JP2012224546A - Single crystal silicon carbide substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single crystal silicon carbide substrate where the small piece of the seed crystal of the single crystal silicon carbide is grown in a horizontal direction by liquid phase epitaxial growth and which has a large area.SOLUTION: The single crystal silicon carbide substrate 13b is produced such that: the composite of a polycrystalline silicon carbide substrate 5 where the polycrystalline silicon carbide substrate 5 whose surface is carbonized partially and the polycrystalline silicon carbide substrate 5 are arranged closely and oppositely via a metal silicon molten liquid 12 is stored in a storage container and heat-treated; the small piece 13a of the seed crystal of the single crystal silicon carbide is made by self-growing the single crystal silicon carbide in liquid phase growth on the carbonized surface 11 of the polycrystalline silicon carbide substrate 5; and the small piece 13a of the seed crystal of the single crystal silicon carbide is grown in a direction orthogonal to an opposite direction by continuing further liquid phase epitaxial growth and has a part where a crystal is grown to a plane direction on its outer periphery.

Description

  The present invention primarily relates to single crystal silicon carbide (SiC) substrates.

  Silicon carbide (SiC) has excellent heat resistance and mechanical strength, is resistant to radiation, can easily control the valence electrons of electrons and holes by adding impurities, and has a wide band gap (6H-type single crystal SiC). About 3.0 eV and 3.3 eV for 4H type single crystal SiC. Therefore, it is said that it is possible to realize high temperature, high frequency, withstand voltage / environment resistance that cannot be realized with existing semiconductor materials such as silicon (Si) and gallium arsenide (GaAs). Expectation is growing as a semiconductor material.

  Regarding the method for producing this single crystal SiC substrate, the conventionally well-known method for producing the single crystal SiC substrate is the Atchison method, in which petroleum coke and quartzite are sintered in an electric furnace to form an ingot. In this method, a bulk substrate is produced, but the size of the substrate is very small, and a product for practical use has not been obtained. On the other hand, research on obtaining high-quality single-crystal SiC substrates with few micropipe defects and crystal defects that can be used in semiconductors has been conducted by sublimation reprecipitation (modified Rayleigh method) and CVD (vapor phase deposition), but high quality. No mass production technology has been established so far that can produce a single crystal SiC substrate for practical use. The following is a representative document of research related to technological development for practical use of a high-quality single crystal SiC substrate.

Japanese Patent Laid-Open No. 2006-1836 Japanese Patent Laid-Open No. 2006-111478 Japanese Patent Laid-Open No. 2005-314167 Japanese Patent Laid-Open No. 2005-41710 Japanese Patent Laid-Open No. 2004-33012 Japanese Patent Laid-Open No. 2003-119097 Japanese Patent Laid-Open No. 2003-511337 JP-A-2002-527339

Summarize and verify the contents of research related to technology development for practical use of high-quality single-crystal SiC substrates.
Patent Documents 1 and 6 are called RAF methods. Sublimation reprecipitation method (improved Rayleigh method) is a method for providing a SiC single crystal substantially free of micropipe defects, spiral dislocations, edge dislocations, and stacking faults. In the first step of growing the thickness of the SiC single crystal in the vertical direction by the step, a surface having an offset angle of ± 20 ° or less from the {1-100} plane or a surface having an offset angle of ± 20 ° or less from the {11-20} plane Is used as a first growth surface, and in the intermediate growth step, a surface inclined by 45 to 90 ° from the (n-1) growth surface and inclined by 60 to 90 ° from the {0001} surface is formed. An n-th growth crystal is produced as an n-growth surface, and in the final growth step, a surface having an offset angle of ± 20 ° or less from the {0001} plane of the (N-1) -th growth crystal is defined as the final growth surface 35 and the final growth. On surface 35 There is a report of growing a bulk SiC single crystal 30 with reduced screw dislocations and edge dislocations.

  In Patent Documents 2 to 4, in the SiC single crystal growth step by the sublimation reprecipitation method (Rayleigh method), the maximum value of the dopant element concentration of the SiC single crystal is less than 5 × 10 17 atoms / cm 3 and the maximum value of the dopant element concentration. Is less than 50 times the minimum value, and unavoidably mixed uncompensated impurities are contained in an atomic density of 1 × 10 15 / cm 3 or more, and a silicon carbide single crystal containing vanadium below the uncompensated impurity concentration and There is a report of a method for growing a SiC single crystal, which is a silicon carbide single crystal wafer obtained by processing and polishing the silicon carbide single crystal and having an electrical resistivity at room temperature of 5 × 10 3 Ωcm or more.

  In Patent Document 5, Si, C and / or SiC, and a protective material are charged, and heated to the crystal growth temperature to wet the inner wall of the graphite crucible with the melt of the protective material. Production of a SiC single crystal, wherein a SiC single crystal is grown in the coexistence of a C-containing Si solution and C and / or SiC in a state where a protective layer that is not mixed with the C-containing Si solution is formed. There is a report of the method.

  Patent Documents 7 and 8 disclose bulk low-impurity silicon carbide single crystal bulk low-impurity silicon carbide single crystal, vapor species containing silicon and vapor-type crystal bulk low-impurity silicon carbide single crystal containing carbon, silicon The vapor species containing carbon and the vapor species containing carbon are grown by deposition on the crystal growth interface. The silicon source vapor is provided by vaporizing liquid silicon and transporting the silicon vapor to a crystal growth crucible. The carbon vapor species can be provided by flowing a carbon-containing source gas (eg, CN) or silicon source vapor over or through a solid carbon source, for example, by flowing silicon vapor through a porous graphite or graphite particle bed. There are reports. Most of the above reports relate to the growth of SiC single crystal substrates by the sublimation reprecipitation method (Rayleigh method), and no studies on liquid phase epitaxial growth have been reported.

  Each of the documents in the preceding paragraph relates to a technology for crystal growth of a SiC single crystal seed substrate vertically in the thickness direction, and a technology for growing the substrate size of the SiC single crystal substrate by crystal growth in the horizontal direction of the SiC single crystal seed substrate. Has not been developed. Therefore, the basic technology for enlarging the SiC single crystal substrate to the practical size close to the Si wafer by increasing the substrate size of the SiC single crystal seed substrate has not been elucidated, and the problems of mass production technology have not been solved.

  The main object of the present invention is to provide a single crystal silicon carbide substrate having a large area obtained by liquid phase epitaxial growth of a single crystal silicon carbide seed crystal piece or seed crystal plate in the horizontal direction.

Means for Solving the Problems and Effects of the Invention

  A single crystal silicon carbide substrate according to a first aspect of the present invention is a polycrystalline silicon carbide substrate in which a polycrystalline silicon carbide substrate whose surface is locally carbonized and a polycrystalline silicon carbide substrate are disposed in close proximity to each other via a metal silicon melt. The composite is stored in a storage container and heat-treated at a temperature of 1500 ° C. or higher and 2300 ° C. or lower in a state where the internal pressure of the storage container is kept under a vacuum under the saturated vapor pressure of silicon so as to be higher than the external pressure. Then, single crystal silicon carbide is self-grown by liquid phase growth on the carbonized surface of the polycrystalline silicon carbide substrate to produce single crystal silicon carbide seed crystal pieces, and further, liquid phase growth is continued, thereby A crystalline silicon carbide seed crystal piece is produced by liquid phase epitaxial growth in a direction perpendicular to the facing direction, and has a portion grown in the plane direction on the outer periphery thereof. .

  According to this configuration, it is possible to realize a single crystal silicon carbide substrate having a large area and having a crystal growth portion in the plane direction on the outer periphery thereof.

  A single-crystal silicon carbide substrate according to a second aspect of the present invention has a polycrystalline silicon carbide substrate having a single-crystal silicon carbide seed crystal piece disposed on a surface thereof and a polycrystalline silicon carbide substrate disposed close to each other through a metal silicon melt. Storing the composite of the polycrystalline silicon carbide substrate in which the metal silicon melt is present around the single crystal silicon carbide seed crystal piece in a direction orthogonal to the facing direction in a storage container; The single crystal silicon carbide seed crystal piece is heat-treated at a temperature of 1500 ° C. or higher and 2300 ° C. or lower while maintaining a vacuum under a saturated vapor pressure of silicon so that the internal pressure is higher than the external pressure, thereby It is generated by liquid phase epitaxial growth in a direction perpendicular to the surface, and has an outer peripheral portion having a crystal grown portion in the plane direction.

  According to this configuration, it is possible to realize a single crystal silicon carbide substrate having a large area and having a crystal growth portion in the plane direction on the outer periphery thereof.

  In the second aspect of the invention, the single crystal silicon carbide seed crystal piece is a polycrystalline carbon carbide in which a polycrystalline silicon carbide substrate having a carbonized surface and a polycrystalline silicon carbide substrate are disposed in close proximity to each other via a metal silicon melt. The silicon substrate composite is stored in a storage container and at a temperature of 1500 ° C. or more and 2300 ° C. or less in a state where the internal pressure of the storage container is kept under a vacuum under the saturated vapor pressure of silicon so as to be higher than the external pressure. The heat treatment may be performed by self-growing single crystal silicon carbide by liquid phase growth on the carbonized surface of the polycrystalline silicon carbide substrate.

  A single crystal silicon carbide substrate according to a third aspect of the present invention includes a polycrystalline silicon carbide substrate having a single crystal silicon carbide seed crystal plate disposed on a surface thereof, and a polycrystalline silicon carbide substrate disposed close to each other through a metal silicon melt. A composite of a polycrystalline silicon carbide substrate in which the metal silicon melt is present around the single crystal silicon carbide seed crystal plate in a direction orthogonal to the facing direction is stored in a storage container; The single crystal silicon carbide seed crystal plate is heat treated at a temperature not lower than 1500 ° C. and not higher than 2300 ° C. while maintaining a vacuum under the saturated vapor pressure of silicon so that the internal pressure becomes higher than the external pressure, thereby It is generated by liquid phase epitaxial growth in a direction perpendicular to the surface, and has an outer peripheral portion having a crystal grown portion in the plane direction.

  According to this configuration, it is possible to realize a single crystal silicon carbide substrate having a large area and having a crystal growth portion in the plane direction on the outer periphery thereof.

  In the third aspect of the invention, the single crystal silicon carbide seed crystal plate has a polycrystalline silicon carbide substrate whose surface is locally carbonized and a polycrystalline silicon carbide substrate arranged close to each other through a metal silicon melt. The composite of the polycrystalline silicon carbide substrate is stored in a storage container and 1500 ° C. or more and 2300 ° C. or less in a state where the internal pressure of the storage container is kept under a vacuum under the saturated vapor pressure of silicon so as to be higher than the external pressure. The single crystal silicon carbide is self-grown by liquid phase growth on the carbonized surface of the polycrystalline silicon carbide substrate to form a single crystal silicon carbide seed crystal piece, and the liquid phase growth is continued. Thus, the single crystal silicon carbide seed crystal piece may be produced by liquid phase epitaxial growth in a direction orthogonal to the facing direction.

  The single crystal silicon carbide seed crystal piece or seed crystal plate may be arranged at a position close to an outer peripheral end of the polycrystalline silicon carbide substrate. Since the rate of crystal growth in the plane direction is accelerated by the influence of convection of C atoms due to the surface tension of the metal silicon melt, the closer to the outer peripheral end of the polycrystalline silicon carbide substrate, the single crystal silicon carbide seed piece or seed crystal The plate is preferably disposed at a position close to the outer peripheral edge of the polycrystalline silicon carbide substrate.

  The carbonization treatment is performed by locally irradiating the surface of the substrate with a laser beam or an electron beam in a state where the polycrystalline silicon carbide substrate of the 3C-SiC aggregate is kept in a vacuum or an inert atmosphere, and 3C-SiC on the surface of the substrate. The aggregate may be grown to crystal grains containing 4H-SiC aggregates, and at the same time, the silicon on the substrate surface may be selectively removed by evaporation to create a carbon-rich silicon carbide composition.

  The storage container may be a container that is made of tantalum metal and that is configured to expose the tantalum carbide layer to the internal space and that is vertically fitted.

  Instead of the polycrystalline silicon carbide substrate on which the single crystal silicon carbide seed crystal piece or seed crystal plate is disposed, the surface is tantalum carbide processed tantalum substrate, or heat resistant in a high vacuum of 1500 ° C. to 2300 ° C. A substrate covered with a material having properties may be used.

The schematic cross section which shows an example of the heat processing apparatus suitable for the production | generation method of the single crystal SiC substrate of this invention. The figure which removed the upper container and lower container of the storage container. FIG. 5 is a process conceptual diagram in which a plurality of single-crystal SiC pieces are generated by self-growth by liquid phase growth on a carbonized surface of a polycrystalline SiC substrate. It is the microscope picture which expanded and observed the surface of the several small piece of single crystal SiC by growing the single crystal SiC piece self-growth on the carbonization process surface of a polycrystalline SiC substrate. It is the microscope picture which expanded and observed the cross section of the state in which the single crystal SiC piece was self-grown on the carbonization process surface of a polycrystalline SiC substrate, and also the single crystal SiC was produced | generated by liquid phase epitaxial growth. It is a conceptual diagram which shows the production | generation process of the single crystal silicon carbide substrate which concerns on the 1st Embodiment of this invention. FIG. 7A shows a state in which a polycrystalline SiC substrate whose surface has been carbonized and a polycrystalline SiC substrate placed adjacent to the polycrystalline SiC substrate are accommodated in the storage container to produce a single crystal SiC substrate. . FIG. 7B shows an arrangement conceptual diagram showing the positional relationship of the plane in the state of FIG. It is a conceptual diagram which shows the production | generation process of the single crystal silicon carbide substrate which concerns on the 2nd Embodiment of this invention. FIG. 9 (a) shows a tantalum substrate on which a single crystal SiC seed crystal piece is arranged and a polycrystalline SiC substrate placed in close proximity to the tantalum substrate in a storage container, and a single crystal SiC substrate having a larger area. Indicates the state that has been generated. FIG. 9B shows an arrangement conceptual diagram showing the positional relationship of the plane in the state of FIG. It is a conceptual diagram which shows the production | generation process of the single crystal silicon carbide substrate which concerns on the example of a change of the 2nd Embodiment of this invention. FIG. 11A shows a case where a polycrystalline SiC substrate on which a single crystal SiC seed crystal piece is arranged and a polycrystalline SiC substrate placed adjacent to the polycrystalline SiC substrate are accommodated in a storage container, and a single crystal having a larger area is stored. The state which produced | generated the SiC substrate is shown. FIG.11 (b) shows the arrangement | positioning conceptual diagram which shows the positional relationship of the plane of the state of Fig.11 (a). It is a conceptual diagram which shows the production | generation process of the single crystal silicon carbide substrate which concerns on the 3rd Embodiment of this invention. FIG. 13A shows a case where a tantalum substrate on which a single crystal SiC seed crystal piece is arranged and a divided polycrystalline SiC substrate placed in close proximity to the tantalum substrate are accommodated in a storage container. The state which produced | generated the crystalline SiC substrate is shown. FIG. 13B shows an arrangement conceptual diagram showing the positional relationship of the plane in the state of FIG. It is a conceptual diagram which shows the production | generation process of the single crystal silicon carbide substrate which concerns on the modification of the 3rd Embodiment of this invention. FIG. 15A shows a state in which a polycrystalline SiC substrate on which a single crystal SiC seed crystal piece is arranged and a divided polycrystalline SiC substrate placed in close proximity to the polycrystalline SiC substrate are accommodated in the storage container. . FIG. 15B is an arrangement conceptual diagram showing the positional relationship of the plane in the state of FIG. It is a conceptual diagram which shows the production | generation process of the single crystal silicon carbide substrate which concerns on the 4th Embodiment of this invention. FIG. 17A shows that a tantalum substrate on which a single crystal SiC seed crystal plate is arranged and a polycrystalline SiC substrate placed in close proximity to the tantalum substrate are accommodated in a storage container, and a single crystal SiC substrate having a larger area is stored. Indicates the state that has been generated. FIG. 17B is an arrangement conceptual diagram showing the positional relationship of the plane in the state of FIG. It is a conceptual diagram which shows the production | generation process of the single crystal silicon carbide substrate which concerns on the modification of the 4th Embodiment of this invention. FIG. 19A shows a case in which a polycrystalline SiC substrate on which a single crystal SiC seed crystal plate is arranged and a polycrystalline SiC substrate placed in close proximity to the polycrystalline SiC substrate are accommodated in a storage container. The state which produced | generated the SiC substrate is shown. FIG. 19B shows an arrangement conceptual diagram showing the positional relationship of the plane in the state of FIG.

  Hereinafter, embodiments of a method for producing a single crystal silicon carbide substrate according to the present invention will be described with reference to the drawings. First, an example of a heating furnace as a heat treatment apparatus suitable for the present embodiment will be described with reference to the schematic cross-sectional view of FIG.

  In FIG. 1, the heating furnace 1 includes a main heating chamber 2, a preheating chamber 3, and a front chamber 4 that is a portion following the preheating chamber 3 to the main heating chamber 2. With this configuration, the storage container 16 in which the polycrystalline SiC substrate and the like are stored sequentially moves from the preheating chamber 3 to the front chamber 4 and the main heating chamber 2, so that the polycrystalline SiC substrate and the like can be kept at a predetermined temperature in a short time. It can be heated at (1500 ° C. to 2300 ° C., preferably 1700 ° C. to 1900 ° C., for example, about 1800 ° C.).

  In this heating furnace 1, as shown in FIG. 1, the connecting portion between the main heating chamber 2 and the front chamber 4 and the connecting portion between the front chamber 4 and the preheating chamber 3 each have a communication portion and are partitioned. It has been. For this reason, each of the chambers 2, 3, and 4 can be controlled in advance under a predetermined pressure. If necessary, the pressure can be adjusted for each of the chambers 2, 3, and 4 by providing a gate valve 7 for each chamber. As a result, when the storage container 16 storing the polycrystalline SiC substrate or the like is moved, the inside of the furnace under a predetermined pressure can be moved by an appropriate moving means (not shown) without touching the outside air, and impurities can be mixed. Can be suppressed.

The preheating chamber 3 is provided with a halogen lamp 6 as a heating means. With this configuration, a temperature within a predetermined range (for example, a range of about 800 ° C. to 1000 ° C.) under a reduced pressure of about 10 ⁻² Pa or less. Inner) can be heated rapidly. As described above, the gate valve 7 is provided at the connecting portion between the preheating chamber 3 and the front chamber 4 to facilitate the pressure control of the preheating chamber 3 and the front chamber 4.

  A storage container 16 in which a polycrystalline SiC substrate or the like is stored is preheated to about 800 ° C. or higher in the preheating chamber 3 while being placed on the table 8. Thereafter, pressure adjustment between the preheating chamber 3 and the front chamber 4 is performed, and after the adjustment is completed, the preheating chamber 3 and the front chamber 4 are moved so as to be placed on a liftable susceptor 9 provided in the front chamber 4.

The storage container 16 moved to the front chamber 4 is moved from the front chamber 4 to the main heating chamber 2 together with the susceptor 9 by a lifting / lowering moving means 30 partially shown. The main heating chamber 2 is preliminarily adjusted under a reduced pressure of about 10 ⁻⁴ Pa by a vacuum pump (not shown), and the temperature is adjusted by the heater 31 so as to reach a desired temperature (for example, 1800 ° C.).

The pressure environment of the heating chamber 2 is preferably a vacuum of about 10 ⁻⁴ Pa or less, but may be a vacuum of about 10 ⁻² Pa or less, for example. Further, for example, after a vacuum of about 10 ⁻² Pa or less, preferably about 10 ⁻⁴ Pa or less, a rare gas atmosphere into which some inert gas is introduced may be used.

  The state of the main heating chamber 2 is set in this way, and the storage container 16 is moved from the front chamber 4 into the main heating chamber 2 at high speed by the moving means 30, whereby the storage container 16 is moved to the desired temperature. Can be rapidly heated in a short time.

  In the main heating chamber 2, a reflecting mirror 32 is installed around the heater 31, and reflects heat from the heater 31 to heat a polycrystalline SiC substrate or the like located inside the heater 31. Is trying to concentrate. The reflecting mirror 32 is preferably formed of gold-plated refractory metal such as W, Ta, or Mo, or high heat-resistant carbide such as WC, TaC, or MoC. Further, the main heating chamber 2 is provided with a window 37 so that the internal temperature of the main heating chamber 2 can be measured by an infrared radiation thermometer 18 installed outside the main heating chamber 2.

  Further, the fitting portion 25 between the moving means 30 and the main heating chamber 2 includes a convex stepped portion 21 provided in the moving means 30 and a concave stepped portion 22 formed in the main heating chamber 2. It consists of and. Further, in order to seal the heating chamber 2, unillustrated seal members (for example, O-rings) are provided at each step portion of the stepped portion 21 of the moving means 30.

  A contaminant removal mechanism 29 is provided inside the heater 31 in the main heating chamber 2. The contaminant removal mechanism 29 removes impurities discharged out of the storage container 16 from the single crystal SiC substrate or the like during the heat treatment so as not to come into contact with the heater 31. Thereby, it is possible to prevent the heater 31 from reacting with the impurities and deteriorating. The contaminant removal mechanism 29 is not particularly limited as long as it can adsorb impurities discharged from a single crystal SiC substrate or the like.

  The heater 31 is a resistance heater made of metal such as W or Ta, and includes a base heater 31 a installed on the susceptor 9 side and an upper heater 31 b provided on the main heating chamber 2 side. When the storage container 16 moves upward together with the base heater 31 a toward the main heating chamber 2 by the moving means 30, the storage container 16 is surrounded by the heater 31. With such a layout of the heater 31, it is possible to control the temperature distribution in the heating region to be uniform with high accuracy in combination with the reflector 32 described above. Note that the heating method of the main heating chamber 2 is not limited to the resistance heater, and for example, a high frequency induction heating type can be adopted.

  Next, the storage container 16 in which a polycrystalline SiC substrate and the like are stored will be described with reference to FIG. FIG. 2 is a perspective view of the storage container with the upper and lower containers removed.

  The storage container 16 is configured by fitting an upper container 16a and a lower container 16b as shown in FIG. The shape of the storage container 16 is substantially hexahedral as shown in the figure, but this is an example, and it may be configured in a cylindrical shape, for example.

  The storage container 16 is made of tantalum metal, and the entire surface thereof is covered with a tantalum carbide layer. Of the tantalum carbide layer, portions covering the inner surfaces of the upper container 16 a and the lower container 16 b are exposed in the internal space of the storage container 16.

  In addition, it is preferable that the play of a fitting part when the upper container 16a and the lower container 16b are fitted together is about 2 mm or less. Thereby, a substantially sealed state is realized, and in the heat treatment process in the main heating chamber 2, the Si pressure in the storage container 16 is increased to a pressure higher than the external pressure (pressure in the main heating chamber 2), and impurities Can be prevented from entering the storage container 16 through the fitting portion.

  Next, with reference to FIG. 3, a method for generating single crystal SiC pieces used when generating single crystal silicon carbide substrates according to second and third embodiments described later will be described. FIG. 3 is a conceptual diagram showing a process of generating a plurality of single-crystal SiC pieces 13 a by self-growth by liquid phase growth on the carbonized surface 11 of the polycrystalline SiC substrate 5.

  The entire surface of the polycrystalline SiC substrate 5 in FIG. 3A is heat-treated, so that the entire surface of the polycrystalline SiC substrate 5 is carbonized, and as shown in FIG. 3B, the polycrystalline SiC substrate 5 The carbonized surface 11 is formed on the entire surface. Then, as shown in FIG. 3 (c), the polycrystalline SiC substrate 5 is placed close to the carbonized surface 11 of the polycrystalline SiC substrate 5, and the metal silicon melt 12 is interposed between the two substrates. When the liquid phase growth is performed, the surface 19 of the polycrystalline SiC substrate 5 is eroded and a plurality of single crystal SiC pieces 13a are self-grown. In this way, as shown in FIG. 3 (d), a plurality of single-crystal SiC pieces 13 a can be generated on the carbonized surface 11 of the polycrystalline SiC substrate 5.

  Here, when the surface of the polycrystalline SiC substrate 5 whose crystal structure is a 3C-SiC aggregate having a C-axis orientation is subjected to heat treatment, the surface is carbonized and 4H-SiC aggregate whose crystal structure is C-axis orientation. It grows into a crystal grain including a body and modifies the surface of the polycrystalline SiC substrate 5 to provide an environment for producing the single crystal SiC piece 13a.

  Further, as described above, the crystal structure of the single crystal SiC piece 13a self-grown on the carbonized surface 11 of the polycrystalline SiC substrate 5 is a 4H—SiC aggregate, and the single crystal SiC piece 13a is on the carbonized surface 11. It is generated on the 4H-SiC aggregate. Therefore, it can be considered that the single crystal SiC piece 13a is generated by liquid phase epitaxial growth.

FIG. 4 is a photomicrograph obtained by magnifying and observing the surface of a plurality of single crystal SiC pieces 13 a self-grown on the carbonized surface 11 of the polycrystalline SiC substrate 5.
FIG. 5 is a photomicrograph of a single crystal SiC piece 13a self-grown on the carbonized surface 11 of the polycrystalline SiC substrate 5 and further magnifying and observing a section in which single crystal SiC is generated by liquid phase epitaxial growth. It is.

  Next, a method for producing a single crystal SiC substrate according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 6 shows a single crystal SiC liquid which is produced by self-growing single crystal SiC by liquid phase epitaxial growth on a carbonized surface 11 having a small area on the surface of the polycrystalline SiC substrate 5 to produce a plurality of single crystal SiC seed crystal pieces 13a. It is a conceptual diagram which shows the process of producing | generating the single crystal SiC substrate 13b with a large area by performing a phase epitaxial growth in a horizontal direction.

  By locally heating a minute portion of the surface of the polycrystalline SiC substrate 5 of FIG. 6A with the laser beam 10, the minute portion of the surface of the polycrystalline SiC substrate 5 is locally localized as shown in FIG. 6B. The carbonization process 11 of the micro area is formed. Then, as shown in FIG. 6C, the polycrystalline SiC substrate 5 is placed close to the carbonized surface 11 having a small area of the polycrystalline SiC substrate 5, and the metal silicon melt is placed in the gap between the substrates. When the liquid phase epitaxial growth is performed with 12 interposed, the surface 19 of the polycrystalline SiC substrate is eroded and the single crystal SiC seed crystal pieces 13 a are self-grown on the carbonized surface 11. Further, by continuing the liquid phase epitaxial growth process, the single crystal SiC seed crystal piece 13a is grown in the single crystal SiC liquid phase epitaxially in the horizontal direction, and a single crystal SiC substrate 13b is generated as shown in FIG. 6 (d). In this way, as shown in FIG. 6 (e), the single crystal SiC seed crystal pieces grown in the horizontal direction from the single crystal SiC seed crystal pieces 13a on the carbonized surface 11 having a small area of the polycrystalline SiC substrate 5 are obtained. A single crystal SiC substrate 13b having an area larger than 13a can be generated.

  FIG. 7A shows a case in which a polycrystalline SiC substrate 5 whose surface minute portions are locally carbonized and a polycrystalline SiC substrate 5 placed in close proximity to the polycrystalline SiC substrate 5 are accommodated in a storage container 16. The state which produced | generated the crystalline SiC substrate 13b is shown. FIG. 7B shows an arrangement conceptual diagram showing the positional relationship of the plane in the state of FIG.

  As can be seen from FIGS. 7 (a) and 7 (b), the four carbonized areas 11 with a small area are arranged at positions close to the outer peripheral end of the polycrystalline SiC substrate 5, Single crystal SiC seed crystal pieces 13 a self-grown at a position corresponding to carbonized surface 11 are arranged at a position near the outer peripheral end of polycrystalline SiC substrate 5. This is because the crystal growth rate in the horizontal direction is accelerated by the influence of convection of C atoms due to the surface tension of the metal silicon melt 12 as it is closer to the outer peripheral end of the polycrystalline SiC substrate 5.

  Then, the single crystal SiC seed crystal piece 13a is grown in the single crystal SiC liquid phase epitaxially in the horizontal direction, and the single crystal SiC substrate 13b is generated. Here, the single crystal SiC substrate 13b is generated in a disc shape by performing single crystal SiC liquid phase epitaxial growth in the horizontal direction outside the single crystal SiC seed crystal piece 13a. Further, the horizontal growth rate of the single crystal SiC liquid phase epitaxial growth is slow in the central direction of the substrate due to the influence of C atom convection, and the growth rate is large in the direction of the outer peripheral portion. As shown in FIG. 7 (b), the single crystal SiC seed crystal pieces 13a are not generated uniformly on the outer side but are generated more largely in the direction of the outer peripheral portion.

  Next, a method for producing a single crystal SiC substrate according to the second embodiment of the present invention will be described with reference to FIGS. In FIG. 8, a single crystal SiC seed crystal piece 13a is disposed on a tantalum carbide-processed surface 15a of a tantalum substrate 15, and a single crystal SiC substrate 13b having a large area is obtained by performing single crystal SiC liquid phase epitaxial growth in the horizontal direction. It is a conceptual diagram which shows the process to produce | generate.

  By heating the entire surface of the tantalum substrate 15, a surface 15 a subjected to tantalum carbide processing is formed on the entire surface of the tantalum substrate 15 as shown in FIG. As shown in FIG. 8B, single crystal SiC seed crystal pieces 13a are arranged on the surface 15a subjected to tantalum carbide processing. Then, as shown in FIG. 8C, the polycrystalline SiC substrate 5 is placed close to the tantalum carbide-processed surface 15a of the tantalum substrate 15, and the metal silicon melt 12 is placed in the gap between the two substrates. When the liquid phase epitaxial growth is performed by interposing, as shown in FIG. 8D, the surface 19 of the polycrystalline SiC substrate is eroded and the single crystal SiC seed crystal pieces 13a are grown in the single crystal SiC liquid phase epitaxially in the horizontal direction. A single crystal SiC substrate 13b is generated. Thus, as shown in FIG. 8E, from the single crystal SiC seed crystal piece 13a grown in the horizontal direction from the single crystal SiC seed crystal piece 13a on the tantalum carbide processed surface 15a of the tantalum substrate 15. A large-area single crystal SiC substrate 13b can be generated.

  FIG. 9A shows that a tantalum substrate 15 on which a single crystal SiC seed crystal piece 13a is disposed and a polycrystalline SiC substrate 5 that is disposed in close proximity to the tantalum substrate 15 are accommodated in a storage container 16, and has a larger area. The state which produced | generated the single crystal SiC substrate 13b is shown. FIG. 9B shows an arrangement conceptual diagram showing the positional relationship of the plane in the state of FIG.

  As can be seen from FIGS. 9A and 9B, the single crystal SiC seed crystal pieces 13 a arranged at the four locations are arranged at positions close to the outer peripheral end of the polycrystalline SiC substrate 5. This is because the crystal growth rate in the horizontal direction is accelerated by the influence of convection of C atoms due to the surface tension of the metal silicon melt 12 as it is closer to the outer peripheral end of the polycrystalline SiC substrate 5.

  Then, the single crystal SiC seed crystal piece 13a is grown in the single crystal SiC liquid phase epitaxially in the horizontal direction, and the single crystal SiC substrate 13b is generated. Here, the single crystal SiC substrate 13b is generated in a disc shape by performing single crystal SiC liquid phase epitaxial growth in the horizontal direction outside the single crystal SiC seed crystal piece 13a. Further, the horizontal growth rate of the single crystal SiC liquid phase epitaxial growth is slow in the central direction of the substrate due to the influence of C atom convection, and the growth rate is large in the direction of the outer peripheral portion. As shown in FIG. 9 (b), the single crystal SiC seed crystal pieces 13a are not generated uniformly on the outer side, but are generated more largely in the direction of the outer peripheral portion.

  Next, a modification of the method for producing a single crystal SiC substrate according to the second embodiment of the present invention will be described with reference to FIGS. FIG. 10 shows a process of forming a single-crystal SiC substrate 13b having a large area by arranging single-crystal SiC seed crystal pieces 13a on the surface of the polycrystalline SiC substrate 5 and performing single-crystal SiC liquid phase epitaxial growth in the horizontal direction. FIG. FIG. 11A shows a case where the polycrystalline SiC substrate 5 on which the single crystal SiC seed crystal piece 13a is arranged and the polycrystalline SiC substrate 5 which is placed in close proximity to the polycrystalline SiC substrate 5 are accommodated in the storage container 16 and larger. The state which produced the single crystal SiC substrate 13b of the area is shown. FIG.11 (b) shows the arrangement | positioning conceptual diagram which shows the positional relationship of the plane of the state of Fig.11 (a).

  The method for producing the single crystal SiC substrate of the present modification is the same as that of the second embodiment described above, and detailed description thereof is omitted. However, the single crystal SiC seed crystal piece 13a is placed on the surface of the polycrystalline SiC substrate 5. The single crystal SiC substrate 13b having a large area can be produced by arranging the single crystal SiC liquid phase epitaxial growth in the horizontal direction.

  Next, a method for producing a single crystal SiC substrate according to the third embodiment of the present invention will be described with reference to FIGS. FIG. 12 shows that a single crystal SiC seed crystal piece 13a is disposed on a tantalum carbide-processed surface 15a of a tantalum substrate 15, and single crystal SiC liquid phase epitaxial growth is performed in a horizontal direction to form a single crystal SiC substrate 13b having a large area. It is a conceptual diagram which shows the process to grow.

  By heat-treating the entire surface of the tantalum substrate 15, a surface 15a subjected to tantalum carbide processing is formed on the entire surface of the tantalum substrate 15 as shown in FIG. On the surface 15a subjected to tantalum carbide processing, as shown in FIG. 12B, single crystal SiC seed crystal pieces 13a are arranged. Then, as shown in FIG. 12C, the polycrystalline SiC substrate 5 facing the single crystal SiC seed crystal piece 13a disposed on the tantalum carbide processed surface 15a of the tantalum substrate 15 is divided to obtain a single crystal SiC seed. As shown in FIG. 12D, when the polycrystalline SiC substrate 5 is placed close to each of the crystal pieces 13a, and the metal silicon melt 12 is interposed in the gap between the substrates, the liquid phase epitaxial growth is performed. In addition, the surface 19 of the polycrystalline SiC substrate 5 is eroded, and the single crystal SiC seed crystal pieces 13a are grown in the single crystal SiC liquid phase epitaxially in the horizontal direction to generate the single crystal SiC substrate 13b. In this way, as shown in FIG. 12E, from the single crystal SiC seed crystal piece 13a grown in the horizontal direction from the single crystal SiC seed crystal piece 13a on the tantalum carbide processed surface 15a of the tantalum substrate 15. A large-area single crystal SiC substrate 13b can be generated.

  FIG. 13 (a) stores the tantalum substrate 15 on which the single crystal SiC seed crystal piece 13a is disposed and the divided polycrystalline SiC substrate 5 disposed adjacent to and opposed to the tantalum substrate 15 inside the storage container 16, The state which produced | generated the single crystal SiC substrate 13b of a large area is shown. FIG. 13B shows an arrangement conceptual diagram showing the positional relationship of the plane in the state of FIG.

  As can be seen from FIG. 13 (a), single crystal SiC seed crystal pieces 13a arranged at four locations on the surface 15a subjected to tantalum carbide processing are arranged at substantially the center of the polycrystalline SiC substrate 5 facing each other. .

  Then, the single crystal SiC seed crystal piece 13a is grown in the single crystal SiC liquid phase epitaxially in the horizontal direction, and the single crystal SiC substrate 13b is generated. Here, the single crystal SiC substrate 13b is generated in a disc shape by performing single crystal SiC liquid phase epitaxial growth in the horizontal direction outside the single crystal SiC seed crystal piece 13a. In addition, as described above, the horizontal growth rate of single crystal SiC liquid phase epitaxial growth is slow in the center direction of the substrate due to the convection of C atoms, but is high in the direction of the outer peripheral portion. Since the substrate 5 is individually divided into single crystal SiC seed crystal pieces 13a, and the single crystal SiC seed crystal pieces 13a are arranged at substantially the center of the polycrystalline SiC substrate 5 disposed adjacent to each other, the single crystal SiC substrate 13b is generated almost uniformly outside the single crystal SiC seed crystal piece 13a.

  Next, a modification of the method for producing a single crystal SiC substrate according to the third embodiment of the present invention will be described with reference to FIGS. FIG. 14 shows a process of arranging a single crystal SiC seed crystal piece 13a on the surface of the polycrystalline SiC substrate 5 and performing single crystal SiC liquid phase epitaxial growth in the horizontal direction to grow the single crystal SiC substrate 13b having a large area. FIG. FIG. 15A shows that the polycrystalline SiC substrate 5 in which the single crystal SiC seed crystal pieces 13 a are arranged and the divided polycrystalline SiC substrate 5 that is placed in close proximity to the polycrystalline SiC substrate 5 are accommodated in the storage container 16. Indicates the state. FIG. 15B is an arrangement conceptual diagram showing the positional relationship of the plane in the state of FIG.

  The method for producing the single crystal SiC substrate of the present modification is the same as that of the third embodiment described above, and detailed description thereof is omitted, but the single crystal SiC seed crystal piece 13a is placed on the surface of the polycrystalline SiC substrate 5. The single crystal SiC substrate 13b having a large area can be produced by arranging the single crystal SiC liquid phase epitaxial growth in the horizontal direction.

  In the second and third embodiments and modifications described above, the single crystal SiC seed crystal pieces 13a arranged on the surface of the tantalum substrate 15 or the polycrystalline SiC substrate 5 are generated by the method described above. However, it may be obtained by a separate method.

  Next, a method for producing a single crystal SiC substrate according to the fourth embodiment of the present invention will be described with reference to FIGS. FIG. 16 shows a single crystal SiC substrate 13c having a larger area by arranging a single crystal SiC seed crystal plate 13b on the surface 15a of the tantalum carbide 15 of the tantalum substrate 15 and performing single crystal SiC liquid phase epitaxial growth in the horizontal direction. It is a conceptual diagram which shows the process of producing | generating.

  By heat-treating the entire surface of the tantalum substrate 15, as shown in FIG. 16A, a surface 15a subjected to tantalum carbide processing is formed on the entire surface of the tantalum substrate 15. As shown in FIG. 16B, a single crystal SiC seed crystal plate 13b is arranged on the surface 15a subjected to tantalum carbide processing. Then, as shown in FIG. 16 (c), the polycrystalline SiC substrate 5 is placed close to the tantalum carbide-processed surface 15 a of the tantalum substrate 15, and the metal silicon melt 12 is placed in the gap between the two substrates. When the liquid phase epitaxial growth is performed by interposing, as shown in FIG. 16D, the surface 19 of the polycrystalline SiC substrate is eroded and the single crystal SiC seed crystal plate 13b is grown in the single crystal SiC liquid phase epitaxially in the horizontal direction. A single crystal SiC substrate 13c is generated. In this way, as shown in FIG. 16 (e), from the single crystal SiC seed crystal plate 13b grown in the horizontal direction from the single crystal SiC seed crystal plate 13b on the tantalum carbide processed surface 15a of the tantalum substrate 15. A single crystal SiC substrate 13c having a large area can be generated.

  17 (a) accommodates a tantalum substrate 15 on which a single crystal SiC seed crystal plate 13b is disposed and a polycrystalline SiC substrate 5 disposed in close proximity to the tantalum substrate 15 in a storage container 16, and has a larger area. The state which produced | generated the crystalline SiC substrate 13c is shown. FIG. 17B is an arrangement conceptual diagram showing the positional relationship of the plane in the state of FIG.

  As can be seen from FIGS. 17A and 17B, the single crystal SiC seed crystal plate 13b undergoes single crystal SiC liquid phase epitaxial growth in the horizontal direction to generate a single crystal SiC substrate 13c. Here, the single crystal SiC substrate 13c is generated in a disc shape by performing single crystal SiC liquid phase epitaxial growth in the horizontal direction outside the single crystal SiC seed crystal plate 13b. Further, as described above, the horizontal growth rate of the single crystal SiC liquid phase epitaxial growth is slow in the center direction of the substrate due to the influence of C atom convection, but is high in the direction of the outer peripheral portion. Since the seed crystal plate 13b is disposed in the approximate center of the polycrystalline SiC substrate 5 disposed in the vicinity, the single crystal SiC substrate 13c is generated substantially uniformly outside the single crystal SiC seed crystal plate 13b.

  Next, a modification of the method for producing a single crystal SiC substrate according to the fourth embodiment of the present invention will be described with reference to FIGS. FIG. 18 shows a process of forming a single crystal SiC substrate 13c having a larger area by disposing a single crystal SiC seed crystal plate 13b on the surface of the polycrystalline SiC substrate 5 and performing a single crystal SiC liquid phase epitaxial growth in the horizontal direction. FIG. FIG. 19A shows a case where the polycrystalline SiC substrate 5 on which the single crystal SiC seed crystal plate 13b is arranged and the polycrystalline SiC substrate 5 which is placed in close proximity to the polycrystalline SiC substrate 5 are accommodated in the storage container 16. The state which produced the single crystal SiC substrate 13c of the area is shown. FIG. 19B shows an arrangement conceptual diagram showing the positional relationship of the plane in the state of FIG.

  The method for producing the single crystal SiC substrate of the present modification is the same as that in the fourth embodiment described above, and detailed description thereof is omitted. However, the single crystal SiC seed crystal plate 13b is placed on the surface of the polycrystalline SiC substrate 5. The single-crystal SiC substrate 13c having a large area can be generated by arranging the single-crystal SiC liquid phase epitaxial growth in the horizontal direction.

  In the fourth embodiment and the modification described above, the single crystal SiC seed crystal plate 13b disposed on the surface of the tantalum substrate 15 or the polycrystalline SiC substrate 5 is the same as that in the first to third embodiments. It may be generated or may be obtained by a separate method.

  Although the preferred embodiment of the present invention has been described above, the above is an example, and can be modified as follows, for example.

  In addition to exposing the tantalum carbide layer 31 on the entire surface of the storage container 16 used in the heat treatment process, the storage container 16 is exposed only in the internal space of the storage container 16 or only on a part of the inner surface of the storage container 16. You may comprise as follows.

  In the second to fourth embodiments, the single crystal SiC seed crystal piece 13a or the single crystal SiC seed crystal plate 13b is disposed on the surface of the tantalum substrate 15 whose surface is tantalum carbide processed. Instead of the tantalum substrate 15, a substrate covered with a material excellent in heat resistance in a high vacuum of 1500 ° C. or higher and 2300 ° C. or lower may be used. For example, a graphite substrate or a tungsten substrate whose surface is covered with tantalum carbide. May be used.

DESCRIPTION OF SYMBOLS 1 Heat processing apparatus 5 Polycrystalline silicon carbide substrate 11 Carbonization process surface 12 Metal silicon melt 13 Single crystal silicon carbide substrate 13a Single crystal silicon carbide seed piece, Single crystal silicon carbide piece 13b Single crystal silicon carbide seed plate, Single crystal carbonization Silicon substrate 13c single crystal silicon carbide substrate,
15 Tantalum substrate 15a Surface 16 processed with tantalum carbide 16 Container 19 Surface of polycrystalline silicon carbide substrate eroded by liquid phase epitaxial growth

Claims (9)

  A polycrystalline silicon carbide substrate in which a polycrystalline silicon carbide substrate and a polycrystalline silicon carbide substrate whose surfaces are locally carbonized and disposed in close proximity to each other through a metal silicon melt is stored in a storage container, The polycrystalline silicon carbide substrate is carbonized by heat treatment at a temperature of 1500 ° C. or higher and 2300 ° C. or lower while maintaining a vacuum under a saturated vapor pressure of silicon so that the internal pressure of the storage container is higher than the external pressure. A single crystal silicon carbide seed crystal piece is produced by self-growth of single crystal silicon carbide on the surface by liquid phase growth, and the liquid crystal growth is continued, so that the single crystal silicon carbide seed crystal piece is orthogonal to the facing direction. A single crystal silicon carbide substrate, which is produced by liquid phase epitaxial growth in a direction to be formed, and has a portion of crystal growth in a plane direction on an outer peripheral portion thereof.   A polycrystalline silicon carbide substrate having a single crystal silicon carbide seed crystal piece disposed on a surface thereof and a polycrystalline silicon carbide substrate are disposed in close proximity to each other through a metal silicon melt, and the single crystal in a direction orthogonal to the facing direction The composite of the polycrystalline silicon carbide substrate in which the metal silicon melt is present around the silicon carbide seed crystal piece is stored in a storage container, and the internal pressure of the storage container is made higher than the external pressure. The single crystal silicon carbide seed crystal pieces are grown by liquid phase epitaxial growth in a direction perpendicular to the facing direction by heat treatment at a temperature of 1500 ° C. or higher and 2300 ° C. or lower while maintaining a vacuum under a saturated vapor pressure of And a single crystal silicon carbide substrate characterized by having a portion of crystal growth in a plane direction on an outer periphery thereof.   The single crystal silicon carbide seed crystal piece is a composite of a polycrystalline silicon carbide substrate in which a polycrystalline silicon carbide substrate having a carbonized surface and a polycrystalline silicon carbide substrate are disposed in close proximity to each other through a metal silicon melt, While being housed in a storage container, the heat treatment is performed at a temperature of 1500 ° C. or more and 2300 ° C. or less in a state where the internal pressure of the storage container is kept under a vacuum under a saturated vapor pressure of silicon so as to be higher than the external pressure, 3. The single crystal silicon carbide substrate according to claim 2, wherein the single crystal silicon carbide substrate is produced by self-growing single crystal silicon carbide by liquid phase growth on the carbonized surface of the polycrystalline silicon carbide substrate.   A polycrystalline silicon carbide substrate having a single crystal silicon carbide seed crystal plate disposed on a surface thereof and a polycrystalline silicon carbide substrate are disposed in close proximity to each other via a metal silicon melt, and the single crystal in a direction orthogonal to the facing direction A composite of a polycrystalline silicon carbide substrate in which the metal silicon melt is present around a silicon carbide seed crystal plate is stored in a storage container, and silicon is used so that the internal pressure of the storage container is higher than the external pressure. The single crystal silicon carbide seed crystal plate is produced by liquid phase epitaxial growth in a direction perpendicular to the facing direction by heat treatment at a temperature of 1500 ° C. or higher and 2300 ° C. or lower while maintaining a vacuum under a saturated vapor pressure of And a single crystal silicon carbide substrate characterized by having a portion of crystal growth in a plane direction on an outer periphery thereof.   The single crystal silicon carbide seed crystal plate is a composite of a polycrystalline silicon carbide substrate in which a polycrystalline silicon carbide substrate whose surface is locally carbonized and a polycrystalline silicon carbide substrate are disposed in close proximity to each other via a metal silicon melt. The body is stored in a storage container, and heat-treated at a temperature of 1500 ° C. or higher and 2300 ° C. or lower in a state where the internal pressure of the storage container is kept under a vacuum under the saturated vapor pressure of silicon so as to be higher than the external pressure. The single crystal silicon carbide is self-grown by liquid phase growth on the carbonized surface of the polycrystalline silicon carbide substrate to form single crystal silicon carbide seed crystal pieces, and further, liquid phase growth is continued, whereby the single crystal carbonization is performed. 5. The single crystal silicon carbide substrate according to claim 4, wherein the single crystal silicon carbide substrate is produced by liquid phase epitaxial growth of a silicon seed crystal piece in a direction orthogonal to the facing direction.   5. The single crystal silicon carbide substrate according to claim 2, wherein the single crystal silicon carbide seed crystal piece or seed crystal plate is disposed at a position close to an outer peripheral end of the polycrystalline silicon carbide substrate.   The carbonization treatment is performed by locally irradiating the surface of the substrate with a laser beam or an electron beam while keeping the 3C-SiC aggregate polycrystalline silicon carbide substrate in a vacuum or in an inert atmosphere. 2. The process of growing the aggregate into crystal grains containing a 4H—SiC aggregate and simultaneously evaporating and removing silicon on the substrate surface to produce a carbon-rich silicon carbide composition. 4. The single crystal silicon carbide substrate according to 3.   The single crystal according to any one of claims 1 to 7, wherein the storage container is made of tantalum metal and is configured to fit the upper and lower parts configured to expose the tantalum carbide layer in the internal space. Silicon carbide substrate.   Instead of the polycrystalline silicon carbide substrate on which the single crystal silicon carbide seed crystal piece or seed crystal plate is disposed, the surface is tantalum carbide processed tantalum substrate, or heat resistant in a high vacuum of 1500 ° C. to 2300 ° C. The single crystal silicon carbide substrate according to claim 2, wherein a substrate covered with a material having a property is used.