JP7338193B2 - Method for manufacturing polycrystalline silicon carbide substrate - Google Patents

Description

The present invention relates to a method for manufacturing a polycrystalline silicon carbide substrate.

Silicon carbide is a compound semiconductor material composed of silicon and carbon. Silicon carbide has a dielectric breakdown field strength ten times that of silicon and a bandgap three times that of silicon, and is excellent as a semiconductor material. Furthermore, since it is possible to control the p-type and n-type necessary for device fabrication in a wide range, it is expected as a material for power devices that exceeds the limit of silicon. In addition, since silicon carbide can provide a high withstand voltage even when the thickness is thinner than that of conventional semiconductor materials, when silicon carbide is used as a semiconductor material, a semiconductor with low ON resistance and low loss can be obtained by making it thin. It is characterized by being able to

However, it is difficult to obtain a silicon carbide single crystal substrate having a large area, and the manufacturing process is complicated, as compared with silicon semiconductors that have been widely used in the past. For these reasons, silicon carbide semiconductors are more difficult to mass-produce and more expensive than silicon semiconductors.

Various attempts have been made so far to reduce the cost of silicon carbide semiconductors. For example, Patent Document 1 discloses a method for manufacturing a silicon carbide substrate, which includes at least a silicon carbide single crystal substrate having a micropipe density of 30/cm ² or less (hereinafter sometimes referred to as a “single crystal substrate”). ) and a silicon carbide polycrystalline substrate (hereinafter sometimes referred to as “polycrystalline substrate”), performing a step of bonding the single crystal substrate and the polycrystalline substrate together, and then thinning the single crystal substrate. to manufacture a substrate in which a single crystal layer is formed on a polycrystalline substrate.

Furthermore, in Patent Document 1, a step of implanting hydrogen ions into the single crystal substrate to form a hydrogen ion-implanted layer is performed before the step of bonding the single crystal substrate and the polycrystalline substrate together. After the step of bonding the crystal substrate and before the step of thinning the single crystal substrate, a heat treatment is performed at a temperature of 350° C. or less, and the single crystal substrate is mechanically separated at the hydrogen ion implanted layer to thin the single crystal substrate. It is described that

Such a method has made it possible to obtain a larger number of silicon carbide bonded substrates from one silicon carbide single crystal ingot.

JP 2009-117533 A

In the method for manufacturing a silicon carbide substrate described in Patent Document 1, a silicon carbide single crystal substrate on which a thin ion-implanted layer is formed by hydrogen ion implantation and a silicon carbide polycrystalline substrate are bonded together and then heated. Then, a part of the single-crystal substrate is peeled off in the hydrogen ion-implanted layer to thin the single-crystal substrate. For this reason, most of the thickness of the manufactured silicon carbide substrate of the silicon carbide substrate described in Patent Document 1 is derived from the polycrystalline substrate. Therefore, for the silicon carbide substrate of Patent Document 1, a polycrystalline substrate having a sufficient thickness and having mechanical strength is used so as not to damage the silicon carbide substrate during handling such as polishing. Therefore, it was necessary to use a polycrystalline substrate having a thickness greater than the thickness required to function as a semiconductor.

Moreover, when the resistance value of the polycrystalline silicon carbide substrate is high, the ON resistance increases, and there is a possibility that the original characteristics of the silicon carbide semiconductor cannot be fully exhibited.

That is, in order to prevent damage to the silicon carbide substrate in the manufacturing process of the silicon carbide substrate, the polycrystalline substrate must be thick enough to have mechanical strength. Moreover, in order to reduce the ON resistance of the obtained silicon carbide semiconductor, the resistance value of the polycrystalline substrate must be low.

Conventionally, a silicon carbide substrate has been obtained by forming a film to a predetermined thickness while adding a dopant such as nitrogen in a chemical vapor deposition method or other chemical vapor deposition method. FIG. 4 is a side view of a supporting substrate, a polycrystalline silicon carbide film, etc., for explaining a manufacturing process of a conventional polycrystalline silicon carbide substrate. Here, FIG. 4A is a schematic diagram showing a cross section of the vapor deposition substrate 500 in a state where thick polycrystalline silicon carbide films 520a and 520b are formed on both sides of the supporting substrate 510, and FIG. 4A and 4B are schematic cross-sectional views showing warping of polycrystalline silicon carbide films 520a′ and 520b′ obtained by removing a support substrate 510 from a vapor deposition substrate 500, and FIG. 5 is a schematic diagram showing a cross section of a polycrystalline silicon carbide substrate 521 obtained by removing warped portions of polycrystalline silicon carbide films 520a′ and 520b′ by polishing or the like. FIG.

Polycrystalline silicon carbide substrates 521a and 521b are formed by forming silicon carbide polycrystalline films 520a and 520b by chemical vapor deposition such as thermal chemical vapor deposition on a supporting substrate 510 such as a silicon supporting substrate or a graphite supporting substrate as a base material. After obtaining the vapor deposition substrate 500, the support substrate 510 is removed. However, when the polycrystalline silicon carbide film is formed, polycrystalline silicon carbide starts to grow from the surface of the support substrate 510. Therefore, as the thickness of the polycrystalline silicon carbide films 520a and 520b increases, the crystal grains of silicon carbide increase. As a result, the silicon carbide polycrystalline films 520a and 520b are likely to be strained. Therefore, when the polycrystalline silicon carbide films 520a and 520b are separated from the supporting substrate 510, the polycrystalline silicon carbide films 520a' and 520b' are greatly warped as shown in FIG. 4B. was there.

When a large warp occurs, as shown in FIG. 4(B), in order to obtain silicon carbide polycrystalline substrates 521a and 521b with a required thickness T, the warped portion is removed, for example, by line A, line It is necessary to scrape off by polishing or the like up to the portion of A'. Therefore, the film thickness of the polycrystalline silicon carbide films 520a and 520b before polishing is such that the polycrystalline silicon carbide films 520a and 520b are formed thickly on the support substrate 510 in consideration of the thickness including the warpage that may occur. There is a need to. In other words, it is necessary to form a thicker film in consideration of the amount to be scraped off, and to polish hard silicon carbide, which is difficult to polish. This greatly affects the productivity of the polycrystalline silicon substrates 521a and 521b and the productivity of the silicon carbide substrate.

Accordingly, it is an object of the present invention to provide a method for manufacturing a polycrystalline silicon carbide substrate that can reduce the amount of warpage that may occur in the polycrystalline silicon carbide substrate, focusing on the above problems.

In the method for producing a polycrystalline silicon carbide substrate of the present invention, after forming a first polycrystalline silicon carbide film on a film-forming target surface of a support substrate by chemical vapor deposition, the film thickness obtained by removing the support substrate is a film forming step of forming a second polycrystalline silicon carbide film by chemical vapor deposition on the film formation target surface of the polycrystalline silicon carbide support substrate having a thickness of 50 μm to 250 μm.

Further, in the method for manufacturing a polycrystalline silicon carbide substrate of the present invention, the second polycrystalline silicon carbide film formed in the film forming step may have a thickness of 70 μm or more.

Further, in the method for manufacturing a silicon carbide polycrystalline substrate of the present invention, when forming the first polycrystalline silicon carbide film, the direction of ejection from the position where the source gas of the first polycrystalline silicon carbide film is ejected; is perpendicular to the film formation target surface of the support substrate, and in the film formation step, the ejection direction from the ejection position of the raw material gas for the second polycrystalline silicon carbide film and the film formation of the polycrystalline silicon carbide support substrate. is perpendicular to the target surface, and the film formation target surface of the polycrystalline silicon carbide support substrate is exposed to the source gas of the first polycrystalline silicon carbide film during the formation of the first polycrystalline silicon carbide film. It is composed of a first surface facing an ejection position and a second surface that is a surface on the back side of the first surface, and the second surface faces the ejection position of the raw material gas of the second polycrystalline silicon carbide film. Alternatively, the second silicon carbide polycrystalline film may be deposited.

Moreover, in the method for manufacturing a polycrystalline silicon carbide substrate of the present invention, in the film forming step, the second polycrystalline silicon carbide films may be formed on both surfaces of the polycrystalline silicon carbide support substrate.

With the method for manufacturing a polycrystalline silicon carbide substrate of the present invention, it is possible to reduce the amount of warpage that may occur in the polycrystalline silicon carbide substrate.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side cross-sectional view schematically showing an example of a film forming apparatus used in a method for manufacturing a polycrystalline silicon carbide substrate according to one embodiment of the present invention; FIG. 2A is a side view of a support substrate, a silicon carbide polycrystalline film, etc., for explaining a manufacturing process in one embodiment of the present invention; FIG. 10 is a diagram showing a state in which polycrystalline silicon carbide support substrates 220a' and 220b' are placed in a film formation chamber 1010 in a modification of the method for manufacturing a polycrystalline silicon carbide substrate. It is a side view of a support substrate, a silicon carbide polycrystalline film, etc. explaining the manufacturing process of the conventional silicon carbide polycrystalline substrate.

A method for manufacturing a silicon carbide polycrystalline substrate 2000 according to the first embodiment of the present invention will be described with reference to the drawings.

As shown in FIGS. 1 and 2, the method for manufacturing the polycrystalline silicon carbide substrate 2000 of the present embodiment is performed by chemical vapor deposition using both the front surface 210a and the rear surface 210b of the support substrate 210 as film formation target surfaces. Crystal films 220a and 220b are deposited (FIG. 2(A)), and then surfaces 220a1 of silicon carbide polycrystalline support substrates 220a' and 220b' having a film thickness of 50 μm to 250 μm obtained by removing the support substrate 210, 220b1 and back surfaces 220a2 and 220b2 (FIG. 2(B)), a film forming step of forming second silicon carbide polycrystalline films 230a and 230b by chemical vapor deposition (FIG. 2(C)). For the deposition of the first polycrystalline silicon carbide films 220a, 220b and the second polycrystalline silicon carbide films 230a, 230b, for example, the film deposition apparatus 1000 shown in FIG. 1 can be used. In this embodiment, as shown in FIG. 2A, a support substrate 210 on which the first polycrystalline silicon carbide films 220a and 220b are formed is referred to as a vapor deposition substrate 200. As shown in FIG. Note that a substrate on which a film is formed only on one side is also regarded as a vapor deposition substrate. Moreover, the method for manufacturing the silicon carbide polycrystalline substrate 2000 of the present embodiment is suitable for manufacturing a silicon carbide polycrystalline substrate having a substrate thickness of about 300 μm to 700 μm, for example.

The film forming apparatus 1000 can form a silicon carbide polycrystalline film on the support substrate 210 or the silicon carbide polycrystalline support substrates 220a' and 220b' by chemical vapor deposition. FIG. 1 illustrates a state in which the supporting substrate 210 is provided to the film forming apparatus 1000 . The film forming apparatus 1000 includes a housing 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 supporting substrate 210 or silicon carbide polycrystalline supporting substrates 220a′ and 220b′, Exhaust gas introduction chamber 1040 for introducing raw material gas and carrier gas discharged from film formation chamber 1010 into gas discharge port 1030 described later, box 1050 covering exhaust gas introduction chamber 1040, and film formation chamber 1010 from outside box 1050. A heater 1060 made of carbon that heats the interior, a gas introduction port 1020 that is provided in the lower part of the film formation chamber 1010 and introduces a source gas and a carrier gas into the film formation chamber 1010, a gas discharge port 1030, and a support substrate. 210 or a substrate holder 1070 that holds a silicon carbide polycrystalline support substrate 220a', 220b'. The substrate holder 1070 also has two pillars 1071 and mounting portions 1072 provided on the pillars 1071 for horizontally mounting the support substrate 210 or the silicon carbide polycrystalline support substrates 220a' and 220b'.

During the deposition of the first polycrystalline silicon carbide films 220a and 220b and the second polycrystalline silicon carbide films 230a and 230b, source gas, carrier gas and the like are introduced from the gas introduction port 1020 provided in the deposition chamber 1010. , is discharged from the bottom of the film formation chamber 1010 into the exhaust gas introduction chamber 1040 , and further discharged from the film formation apparatus 1000 through the gas discharge port 1030 .

Next, as an example of a method for manufacturing the silicon carbide polycrystalline substrate 2000 according to one embodiment of the present invention, a method using the aforementioned film forming apparatus 1000 will be described. The following description is an example of the method for manufacturing the silicon carbide polycrystalline substrate 2000 of the present embodiment, and the conditions such as temperature, pressure, gas atmosphere, etc., and the procedure may be changed within a range that causes no problem.

First, in the film forming apparatus 1000, the first silicon carbide polycrystalline films 220a and 220b are formed on the support substrate 210 by chemical vapor deposition. As the support substrate 210, a support substrate made of graphite or a support substrate made of silicon can be preferably used in consideration of ease of removing the support substrate 210 in a later step.

The supporting substrate 210 is placed on the mounting portion 1072, and the supporting substrate is heated by the heater 1060 to the film formation reaction temperature in an inert gas atmosphere such as Ar under reduced pressure. When the film formation reaction temperature (for example, about 1200° C.) is reached, the supply of the inert gas is stopped, and the material gas and carrier gas containing the components of the first silicon carbide polycrystalline films 220 a and 220 b are introduced into the film formation chamber 1010 . supply. The first silicon carbide polycrystalline films 220a and 220b can be formed on both surfaces of the heated support substrate 210 by the chemical reaction on the film formation target surface of the support substrate 210 and in the gas phase. As a result, as shown in FIG. 2A, a vapor deposition substrate 200 is obtained in which the first silicon carbide polycrystalline films 220a and 220b are formed on the support substrate 210. Next, as shown in FIG.

The raw material gas is not particularly limited as long as it can form the first polycrystalline silicon carbide films 220a and 220b. A raw material gas 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 ), tetrachlorosilane (SiCl ₄ ) can be used. Hydrocarbons such as methane (CH ₄ ), propane (C ₃ H ₈ ), and acetylene (C ₂ H ₂ ) can be used as the C source gas. 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 source gases.

As the carrier gas, a generally used carrier gas may be used as long as the source gas can be spread to the supporting substrate 210 without interfering with the formation of the first polycrystalline silicon carbide films 220a and 220b. can be done. For example, H ₂ gas, which has excellent thermal conductivity and an etching effect on silicon carbide, can be used as a carrier gas. Also, an impurity doping gas can be supplied as a third gas at the same time as these raw material gas and carrier gas. For example, nitrogen (N ₂ ) can be used when the conductivity type of the silicon carbide polycrystalline substrate 2000 is n-type, and trimethylaluminum (TMA) can be used when it is p-type.

When forming the first silicon carbide polycrystalline films 220a and 220b, the above gases are appropriately mixed and supplied. Further, the mixing ratio of the gases may be changed during the film forming process depending on the properties of the desired polycrystalline silicon carbide film.

In addition, the first polycrystalline silicon carbide films 220a and 220b serve as the polycrystalline silicon carbide supporting substrates 220a' and 220b', and are the targets of film formation during the film forming process of forming the second polycrystalline silicon carbide films 230a and 230b. becomes. Therefore, in order to obtain a stable shape of the silicon carbide polycrystalline substrate 2000, it is necessary that the object to be film-formed has a certain degree of strength. For this reason, the film thickness of the silicon carbide polycrystalline support substrates 220a' and 220b' is set to 50 μm or more.

In addition, if the first polycrystalline silicon carbide films 220a and 220b are made too thick, strain due to crystal growth tends to increase. When 2000 is obtained, there is a possibility that warpage that becomes a problem when used for manufacturing devices or the like remains. Accordingly, the thickness of the silicon carbide polycrystalline support substrates 220a' and 220b' is set to 250 μm or less.

Next, the support substrate 210 is removed from the vapor deposition substrate 200 . When the supporting substrate 210 made of graphite is used as the supporting substrate 210 , the supporting substrate 210 can be removed by burning the deposition substrate 200 . For the step of removing the support substrate 210 by combustion, for example, a combustion furnace equipped with a heater made of molybdenum disilicide can be used. While holding the vapor deposition substrate 200 in a combustion furnace and supplying oxidizing gas such as O ₂ and air into the combustion furnace, the inside of the combustion furnace is heated to several hundred degrees (for example, 800 ° C.) by a heater under normal pressure or reduced pressure. degree). By heating, only the supporting substrate 210 is burned to obtain polycrystalline silicon carbide supporting substrates 220a' and 220b' as shown in FIG. 2(B). 2A and 2B, a silicon carbide polycrystalline support substrate 220a′ is obtained from the first silicon carbide polycrystalline film 220a, and a silicon carbide polycrystalline support substrate is obtained from the first silicon carbide polycrystalline film 220b. It shows that a substrate 220b' is obtained.

When a support substrate made of silicon is used as the support substrate 210, the vapor deposition substrate 200 is immersed in nitric hydrofluoric acid (mixed acid of nitric acid and hydrofluoric acid) to remove only the support substrate 210 made of silicon. By dissolving, silicon carbide polycrystalline support substrates 220a' and 220b' are obtained as shown in FIG. 2(B).

When the entire surface of the support substrate 210 is covered with the first silicon carbide polycrystalline films 220a and 220b, the support substrate 210 is exposed by cutting the outer peripheral edge of the vapor deposition substrate 200 to expose the support substrate 210. It may also include a cutting step to allow.

Next, the polycrystalline silicon carbide supporting substrates 220a′ and 220b′ are placed on the mounting portion 1072 of the film forming apparatus 1000, and the second film formation target surfaces of the polycrystalline silicon carbide supporting substrates 220a′ and 220b′ are coated with the second film-forming target surfaces. A film forming process is performed to form silicon carbide polycrystalline films 230a and 230b. The film forming procedure, raw materials, etc. in the film forming process can be performed in the same manner as in the film forming of the first silicon carbide polycrystalline films 220a and 220b. The silicon carbide polycrystalline support substrates 220a' and 220b' can each be used as a film formation target instead of the support substrate.

FIG. 2(C) is a diagram showing a polycrystalline silicon carbide substrate 2000 obtained by performing a film forming process on polycrystalline silicon carbide supporting substrates 220a' and 220b'. As shown in FIG. 2(C), the second silicon carbide polycrystalline silicon carbide polycrystalline supporting substrates 220a′ and 220b′ are formed on both front surfaces 220a1 and 220b1 and back surfaces 220a2 and 220b2 of the silicon carbide polycrystalline support substrates 220a′ and 220b′, respectively. Crystal films 230a and 230b are formed. In addition, in order to suppress the occurrence of problematic warping in the obtained polycrystalline silicon carbide substrate 2000, the thickness of the second polycrystalline silicon carbide films 230a and 230b formed in the film forming process is set to 70 μm or more. It is preferable to As described above, silicon carbide polycrystalline substrate 2000 is obtained.

In the method for manufacturing a polycrystalline silicon carbide substrate 2000 of the present embodiment, the first polycrystalline silicon carbide films 220a and 220b are formed on the film formation target surface of the support substrate 210 by chemical vapor deposition, and then the support substrate 210 is removed. a film formation step of forming second silicon carbide polycrystalline films 230a and 230b by chemical vapor deposition on the film formation target surfaces of the silicon carbide polycrystalline support substrates 220a′ and 220b′ having a film thickness of 50 μm to 250 μm obtained by . As the film thickness of the first polycrystalline silicon carbide films 220a and 220b increases, the size of crystal grains of the deposited silicon carbide increases with increasing distance from the support substrate 210. FIG. For this reason, when the film thickness to be formed in one film forming process is increased, a large warp may occur. However, according to the method of the present embodiment, silicon carbide polycrystalline support substrates 220a' and 220b' having a thickness of 50 μm to 250 μm are first formed, and then second silicon carbide polycrystalline films 230a and 230b are formed thereon. It is possible to suppress the occurrence of large warpage. As described above, according to the method of the present embodiment, it is possible to reduce the amount of warpage that may occur in the polycrystalline silicon carbide substrate 2000 and which poses a problem in the manufacturing process of devices and the like.

In addition, since the second polycrystalline silicon carbide films 230a and 230b are formed on both the front surfaces 220a1 and 220b1 and the back surfaces 220a2 and 220b2 of the silicon carbide polycrystalline support substrates 220a' and 220b' in the film forming process, The thickness of the second silicon carbide polycrystalline films 230a and 230b formed in the film formation process can be halved compared to the case of forming the film only on one side. Therefore, by forming films on both surfaces of the silicon carbide polycrystalline support substrates 220a' and 220b', the amount of warpage that may occur in the silicon carbide polycrystalline substrate 2000 can be further reduced.

It should be noted that the present invention is not limited to the above-described embodiments, but includes other processes and the like that can achieve the object of the present invention, and the following modifications and the like are also included in the present invention.

When forming the first polycrystalline silicon carbide films 220a and 220b, the direction of ejection from the ejection position (gas inlet 1020) of the raw material gas for the first polycrystalline silicon carbide films 220a and 220b and the direction of ejection of the first polycrystalline silicon carbide films 220a and 220b The film formation target surfaces (front surface 210a, back surface 210b) (FIG. 1) of the support substrate 210 on which the films 220a and 220b are formed are perpendicular to each other, and the second silicon carbide polycrystalline films 230a and 230b are formed in the film formation process. and the film formation target surfaces of the silicon carbide polycrystalline support substrates 220a′ and 220b′ on which the second polycrystalline silicon carbide films 230a and 230b are formed. are perpendicular to each other, and the film-forming target surfaces of the polycrystalline silicon carbide supporting substrates 220a' and 220b' are aligned with the surfaces of the first polycrystalline silicon carbide films 220a and 220b when the first polycrystalline silicon carbide films 220a and 220b are formed. A first surface (back surface 220a2 of polycrystalline silicon carbide support substrate 220a′, front surface 220b1 of polycrystalline silicon carbide support substrate 220b′) facing the source gas ejection position (gas inlet 1020), and the back surface of the first surface (front surface 220a1 of polycrystalline silicon carbide support substrate 220a′, back surface 220b2 of polycrystalline silicon carbide support substrate 220b′), which is the second surface of polycrystalline silicon carbide film 230a. , 230b (gas introduction port 1020), the second silicon carbide polycrystalline films 230a and 230b may be deposited (FIG. 3).

In the above-described embodiment, as indicated by the arrow in FIG. 1, the gas such as the raw material gas is ejected vertically from the gas inlet 1020 and spreads horizontally from the bottom to the top of the film forming chamber 1010. flow towards The support substrate 210 on which the first silicon carbide polycrystalline films 220a and 220b are to be formed is placed on the substrate holder 1070 so that the film formation target surfaces (front surface 210a and rear surface 210b) are horizontal. That is, in the above-described embodiment, the ejection direction of the source gas from the source gas ejection position (gas introduction port 1020) and the film formation of the support substrate 210 on which the first polycrystalline silicon carbide films 220a and 220b are formed. are perpendicular to the target surface (front surface 210a, back surface 210b). At this time, the upward gas flow from the gas inlet 1020 may cause strain in the formed first silicon carbide polycrystalline films 220a and 220b. Therefore, in the film forming step of forming the second polycrystalline silicon carbide films 230a and 230b, silicon carbide is added so as to offset the generated strain according to the film forming conditions and the desired performance of the polycrystalline silicon carbide substrate 2000. Polycrystalline support substrates 220a', 220b' may be arranged.

In the above-described embodiment, the second silicon carbide polycrystalline films 230a, 230b are formed on both surfaces (front surfaces 220a1, 220b1 and back surfaces 220a2, 220b2) of the silicon carbide polycrystalline support substrates 220a′, 220b′, and carbonized. The silicon polycrystalline support substrates 220a' and 220b' are mounted on the substrate holder 1070 so that the film formation target surfaces (surfaces 220a1 and 220b1 and back surfaces 220a2 and 220b2) are horizontal. Therefore, in the film forming process, the ejection direction of the raw material gas from the ejection position (gas inlet 1020) of the raw material gas of the second silicon carbide polycrystalline films 230a and 230b and the second silicon carbide polycrystalline films 230a and 230b are formed. The film formation target surfaces (surfaces 220a1 and 220b1 and back surfaces 220a2 and 220b2) of the silicon carbide polycrystalline support substrates 220a' and 220b' to be filmed are perpendicular to each other. In addition, the film-forming target surfaces of the polycrystalline silicon carbide supporting substrates 220a′ and 220b′ are subjected to ejection of raw material gas for the first polycrystalline silicon carbide films 220a and 220b when the first polycrystalline silicon carbide films 220a and 220b are formed. A first surface (back surface 220a2 of polycrystalline silicon carbide support substrate 220a′, front surface 220b1 of polycrystalline silicon carbide support substrate 220b′) facing the position (gas inlet 1020) It consists of two surfaces (front surface 220a1 of polycrystalline silicon carbide support substrate 220a′ and back surface 220b2 of polycrystalline silicon carbide support substrate 220b′). In order to cancel the strain when it occurs in the first polycrystalline silicon carbide films 220a and 220b, for example, as shown in FIG. surface 220a1 of the polycrystalline silicon carbide support substrate 220b' and the back surface 220b2 of the polycrystalline silicon carbide substrate 220b') are directed toward the ejection position (gas inlet 1020) of the raw material gas for the second polycrystalline silicon carbide films 230a and 230b, and the second polycrystalline silicon carbide Films 230a and 230b may be deposited. As a result, for example, in the silicon carbide polycrystalline support substrate 220a′, the gas flow direction was from the back surface 220a2 to the front surface 220a1 when the first polycrystalline silicon carbide film 220a was formed. When the silicon carbide polycrystalline film 230a is formed, the direction of gas flow is from the front surface 220a1 to the rear surface 220a2. That is, when forming the first polycrystalline silicon carbide films 220a and 220b to be the polycrystalline silicon carbide supporting substrates 220a′ and 220b′ on the polycrystalline silicon carbide supporting substrates 220a′ and 220b′, The flow directions of gases such as raw material gases to the polycrystalline silicon carbide supporting substrates 220a' and 220b' are different from when the second polycrystalline silicon carbide films 230a and 230b are formed on the supporting substrates 220a' and 220b'. In this way, the silicon carbide polycrystalline supporting substrate 220a′ (the first silicon carbide polycrystalline film) is formed during the deposition of the first polycrystalline silicon carbide films 220a and 220b and during the deposition of the second polycrystalline silicon carbide films 230a and 230b. By preventing bias in the flow direction of the raw material gas with respect to the polycrystalline film 220a), the distortion of the polycrystalline silicon carbide film that may be caused by the flow of the gas is offset, and the distortion that may occur in the polycrystalline silicon carbide substrate 2000 is offset. The amount of warpage can be reduced.

Further, in the above-described embodiment, an example of forming the second polycrystalline silicon carbide films 230a and 230b on both sides of the polycrystalline silicon carbide support substrate 220a' was shown, but they may be formed on one side. That is, for example, the polycrystalline silicon carbide supporting substrate 220a′ is placed on a pedestal or the like on which the entire one side of the polycrystalline silicon carbide supporting substrate 220a′ is grounded, and the one side and the opposite side of the polycrystalline silicon carbide supporting substrate 220a′ are grounded. A silicon carbide polycrystalline film may be deposited only on the surface.

Further, in the above-described embodiment, the formation of the first polycrystalline silicon carbide films 220a and 220b and the formation of the second polycrystalline silicon carbide films 230a and 230b are performed in a series of steps. The polycrystalline silicon carbide supporting substrates 220a' and 220b' may be manufactured as intermediates, and the second polycrystalline silicon carbide films 230a and 230b may be formed as a separate manufacturing process. Alternatively, the vapor deposition substrate 200 and the silicon carbide polycrystalline support substrates 220a' and 220b' may be purchased and obtained, and the film formation process may be performed on them.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited by these Examples.

In this example, a polycrystalline silicon carbide substrate was manufactured using the film forming apparatus 1000 of the above-described embodiment.

(Example 1)
First, first silicon carbide polycrystalline films 220 a and 220 b were formed on the support substrate 210 . In addition, in this embodiment, this step is referred to as a "first step". A graphite substrate having a diameter of 150 mm and a thickness of 50 μm was used as a support substrate. After the supporting substrate 210 was placed on the mounting portion 1072 of the film forming apparatus 1000 and the inside of the film forming chamber 1010 was evacuated by an exhaust pump (not shown), the chamber was heated to 1350.degree. SiCl ₄ and CH ₄ were used as raw material gases, H ₂ was used as carrier gas, and N ₂ was used as impurity doping gas. The first silicon carbide polycrystalline films 220a and 220b are formed by mixing the above gases at a ratio of SiCl ₄ :CH ₄ :H ₂ :N ₂ =1:1:10:10 and supplying them into the film forming chamber 1010 . Then, film formation was performed for 100 minutes. As described above, a vapor deposition substrate 200 was obtained in which the first silicon carbide polycrystalline films 220a and 220b having a thickness of 50 μm were formed on the support substrate 210 .

Next, using a combustion furnace equipped with a heater made of molybdenum disilicide, the vapor deposition substrate 200 is burned at 800° C. for 100 hours in an atmospheric environment to remove the support substrate 210 and obtain a polycrystalline silicon carbide support substrate 220a′. , 220b′.

Next, using the polycrystalline silicon carbide support substrate 220a′, a step of forming second polycrystalline silicon carbide films 230a and 230b was performed. In addition, in the present embodiment, the film forming process is referred to as a "second process". Similar to the deposition of the first silicon carbide polycrystalline films 220a and 220b, the deposition apparatus 1000 was used to deposit the above gases at a ratio of _SiCl4 : _CH4 : _H2 : _N2 =1:1:10:10. The mixture was supplied into the film forming chamber 1010, and film formation was performed at 1350° C. for 300 minutes. At this time, the rear surface 220a2 of the polycrystalline silicon carbide support substrate 220a′, which is the surface facing the gas inlet 1020 during the deposition of the first polycrystalline silicon carbide film 220a, is directed toward the gas inlet 1020, and the mounting portion 1072 is placed. placed on. As a result, a polycrystalline silicon carbide substrate 2000 having a thickness of 350 μm was obtained, in which the second polycrystalline silicon carbide films 230a and 230b having a thickness of 150 μm were formed on both surfaces of the polycrystalline silicon carbide supporting substrate 220a′.

Regarding the warpage of the silicon carbide polycrystalline support substrate 220a′ and the silicon carbide polycrystalline substrate 2000, the center line of the film formation target surface of the silicon carbide polycrystalline substrate was measured with an oblique incidence type optical measuring instrument, and the maximum of the obtained measurement values was The difference between the value and the minimum value was defined as the amount of warpage. Five points were measured: the center, the edge of the circumference, and the point between the center and the edge of the circumference, the distance from the center being the same as the distance from the edge of the circumference. When the amount of warpage was greater than 50 μm, it was determined that the manufactured polycrystalline silicon carbide substrate 2000 had warpage that could cause problems in the manufacturing process of devices and the like. Table 1 shows the results. In Table 1, the amount of warpage of the polycrystalline silicon carbide supporting substrate 220a' is shown as the amount of warpage after the first step, and the amount of warpage of the polycrystalline silicon carbide substrate 2000 is shown as the amount of warpage after the second step. .

(Example 2, Example 3, Comparative Example 1, Comparative Example 2)
As Example 2, Example 3, Comparative Example 1, and Comparative Example 2, the film formation times of the first step and the second step were changed from Example 1 to obtain silicon carbide polycrystalline films with different thicknesses. A silicon carbide polycrystalline substrate was manufactured under the same conditions as in Example 1, except for the above. In Comparative Example 1, the time of the second step was set to 0, and a silicon carbide polycrystalline substrate having a thickness of 350 μm was obtained only by the first step. In Example 2, Example 3, Comparative Example 1, and Comparative Example 2, polycrystalline silicon carbide substrates having a thickness of 350 μm, which is the same as in Example 1, were manufactured. Table 1 shows the film formation time conditions and the obtained film thickness. For the silicon carbide polycrystalline substrates obtained in the first step and the second step, the amount of warpage was confirmed in the same manner as in Example 1.

(Example 4)
As Example 4, in the film forming process using the polycrystalline silicon carbide supporting substrate 220a′, the surface (surface 220a1) not facing the gas inlet 1020 was formed with the gas inlet when forming the first polycrystalline silicon carbide film 220a. A silicon carbide polycrystalline substrate was manufactured under the same conditions as in Example 3, except that it was placed on the placing portion 1072 toward 1020 . For the silicon carbide polycrystalline substrates obtained in the first step and the second step, the amount of warpage was confirmed in the same manner as in Example 1.

(Evaluation results)

As a result of measuring the amount of warpage, in the polycrystalline silicon carbide substrates 2000 of Examples 1 to 4, the amount of warpage of the polycrystalline silicon carbide substrate in the second step was within 50 μm, which may cause problems in the manufacturing process of devices and the like. No warpage was confirmed. In Comparative Examples 1 and 2 in which the film thickness in the first step was increased, the amount of warpage of the polycrystalline silicon carbide substrate was increased, and warpage that could cause problems was confirmed. In Comparative Example 2, the amount of warpage in the second step was smaller than the amount of warpage in the first step, but it did not become 50 μm or less, and warpage that could cause problems remained.

In addition, in Example 4, in which the concave back surface 220a2 of the silicon carbide polycrystalline support substrate 220a′ was placed facing the gas inlet 1020, the silicon carbide obtained in the second step compared to Example 3. The amount of warpage of the polycrystalline substrate 2000 is reduced. For this reason, when warping occurs in the first step, the concave surface of the polycrystalline silicon carbide substrate should face the gas inlet 1020 to make it easier to come into contact with the raw material gas. It was shown to be more effective in suppressing the amount of warpage that can occur in the crystal substrate.

Examples 1 to 4, which are exemplary embodiments of the present invention, show that the amount of warpage that can occur in the manufactured polycrystalline silicon carbide substrate can be reduced in manufacturing the polycrystalline silicon carbide substrate.

2000 Silicon carbide polycrystalline substrates 220a, 220b First silicon carbide polycrystalline films 230a, 230b Second silicon carbide polycrystalline films 220a', 220b' Silicon carbide polycrystalline support substrate 210 Support substrates 220a2, 220b1 First surfaces 220a1, 220b2 2nd side 1020 Gas introduction port (source gas ejection position)

Claims (3)

A polycrystalline silicon carbide supporting substrate having a film thickness of 50 μm to 250 μm is obtained by forming a first polycrystalline silicon carbide film on a film-forming target surface of a supporting substrate by chemical vapor deposition and then removing the supporting substrate. including a film forming step of forming a second silicon carbide polycrystalline film on the film target surface by chemical vapor deposition;
At the time of forming the first silicon carbide polycrystalline film,
the ejection direction from the ejection position of the raw material gas for the first silicon carbide polycrystalline film is perpendicular to the film formation target surface of the support substrate;
In the film forming step,
the ejection direction from the ejection position of the raw material gas for the second polycrystalline silicon carbide film is perpendicular to the film formation target surface of the polycrystalline silicon carbide support substrate;
The film formation target surface of the polycrystalline silicon carbide support substrate is a first surface that faces the injection position of the raw material gas of the first polycrystalline silicon carbide film during the film formation of the first polycrystalline silicon carbide film. , and a second surface that is the surface on the back side of the first surface,
The second silicon carbide polycrystalline film having the same thickness is formed on the first surface and the second surface with the second surface facing the injection position of the raw material gas of the second silicon carbide polycrystalline film. and a method for producing a polycrystalline silicon carbide substrate having a thickness of 300 μm to 700 μm, wherein the amount of warp after the film formation step is within 40 μm . 2. The method for manufacturing a polycrystalline silicon carbide substrate according to claim 1, wherein the thickness of said second polycrystalline silicon carbide film formed in said film forming step is 70 [mu]m or more. 3. The method for producing a polycrystalline silicon carbide substrate according to claim 1, wherein in said film forming step, said second polycrystalline silicon carbide films are formed on both surfaces of said polycrystalline silicon carbide supporting substrate.

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