JP2021066624A - Manufacturing method of silicon carbide polycrystalline substrate - Google Patents

Abstract

To provide a manufacturing method of a silicon carbide polycrystalline substrate, for manufacturing a silicon carbide polycrystalline substrate having small warp, by suppressing generation of large warp on the silicon carbide polycrystalline substrate.SOLUTION: A manufacturing method of a silicon carbide polycrystalline substrate includes a first silicon carbide polycrystalline film deposition step for depositing a first silicon carbide polycrystalline film at the temperature of 1,400°C-1,500°C on a support substrate by a chemical vapor growth method, and a second silicon carbide polycrystalline film deposition step for depositing a second silicon carbide polycrystalline film on the first silicon carbide polycrystalline film, at the temperature of 1,200°C-1,300°C, namely, at a lower temperature by 100°C-200°C than a deposition temperature of the first silicon carbide polycrystalline film.SELECTED DRAWING: Figure 2

Description

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

Silicon carbide is a compound semiconductor material composed of silicon and carbon. Silicon carbide has an dielectric breakdown electric field strength 10 times that of silicon and a band gap 3 times that of silicon, and is excellent as a semiconductor material. Furthermore, since it is possible to control the p-type and n-type required for manufacturing devices in a wide range, it is expected as a material for power devices that exceeds the limit of silicon.

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

So far, various measures have been taken to reduce the cost of silicon carbide semiconductors. For example, Patent Document 1 describes a method for manufacturing a silicon carbide substrate, wherein at least a silicon carbide single crystal substrate and a silicon carbide polycrystalline substrate having a micropipe ^{density of 30 pieces / cm 2 or less are prepared, and the silicon carbide is described.} It is described that a step of laminating a single crystal substrate and the silicon carbide polycrystalline substrate is performed, and then a step of thinning the single crystal substrate is performed to produce a substrate having a single crystal layer formed on the polycrystalline substrate. ing.

Further, in Patent Document 1, before the step of bonding the single crystal substrate and the polycrystalline substrate, a step of injecting hydrogen ions into the single crystal substrate to form a hydrogen ion injection layer is performed, and the single crystal substrate and the polycrystalline substrate are combined. After the step of bonding with the crystal substrate and before the step of thinning the single crystal substrate, the step of performing heat treatment at a temperature of 350 ° C. or lower to thin the single crystal substrate is mechanically performed by the hydrogen ion injection layer. Describes a method for manufacturing a silicon carbide substrate as a step of peeling.

By such a method, more silicon carbide bonded substrates can be obtained from one silicon carbide single crystal ingot.

JP-A-2009-117533 Japanese Unexamined Patent Publication No. 10-251062

Most of the silicon carbide bonded substrates produced by the method of Patent Document 1 are polycrystalline substrates. Therefore, the size of the warp of the silicon carbide bonded substrate, which is obtained by bonding the polycrystalline substrate and the single crystal substrate, is dominated by the influence of the warp size of the polycrystalline substrate. In the device manufacturing process using the silicon carbide bonded substrate, if the amount of warpage of the silicon carbide bonded substrate is large, there are problems such as poor pattern formation in the photolithography process and non-uniform ion implantation depth in the ion implantation process. Therefore, the warpage of the polycrystalline substrate used for the silicon carbide bonded substrate is required to be small.

In response to the above-mentioned problems related to the warp of the silicon carbide polycrystalline substrate, Patent Document 2 describes the coefficient of thermal expansion of the carbon support substrate used for forming the silicon carbide polycrystalline film by the chemical vapor deposition method. it is described that in the range of ^{3.0 × 10 -6 /K~5.0×10 -6 / K} . By using a carbon support substrate of the thermal expansion coefficient (approx. ^{4.3 × 10 -6 /K~4.5×10 -6 / K} ) and thermal expansion coefficient near the silicon carbide polycrystal film, a carbon support substrate carbide Warpage is reduced by reducing the difference in volume shrinkage when the silicon carbide polycrystalline film is formed and then cooled due to the difference in the coefficient of thermal expansion from that of the silicon carbide polycrystalline film, and by reducing the stress generated in the silicon carbide polycrystalline film. A method for obtaining a reduced silicon carbide polycrystalline film has been shown.
However, the above-mentioned factors are not the only factors that cause the warp of the silicon carbide polycrystalline film. By forming a silicon carbide polycrystalline film on a carbon support substrate made of a material different from that of the silicon carbide polycrystalline film, the particle size of the silicon carbide polycrystalline film is small at the initial stage when the silicon carbide polycrystalline film is formed, and then As the film formation of the silicon carbide polycrystalline film progresses, the particle size of the silicon carbide polycrystalline film formed increases. This causes a difference in the particle size of the silicon carbide polycrystalline film in the formed silicon carbide polycrystalline film, which causes a difference in the internal stress in the silicon carbide polycrystalline film. It contributes to increasing the warp of the film. In the process of removing the support substrate and processing the silicon carbide polycrystalline film into the silicon carbide polycrystalline substrate, the warp of the silicon carbide polycrystalline substrate is sufficient even if the portion of the silicon carbide crystal film where the particle size changes is scraped off. There was a problem that it did not become smaller.

Further, in the process of processing the silicon carbide polycrystalline film into the silicon carbide polycrystalline substrate, surface grinding or surface polishing may be performed in order to adjust the silicon carbide polycrystalline film to a predetermined thickness and flatness. is there. In these processes, poor thickness, flatness, or warpage may occur due to the large warpage of the silicon carbide polycrystalline film, which deteriorates the yield in the processing process for the silicon carbide polycrystalline substrate. It was a factor. In addition, for the purpose of improving these processing defects, for example, when forming a silicon carbide film, the thickness of the silicon carbide polycrystalline film may be increased. In order to increase the thickness of the silicon carbide polycrystalline film, there is a problem that the manufacturing cost and productivity are deteriorated due to an increase in the amount of gas used and a long film formation time.

Therefore, an object of the present invention is to provide a method for manufacturing a silicon carbide polycrystalline substrate, which suppresses the occurrence of a large warp in the silicon carbide polycrystalline substrate and manufactures the silicon carbide polycrystalline substrate with a small warp. To do.

In the method for producing a silicon carbide polycrystalline substrate of the present invention, a first silicon carbide polycrystalline film is formed on a support substrate by a chemical vapor phase growth method at a temperature of 1400 ° C to 1500 ° C. Crystal film forming step and the second silicon carbide polycrystalline film on the first silicon carbide polycrystalline film at 1200 ° C to 1300 ° C and higher than the film forming temperature of the first silicon carbide polycrystalline film. It includes a second silicon carbide polycrystalline film forming step of forming a film at a temperature lower than 100 ° C. to 200 ° C.

According to the method for producing a silicon carbide polycrystalline substrate of the present invention, it is possible to suppress the occurrence of a large warp in the silicon carbide polycrystalline substrate and produce a silicon carbide polycrystalline substrate with a small warp.

Cross-sectional view schematically showing an example of a film forming apparatus for forming a silicon carbide polycrystalline film by a chemical vapor deposition method (CVD method) in the method for producing a silicon carbide polycrystalline substrate according to an embodiment of the present invention. Is. It is sectional drawing which shows typically the side surface of the support substrate, the silicon carbide polycrystalline film, and the silicon carbide polycrystalline substrate in each step in the manufacturing method of the silicon carbide polycrystalline substrate which concerns on one Embodiment of this invention. It is sectional drawing which shows typically the side surface of the support substrate, the silicon carbide polycrystalline film, and the silicon carbide polycrystalline substrate in each step in the conventional method of manufacturing the silicon carbide polycrystalline substrate. It is sectional drawing which shows typically the distribution of the particle diameter of the silicon carbide polycrystalline film in the laminated body of the support substrate and the silicon carbide polycrystalline film obtained by the conventional manufacturing method of the silicon carbide polycrystalline substrate. A cross section schematically showing the distribution of the particle size of the silicon carbide polycrystalline film in the laminate of the support substrate and the silicon carbide polycrystalline film obtained by the method for producing the silicon carbide polycrystalline substrate according to the embodiment of the present invention. It is a figure.

A method for manufacturing a silicon carbide polycrystalline substrate according to an embodiment of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments.

FIG. 1 shows a film forming apparatus 1000 which is an example of a film forming apparatus for forming a silicon carbide polycrystalline film by a chemical vapor deposition method in the method for producing a silicon carbide polycrystalline substrate according to an embodiment of the present invention. It is sectional drawing which shows typically. FIG. 2 schematically shows a cross section of a carbon support substrate, a silicon carbide polycrystalline film, a laminate, and a silicon carbide polycrystalline substrate in each step in the method for manufacturing a silicon carbide polycrystalline substrate according to an embodiment of the present invention. It is a figure shown in. FIG. 2 (A) is a diagram showing a support substrate 100, FIG. 2 (B) is a diagram showing a laminate 400A obtained by the first silicon carbide polycrystalline film forming step, and FIG. 2 (C) is a diagram. It is a figure which shows the laminated body 400B obtained by the 2nd silicon carbide polycrystalline film film forming process, and FIG. 2 (D) is the silicon carbide polycrystalline substrate obtained by subjecting the laminated body 400B to the removal step of the support substrate 100. It is a figure which shows 500.

The method for producing a silicon carbide polycrystalline substrate of the present embodiment is a first method in which a first silicon carbide polycrystalline film 200 is formed on a support substrate 100 at a temperature of 1400 ° C. to 1500 ° C. by a chemical vapor phase growth method. The silicon carbide polycrystalline film forming step and the formation of the second silicon carbide polycrystalline film 300 on the first silicon carbide polycrystalline film 200 at 1200 ° C. to 1300 ° C. and the first silicon carbide polycrystalline film 200. It includes a second silicon carbide polycrystalline film forming step of forming a film at a temperature 100 ° C. to 200 ° C. lower than the film temperature. The present inventor has found that the warpage of the manufactured silicon carbide polycrystalline substrate 500 can be reduced by the method for producing the silicon carbide polycrystalline substrate of the present embodiment.

Next, each step will be described in the order of a first silicon carbide polycrystalline film forming step, a second silicon carbide polycrystalline film forming step, and a step of removing the support substrate 100. The following description is an example of the method for manufacturing the silicon carbide polycrystalline substrate 500 of the present embodiment, and each condition such as temperature, pressure, gas atmosphere, and the procedure may be changed within a range where there is no problem. Further, in the following, a case where the first silicon carbide polycrystalline film 200 is formed on both sides of the support substrate 100 as a film forming target to manufacture the silicon carbide polycrystalline substrate 500 will be described. A silicon carbide polycrystalline substrate may be produced by forming a silicon carbide polycrystalline film on one side of the carbon support substrate as a film forming target. Whether the target of film formation is one side or both sides of the carbon support substrate may be appropriately determined depending on the conditions such as the production plan of the silicon carbide polycrystalline substrate and the structure of the vapor deposition furnace.

(First Silicon Carbide Polycrystal Film Filming Step)
The first silicon carbide polycrystalline film forming step is a step of forming the first silicon carbide polycrystalline film 200 on the support substrate 100 by a chemical vapor deposition method at a temperature of 1400 ° C. to 1500 ° C. The first silicon carbide polycrystalline film film forming step can be performed, for example, by using the film forming apparatus 1000 shown in FIG.

The film forming apparatus 1000 can be used to form the first silicon carbide polycrystalline film 200 on the support substrate 100 by the chemical vapor deposition method. The film forming apparatus 1000 includes a housing 1100 which is an exterior of the film forming apparatus 1000, a film forming chamber 1010 for forming the first silicon carbide polycrystal film 200 on the support substrate 100, and a raw material discharged from the film forming chamber 1010. A carbon-made film forming chamber 1010 that heats the inside of the film forming chamber 1010 from the outside of the exhaust gas introduction chamber 1040 that introduces gas or carrier gas into the gas discharge port 1030 described later, the box 1050 that covers the exhaust gas introduction chamber 1040, and the box 1050. It has a heater 1060, a gas introduction port 1020 provided below the film formation chamber 1010 for introducing a raw material gas or a carrier gas into the film formation chamber 1010, a gas discharge port 1030, and a substrate holder 1070 for holding a support substrate 100. .. Further, the substrate holder 1070 has two pillars 1071 and a mounting portion 1072 provided on the pillar 1071 on which the support substrate 100 is horizontally mounted.

At the time of film formation of the first silicon carbide polycrystal film 200, the raw material gas, carrier gas, etc. are introduced from the gas introduction port 1020 provided in the film formation chamber 1010, and the exhaust gas introduction chamber 1040 is introduced from the lower part of the film formation chamber 1010. Is discharged to the outside of the film forming apparatus 1000 from the gas discharge port 1030.

Further, the shape such as the thickness of the support substrate 100 and the size of the surface to be formed is not particularly limited, and a material suitable for the desired silicon carbide polycrystalline substrate 500 can be used. As the support substrate 100, for example, a carbon support substrate can be used.

Next, a procedure for forming the first silicon carbide polycrystalline film 200 on the support substrate 100 by a chemical vapor deposition method using the film forming apparatus 1000 will be described.

The support substrate 100 (FIG. 2 (A)) is placed on the mounting portion 1072, and the support substrate 100 is heated by the heater 1060 in a reduced pressure state under an inert gas atmosphere such as Ar to the reaction temperature of the film formation. .. When the reaction temperature of the film formation is reached, the supply of the inert gas is stopped, the temperature is maintained, and the raw material gas or carrier gas containing the component of the first silicon carbide polycrystalline film 200 is supplied into the film formation chamber 1010. .. The first silicon carbide polycrystalline film 200 can be formed on both surfaces of the heated support substrate 100 by a chemical reaction on the surface of the support substrate 100 to be formed or in the gas phase. Then, by cooling to room temperature, as shown in FIG. 2B, a laminated body 400A in which the first silicon carbide polycrystalline film 200 is formed on the support substrate 100 is obtained.

The raw material gas is not particularly limited as long as the first silicon carbide polycrystalline film 200 can be formed, and the Si-based raw material gas and the C-based raw material gas generally used for forming the silicon carbide polycrystalline film are not particularly limited. Can be used. For example, as the Si-based raw material gas, silane (SiH ₄ ) can be used, monochlorosilane (SiH ₃ Cl), dichlorosilane (SiH ₂ Cl ₂ ), trichlorosilane (SiHCl ₃ ), tetrachlorosilane (SiCl _4). ) And other chlorine-based Si raw material-containing gas (chloride-based raw material) containing Cl having an etching action can be used. As the C-based raw material gas, for example, _{hydrocarbons such as methane (CH 4} ), propane (C ₃ H ₈ ), and acetylene (C ₂ H ₂ ) 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 the raw material gas can be developed on the support substrate 100 without inhibiting the formation of the silicon carbide polycrystalline film. _{For example, an H 2} gas having excellent thermal conductivity and having an etching action on silicon carbide can be used as a carrier gas. Further, at the same time as these raw material gas and carrier gas, as a third gas, an impurity doping gas in an amount commensurate with the target conductivity can be simultaneously supplied. _{For example, nitrogen (N 2} ) can be used when the conductive type of the silicon carbide polycrystalline substrate 500 is n-type, and trimethylaluminum (TMA) can be used when the conductive type is p-type.

When forming the first silicon carbide polycrystalline film 200, the above gas can be appropriately mixed and supplied. Moreover, you may supply individually without mixing the said gas. Further, the mixing ratio of the gas may be changed during the process of forming the first silicon carbide polycrystalline film, depending on the desired properties of the silicon carbide polycrystalline film.

The film formation temperature of the first silicon carbide polycrystalline film 200 in the present embodiment is 1400 ° C to 1500 ° C. The thickness of the first silicon carbide polycrystalline film 200 can be, for example, about 50 μm to 150 μm.

By the above-mentioned first silicon carbide polycrystalline film forming step, a laminate 400A of the support substrate 100 and the first silicon carbide polycrystalline film 200 can be obtained. The laminate 400A is subjected to the second silicon carbide polycrystalline film forming step.

(Second silicon carbide polycrystalline film film forming process)
Next, a second silicon carbide polycrystalline film forming step is performed. In the second silicon carbide polycrystalline film forming step, the second silicon carbide polycrystalline film 300 is placed on the first silicon carbide polycrystalline film 200 at 1200 ° C. to 1300 ° C. and the first silicon carbide polycrystalline film 200. This is a step of forming a film at a temperature 100 ° C. to 200 ° C. lower than the film forming temperature of. The second silicon carbide polycrystal film forming step is continuously performed in the first silicon carbide polycrystal film forming step through, for example, the film forming apparatus 1000 shown in FIG. 1 through a temperature lowering step described later. Alternatively, the laminate 400A may be cooled to about room temperature and then subjected to the second silicon carbide polycrystal film forming step.

When the second silicon carbide polycrystal film forming step is continuously performed in the first silicon carbide polycrystal film forming step, the supply of the raw material gas, the doping gas, and the carrier gas is stopped, and the inside of the film forming chamber 1010 is stopped. Is lowered to the film formation temperature of the second silicon carbide polycrystal film 300, that is, 1200 ° C. to 1300 ° C., and 100 ° C. to 200 ° C. lower than the film formation temperature of the first silicon carbide polycrystal film 200. (Temperature lowering process). When the temperature reaches a predetermined temperature, the temperature is maintained and the supply of the raw material gas, the doping gas, and the carrier gas is restarted to form the second silicon carbide polycrystalline film 300 having a predetermined thickness. The film forming conditions of the second silicon carbide polycrystalline film forming step may be the same as those of the first silicon carbide polycrystalline film forming step except for the temperature condition, or the conditions such as the gas mixing ratio may be changed. .. Incidentally, when stopping the supply of the source gas or the like in the cooling step, to the extent that the gas volume of the film forming chamber 1010 does not shrink, it is preferable to supply the inert gas of the carrier gas and Ar such as H _2.

The film formation temperature in the second silicon carbide polycrystalline film forming step is the first silicon carbide polycrystalline film in order to reduce the internal stress difference between the first silicon carbide polycrystalline film 200 and the second silicon carbide polycrystalline film 300. The difference between the size of the crystal grains of the 200 silicon carbide polycrystals and the size of the crystal grains of the silicon carbide polycrystal of the second silicon carbide polycrystal film 300 is set to be small. For example, the size of the crystal grains of the first silicon carbide polycrystalline film 200 and the size of the crystal grains at the initial stage of film formation of the second silicon carbide polycrystalline film 300 are about the same, and the inside of the second silicon carbide polycrystalline film 300 It is preferable that the difference in crystal grain size in the thickness direction is small. As a method for setting the film formation temperature in each step, for example, a preliminary test is performed to manufacture a silicon carbide polycrystalline substrate under various temperature conditions, and a cross section of the obtained silicon carbide polycrystalline substrate is scanned with a scanning electron microscope ( By observing using SEM), the distribution of the size distribution of the crystal grains of the silicon carbide polycrystalline of each film can be confirmed, and the temperature condition in which the difference in size is small can be adopted. The thickness of the second silicon carbide polycrystalline film may be appropriately set in consideration of the thickness of the silicon carbide polycrystalline substrate 500 to be manufactured and the thickness of the first silicon carbide polycrystalline film 200, for example, from 300 μm to 300 μm. It can be about 800 μm. After the second silicon carbide polycrystalline film 300 having a predetermined thickness is formed, the supply of the raw material gas and the like is stopped. By the above-mentioned second silicon carbide polycrystalline film forming step, the laminate 400B shown in FIG. 2C is obtained. The laminate 400B is cooled to about room temperature and then subjected to a step of removing the support substrate 100.
(Removal process)
Next, the laminated body 400B obtained by the second silicon carbide polycrystalline film forming step is subjected to a removing step of removing the support substrate 100 from the laminated body 400B.

The step of removing the support substrate 100 is a step of removing the support substrate 100 from the laminate 400B to obtain the silicon carbide polycrystalline substrate 500. First, in the laminated body 400B, when the support substrate 100 is not exposed, the silicon carbide polycrystalline film (first silicon carbide polycrystalline film 200 and second silicon carbide polycrystalline film 200) laminated on the outer peripheral end of the support substrate 100 The film 300) is ground using a diamond grindstone or the like to expose at least a part of the support substrate 100. When a carbon support substrate is used as the support substrate 100, for example, the laminate 400B can be removed by heating the laminate 400B to several hundred degrees (for example, about 800 ° C. to 1000 ° C.) and burning the support substrate 100. it can. For the step of removing the support substrate 100 by combustion, for example, a combustion furnace equipped with a heater made of molybdenum disilicate can be used. The laminate 400B is held in the combustion furnace, and _{while supplying an oxidizing gas such as O 2} or air to the combustion furnace, the inside of the combustion furnace is heated by a heater under a normal pressure or a reduced pressure state. By heating, only the support substrate 100 is burned to obtain the silicon carbide polycrystalline substrate 500 as shown in FIG. 2 (D). In addition, in order to eliminate the warp of the obtained silicon carbide polycrystalline substrate 500 and to obtain a desired thickness, if necessary, after removing the support substrate 100, further grinding or polishing is performed. May be good.

The silicon carbide polycrystalline substrate 500 obtained by the above method for producing a silicon carbide polycrystalline substrate has, for example, a warp amount of 100 μm or less. Therefore, the silicon carbide polycrystalline substrate 500 having a small warp can be obtained by the method for producing the silicon carbide polycrystalline substrate of the present embodiment.

(Distribution of crystal grain size)
Next, in the conventional method for producing a silicon carbide polycrystalline substrate and the method for producing a silicon carbide polycrystalline substrate of the present embodiment, the distribution of the grain size of the silicon carbide polycrystalline film in the silicon carbide polycrystalline film is compared. explain.

In the conventional method for manufacturing a silicon carbide polycrystalline substrate, a silicon carbide polycrystalline film 700 having a desired thickness is formed on the support substrate 100 shown in FIG. 3 (A) to form a laminate 800 (FIG. 3 (B)). After obtaining the above, the support substrate 100 is removed to obtain a silicon carbide polycrystalline substrate 700A (FIG. 3 (C)), and the warp is reduced by, for example, grinding to the portion of line A in FIG. 3 (C). The silicon carbide polycrystalline substrate 900 (FIG. 3 (D)) is obtained. In the conventional method for manufacturing a silicon carbide polycrystalline substrate, the silicon carbide polycrystalline film 700 is often formed at a temperature lower than 1400 ° C.

Here, in the laminate 800 (FIG. 3 (B)) obtained by the conventional method for producing a silicon carbide polycrystalline substrate, the distribution of crystal grains of the silicon carbide polycrystalline substrate is as shown in FIG. That is, the closer to the support substrate 100, the smaller the crystal grains (for example, the average particle size is about 10 μm), and as the thickness of the silicon carbide polycrystalline film 700 increases, the crystal grains of the silicon carbide polycrystalline film become larger (for example, the average particle size). Is about 50 μm). When the silicon carbide polycrystalline film 700 having the thickness required to obtain the silicon carbide polycrystalline substrate 900 with reduced warpage is formed, the difference in the size of the silicon carbide polycrystalline film 700 in the thickness direction within the silicon carbide polycrystalline film 700. The silicon carbide polycrystalline substrate 700A (FIG. 3 (C)) obtained by removing the support substrate 100 from the laminate 800 was in contact with the support substrate 100. A large convex warp may occur from the surface toward the outside of the silicon carbide polycrystalline substrate 700A in the thickness direction. Therefore, for example, when used for manufacturing a substrate bonded to a silicon carbide single crystal substrate, a warped portion generated in the silicon carbide polycrystalline substrate 700A is ground and polished to have a predetermined flatness and a predetermined thickness. As a result, it takes a lot of time and effort to process the silicon carbide polycrystalline substrate 900 (FIG. 3 (D)) with reduced warpage, and there is a problem that the yield, cost, and productivity are deteriorated.

On the other hand, in the method for producing a silicon carbide polycrystalline substrate of the present embodiment, the first silicon carbide polycrystalline film 200 is formed on the support substrate 100 by a chemical vapor phase growth method at a temperature of 1400 ° C to 1500 ° C. The first silicon carbide polycrystalline film forming step and the second silicon carbide polycrystalline film 300 on the first silicon carbide polycrystalline film 200 at 1200 ° C. to 1300 ° C. and the first silicon carbide polycrystalline film 200. Includes a second silicon carbide polycrystalline film film forming step of forming a film at a temperature 100 ° C. to 200 ° C. lower than the film forming temperature of.

In the first silicon carbide polycrystalline film 200, as shown in FIG. 5, since the film formation temperature of the silicon carbide polycrystalline film in the conventional method for producing a silicon carbide polycrystalline substrate is higher than the general film formation temperature, the silicon carbide polycrystalline film 200 is used. The size of crystal grains tends to be large (for example, the average particle size is about 50 μm). If the film formation is continued at the same temperature as in the conventional method for manufacturing a silicon carbide polycrystalline substrate, the size of the crystal grains of the silicon carbide polycrystalline substrate to be formed increases as the thickness increases. Therefore, in the method for producing a silicon carbide polycrystalline substrate of the present embodiment, the second silicon carbide polycrystalline film manufacturing step is 1200 ° C. to 1300 ° C., which is 100 higher than the film formation temperature of the first silicon carbide polycrystalline film 200. The second silicon carbide polycrystalline film 300 is formed at a low temperature of ° C. to 200 ° C. As a result, the size of the crystal grains of the silicon carbide polycrystalline film at the initial stage of film formation of the second silicon carbide polycrystalline film 300 is the crystal of the silicon carbide polycrystalline film of the first silicon carbide polycrystalline film 200, although the film formation temperature is low. It tends to increase due to the influence of grain size (for example, the average particle size is about 50 μm). Further, as shown in FIG. 5, since the film formation temperature of the second silicon carbide polycrystalline film 300 is low, the size of the crystal grains of the silicon carbide polycrystalline film 300 is large even if the thickness of the second silicon carbide polycrystalline film 300 is increased. The size of the crystal grains of the silicon carbide polycrystalline film 200 of the first silicon carbide polycrystalline film 200 and the crystal grains of the silicon carbide polycrystalline film formed in the latter half of the film forming process of the second silicon carbide polycrystalline film 300 The difference from the size becomes small. That is, in the silicon carbide polycrystalline substrate 500 obtained by the method for producing the silicon carbide polycrystalline substrate of the present embodiment, the difference in the size of the crystal grains of the silicon carbide polycrystalline substrate becomes small in the thickness direction.

From the above, in the method for producing a silicon carbide polycrystalline substrate of the present embodiment, the difference in the size of the crystal grains of the silicon carbide polycrystalline substrate in the thickness direction is small and the difference in internal stress is small, so that the support substrate 100 is removed. At that time, it is possible to suppress the occurrence of a large warp in the silicon carbide polycrystalline substrate 500 and obtain the silicon carbide polycrystalline substrate 500 having a smaller warp than the conventional manufacturing method. As a result, in the processing and manufacturing of the silicon carbide polycrystalline substrate, the thickness and flatness due to the large warp of the silicon carbide polycrystalline substrate in the surface grinding and surface polishing for adjusting to a predetermined thickness and flatness. It is possible to process and manufacture a silicon carbide polycrystalline substrate having a small warp without deteriorating the degree or warpage. Further, since the manufactured silicon carbide polycrystalline substrate 500 has a small warp, it is not necessary to form a silicon carbide polycrystalline film that is significantly thicker than the thickness used as the silicon carbide polycrystalline substrate, and the silicon carbide polycrystalline substrate can be used. It is possible to reduce the burden of grinding and polishing to eliminate warpage and waste of materials, reduce costs, and improve yield and productivity.

Further, in particular, according to the method for producing a silicon carbide polycrystalline substrate of the present embodiment, even in the case of producing a silicon carbide polycrystalline substrate having high conductivity (for example, about 0.1 Ω · cm or more), Warpage of silicon carbide polycrystalline substrate is reduced without heat treatment in a temperature range where nitrogen atoms in silicon carbide are difficult to desorb from the surface (for example, a high temperature range such as a temperature higher than 2200 ° C.) without impairing high conductivity. it can. Therefore, the silicon carbide polycrystalline substrate manufactured by the manufacturing method of the present embodiment can be used in the device manufacturing process as a vertical silicon carbide substrate for a diode in addition to the horizontal type, and the silicon carbide polycrystalline substrate can be used. Since the amount of warpage is small, poor pattern formation in the photolithography process and non-uniformity of the ion penetration depth in the ion injection process are reduced, and an improvement in yield can be expected.

In addition, the best configuration, method, and the like for carrying out the present invention are disclosed in the above description, but the present invention is not limited thereto. That is, although the present invention has been particularly described mainly with respect to a specific embodiment, the shape, material, quantity, and the shape, material, quantity, etc. In other detailed configurations, those skilled in the art can make various modifications. Therefore, the description that limits the shape, material, etc. disclosed above is merely an example for facilitating the understanding of the present invention, and does not limit the present invention. Therefore, those shapes, materials, etc. The description by the name of the member which removes a part or all of the limitation such as is included in the present invention.

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 to these Examples.

[Manufacturing of silicon carbide polycrystalline substrate and evaluation of silicon carbide polycrystalline substrate]
(Example 1)
The silicon carbide polycrystalline film was formed using the film forming apparatus 1000 of the above-described embodiment. First, a carbon support substrate having a diameter of 6 inches and a thickness of 500 μm was fixed to the substrate holder 1070 of the film forming apparatus 1000. The pressure inside the furnace was reduced by an exhaust pump while flowing Ar gas into the film forming chamber 1010, and then heated to 1400 ° C., and after reaching 1400 ° C., the supply of Ar gas was stopped. _{SiCl 4} and CH ₄ were used as the raw material gas, _{N 2} was used as the doping gas, and H ₂ was used as the carrier gas. In the first silicon carbide polycrystal film forming step, the mixing ratio SiCl of these gases _{4: CH 4: H 2:} N 2 = 1: 1: 10: as 20, the total inflow 22 slm (standard L / As min), film formation was carried out at 1400 ° C. for 2 hours. A first silicon carbide polycrystalline film having a thickness of 100 μm was formed on both sides of the carbon support substrate to obtain a laminate of the carbon support substrate and the silicon carbide polycrystalline film.

Next, a second silicon carbide polycrystalline film forming step was performed. After forming the first silicon carbide polycrystal film, the supply of the raw material gas and the doping gas was stopped, the temperature of the film forming chamber was lowered to 1200 ° C. while supplying only the carrier gas, and then the temperature was maintained. Gas was supplied under the same conditions as in the first silicon carbide polycrystal film forming step to form a second silicon carbide polycrystal film having a thickness of 400 μm. As described above, a laminate of the carbon support substrate and the silicon carbide polycrystalline film was obtained, the laminate was cooled to room temperature, and then the support substrate was removed. The silicon carbide polycrystalline film laminated on the outer peripheral end of the laminate was ground with a diamond grindstone to expose the side surface of the carbon support substrate over the entire circumference. Next, using a combustion furnace equipped with a heater made of molybdenum disilicate, the carbon support substrate was burnt off by heating at a temperature of 1000 ° C. for 100 hours in an air atmosphere. As a result, a silicon carbide polycrystalline substrate was obtained.

Next, the amount of warpage of the obtained silicon carbide polycrystalline substrate was measured. The center line of the film-deposited surface of the silicon carbide polycrystalline substrate was measured with an obliquely incident optical measuring instrument, and the difference between the maximum value and the minimum value of the obtained measured values was defined as the amount of warpage. The measurement was performed at 5 points, and the measurement was performed at the center, the circumferential end, and the point between the center and the circumferential end, where the distance from the center and the distance from the circumferential end are the same. When the amount of warpage is larger than 100 μm, it was determined that the manufactured silicon carbide polycrystalline substrate has warpage that may cause a problem in the manufacturing process of the device or the like. The measurement results of the amount of warpage are shown in Table 1.

(Example 2, Example 3, Comparative Example 1 to Comparative Example 4)
A silicon carbide polycrystalline substrate was produced in the same manner as in Example 1 except that the temperatures of the first silicon carbide polycrystalline film forming step and the second silicon carbide reaching crystal film forming step were variously changed. The film formation temperature in the first silicon carbide polycrystalline film step was 1400 ° C. for Example 2, Comparative Example 1, and Comparative Example 2, and 1500 ° C. for Example 3, Comparative Example 3, and Comparative Example 4. The film formation temperature of the second silicon carbide polycrystalline film step was 1300 ° C. in Example 2 and Example 3, 1350 ° C. in Comparative Example 1, 1100 ° C. in Comparative Example 2 and Comparative Example 4, and 1400 ° C. in Comparative Example 3. did. The amount of warpage of the obtained silicon carbide polycrystalline substrate was measured in the same manner as in Example 1, and the measurement results are shown in Table 1.

[Discussion of evaluation results]
Based on the above evaluation results, in Examples 1 to 3 which are exemplary embodiments of the present invention, the amount of warpage of the produced silicon carbide polycrystalline substrate is smaller than that of Comparative Examples 1 to 4, and the amount of warpage is small. Was 60 μm to 80 μm. When the temperature difference between the first silicon carbide polycrystalline film forming step and the second silicon carbide polycrystalline film forming step is small as in Comparative Example 1 and Comparative Example 2, the first silicon carbide polycrystalline film and the second It was considered that the difference in particle size in the silicon carbide polycrystalline film was not as small as in the examples, and the amount of warpage was large. Further, as in Comparative Examples 2 and 4, when the temperature of the second silicon carbide polycrystalline film forming step is significantly lowered, the particle size of the silicon carbide polycrystalline film in the second silicon carbide polycrystalline film becomes the first carbide. It was considered that the particle size was smaller than that of the silicon carbide polycrystalline in the silicon polycrystalline film, a difference in particle size was generated, and the amount of warpage was large. From the results of the above Examples and Comparative Examples, it is possible to produce a silicon carbide polycrystalline substrate having a small warp by suppressing the occurrence of a large warp by the method for producing a silicon carbide polycrystalline film of the present invention. Shown.

100 Support substrate 200 1st silicon carbide polycrystalline film 300 2nd silicon carbide polycrystalline film 400A, 400B Laminated product 500 Silicon carbide polycrystalline substrate

Claims (1)

A first silicon carbide polycrystalline film forming step of forming a first silicon carbide polycrystalline film on a support substrate at a temperature of 1400 ° C. to 1500 ° C. by a chemical vapor deposition method.
On the first silicon carbide polycrystalline film, the second silicon carbide polycrystalline film is placed at a temperature of 1200 ° C. to 1300 ° C., which is 100 ° C. to 200 ° C. lower than the film formation temperature of the first silicon carbide polycrystalline film. A method for producing a silicon carbide polycrystalline substrate, which comprises a second silicon carbide polycrystalline film forming step.

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