaust side. The film formation pressure was set to 0.27Pa, 0.53Pa, 1.06Pa, and 1.6Pa on the glass substrate, respectively, and the film was formed in order with a thickness of 0.2 μm, and the atomic concentration of Ar in the film was analyzed by secondary ion mass spectrometry. Measured by method (SIMS). The results obtained are shown in Fig. 6. In FIG. 6, the vertical axis shows the atomic concentration of Ar, and the horizontal axis shows the depth from the sample surface. In addition, FIG. 6 also shows the ionic strength of silicon with the vertical axis representing the secondary ionic strength and the horizontal axis representing the depth from the sample surface.

【0049】

As shown in FIG. 6, the DC sputtering apparatus could not include Ar of 10 × 1020 / cm3 or more in the amorphous silicon film. The present inventors speculate that this is related to the film formation rate as one of the causes. In FIG. 6, the Ar concentration at 1.06 Pa is an abnormality for some reason and is not reliable data.

【0050】

From the above data, it was shown that it is better to use the RF type sputtering apparatus capable of containing the rare gas element in the film at a high concentration than the DC type sputtering apparatus.

【0051】

The present invention having the above configuration will be described in more detail with reference to the following examples.

【0052】

(Example) [Example 1] The procedure for producing a typical TFT using the present invention is briefly shown with reference to FIG.

【0053】

In FIG. 1 (A), 100 is a substrate having an insulating surface, 101 is an insulating film serving as a blocking layer, and 102 is a semiconductor film having an amorphous structure.

【0054】

In FIG. 1A, a glass substrate, a quartz substrate, a ceramic substrate, or the like can be used as the substrate 100. Further, a silicon substrate, a metal substrate, or a stainless steel substrate on which an insulating film is formed may be used. Further, a plastic substrate having heat resistance that can withstand the processing temperature of this step may be used.

【0055】

First, as shown in FIG. 1A, a base insulating film 101 made of an insulating film such as a silicon oxide film, a silicon nitride film, or a silicon oxide film (SiOxNy) is formed on the substrate 100. A typical example consists of a two-layer structure as the underlying insulating film 101, and a first silicon oxide nitride film formed using SiH4, NH3, and N2O as reaction gases is formed with 50 to 100 nm, SiH4, and N2O as reaction gases. A structure is adopted in which the second silicon oxide film to be filmed is laminated to a thickness of 100 to 150 nm. Further, it is preferable to use a silicon nitride film (SiN film) having a film thickness of 10 nm or less or a second silicon oxide nitride film (SiNxOy film (X >> Y)) as one layer of the underlying insulating film 101. Since nickel tends to move to a region having a high oxygen concentration during gettering, it is extremely effective to use a silicon nitride film as the underlying insulating film in contact with the semiconductor film. Further, a three-layer structure in which the first silicon oxide nitride film, the second silicon oxide nitride film, and the silicon nitride film are sequentially laminated may be used.

【0056】

Next, the first semiconductor film 102 having an amorphous structure is formed on the underlying insulating film. The first semiconductor film 102 uses a semiconductor material containing silicon as a main component. Typically, an amorphous silicon film or an amorphous silicon germanium film is applied, and the film is formed to a thickness of 10 to 100 nm by a plasma CVD method, a reduced pressure CVD method, or a sputtering method. In order to obtain a semiconductor film having a high-quality crystal structure in the subsequent crystallization, the concentration of impurities such as oxygen and nitrogen contained in the film of the first semiconductor film 102 having an amorphous structure is 5 × 10 18 / cm3. It is recommended to reduce it to (atomic concentration measured by secondary ion mass spectrometry (SIMS)) or less. These impurities become a factor that hinders the subsequent crystallization, and also becomes a factor that increases the density of the capture center and the recombination center even after the crystallization. Therefore, it is desirable not only to use a high-purity material gas, but also to use an ultra-high vacuum-compatible CVD device equipped with a mirror surface treatment (electric field polishing treatment) in the reaction chamber and an oil-free vacuum exhaust system.

【0057】

Next, as a technique for crystallizing the first semiconductor film 102 having an amorphous structure, the technique described in JP-A-8-78329 is used here for crystallization. The technique described in the publication is a crystal structure in which a metal element that promotes crystallization is selectively added to an amorphous silicon film (also called an amorphous silicon film) and heat treatment is performed to expand the crystal structure starting from the addition region. It forms a semiconductor film having First, on the surface of the first semiconductor film 102 having an amorphous structure, a nickel acetate solution containing 1 to 100 ppm of a metal element having a catalytic action (nickel in this example) that promotes crystallization is applied in terms of weight. It is applied with a spinner to form the nickel-containing layer 103. (FIG. 1 (B)) As a means other than the method for forming the nickel-containing layer 103 by coating, a means for forming an ultrathin film by a sputtering method, a vapor deposition method, or a plasma treatment may be used. Further, although an example of coating on the entire surface is shown here, a mask may be formed to selectively form a nickel-containing layer.

【0058】

Next, heat treatment is performed to perform crystallization. In this case, in the crystallization, VDD is formed in the portion of the semiconductor film in contact with the metal element that promotes the crystallization of the semiconductor, and the crystallization proceeds with this as the nucleus. In this way, the first semiconductor film 104 having the crystal structure shown in FIG. 1 (C) is formed. The oxygen concentration contained in the first semiconductor film 104 after crystallization is preferably 1 × 1020 / cm3 or less. Here, after the heat treatment for dehydrogenation (450 ° C, 1 hour), the heat treatment for crystallization (4 to 24 hours at 550 ° C to 650 ° C) is performed. Further, when crystallization is performed by irradiation with strong light, any one of infrared light, visible light, or ultraviolet light or a combination thereof can be used, but typically, a halogen lamp or a metal halide is used. Use light emitted from a lamp, xenon arc lamp, carbon arc lamp, high pressure sodium lamp, or high pressure mercury lamp. The lamp light source may be turned on for 1 to 60 seconds, preferably 30 to 60 seconds, and this may be repeated 1 to 10 times to instantaneously heat the semiconductor film to about 600 to 1000 ° C. If necessary, heat treatment may be performed to release hydrogen contained in the first semiconductor film 104 having an amorphous structure before irradiating with strong light. Further, crystallization may be carried out by simultaneously performing heat treatment and irradiation with strong light. Considering productivity, it is desirable to perform crystallization by irradiating with strong light.

【0059】

A metal element (here, nickel) remains in the first semiconductor film 104 thus obtained. Even if it is not uniformly distributed in the membrane, it remains at a concentration of more than 1 × 1019 / cm3 at an average concentration. Of course, it is possible to form various semiconductor elements such as TFTs even in such a state, but the elements are removed by the methods shown below.

【0060】

Next, in order to increase the crystallization rate (ratio of crystal components in the total volume of the film) and repair defects left in the crystal grains, the first semiconductor film 104 having a crystal structure is irradiated with laser light. Is preferable. Before irradiating with laser light, it is desirable to remove the oxide film on the surface of the silicon film having a crystal structure with dilute hydrofluoric acid or the like. When irradiated with laser light, a thin oxide film (not shown) is formed on the surface. Excimer laser light with a wavelength of 400 nm or less and the second and third harmonics of the YAG laser are used for this laser light.

【0061】

Since the oxide film formed by irradiation with the laser beam after crystallization is insufficient, an oxide film (called a chemical oxide) is further formed with an ozone-containing aqueous solution (typically ozone water) to add up the total. A barrier layer 105 made of an oxide film of 1 to 10 nm is formed, and a second semiconductor film 106 containing a rare gas element is formed on the barrier layer 105. (FIG. 1 (D)) Here, the oxide film formed when the first semiconductor film 104 having a crystal structure is irradiated with laser light is also regarded as a part of the barrier layer. The barrier layer 105 functions as an etching stopper when only the second semiconductor film 106 is selectively removed in a later step. Further, instead of the ozone-containing aqueous solution, a chemical oxide can be similarly formed by treating with an aqueous solution in which sulfuric acid, hydrochloric acid, nitric acid or the like and hydrogen peroxide solution are mixed. Further, as another method for forming the barrier layer 105, ozone may be generated by irradiation with ultraviolet rays in an oxygen atmosphere to oxidize the surface of the semiconductor film having the crystal structure. Further, as another method for forming the barrier layer 105, an oxide film of about 1 to 10 nm may be deposited by a plasma CVD method, a sputtering method, a vapor deposition method, or the like to form the barrier layer. Further, as another method for forming the barrier layer 105, a clean oven may be used and heated to about 200 to 350 ° C. to form a thin oxide film. The barrier layer 105 formed by any one of the above methods or a combination of these methods has a film thickness in which nickel in the first semiconductor film can move to the second semiconductor film by later gettering. Alternatively, it is necessary to set the film thickness.

【0062】

Here, the second semiconductor film 106 containing a rare gas element is formed by a sputtering method to form a gettering site. As the rare gas element, one or more kinds selected from helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) are used. Of these, argon (Ar), which is an inexpensive gas, is preferable. Here, a target made of silicon is used in an atmosphere containing rare gas elements, the film formation pressure is 0.1 Pa to 5 Pa, and the RF power density is 0.137 W / cm.²~ 6.847W / cm²To form a second semiconductor film. There are two meanings to include rare gas element ions, which are inert gases, in the membrane. One is to form a dangling bond and distort the semiconductor film, and the other is to distort between the lattices of the semiconductor film. Distortion between the lattices of a semiconductor film is remarkably obtained when an element having an atomic radius larger than that of silicon such as argon (Ar), krypton (Kr), and xenon (Xe) is used. Further, by containing a rare gas element in the film, not only lattice strain but also unpaired bonds are formed to contribute to the gettering action.

【0063】

In addition, when a second semiconductor film is formed using a target containing phosphorus, which is a one-conductive impurity element, gettering can be performed using the Coulomb force of phosphorus in addition to gettering with a rare gas element. it can.

【0064】

Further, since nickel tends to move to a region having a high oxygen concentration during gettering, the oxygen concentration contained in the second semiconductor film 106 is higher than the oxygen concentration contained in the first semiconductor film. For example 1x10²⁰/cm³Since it is desirable to set the above, the film formation pressures 1.2Pa, 1.0Pa, 0.8Pa, 0.6Pa, 0.4Pa, and 0.2Pa satisfy this oxygen concentration.

【0065】

Further, in the film formation by the sputtering method shown in FIG. 1 (D), when a rare gas element is also added to the first semiconductor film, the added portion acts as a gettering site, so that the gettering effect is reduced. There is concern that it will end up. Therefore, it is desirable to appropriately adjust the sputtering conditions so that the rare gas element is not added to the first semiconductor film. Further, when the film is formed by the sputtering method, the barrier layer functions to prevent the addition of rare gas elements, so that the film thickness and film quality of the barrier layer are important. According to the experiments of the present inventors, an oxide film formed when irradiated with laser light was formed in order to increase the crystallization rate and repair defects left in the crystal grains, and further, the oxide film was formed with an ozone-containing aqueous solution. An oxide film having a total of 10 nm or less obtained by forming is preferable as the barrier layer. On the other hand, when the barrier layer is formed only by the oxide film in the ozone-containing aqueous solution after removing the oxide film formed by irradiating the laser beam, the rare gas element is the first semiconductor in the film formation by the sputtering method. A small amount was added to the membrane, which was insufficient as a barrier layer.

【0066】

Next, heat treatment is performed to perform gettering to reduce or remove the concentration of the metal element (nickel) in the first semiconductor film. (Fig. 1 (E)) As the heat treatment for gettering, a treatment of irradiating strong light or a heat treatment may be performed. Due to this gettering, the metal element moves in the direction of the arrow in FIG. 1 (E) (that is, the direction from the substrate side toward the surface of the second semiconductor film), and the first semiconductor film covered with the barrier layer 107. The metal element contained in 106 is removed, or the concentration of the metal element is reduced. The distance that the metal element moves during gettering may be at least as long as the thickness of the first semiconductor film, and gettering can be completed in a relatively short time. Here, all the nickel is moved to the second semiconductor film 109 so that the nickel does not segregate on the first semiconductor film 106, and there is almost no nickel contained in the first semiconductor film 106, that is, the nickel concentration in the film is 1 ×. Ten¹⁸/cm³Below, preferably 1x10¹⁷/cm³Getter enough to be as follows.

【0067】

The second semiconductor film may be partially crystallized depending on the conditions of the gettering heat treatment or the film thickness of the second semiconductor film. If the second semiconductor film crystallizes, dangling bonds, lattice distortion, and unpaired binding hands decrease, leading to a reduction in the gettering effect. Therefore, heat treatment in which the second semiconductor film does not crystallize is preferable. Or the thickness of the second semiconductor film. In any case, the second semiconductor film, that is, the amorphous silicon film containing the rare gas element, is less likely to undergo crystallization than the amorphous silicon film containing the rare gas element, and is therefore most suitable as a gettering site. Is.

【0068】

Further, depending on the conditions of the heat treatment of the gettering, the crystallization rate of the first semiconductor film can be increased at the same time as the gettering, and the defects left in the crystal grains can be repaired, that is, the crystallinity can be improved. ..

【0069】

In the present specification, gettering means that a metal element in a gettered region (here, a first semiconductor film) is released by thermal energy and moves to a gettering site by diffusion. Therefore, gettering depends on the processing temperature, and the higher the temperature, the shorter the gettering.

【0070】

When the treatment of irradiating strong light is used, the lamp light source for heating is turned on for 1 to 60 seconds, preferably 30 to 60 seconds, and this is repeated 1 to 10 times, preferably 2 to 6 times. The emission intensity of the lamp light source is arbitrary, but the semiconductor film is instantaneously heated to about 600 to 1000 ° C, preferably about 700 to 750 ° C.

【0071】

When the heat treatment is performed, the heat treatment may be performed at 450 to 800 ° C. for 1 to 24 hours, for example, 550 ° C. for 14 hours in a nitrogen atmosphere. Further, in addition to the heat treatment, strong light may be irradiated.

【0072】

Next, using the barrier layer 107 as an etching stopper, only the second semiconductor film shown in 109 is selectively removed, then the barrier layer 107 is removed, and the first semiconductor film 106 is desired by using a known patterning technique. The semiconductor layer 110 having the shape of is formed. (Fig. 1 (F)) As a method for selectively etching only the second semiconductor film, dry etching using ClF3 without using plasma, or an aqueous solution containing hydrazine or tetraethylammonium hydroxide (chemical formula (CH3) 4NOH) is used. It can be performed by wet etching with an alkaline solution. In addition, after removing the second semiconductor film, when the nickel concentration on the surface of the barrier layer was measured by TXRF, nickel was detected at a high concentration, so it is desirable to remove the barrier layer, and an etchant containing hydrofluoric acid. It may be removed by. Further, it is desirable to form a thin oxide film on the surface with ozone water after removing the barrier layer and before forming a mask made of a resist.

【0073】

Next, the surface of the semiconductor layer is washed with an etchant containing hydrofluoric acid, and then an insulating film containing silicon as a main component to be the gate insulating film 108 is formed. It is desirable that the surface cleaning and the formation of the gate insulating film be performed continuously without being exposed to the atmosphere.

【0074】

Next, after cleaning the surface of the gate insulating film 108, the gate electrode 109 is formed. Next, an impurity element (P, As, etc.) that imparts n-type to the semiconductor, here phosphorus, is appropriately added to form the source region 110 and the drain region 111. After the addition, heat treatment, irradiation with strong light, or irradiation with laser light is performed to activate the impurity element. Further, at the same time as activation, plasma damage to the gate insulating film and plasma damage to the interface between the gate insulating film and the semiconductor layer can be recovered. In particular, it is very effective to irradiate the second harmonic of the YAG laser from the front surface or the back surface to activate the impurity element in an atmosphere of room temperature to 300 ° C. The YAG laser is a preferred activation method because it requires less maintenance.

【0075】

In the subsequent steps, the interlayer insulating film 113 is formed, hydrogenated to form contact holes reaching the source region and drain region, and the source electrode 114 and drain electrode 115 are formed to form a TFT (n-channel type TFT). To complete. (Fig. 1 (G)) [0076]

Further, the present invention is not limited to the TFT structure shown in FIG. 1 (G), and if necessary, a low-concentration drain (LDD: Lightly Doped Drain) having an LDD region between the channel formation region and the drain region (or source region) is provided. ) It may be a structure. In this structure, a region in which an impurity element is added at a low concentration is provided between a channel formation region and a source region or a drain region formed by adding an impurity element in a high concentration, and this region is referred to as an LDD region. I'm calling. Further, a so-called GOLD (Gate-drain Overlapped LDD) structure in which the LDD region is arranged so as to overlap the gate electrode via the gate insulating film may be used.

【0077】

Further, although the n-channel type TFT has been described here, it goes without saying that the p-channel type TFT can be formed by using the p-type impurity element instead of the n-type impurity element.

【0078】

Further, although the top gate type TFT has been described here as an example, the present invention can be applied regardless of the TFT structure, and for example, it can be applied to a bottom gate type (reverse stagger type) TFT and a forward stagger type TFT. Is possible.

【0079】

[Example 2] Here, an example in which the strained semiconductor film obtained by the present invention is used as the active layer of the TFT is shown.

【0080】

In this embodiment, as a semiconductor film having distortion, the film formation pressure is 0.2 to 1.0 by discharging at room temperature (22 to 28 ° C, preferably 25 ° C) and RF (1 kHz to 30 MHz, preferably 10 to 20 MHz). It is kept in the range of Pa, and an amorphous silicon film is formed by a sputtering method using a silicon target in an Ar atmosphere. By setting the film forming conditions shown above, the semiconductor device of the present invention has an Ar concentration of 1 × 10 in the amorphous silicon layer.²⁰~6×10²⁰/cm³And the compressive stress in the amorphous silicon layer is -10.0 × 10.¹⁰dynes / cm2 ~ -5.0 × 10⁹dynes / cm²Therefore, it is possible to manufacture a semiconductor device having a distorted amorphous silicon (amorphous silicon) film and less likely to cause film peeling.

【0081】

Further, since the structure other than the active layer may be produced by using a known technique, the description thereof will be omitted here. Further, this embodiment can be applied regardless of the TFT structure, and can be applied to, for example, a bottom gate type (reverse stagger type) TFT, a forward stagger type TFT, and a top gate type TFT.

【0082】

[Example 3] Various modules are used for the pixel portion and the drive circuit formed by using the semiconductor film having a crystal structure or the semiconductor film having an amorphous structure formed by carrying out the present invention as the active layer of the TFT. It can be used for (active matrix type liquid crystal module, active matrix type EL (Electro Luminescence) module, active matrix type EC module). That is, the present invention can be applied to all electronic devices incorporating them in the display unit.

【0083】

Such electronic devices include video cameras, digital cameras, head-mounted displays (goggles-type displays), car navigation systems, projectors, car stereos, personal computers, personal digital assistants (mobile computers, mobile phones, electronic books, etc.). Can be mentioned. Examples of them are shown in FIGS. 7 to 9.

【0084】

FIG. 7A is a personal computer, which includes a main body 2001, an image input unit 2002, a display unit 2003, a keyboard 2004, and the like. The present invention can be applied to the display unit 2003.

【0085】

FIG. 7B shows a video camera, which includes a main body 2101, a display unit 2102, an audio input unit 2103, an operation switch 2104, a battery 2105, an image receiving unit 2106, and the like. The present invention can be applied to the display unit 2102.

【0086】

FIG. 7C shows a mobile computer (mobile computer), which includes a main body 2201, a camera unit 2202, an image receiving unit 2203, an operation switch 2204, a display unit 2205, and the like. The present invention can be applied to the display unit 2205.

【0087】

FIG. 7D shows a goggle type display, which includes a main body 2301, a display unit 2302, an arm unit 2303, and the like. The present invention can be applied to the display unit 2302.

【0088】

FIG. 7 (E) is a player that uses a recording medium (hereinafter referred to as a recording medium) on which a program is recorded, and includes a main body 2401, a display unit 2402, a speaker unit 2403, a recording medium 2404, an operation switch 2405, and the like. This player can use a DVD (Digtial Versatile Disc), a CD, or the like as a recording medium for listening to music, watching movies, playing games, or playing the Internet. The present invention can be applied to the display unit 2402.

【0089】

FIG. 7 (F) is a digital camera, which includes a main body 2501, a display unit 2502, an eyepiece unit 2503, an operation switch 2504, an image receiving unit (not shown), and the like. The present invention can be applied to the display unit 2502.

【0090】

FIG. 8A shows a front-type projector, which includes a projector 2601, a screen 2602, and the like. The present invention can be applied to the liquid crystal module 2808 which constitutes a part of the projection device 2601.

【0091】

FIG. 8B shows a rear projector, which includes a main body 2701, a projection device 2702, a mirror 2703, a screen 2704, and the like. The present invention can be applied to the liquid crystal module 2808 which constitutes a part of the projection device 2702.

【0092】

Note that FIG. 8C is a diagram showing an example of the structure of the projection devices 2601 and 2702 in FIGS. 8 (A) and 8 (B). The projection devices 2601 and 2702 are composed of a light source optical system 2801, a mirror 2802, 2804 to 2806, a dichroic mirror 2803, a prism 2807, a liquid crystal module 2808, a retardation plate 2809, and a projection optical system 2810. The projection optical system 2810 is composed of an optical system including a projection lens. Although this embodiment shows an example of a three-plate type, the present embodiment is not particularly limited, and for example, a single-plate type may be used. Further, even if the practitioner appropriately provides an optical lens, a film having a polarizing function, a film for adjusting the phase difference, an optical system such as an IR film, in the optical path indicated by the arrow in FIG. 8 (C). Good.

【0093】

Further, FIG. 8 (D) is a diagram showing an example of the structure of the light source optical system 2801 in FIG. 8 (C). In this embodiment, the light source optical system 2801 includes a reflector 2811, a light source 2812, lens arrays 2813 and 2814, a polarization conversion element 2815, and a condenser lens 2816. The light source optical system shown in FIG. 8 (D) is an example and is not particularly limited. For example, the practitioner may appropriately provide an optical system such as an optical lens, a film having a polarizing function, a film for adjusting a phase difference, or an IR film in the light source optical system.

【0094】

However, in the projector shown in FIG. 8, a case where a transmission type electro-optic device is used is shown, and an application example in a reflection type electro-optic device and an EL module is not shown.

【0095】

FIG. 9A shows a mobile phone, which includes a main body 2901, an audio output unit 2902, an audio input unit 2903, a display unit 2904, an operation switch 2905, an antenna 2906, an image input unit (CCD, image sensor, etc.) 2907 and the like. The present invention can be applied to the display unit 2904.

【0096】

FIG. 9B is a portable book (electronic book), which includes a main body 3001, a display unit 3002, 3003, a storage medium 3004, an operation switch 3005, an antenna 3006, and the like. The present invention can be applied to the display units 3002 and 3003.

【0097】

FIG. 9C shows a display, which includes a main body 3101, a support base 3102, a display unit 3103, and the like. The present invention can be applied to the display unit 3103.

【0098】

By the way, the display shown in FIG. 9C is a small or medium-sized display or a large-sized display, for example, a display having a screen size of 5 to 20 inches. Further, in order to form a display unit having such a size, it is preferable to use a substrate having a side of 1 m and perform multi-chamfering for mass production.

【0099】

As described above, the scope of application of the present invention is extremely wide, and it can be applied to manufacturing methods of electronic devices in all fields. Further, the electronic device of the present embodiment can be realized by using a configuration composed of any combination of the embodiment, the first embodiment, and the second embodiment.

【0100】

[Effect of the invention]

According to the present invention, a high concentration in the membrane, specifically 1 × 10¹⁹/cm³~1×10²²/cm³Argon can be contained at the concentration of the above, and an amorphous silicon film having a strain that is less likely to cause film peeling can be formed by a sputtering method.

[Simple explanation of drawings]

[Figure 1]

It is a figure which shows the manufacturing process of the semiconductor device of this invention.

[Figure 2]

SIMS data (dependency on film formation pressure) showing the Ar concentration in the silicon film formed by the sputtering method (RF method).

[Fig. 3]

It is a graph which shows the relationship between the film formation pressure and the internal stress in the silicon film formed by the sputtering method (RF method).

[Fig. 4]

It is a graph which shows the relationship between the Ar concentration and the internal stress in the silicon film formed by the sputtering method (RF method).

[Fig. 5]

SIMS data (RF power dependence) showing the Ar concentration in the silicon film formed by the sputtering method (RF method).

[Fig. 6]

SIMS data showing the Ar concentration in the silicon film formed by the sputtering method (DC method). (Comparison example) [Fig. 7]

The figure which shows an example of the electronic device.

[Fig. 8]

The figure which shows an example of the electronic device.

[Fig. 9]

The figure which shows an example of the electronic device.