JP7400389B2 - Silicon carbide polycrystalline film, silicon carbide polycrystalline film manufacturing method, and silicon carbide polycrystalline film forming apparatus - Google Patents

Description

The present invention relates to a silicon carbide polycrystalline film, a method for manufacturing a silicon carbide polycrystalline film, and a film forming apparatus for a silicon carbide polycrystalline film.

Silicon carbide used as a material for polycrystalline films is a compound semiconductor material composed of silicon and carbon. Not only does it have an excellent dielectric breakdown field strength that is 10 times that of silicon, and a band gap that is three times that of silicon, but it is also possible to control the p-type and n-type over a wide range, which is necessary for device fabrication. , is expected to be a material for power devices that exceeds the limits of silicon.

Further, since silicon carbide can obtain a high withstand voltage even with a thinner thickness, a semiconductor having a small ON resistance and a low loss can be obtained by forming the silicon carbide thinly.

However, silicon carbide semiconductors cannot be mass-produced compared to Si semiconductors, which are more expensive than Si semiconductors, because large-area wafers cannot be obtained and the manufacturing process is complicated. .

Therefore, various efforts have been made to reduce the cost of silicon carbide semiconductors. For example, Patent Document 1 discloses a method for manufacturing a silicon carbide substrate, which features at least a silicon carbide single crystal substrate with a density of 30 micropipes/cm ² or less and a silicon carbide polycrystalline substrate. It is described that a substrate in which a silicon carbide single crystal layer is formed on a silicon carbide polycrystalline substrate is manufactured by performing a step of bonding the silicon carbide single crystal substrate and then performing a step of thinning the silicon carbide single crystal substrate.

Further, Patent Document 1 discloses that before the step of bonding a silicon carbide single crystal substrate and a silicon carbide polycrystalline substrate, a step of implanting hydrogen ions into the silicon carbide single crystal substrate to form a hydrogen ion implanted layer is performed. After the step of bonding the silicon carbide single crystal substrate and the silicon carbide polycrystalline substrate together, and before the step of thinning the silicon carbide single crystal substrate, heat treatment is performed at a temperature of 350° C. or lower to form the silicon carbide single crystal substrate. A method for manufacturing a silicon carbide substrate is described in which the step of thinning the film is a step of mechanically peeling off a hydrogen ion implanted layer.

With this method, more silicon carbide wafers can be obtained from one silicon carbide single crystal ingot.

JP2009-117533A

However, the method for manufacturing silicon carbide wafers described above involves bonding a single-crystal silicon carbide substrate on which a thin ion-implanted layer has been formed by hydrogen ion implantation to a polycrystalline silicon carbide substrate, and then heating the single-crystal silicon carbide substrate to form a thin ion-implanted layer. Because they are manufactured by exfoliating a crystalline silicon carbide substrate, the silicon carbide wafer has a polycrystalline silicon carbide substrate for the majority of its thickness. For this reason, a polycrystalline silicon carbide substrate of sufficient thickness is used for the silicon carbide wafer so that it has mechanical strength so as not to be damaged during handling such as polishing. Therefore, the thickness of the polycrystalline silicon carbide substrate must be greater than the thickness required to function as a semiconductor.

However, as the thickness of the polycrystalline silicon carbide substrate increases, the resistance value increases. When the resistance value is high, the ON resistance becomes large, and the original characteristics of the silicon carbide semiconductor cannot be fully exhibited.

In other words, in order to prevent damage to the single-crystal silicon carbide substrate during the manufacturing process, a polycrystalline silicon carbide substrate with sufficient mechanical strength is required, while at the same time reducing the ON resistance of the resulting silicon carbide semiconductor. In order to achieve this, the resistance value of the polycrystalline silicon carbide substrate needs to be low.

In order to lower the resistance value of a polycrystalline silicon carbide substrate, it is necessary to increase the carrier concentration in the substrate, and silicon carbide is generally doped with nitrogen, which is a group V element. For example, in power devices such as Schottky barrier diodes, a large current flows in the vertical direction of the substrate, so the resistivity is required to be 20 mΩcm or less, and to meet this resistivity, polycrystalline silicon carbide is required. The amount of nitrogen doped into the substrate needs to be in the range of 2×10 ¹⁹ to 1×10 ²⁰ atoms/cm ³ .

Conventionally, this polycrystalline silicon carbide substrate has been obtained by forming a film to a predetermined thickness by a vapor phase growth method such as a thermal CVD method while adding nitrogen as a dopant. Nitrogen is doped into the silicon carbide polycrystal by substituting carbon (C) in the silicon carbide polycrystal. However, since the Si--C bond is strong, it is necessary to introduce a large amount of nitrogen gas into the film-forming chamber of the film-forming apparatus during film formation.

Further, the incorporation of nitrogen into the silicon carbide polycrystalline film when growing it depends on the film formation temperature. For example, even if the partial pressure of nitrogen in the film-forming atmosphere remains the same, the lower the film-forming temperature, the more the amount of nitrogen taken into the film increases. However, the rate of forming a silicon carbide polycrystalline film by thermal CVD increases as the temperature increases. A silicon carbide polycrystalline film is usually formed at a high temperature of 1300 to 1400° C. in consideration of the film formation rate. However, in this temperature range, the amount of nitrogen doped is smaller than in the range of 2×10 ¹⁹ to 1×10 ²⁰ atoms/cm ³ . Therefore, in forming a silicon carbide polycrystalline film, it has been a challenge to achieve both high nitrogen doping and film formation rate.

In view of the above problems, the present invention provides a silicon carbide polycrystalline substrate that can easily obtain a silicon carbide polycrystalline substrate with a high nitrogen doping amount without reducing the deposition rate of a silicon carbide polycrystalline film by thermal CVD method. An object of the present invention is to provide a method for manufacturing a silicon polycrystalline film, a silicon carbide polycrystalline film, and a film forming apparatus for a silicon carbide polycrystalline film.

The present inventors introduced plasma-treated nitrogen in the process of forming a silicon carbide polycrystalline film on a silicon substrate or a carbon substrate, which is the base material of the polycrystalline silicon carbide substrate, thereby increasing the film formation rate. It has been discovered that a silicon carbide polycrystalline substrate with high electrical conductivity can be obtained by increasing the amount of nitrogen taken into the film and increasing the carrier concentration in the silicon carbide polycrystalline substrate without reducing the electrical conductivity.

In order to solve the above problems, the method for producing a silicon carbide polycrystalline film of the present invention uses chemical vapor deposition to deposit an average film thickness on a support substrate of 50 μm to 500 μm and a nitrogen atom concentration of 2×10 ¹⁹ atoms/cm ³ to 1× It includes a film forming step of forming a silicon carbide polycrystalline film of 10 ²⁰ pieces/cm ³ , the film forming temperature in the film forming step is 1000°C to 1500°C, and plasma is used as a doping gas in the film forming step. Use standard nitrogen gas.

The film forming step may be a step of forming a silicon carbide polycrystalline film having a nitrogen atom concentration of 2×10 ¹⁹ atoms/cm ³ or more.

Furthermore, in order to solve the above problems, the silicon carbide polycrystalline film of the present invention has an average film thickness of 50 μm to 500 μm and a resistivity of 5 to 18 mΩ·cm.

The silicon carbide polycrystalline film may have a nitrogen atom concentration of 2×10 ¹⁹ atoms/cm ³ or more.

In order to solve the above problems, the silicon carbide polycrystalline film forming apparatus of the present invention includes a film forming chamber for forming a silicon carbide polycrystalline film, a plasma processing section for plasma processing nitrogen gas, and a plasma processing section for plasma processing nitrogen gas. A first nitrogen gas introduction tube introduces nitrogen gas into the plasma processing section, and a second nitrogen gas introduction tube introduces plasma-treated nitrogen gas from the plasma processing section into the film forming chamber.

According to the present invention, a silicon carbide polycrystalline film that can easily obtain a silicon carbide polycrystalline substrate with a high nitrogen doping amount without reducing the deposition rate of a silicon carbide polycrystalline film by thermal CVD method. A manufacturing method, a silicon carbide polycrystalline film, and a silicon carbide polycrystalline film forming apparatus can be provided.

FIG. 1 is a schematic cross-sectional view of a silicon carbide polycrystalline film forming apparatus according to the present invention.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

[Method for manufacturing silicon carbide polycrystalline film]
The method for manufacturing a silicon carbide polycrystalline film of the present invention includes a film forming step of forming a silicon carbide polycrystalline film as described below.

<Film formation process>
In this step, a polycrystalline silicon carbide film having an average thickness of 50 μm to 500 μm is formed on the support substrate by chemical vapor deposition. A silicon substrate or a carbon substrate can be used as a support substrate on which a polycrystalline film is formed. Furthermore, the thickness of the support substrate, the size of the surface to be filmed, and other shapes are not particularly limited, and any support substrate suitable for the desired polycrystalline silicon carbide substrate can be used.

A specific example of chemical vapor deposition is a thermal CVD method. Specifically, raw material gas, carrier gas, etc. containing the components of the silicon carbide polycrystalline film are supplied onto the heated support substrate, and the silicon carbide polycrystalline film is formed by a chemical reaction on the surface of the support substrate or in the gas phase. An example is a method of depositing.

The raw material gas is not particularly limited as long as it can form the silicon carbide polycrystalline film of the present invention, and may include Si-based raw material gas and C-based raw material gas that are generally used to form a silicon carbide polycrystalline film. can be used. For example, as the Si-based source gas, silane (SiH ₄ ) can be used, as well as monochlorosilane (SiH ₃ Cl), dichlorosilane (SiH ₂ Cl ₂ ), trichlorosilane (SiHCl ₃ ), and tetrachlorosilane (SiCl ₄ ) A chlorine-based Si raw material-containing gas (chloride-based raw material) containing Cl that has an etching effect can be used. As the C-based raw material gas, for example, hydrocarbons such as methane (CH ₄ ), propane (C ₃ H ₈ ), acetylene (C ₂ H ₂ ), etc. can be used. In addition to the above, trichloromethylsilane (CH ₃ Cl ₃ Si), trichlorophenylsilane (C ₆ H ₅ Cl ₃ Si), dichloromethylsilane (CH ₄ Cl ₂ Si), dichlorodimethylsilane ((CH ₃ ) ₂ SiCl ₂ ), chlorotrimethylsilane ((CH ₃ ) ₃ SiCl), and other gases containing both Si and C can also be used as the raw material gas.

Further, as the carrier gas, a commonly used carrier gas can be used as long as it can spread the raw material gas to the supporting substrate without inhibiting the formation of the silicon carbide polycrystalline film. For example, H ₂ gas, which has excellent thermal conductivity and has an etching effect on silicon carbide, can be used as the carrier gas. Further, plasma-treated nitrogen gas, which will be described later, is simultaneously supplied as an impurity doping gas.

In the film forming process, the silicon carbide polycrystalline film is formed so that the average film thickness is 50 μm to 500 μm. The silicon carbide polycrystalline film is used in conjunction with a silicon carbide single crystal substrate, and is required to be thick enough to have mechanical strength so that the silicon carbide single crystal substrate is not damaged during handling. . A polycrystalline silicon carbide film having an average thickness within the above range can satisfy mechanical strength. If the average film thickness is less than 50 μm, the mechanical strength may be insufficient. Further, if the average film thickness is 500 μm, the film has sufficient mechanical strength, so making the film thicker than this may increase manufacturing time and manufacturing cost.

Note that the average film thickness can be measured, for example, by cutting a silicon carbide polycrystalline film and observing the cross section using an SEM (scanning electron microscope) or the like. For example, the average thickness of the silicon carbide polycrystalline film at three points in total, one point in the center of the silicon carbide polycrystalline film and two points 10 mm inside the ends at both ends, can be taken as the average film thickness.

Further, in the film forming step, it is preferable to form the silicon carbide polycrystalline film so that the nitrogen atom concentration is 2×10 ¹⁹ atoms/cm ³ or more. If the nitrogen atom concentration is above, the resistivity required can be satisfied when the silicon carbide polycrystalline film is used in a power device such as a Schottky barrier diode. If the nitrogen atom concentration of the silicon carbide polycrystalline film is within the range of 2×10 ¹⁹ atoms/cm ³ to 1×10 ²⁰ atoms/cm ³ , the required resistivity can be satisfied with a margin.

(Film forming temperature)
In the film forming process, the film forming temperature is set at 1000°C to 1500°C. If the film is formed at a temperature within this range, the silicon carbide polycrystalline film can be formed at a sufficiently fast film formation rate while controlling the film thickness.

If the film forming temperature is lower than 1000° C., the overall film forming rate will drop significantly, and there is a possibility that efficiency in terms of productivity will drop. Furthermore, if the film forming temperature exceeds 1500° C., although the film forming rate increases, the control performance of the film thickness of the silicon carbide polycrystalline film may deteriorate and the film thickness may vary. Note that when a silicon substrate is used as the support substrate, the maximum temperature during film formation is preferably set to 1350° C. or lower in order to suppress deformation of the silicon substrate due to heating.

(Nitrogen gas in plasma state)
In the film forming process, nitrogen gas in a plasma state is used as a doping gas. Thereby, the nitrogen atom concentration of the silicon carbide polycrystalline film can be set to 2×10 ¹⁹ atoms/cm ³ to 1×10 ²⁰ atoms/cm ³ .

By applying a large amount of energy to nitrogen gas, the electrons orbiting the atoms fly out, and the nitrogen atoms, which have fewer electrons, enter an unstable and active state, that is, a plasma state. Nitrogen atoms in a plasma state tend to cause chemical reactions with surrounding substances in an attempt to return to a stable state. In the present invention, by utilizing this property, it is possible to increase the amount of nitrogen doped into silicon carbide polycrystal.

The plasma treatment method for nitrogen gas to obtain nitrogen gas in a plasma state is not particularly limited as long as it is a method that can give large electrical energy or microwaves to nitrogen atoms, which are the source of plasma, and bring them into a plasma state. . Examples include thermal plasma in which plasma is continuously generated by applying a direct current voltage and reaches a high temperature of several thousand to tens of thousands of degrees, and low-temperature plasma in which the temperature rise of plasma gas is suppressed by a pulsed power source. In the present invention, since the silicon carbide polycrystalline film is formed at a temperature of 1000° C. to 1500° C., it is possible to use thermal plasma that is too high in temperature, but low-temperature plasma is easier to handle.

<Other processes>
The method for manufacturing a silicon carbide polycrystalline film of the present invention can include further steps in addition to the film forming step. For example, a mounting process in which the supporting substrate is placed in the film forming chamber of a film forming apparatus, a heating process in which the supporting substrate is heated to a predetermined temperature between the mounting process and the film forming process, and a supporting substrate before chemical vapor deposition. Another example is a step of flowing an inert gas such as argon in order to place the support substrate under an inert atmosphere so that any reaction that would inhibit film formation does not occur.

[Silicon carbide polycrystalline film]
By the method for manufacturing a silicon carbide polycrystalline film of the present invention described above, a silicon carbide polycrystalline film having an average thickness of 50 μm to 500 μm and a resistivity of 5 to 18 mΩ·cm can be obtained. Although this silicon carbide polycrystalline film has a typical thickness, it has a higher nitrogen atom concentration and lower resistivity than conventional silicon carbide polycrystalline films, so it is used in power devices such as Schottky barrier diodes. It is a useful membrane.

In addition, if the nitrogen atom concentration of the silicon carbide polycrystalline film is 2×10 ¹⁹ atoms/cm ³ or more, the resistivity required when using the silicon carbide polycrystalline film for power devices such as Schottky barrier diodes can be achieved. can be met. Furthermore, if the nitrogen atom concentration of the silicon carbide polycrystalline film is within the range of 2×10 ¹⁹ atoms/cm ³ to 1×10 ²⁰ atoms/cm ³ , the required resistivity can be easily met. can.

[Silicon carbide polycrystalline film deposition equipment]
Regarding the silicon carbide polycrystalline film forming apparatus 1000 shown in FIG. 1 as one embodiment of the silicon carbide polycrystalline film forming apparatus that can be used in the above-described silicon carbide polycrystalline film manufacturing method of the present invention, explain.

Film forming apparatus 1000 is an apparatus that can be used to form a silicon carbide polycrystalline film on support substrate 100 by thermal CVD. The film forming apparatus 1000 includes a casing 1100 serving as an exterior of the film forming apparatus 1000, a film forming chamber 1010 for forming a silicon carbide polycrystalline film on a support substrate 100, and a source gas and carrier discharged from the film forming chamber 1010. An exhaust gas introduction chamber 1040 that introduces gas etc. to a gas exhaust port 1030 (described later), a box 1050 that covers the exhaust gas introduction chamber 1040, and a carbon heater 1060 that heats the inside of the film forming chamber 1010 from the outside of the box 1050. A gas exhaust port 1030 that is provided at the bottom of the film forming chamber 1010 and discharges source gas, carrier gas, etc. to the outside of the film forming apparatus, and a substrate holder 1070 that holds the support substrate 100 are provided. Further, the substrate holder 1070 includes two pillars 1071 and a mounting section 1072 provided on the pillars 1071 on which the support substrate 100 is horizontally mounted.

The film forming apparatus 1000 also includes a Si-based source gas introduction pipe 200 that introduces a Si-based source gas accompanied by a carrier gas into the film-forming chamber 1010, and a C-based source gas introduced into the film-forming chamber 1010 along with a carrier gas. and a C-based raw material gas introduction pipe 300 for introducing C-based raw material gas.

Further, the film forming apparatus 1000 includes a plasma processing section 400 for plasma processing nitrogen gas, a first nitrogen gas introduction tube 500 for introducing nitrogen gas from the outside into the plasma processing section 400, and a plasma processing section 500 for introducing nitrogen gas into the plasma processing section 400 from the outside. A second nitrogen gas introduction pipe 600 is provided for introducing nitrogen gas from the section 400 into the film forming chamber 1010. It is important that the second nitrogen gas introducing tube 600 through which nitrogen gas flows after plasma processing is made of a material that does not react with nitrogen in a plasma state so that nitrogen in a plasma state can be sent into the deposition chamber 1010. Examples of such materials include Teflon (registered trademark)-based fluororesin, alumina, and the like. Since the second nitrogen gas introduction pipe 600 is used in a high temperature region, it is preferably a heat-resistant alumina pipe.

<Plasma processing section 400>
The plasma processing unit 400 is not particularly limited as long as nitrogen gas can be turned into a plasma state, and various plasma processing devices such as a high-frequency induction thermal plasma device and a low-temperature plasma device can be provided.

In particular, from the viewpoint of ease of handling as a plasma processing section of the film forming apparatus 1000, it is preferable to include a low-temperature plasma device that does not reach high temperatures. It is preferable to provide an atmospheric pressure low temperature plasma device that does not require large-scale equipment and can be easily incorporated into a production line.

Furthermore, atmospheric pressure low-temperature plasma equipment has a method in which the material to be processed passes through the plasma gas generated by applying a high voltage between two facing electrodes and feeding a processing gas, or a method in which the material to be processed passes through the plasma gas generated by applying a high voltage between two facing electrodes, or A direct method device uses the material as one side of the electrode to generate plasma between the electrode and the material, and the plasma generation electrode unit is installed in the nitrogen gas passage, allowing nitrogen gas to pass through at high speed. An example is a jet type device that emits gas activated by plasma.

In the present invention, it is preferable to process the nitrogen gas into a plasma state by passing the nitrogen gas through the plasma generation electrode unit using a jet method. For example, an AC voltage of 10 KV is applied to an electrode unit in which a high voltage electrode with a width of 10 mm and a ground electrode are arranged facing each other with an interval of 1.5 mm, and nitrogen gas is passed through the electrode unit at a flow rate of 5 L/min. By this, radical nitrogen in a plasma state can be obtained. In such plasma processing, the temperature of nitrogen gas in a plasma state is 150° C. or lower.

Note that it is preferable that the plasma processing section 400 be placed as close as possible to the film forming chamber 1010 so that the length of the second nitrogen gas introduction tube 600 is shortened. This makes it possible to prevent nitrogen gas in a plasma state from chemically reacting with surrounding substances before it is introduced into the film forming chamber 1010. For example, if the second nitrogen gas introduction tube 600 has an inner diameter of about 5 mm to 10 mm and a length of 50 cm or less, most of the nitrogen gas in the plasma state will be introduced into the film forming chamber 1010 while maintaining that state. be done.

Next, an example of a procedure for forming a silicon carbide polycrystalline film on support substrate 100 by chemical vapor deposition using film forming apparatus 1000 will be described.

First, the support substrate 100 is placed on the mounting part 1072, and the support substrate 100 is heated by the heater 1060 under reduced pressure in an inert gas atmosphere such as Ar to the reaction temperature for film formation. When the reaction temperature for film formation is reached, the supply of inert gas is stopped, the temperature is maintained, and the source gas containing the components of the silicon carbide polycrystalline film, carrier gas, and nitrogen gas in a plasma state are introduced into the film formation chamber 1010. supply. A silicon carbide polycrystalline film can be formed on both surfaces of the heated support substrate 100 by a chemical reaction in the film formation target surface of the support substrate 100 or in the gas phase. Thereafter, by cooling to room temperature, a laminate in which a silicon carbide polycrystalline film is formed on support substrate 100 is obtained.

Note that the Si-based source gas and the C-based source gas may be introduced into the film forming chamber 1010 as a mixed gas through one introduction tube. However, it is preferable that nitrogen gas in a plasma state be introduced into the film forming chamber 1010 separately from the Si-based source gas, C-based source gas, and carrier gas. If nitrogen gas in a plasma state is mixed with a Si-based source gas, a C-based source gas, or a carrier gas before being introduced into the film forming chamber 1010, the nitrogen gas in a plasma state will chemically react with the source gas, etc. I did it. This is because a sufficient amount of nitrogen gas in a plasma state may not be introduced into the film forming chamber 1010.

Hereinafter, the present invention will be explained in more detail based on Examples. However, the present invention is not limited to the contents of the following examples.

[Example 1]
(Manufacture of silicon carbide polycrystalline substrate)
A supporting substrate with a diameter of 150 mm was placed on a substrate holder in the film forming chamber 1010 of the film forming apparatus 1000, and the pressure inside the furnace was reduced to 22 kPa using an exhaust pump while Ar gas was flowing into the film forming chamber 1010, and then the temperature was increased to 1400°C. After the temperature reached 1400° C., the supply of Ar gas was stopped. Thereafter, SiCl ₄ and CH ₄ are used as source gases, nitrogen gas in a plasma state is used as a doping gas, and H ₂ is used as a carrier gas. A silicon carbide polycrystalline film was formed for 10 hours by introducing nitrogen gas into the film forming chamber 1010 through the second nitrogen gas introduction pipe 600.

The plasma processing unit 400 is a jet-type plasma generator (SPJ-X01HP manufactured by Aqua Co., Ltd.) equipped with an electrode unit in which a high-voltage electrode with a width of 10 mm and a ground electrode are arranged facing each other with an interval of 1.5 mm. )It was used. An AC voltage of 10 KV was applied to the electrode unit, nitrogen gas was passed through the electrode unit at a flow rate of 5 L/min, and nitrogen gas in a plasma state at a temperature of 150° C. was introduced into the film forming chamber 1010.

Table 1 shows the temperature and pressure inside the film forming chamber 1010, the amount of each gas introduced, and the film forming time in the film forming process of Example 1.

(Measurement of average film thickness)
The obtained silicon carbide polycrystalline film was cut and the cross section was observed using SEM, and silicon carbide polycrystalline film was observed at three points in total: one point in the center of the silicon carbide polycrystalline film and two points 10 mm inside from both ends. The average film thickness of the film was calculated, and this was taken as the average film thickness. Note that although the silicon carbide polycrystalline film is formed on both sides of support substrate 100, the average film thickness is for the film formed on one side of support substrate 100.

(Measurement of nitrogen doping amount)
The nitrogen atom concentration in the silicon carbide polycrystalline film was measured using a secondary ion mass spectrometer.

(Measurement of resistivity)
The resistivity of the silicon carbide polycrystalline film was measured based on JIS R1637.

[Example 2]
A silicon carbide polycrystalline substrate was manufactured under the same conditions as in Example 1, except that the amount of nitrogen introduced was 2500 sccm, and the film thickness, nitrogen doping amount, and resistivity were measured.

[Example 3]
A silicon carbide polycrystalline substrate was manufactured under the same conditions as in Example 1, except that the amount of nitrogen introduced was 12,500 sccm, and the film thickness, nitrogen doping amount, and resistivity were measured.

[Conventional example 1]
A silicon carbide polycrystalline substrate was manufactured under the same conditions as in Example 1, except that the film was formed using nitrogen gas as a doping gas without plasma treatment, and the film thickness, nitrogen doping amount, and resistivity were measured.

Table 2 shows the measurement results of the film thickness, nitrogen doping amount, and resistivity of the silicon carbide polycrystalline substrates manufactured under the conditions of Examples 1 to 3 and Conventional Example 1.

From the results in Table 2, Examples 1 to 3 and Conventional Example 1 had the same average film thickness and the same film forming process time, so Examples 1 to 3 were the same as Conventional Example 1. Similar deposition rates were maintained. On the other hand, the silicon carbide polycrystalline films of Examples 1 to 3 obtained by plasma treatment of nitrogen gas have a higher nitrogen doping amount than the silicon carbide polycrystalline film of Conventional Example 1 which was not subjected to plasma treatment. This resulted in an increase in resistivity and a decrease in resistivity.

[summary]
As described above, according to the present invention, by introducing plasma-treated nitrogen in the step of forming a silicon carbide polycrystalline film on a silicon substrate or a carbon substrate that serves as a support substrate for a polycrystalline silicon carbide substrate, By increasing the amount of nitrogen taken into the silicon carbide polycrystalline film and increasing the carrier concentration in the silicon carbide polycrystalline substrate without reducing the film formation rate, the silicon carbide polycrystalline substrate has a high electrical conductivity. It becomes possible to obtain. Therefore, it is expected to be useful as a technique for industrially manufacturing silicon carbide polycrystalline substrates.

100 Support substrate 200 Si-based raw material gas introduction pipe 300 C-based raw material gas introduction pipe 400 Plasma processing section 500 First nitrogen gas introduction pipe 600 Second nitrogen gas introduction pipe 1000 Film forming apparatus 1010 Film forming chamber 1030 Gas outlet 1040 Exhaust gas Introduction chamber 1050 Box 1060 Heater 1070 Substrate holder 1071 Pillar 1072 Placement section 1100 Housing

Claims (3)

A film forming step of forming a silicon carbide polycrystalline film with an average film thickness of 50 μm to 500 μm on a supporting substrate by chemical vapor deposition,
The film forming temperature in the film forming step is 1000°C to 1500°C,
using nitrogen gas in a plasma state as a doping gas in the film forming process;
A method for manufacturing a silicon carbide polycrystalline film. 2. The method of manufacturing a silicon carbide polycrystalline film according to claim 1, wherein the film forming step is a step of forming a silicon carbide polycrystalline film having a nitrogen atom concentration of 2×10 ¹⁹ atoms/cm ³ or more. a deposition chamber for depositing a silicon carbide polycrystalline film;
a plasma processing unit that processes nitrogen gas with plasma;
a first nitrogen gas introduction pipe for introducing the nitrogen gas into the plasma processing section;
a second nitrogen gas introduction pipe for introducing plasma-treated nitrogen gas from the plasma processing section to the film forming chamber;
a heating means for setting the film-forming temperature to 1000°C to 1500°C;
a Si-based raw material gas introduction pipe for introducing a Si-based raw material gas accompanied by a carrier gas into the film forming chamber;
a C-based raw material gas introduction pipe for introducing a C-based raw material gas accompanied by a carrier gas into the film forming chamber;
A silicon carbide polycrystalline film forming apparatus comprising:

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