JP2007273525A - Manufacturing method of cubic single crystal silicon carbide substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a cubic single crystal silicon carbide substrate which consists of only silicon carbide, is self-supporting, has little defect and is excellent in crystallinity. <P>SOLUTION: When starting to manufacture, a SOI substrate 1 comprising a silicon substrate 2, an embedded insulation film 3 and a surface silicon film 4 is prepared as a material. The surface silicon film 4 of the SOI substrate 1 is carbonized to transform into a single crystal silicon carbide film 5. A single crystal silicon carbide film 6 is formed on the film 5 by means of epitaxial growth. An amorphous silicon carbide film 7 is formed on the film 6 by means of vapor phase growth method. The silicon substrate 2 and the embedded insulation film 3 are removed. The substrate is heated to make the film 7 into a single crystal. Thus, a multilayer structure consisting of the single crystal silicon carbide films 5 and 6 and the single crystal silicon carbide film generated by making the amorphous silicon carbide film 7 into a single crystal is formed as the cubic single crystal silicon carbide substrate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a single-crystal silicon carbide substrate that is made of only silicon carbide and has few defects and excellent crystallinity, and in particular, cubic single-crystal silicon carbide that can be used as a semiconductor substrate or a substrate for crystal growth. The present invention relates to a method for manufacturing a substrate.

Silicon carbide (SiC) is attracting attention as a semiconductor material having a high temperature and a high breakdown voltage because it has excellent heat resistance and stability and has a wide band gap.
Conventionally, as a method for producing single crystal silicon carbide, a sublimation method using a seed crystal substrate having a seed crystal on the surface and silicon carbide raw material powder is generally employed. In the sublimation method, the silicon carbide raw material powder and the seed crystal substrate are arranged at a predetermined distance in a heating furnace, and the silicon carbide raw material powder and the seed crystal substrate are heated. At this time, the silicon carbide raw material powder is heated so as to be slightly higher in temperature than the seed crystal substrate. As a result, the silicon carbide raw material powder is sublimated and recrystallized into a seed crystal on the seed crystal substrate to grow crystals. However, in the sublimation method, it is difficult to produce a low-temperature type crystal (cubic silicon carbide) due to the limitation of the growth temperature, and it is impossible to realize a single crystal cubic silicon carbide substrate having a large area and being homogeneous. was there.

  On the other hand, as another manufacturing method of single crystal silicon carbide, a silicon substrate produced by the Czochralski method (CZ method) is used as a base substrate, and a silicon source gas and a carbon source gas are supplied simultaneously or alternately to a reactor. A method of forming single crystal cubic silicon carbide on a silicon substrate by a vapor phase growth method has been proposed (see, for example, Patent Document 1).

JP-A-9-52798

As described above, the manufacturing method using the sublimation method has a problem that it is difficult to manufacture a single crystal cubic silicon carbide substrate having a large area and a uniform area.
On the other hand, in the manufacturing method using the vapor phase growth method, a highly uniform single crystal cubic silicon carbide substrate can be produced. However, the physical properties of the base substrate made of single crystal silicon and the single crystal cubic silicon carbide are as follows. There is a problem that defects occur in the silicon carbide crystal due to a difference (for example, lattice constant). In addition, since the single crystal growth process is difficult and requires a complicated process, when single crystal cubic silicon carbide is grown, various defects such as stacking faults increase in the crystal, resulting in high quality. There was a problem that it was difficult to obtain a single crystal silicon carbide substrate.

  The present invention has been made to solve the above-mentioned problems, and its object is to produce a cubic single-crystal silicon carbide substrate that is free-standing and made of only silicon carbide and has few defects and excellent crystallinity. It is in.

The method for manufacturing a cubic single crystal silicon carbide substrate according to the present invention manufactures an SOI substrate comprising a silicon substrate, a buried insulating film formed on the silicon substrate, and a surface silicon film formed on the buried insulating film. As a material prepared at the start, a carbonization process for carbonizing the surface silicon film of the SOI substrate to transform it into a single crystal silicon carbide film, and a single crystal silicon carbide by epitaxial growth on the single crystal silicon carbide film A first silicon carbide film-forming step for forming a film, and a second method for forming an amorphous silicon carbide film on the single-crystal silicon carbide film formed in the first silicon carbide film-forming step by vapor deposition. A silicon carbide film forming step, a removal step of removing the silicon substrate and the buried insulating film, and heating the substrate after the removal step to form the amorphous carbonization. A single crystallization process for single-crystallizing the recon film, the single crystal silicon carbide film formed in the carbonization process, the single crystal silicon carbide film formed in the first silicon carbide film formation process, and the single crystal A laminated structure composed of a single crystal silicon carbide film formed in the crystallization process is a cubic single crystal silicon carbide substrate.
Moreover, in one structural example of the manufacturing method of the cubic single crystal silicon carbide substrate of the present invention, the single crystallization treatment step is such that the substrate after the removal step is heated at a temperature of 800 ° C. or higher and lower than 1500 ° C. It is what.
Further, in one configuration example of the method for manufacturing a cubic single crystal silicon carbide substrate of the present invention, the single crystallization process is stopped when a single crystal silicon carbide film having a desired thickness is obtained, A part of the crystalline silicon carbide film is left.
Also, one configuration example of the method for manufacturing a cubic single crystal silicon carbide substrate according to the present invention includes a single crystal silicon carbide film formed in the carbonization treatment step and a single crystal carbonization formed in the first silicon carbide film formation step. The total thickness of the silicon film and the amorphous silicon carbide film formed in the second silicon carbide film forming step is set to 50 μm or more.

  According to the present invention, the surface silicon film of the SOI substrate is carbonized, and the single crystal silicon carbide film is epitaxially grown on the single crystal silicon carbide film after the carbonization process. Can be reduced. In the present invention, the single crystal silicon carbide film to be epitaxially grown is made thinner than the amorphous silicon carbide film, thereby preventing an increase in various defects such as stacking faults generated in the single crystal silicon carbide film, and increasing the strength as a substrate. Since the amorphous silicon carbide film is easy to manufacture, the silicon substrate and the buried insulating film are removed, and then the amorphous silicon carbide film is single-crystallized by heat treatment, so that there are few defects and crystallinity. An excellent free-standing cubic single crystal silicon carbide substrate can be realized. Furthermore, according to the present invention, the buried insulating film can have a function as a buffer layer that relieves thermal stress generated from the difference in thermal expansion coefficient between the single crystal silicon carbide film and the amorphous silicon carbide film and the silicon substrate. Therefore, cracking of the single crystal silicon carbide film and the amorphous silicon carbide film due to thermal stress in the first silicon carbide film forming process and the second silicon carbide film forming process can be avoided.

  Further, in the present invention, the single crystallization process is stopped when a single crystal silicon carbide film having a desired thickness is obtained, and a part of the amorphous silicon carbide film is left, thereby shortening the heating of the substrate. Can finish in time.

  In the present invention, the single crystal silicon carbide film formed in the carbonization treatment step, the single crystal silicon carbide film formed in the first silicon carbide film formation step, and the amorphous carbonization formed in the second silicon carbide film formation step By setting the total thickness of the silicon films to 50 μm or more, a self-supporting cubic single crystal silicon carbide substrate can be realized.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a process cross-sectional view illustrating a method for manufacturing a cubic single crystal silicon carbide substrate according to an embodiment of the present invention.
First, a single crystal silicon substrate 2, a buried insulating film 3 made of silicon oxide formed on the single crystal silicon substrate 2, and a surface silicon film 4 having a predetermined thickness formed on the buried insulating film 3. An SOI (Silicon On Insulator) substrate 1 is prepared (FIG. 1A). The thickness of the surface silicon film 4 is, for example, 100 nm.

  Subsequently, the surface silicon film 4 of the SOI substrate 1 is transformed into a cubic single crystal silicon carbide (3C—SiC) film 5 by carbonizing at about 1000 to 1350 ° C. in a hydrocarbon atmosphere (FIG. 1). (B)). Thus, a base substrate having a single crystal cubic silicon carbide film 5 formed on the surface was prepared.

  Next, this base substrate is horizontally installed in a reactor of a cylindrical horizontal furnace, and the reactor is sealed. Nitrogen gas or hydrogen gas is allowed to flow into the reactor at a flow rate of about 10 SLM for about 10 minutes, and oxygen gas is sufficiently expelled from the reactor. Thereafter, the temperature of the base substrate is raised to 1150 to 1300 ° C. in a nitrogen gas atmosphere, and hydrogen gas as a material gas and a carrier gas is supplied into the reactor, and epitaxial growth is performed on the single crystal cubic silicon carbide film 5. A single crystal cubic silicon carbide film 6 is formed to a thickness of, for example, about 100 nm (FIG. 1C). Subsequently, an amorphous silicon carbide film 7 is formed on the single crystal cubic silicon carbide film 6 by a vapor phase growth method (FIG. 1D). Growth of the single crystal silicon carbide film forming step (first silicon carbide film forming step) in FIG. 1C and the amorphous silicon carbide film forming step (second silicon carbide film forming step) in FIG. Details of the conditions are shown in Table 1.

As the material gas, dichlorosilane (SiH ₂ Cl ₂ ) is used as the silicon source gas, but SiH ₄ , SiCl ₄ , SiHCl ₃ or the like may be used. Although acetylene (C ₂ H ₂ ) is used as the carbon source gas, CH ₄ , C ₂ H ₆ , C ₃ H _8, etc. can also be used. In addition, a component containing both silicon and carbon such as (CH ₃ ) ₄ Si without using silicon and carbon material gases separately to form a single crystal silicon carbide film and a polycrystalline silicon carbide film. It is also possible to form a film only with a gas obtained by vaporizing.

When the total thickness of the single crystal cubic silicon carbide films 5 and 6 and the amorphous silicon carbide film 7 becomes 50 μm or more which can be self-supported by silicon carbide alone, the amorphous structure shown in FIG. The silicon carbide film forming process is completed.
Subsequently, the single crystal silicon substrate 2 and the buried insulating film 3 are sequentially removed from the back side with a chemical such as hydrofluoric acid. Thus, a self-supporting silicon carbide substrate composed of the single crystal cubic silicon carbide films 5 and 6 and the amorphous silicon carbide film 7 as shown in FIG.

  Finally, the silicon carbide substrate is heat-treated in an inert gas atmosphere such as argon or helium at a temperature of 800 ° C. or higher and lower than 1500 ° C. to change the amorphous silicon carbide film 7 into a single crystal cubic silicon carbide film. A single crystallization treatment step is performed. This single crystallization treatment step is stopped when a single crystal cubic silicon carbide film having a necessary thickness is obtained, and a part of the amorphous silicon carbide film 7 is left. In this way, a self-standing type comprising the single crystal cubic silicon carbide film formed by single crystallization of the single crystal cubic silicon carbide films 5 and 6 and the amorphous silicon carbide film 7 and the remaining amorphous silicon carbide film 7. A cubic single crystal silicon carbide substrate is completed.

  As described above, in the present embodiment, the surface silicon film 4 of the SOI substrate 1 is carbonized, and the single crystal cubic silicon carbide film 6 is epitaxially grown on the single crystal cubic silicon carbide film 5 after the carbonization. Therefore, the lattice constant difference between the base substrate (single crystal silicon) and the single crystal cubic silicon carbide, which has been a problem in the conventional manufacturing method, can be eliminated, and the single crystal cubic silicon carbide films 5 and 6 are generated. Defects can be reduced. Also, by keeping the single crystal cubic silicon carbide film 6 to a thickness of about 100 nm, which is thinner than the amorphous silicon carbide film 7, various defects such as stacking faults occurring in the single crystal cubic silicon carbide film 6 are increased. An amorphous silicon carbide film 7 that is easy to manufacture is formed as a portion that prevents and gives strength as a substrate, and the amorphous silicon carbide film 7 is converted into a single crystal by heat treatment after the single crystal silicon substrate 2 and the embedded insulating film 3 are removed. Therefore, a self-supporting cubic single crystal silicon carbide substrate with few defects and excellent crystallinity can be realized. A single crystal cubic silicon carbide film formed by single crystallization of the single crystal cubic silicon carbide films 5 and 6 and the amorphous silicon carbide film 7 can be formed to a thickness necessary for a semiconductor substrate or a crystal growth substrate. Good.

  Further, in this embodiment, by using the SOI substrate 1 as a starting material for the manufacturing process, amorphous silicon oxide is formed between the single crystal cubic silicon carbide films 5 and 6 and the single crystal silicon substrate 2. Since the buried insulating film 3 is sandwiched, and the buried insulating film 3 is softened by the deposition temperature during the formation of the single crystal cubic silicon carbide film 6 and the amorphous silicon carbide film 7, the single crystal cubic crystal The buried insulating film 3 can have a function as a buffer layer that relieves thermal stress generated from the difference in thermal expansion coefficient between the silicon carbide film 6 and the amorphous silicon carbide film 7 and the single crystal silicon substrate 2. Thereby, cracks of single crystal cubic silicon carbide film 6 and amorphous silicon carbide film 7 and warpage of single crystal silicon substrate 2 due to thermal stress can be avoided.

  The present invention can be applied to a manufacturing technique of a single crystal silicon carbide substrate.

It is process sectional drawing which shows the manufacturing method of the cubic single crystal silicon carbide substrate which concerns on embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... SOI substrate, 2 ... Single crystal silicon substrate, 3 ... Embedded insulating film, 4 ... Surface silicon film, 5, 6 ... Single crystal cubic silicon carbide film, 7 ... Amorphous silicon carbide film.

Claims (4)

As a material prepared at the start of manufacturing an SOI substrate comprising a silicon substrate, a buried insulating film formed on the silicon substrate, and a surface silicon film formed on the buried insulating film, the surface silicon film of the SOI substrate is prepared. A carbonization treatment step of carbonizing and transforming into a single crystal silicon carbide film,
A first silicon carbide film forming step of forming a single crystal silicon carbide film on the single crystal silicon carbide film by an epitaxial growth method;
A second silicon carbide film forming step of forming an amorphous silicon carbide film on the single crystal silicon carbide film formed in the first silicon carbide film forming step by vapor phase growth;
A removing step of removing the silicon substrate and the buried insulating film;
A single crystallization treatment step of heating the substrate after the removal step to single-crystallize the amorphous silicon carbide film,
A laminated structure including a single crystal silicon carbide film formed in the carbonization process, a single crystal silicon carbide film formed in the first silicon carbide film formation process, and a single crystal silicon carbide film formed in the single crystallization process A cubic single crystal silicon carbide substrate, characterized in that a cubic single crystal silicon carbide substrate is used. In the manufacturing method of the cubic system single crystal silicon carbide substrate according to claim 1,
In the method for manufacturing a cubic single crystal silicon carbide substrate, the single crystallization treatment step heats the substrate after the removal step at a temperature of 800 ° C. or higher and lower than 1500 ° C. In the manufacturing method of the cubic system single crystal silicon carbide substrate according to claim 1,
Cubic single crystal silicon carbide characterized in that the single crystallization treatment step is stopped when a single crystal silicon carbide film having a desired thickness is obtained and a part of the amorphous silicon carbide film is left. A method for manufacturing a substrate. In the manufacturing method of the cubic system single crystal silicon carbide substrate according to claim 1,
A single crystal silicon carbide film formed in the carbonization process, a single crystal silicon carbide film formed in the first silicon carbide film formation process, and an amorphous silicon carbide film formed in the second silicon carbide film formation process. A method for producing a cubic single crystal silicon carbide substrate, wherein the total thickness is 50 μm or more.

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