JP2006298722A - Method for manufacturing single crystal silicon carbide substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a single crystal silicon carbide (SiC) substrate which is inexpensive and in which the deterioration of quality caused by the defect of a seed crystal is reduced. <P>SOLUTION: An SiC single crystal 28 being the seed crystal is arranged opposite to a C-atom feeding substrate 17 in a closed vessel 16, and then high temperature thermal treatment is performed. A metallic Si melt 18 is interposed between the SiC single crystal 28 and the C-atom feeding substrate 17, and liquid phase epitaxial growth is carried out. The SiC single crystal 28 being the seed crystal is formed to have a surface area smaller than that of the C-atom feeding substrate 17, and a plurality of SiC single crystals 28 are arranged. When the single crystal SiC 20 is formed on the upper surface part of the seed crystal 28, the metallic Si melt 18 is made to be present around the single crystal SiC 20 in the direction opposing to the C-atom feeding substrate 17 and in the vertical direction. Thus, the single crystal silicon carbide 20 is epitaxially grown in the direction opposing to the C-atom feeding substrate 17 and in the vertical direction (wherein the surface area is expanded). Thereby, the substrate 27 having a surface area larger than that of the seed crystal 28 is obtained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a single-crystal silicon carbide substrate that can reduce the adverse effects of defects such as micropipes in a seed crystal and is low in cost.

  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. Further, hexagonal SiC has a lattice constant close to that of gallium nitride (GaN), and is expected as a GaN substrate.

And as a method of manufacturing this kind of single crystal SiC, the method as shown, for example in patent document 1 or patent document 2 is proposed.
In the method of Patent Document 1, a single crystal SiC substrate and a plate material composed of Si atoms and C atoms are faced in parallel with a minute gap therebetween, and in that state, an inert gas atmosphere and an SiC saturated vapor at atmospheric pressure or lower Under an atmosphere, a temperature gradient is provided so that the single crystal SiC substrate side is at a lower temperature than the plate material. Then, by performing heat treatment, Si atoms and C atoms are sublimated and recrystallized in a minute gap, and a single crystal is deposited on a single crystal SiC substrate.

However, in the sublimation recrystallization method as in Patent Document 1, defects (especially, tubular voids having a diameter of several microns to about 0.1 mm called “micropipe defects”) that the single crystal SiC substrate as a seed crystal has, This easily propagates to the deposited single crystal epitaxial structure, which is a major obstacle when the manufactured single crystal SiC is used as the power device described above. This point is also pointed out by Patent Document 2, and as a method for solving this problem, in Patent Document 2, a first epitaxial layer is formed on a single crystal SiC by a liquid phase epitaxial growth method (LPE), and a micro-appeared on the substrate By continuing to grow this epitaxial layer until the pipe defect has a thickness that is almost not replicated in the epitaxial layer, the micropipe defect propagated from the substrate to the epitaxial layer is blocked, and then the surface is formed by vapor phase deposition (CVD). Proposed a method of forming a second epitaxial layer. According to Patent Document 2, it is possible to grow a silicon carbide epitaxial layer with few defects.
JP 11-315000 A Japanese National Patent Publication No. 10-509943

  The method of Patent Document 2 can substantially reduce the influence of micropipe defects in the seed crystal by using the liquid phase epitaxial growth method. However, for example, when there are a large number of large-diameter micropipes in the seed crystal SiC, in general, the liquid phase epitaxial growth method is very slow compared with the sublimation recrystallization method in order to block it (see FIG. Coupled with that of 10 μs or less per hour), it takes a very long time and the productivity is greatly reduced.

  In addition to the above micropipes, defects such as step bunching, morphology, and polishing damage existing in the seed crystal have an adverse effect on the liquid phase epitaxial growth layer, which also reduces the stability of the quality of the single crystal SiC. I was sorry. Eventually, in order to obtain high-quality single crystal SiC, expensive single crystal SiC with few defects must be used as a seed crystal, which also contributes to an increase in cost.

  In both Patent Document 1 and Patent Document 2, single crystal SiC is deposited or grown on single crystal SiC as a seed crystal, and the single crystal SiC used as a seed is considerably expensive. Therefore, it has been desired to develop a method for growing single crystal SiC at a low cost.

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above. Next, means for solving the problems and the effects thereof will be described.

  ◆ According to the first aspect of the present invention, the following method for producing a single crystal silicon carbide substrate is provided. A single crystal silicon carbide serving as a seed crystal is subjected to high-temperature heat treatment in a closed container while facing the C atom supply substrate, thereby interposing a metal silicon melt between the single crystal silicon carbide and the C atom supply substrate. Liquid phase epitaxial growth is performed. The single crystal silicon carbide as the seed crystal has an area smaller than that of the C atom supply substrate. The single crystal silicon carbide is grown by liquid phase epitaxial growth in a direction perpendicular to the direction facing the C atom supply substrate to obtain a single crystal silicon carbide substrate having an area larger than the initial area of the seed crystal.

  In this method, since liquid phase epitaxial growth is performed so as to extend from the area of the single crystal silicon carbide serving as a seed crystal, defects such as micropipes or the like of the initial seed crystal appear only in a small area portion of the seed crystal. Therefore, a single crystal silicon carbide substrate having almost no defects can be provided at least in a portion other than the portion corresponding to the seed crystal.

  ◆ According to the second aspect of the present invention, the following method for producing a single crystal silicon carbide substrate is provided. A single crystal silicon carbide serving as a seed crystal is subjected to high-temperature heat treatment in a closed container while facing the C atom supply substrate, thereby interposing a metal silicon melt between the single crystal silicon carbide and the C atom supply substrate. Liquid phase epitaxial growth is performed. The metal silicon melt is present around single crystal silicon carbide in a direction perpendicular to the direction facing the C atom supply substrate. The single crystal silicon carbide is grown by liquid phase epitaxial growth in a direction perpendicular to the direction facing the C atom supply substrate.

  In this method, liquid phase epitaxial growth is performed so as to spread from the single crystal silicon carbide serving as a seed crystal to the periphery, so that even if a defect such as a micropipe of the seed crystal propagates in a portion corresponding to the seed crystal, it spreads. There is almost no adverse effect of defects in the seed crystal on the portion that has grown to a large thickness. Therefore, a single crystal silicon carbide substrate having almost no defects can be provided at least in a portion other than the portion corresponding to the seed crystal.

  In the above method for producing a single crystal silicon carbide substrate, the single crystal silicon carbide serving as a seed crystal is preferably configured in a circular shape.

  Thereby, the single crystal silicon carbide can be uniformly liquid phase epitaxially grown, the quality of the produced single crystal substrate can be improved, the production efficiency of the substrate can be improved, and the time required for the production can be reduced. . In addition, since the area of the seed crystal (the part that functions as) can be reduced, it is easy to reduce the cost of the seed crystal.

  In the above method for producing a single crystal silicon carbide substrate, it is preferable that a plurality of single crystal silicon carbides serving as seed crystals are provided for one C atom supply substrate.

  As a result, a plurality of single crystal substrates can be obtained by a single growth process, so that the production efficiency can be further improved and the production cost can be reduced.

  In the above method for producing a single crystal silicon carbide substrate, it is preferable that the single crystal silicon carbide substrate is grown twice or more in area ratio than the original seed crystal.

  As a result, a large-area substrate can be obtained, and the manufacturing efficiency can be further improved.

  In the method for producing a single crystal silicon carbide substrate, the single crystal silicon carbide serving as a seed crystal is formed of unevenness provided on the surface of the plate member made of single crystal silicon carbide facing the C atom supply substrate. It is preferably configured as a relative convex portion.

  Thereby, many seed crystals (parts that function as) can be made in a short time by applying appropriate irregularities to the plate member. Therefore, it can be better adapted to cost reduction by mass production.

  ◆ In the method for producing a single crystal silicon carbide substrate, liquid phase epitaxial growth is performed by interposing a metal silicon melt between the C-member supply substrate for seed crystal whose surface is roughened and the plate member. Preferably, the convex portion is formed on the plate member at a portion facing the convex portion of the seed crystal C atom supply substrate.

  As a result, an unevenness is formed on the seed crystal C atom supply substrate so as to face the plate member, and liquid phase epitaxial growth is performed on the plate member corresponding to the convex portion of the seed crystal C atom supply substrate. Can be formed. Accordingly, it is not necessary to directly process the plate member made of single crystal silicon carbide to form the convex portion, so that the formation cost of the convex portion can be reduced.

  In the method for producing a single crystal silicon carbide substrate, the single crystal silicon carbide serving as the seed crystal is preferably installed as a thin plate-like member on the surface of the tantalum substrate having a tantalum carbide processed surface. .

  Thereby, since it is only necessary to install single crystal silicon carbide as a seed crystal only as a member having a small area, the manufacturing cost can be greatly reduced.

  In addition, according to the third aspect of the present invention, it is possible to provide a single crystal silicon carbide substrate manufactured by the above method and having a high quality region with almost no defects.

  Next, embodiments of the invention will be described. First, an example of a heat treatment apparatus suitable for carrying out the method for producing a single crystal SiC substrate of the present invention will be described with reference to the schematic cross-sectional view of FIG.

  In FIG. 1, the heat treatment apparatus 1 is mainly composed of a main heating chamber 2, a preheating chamber 3, and a front chamber 4 in a portion following the preheating chamber 3 to the main heating chamber 2. With this configuration, the hermetically sealed container 16 in which a single crystal SiC holding plate 5 or the like to be described later is moved sequentially from the preheating chamber 3 to the front chamber 4 and the main heating chamber 2, thereby shortening the single crystal SiC holding plate 5. It can be heated at a predetermined temperature (for example, about 1200 ° C. to about 2300 ° C.) over time.

  As shown in FIG. 1, the heat treatment apparatus 1 has a connecting portion between the main heating chamber 2 and the front chamber 4 and a connecting portion between the front chamber 4 and the preheating chamber 3 each having a communication portion. 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 closed container 16 containing the single crystal SiC holding plate 5 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. Can be prevented.

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 ⁻⁵ 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.

  The sealed container 16 in which the single crystal SiC holding plate 5 or the like for liquid phase epitaxial growth is accommodated is preheated to about 800 ° C. or more in the state of being placed on the table 8 in the preheating chamber 3. 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 sealed container 16 that has 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 the lifting and lowering moving means 10 partially shown. The main heating chamber 2 is preliminarily adjusted under a reduced pressure of about 10 ⁻¹ Pa by a vacuum pump (not shown), and is set to a predetermined temperature range (for example, about 1200 ° C. to about 2300 ° C.) by the heater 11. The temperature is adjusted. The pressure environment of the main heating chamber 2 is, for example, a vacuum of about 10 ⁻² Pa or less, preferably 10 ⁻⁵ Pa or less, or a vacuum of about 10 ⁻² Pa or less, preferably 10 ^−. It is preferable to be in a dilute gas atmosphere in which some inert gas is introduced after the vacuum of ⁵ Pa or less.

  When the state of the main heating chamber 2 is set in this way and the sealed container 16 is moved from the front chamber 4 into the main heating chamber 2, the closed container 16 is rapidly shortened to a range of about 1400 ° C. to 2300 or less, for example. Can be heated in time. In the main heating chamber 2, a reflecting mirror 12 is installed around the heater 11, and reflects the heat from the heater 11 to the single crystal SiC holding plate 5 side located inside the heater 11. The heat is concentrated.

  The fitting portion 25 between the moving means 10 and the main heating chamber 2 includes a convex stepped portion 21 provided in the moving means 10 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, an unillustrated seal member (for example, an O-ring) is provided at each step portion of the stepped portion 21 of the moving means 10.

  A contaminant removal mechanism 29 is provided inside the heater 11 in the main heating chamber 2. The contaminant removal mechanism 29 removes impurities discharged from the single crystal SiC holding plate 5 or the like during the heat treatment so as not to come into contact with the heater 11. Thereby, it is possible to prevent the heater 11 from reacting and deteriorating with impurities discharged from the single crystal SiC holding plate 5 or the like. The contaminant removal mechanism 29 is not particularly limited as long as it can adsorb impurities discharged from the single crystal SiC holding plate 5 or the like.

  The heater 11 is a resistance heater made of metal such as tantalum, and includes a base heater 11 a installed on the susceptor 9 side and an upper heater 11 b provided on the main heating chamber 2 side. When the closed container 16 is moved upward together with the base heater 11 a to the main heating chamber 2 by the moving means 10, the closed container 16 is surrounded by the heater 11. Such a layout of the heater 11 makes it possible to uniformly heat the sealed container 16 together with the above-described reflecting mirror 12. 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 sealed container 16 used for SiC liquid phase epitaxial growth and the substrate disposed therein will be described with reference to FIGS. FIG. 2 is a view in which the upper container and the lower container are removed. FIG. 3 is a schematic cross-sectional view showing the state of the sealed container before the heat treatment.

  The above-described sealed container 16 is configured by fitting an upper container 16a and a lower container 16b as shown in FIGS. Although the shape of the airtight container 16 is substantially hexahedral as shown in FIG. 2, this is an example, and may be configured in a cylindrical shape, for example. An appropriate material can be adopted as the material of the sealed container 16, but it is preferably formed of, for example, tantalum or tantalum carbide.

  Moreover, it is preferable that the play of a fitting part when the upper container 16a and the lower container 16b are fitted as shown in FIG. 3 is about 2 mm or less. Thereby, mixing of impurities into the sealed container 16 can be suppressed, and furthermore, the Si partial pressure in the sealed container 16 is controlled not to be about 10 Pa or less during the heat treatment in the main heating chamber 2. Can do. For this reason, the SiC partial pressure and the Si partial pressure in the sealed container 16 are increased, the single crystal SiC holding plate 5 accommodated in the sealed container 16, the C atom supply substrate 17, the metal Si melt 18 and the like (details will be described later). Sublimation is suppressed. In other words, if the play of the fitting part is larger than about 2 mm, it becomes difficult to control the Si partial pressure in the sealed container 16 to a predetermined pressure, and impurities can cause the fitting part to move. This is not preferable because the risk of entering the sealed container 16 increases.

  In the sealed container 16, as shown in FIG. 3, the single crystal SiC holding plate 5, the Si substrate 14, and the C atom supply substrate 17 are sequentially stacked from the bottom to the top. The single crystal SiC holding plate 5 is disposed so as to face the C atom supply substrate 17 with the Si substrate 14 interposed therebetween. If necessary, a weight may be placed on the Si substrate 14.

  In the present embodiment, the single crystal SiC holding plate 5 is made of a circular plate-like member that is entirely made of single crystal SiC, and has a surface on one side thereof (ie, a surface facing the C atom supply substrate 17 side). Are recessed at appropriate intervals to form the recesses 5a. Further, a portion other than the concave portion 5a (a portion relatively corresponding to the convex portion) is a flat surface 5b for generating single crystal SiC. In the present embodiment, the flat surface 5b serves as a seed crystal.

  As the single crystal SiC holding plate 5, for example, a single crystal 6H—SiC wafer cut by a sublimation method and cut into a desired size can be used. Alternatively, a single crystal 6H or 4H—SiC substrate whose surface has been improved by heat treatment can also be used. In addition, as a surface processing method for forming the concave portion 5a, an appropriate method such as machining can be employed.

  In the present embodiment, a polycrystalline SiC substrate is used as the upper C atom supply substrate 17, but, for example, a different single crystal SiC substrate, a carbon substrate, a porous SiC substrate, a sintered SiC substrate, At least one substrate selected from the group consisting of crystalline SiC substrates can be used. Carbon substrates, porous SiC substrates, sintered SiC substrates, and amorphous SiC substrates have a larger surface energy than polycrystalline SiC substrates. Among them, carbon substrates increase the growth rate in order to increase the supply amount of C atoms. This is preferable because the throughput can be improved. Furthermore, a carbon substrate, a porous SiC substrate, a sintered SiC substrate, and an amorphous SiC substrate are superior in workability compared to a polycrystalline SiC substrate, and are advantageous in terms of cost.

  When a polycrystalline SiC substrate is used as the C atom supply substrate 17 as in the present embodiment, for example, it is cut out to a desired size from SiC used as a dummy wafer in a Si semiconductor manufacturing process manufactured by a CVD method. Can be used. The polycrystalline SiC substrate preferably has an average particle diameter of 1 μm to 10 μm and a uniform particle diameter. As the crystal structure of the polycrystalline SiC substrate, any of 3C—SiC, 4H—SiC, and 6H—SiC can be used.

  At least the flat surface 5b of the single crystal SiC holding plate 5 and the surface facing the SiC side of the C atom supply substrate 17 are all polished to a mirror surface, and oils, oxide films, metals, etc. attached to the surface Has been removed by washing or the like.

And after the airtight container 16 which accommodated the laminated structure ^demonstrated above was installed in the preheating chamber 3 of the heat processing apparatus 1 of FIG. 1, as above-mentioned, it is ^800-5 degreeC or less (preferably ^10-5 Pa or less) 1000 ° C. or higher). At this time, the inside of the main heating chamber 2 is similarly set to 10 ⁻² Pa or less and then preheated to 1400 ° C. to 2300 ° C.

  After the above preheating step, the gate valve 7 is opened, and the sealed container 16 is moved onto the susceptor 9 in the front chamber 4 and then heated to 1400 ° C. to 2300 ° C. by the moving means 10. 2 is moved up into 2. As a result, the sealed container 16 is rapidly heated to 1400 ° C. to 2300 ° C. in a short time within 30 minutes, and the above-described Si substrate 14 is melted, and as shown in FIG. An ultrathin metal Si melt layer 18 is formed between the C atom supply substrate 17.

  The heat treatment temperature in the main heating chamber 2 may theoretically be a temperature at which the Si substrate 14 installed in the sealed container 16 is melted, but is preferably set to a high temperature of 1400 ° C. to 2300 ° C. This is because the higher the processing temperature is, the better the wettability between the Si Si melt formed by melting the Si substrate 14 and SiC, and the metal Si melt layer 18 becomes a single crystal SiC holding plate 5 by capillary action. This is because it easily penetrates between the C atom supply substrate 17 and the C atom supply substrate 17. As a result, an extremely thin metal Si melt layer 18 having a thickness of 50 μm or less can be interposed between the single crystal SiC holding plate 5 (the above-described flat surface 5 b) and the C atom supply substrate 17.

  In addition, it is preferable to heat up said heat processing to 1400 degreeC-2300 degreeC in as short time as possible. This is because crystal growth can be completed in a short time and the efficiency of crystal growth can be improved.

  Here, when the growth mechanism of the single crystal SiC is overviewed, the melted Si enters between the single crystal SiC holding plate 5 and the upper C atom supply substrate 17 in accordance with the heat treatment, and both the substrates 5, 17. A metal Si melt layer 18 having a thickness of about 30 μm to 50 μm is formed at the interface. The metal Si melt layer 18 becomes thinner as the heat treatment temperature becomes higher, for example, about 30 μm. Then, the C atoms flowing out from the C atom supply substrate 17 are supplied to the flat surface 5b of the single crystal SiC holding plate 5 through the metal Si melt layer 18, and liquid phase epitaxial growth is performed on the flat surface as 4H-SiC single crystal 20. To do.

  In the configuration of the present embodiment, the surface of the single crystal SiC holding plate 5 is recessed as described above, so that the thickness of the metal Si melt layer 18 is minimized at the flat surface 5b. However, it is large in the other part (the part of the recess 5a). Therefore, most of the C atoms released from the C atom supply substrate 17 are supplied to the flat surface 5b, and the SiC single crystal 20 first grows to the flat surface 5b. In other words, the depth and shape of the recess 5a are set as appropriate so that C atoms from the C atom supply substrate 17 are supplied to the flat surface 5b and hardly supplied to the recess 5a. is there.

  The SiC single crystal 20 appearing on the flat surface 5b as shown in FIG. 4 is epitaxially grown in the direction toward the C atom supply substrate 17 (thickness direction). However, in this embodiment, since the growth crystal 20 appears only in the flat surface 5b at the initial stage of the growth process, the metal Si melt layer is also present around the growth crystal 20 (periphery in the direction perpendicular to the thickness direction). There are 18 melts around. Accordingly, the SiC single crystal 20 is epitaxially grown in a direction substantially perpendicular to the direction (the thickness direction of the metal Si melt layer 18) facing the C atom supply substrate 17, as shown in FIG.

  With this epitaxial growth, the upper C atom supply substrate 17 is scraped off so that the portion facing the flat surface 5b is dissolved to form a recess 19 (FIG. 3). As the SiC single crystal 20 grows in the lateral direction, the formation area of the recess 19 increases as shown in FIG.

  As described above, in the present embodiment, the flat surface (which is a portion functioning as a seed crystal in the single crystal SiC holding plate 5) rather than the area where the C atom supply substrate 17 faces the metal Si melt layer 18. The area of 5b is small. In other words, the recess 5a is formed around the flat surface 5b (periphery in the direction perpendicular to the direction facing the C atom supply substrate 17), and the metal Si melt 18 is present in the recess 5a. I have to. Then, as shown in FIGS. 4 to 5, the SiC single crystal 20 is grown by liquid phase epitaxial growth in a direction perpendicular to the direction facing the C atom supply substrate 17, and a single crystal having an area larger than the initial area of the flat surface 5b is obtained. A crystalline SiC substrate 27 is configured to be obtained.

  Therefore, in the single crystal SiC substrate 27 obtained by this method, in the portion corresponding to the seed crystal (the portion on the flat surface 5b), even if defects such as micropipes of the seed crystal propagate to some extent, The other portions grown in the lateral direction can provide a high-quality single crystal SiC substrate having almost no defects as described above. This effect is achieved by growing single-crystal SiC to be produced so that the area ratio of the single-crystal SiC is twice or more than the initial seed crystal (part of the flat surface 5b), thereby obtaining high-quality single-crystal SiC in a wide area. It becomes even more prominent.

  Further, in the present embodiment, as shown in FIG. 3, the flat surface 5 b serving as a seed crystal in the single crystal SiC holding plate 5 is disposed so as to be plural with respect to one C atom supply substrate 17. . Therefore, since a plurality of single crystal SiC substrates 27 can be manufactured as shown in FIG. 5 by a single heat treatment, the manufacturing efficiency can be improved and the manufacturing cost can be reduced.

  In the present embodiment, in particular, the single crystal SiC serving as a seed crystal is a relative one of the unevenness provided on the surface of the single crystal SiC holding plate 5 that is entirely made of single crystal SiC and facing the C atom supply substrate 17. In particular, it is configured as a convex portion (the flat surface 5b). Therefore, it is easy to form a large number of flat surfaces 5b as seed crystals at one time using machining or the like, which is suitable for mass production of the single crystal SiC substrate 27.

[Second Embodiment]
In the second embodiment, the SiC single crystal 28 serving as a seed crystal is arranged on a flat tantalum substrate 15 provided so as to face the C atom supply substrate 17 over the entire surface, as shown in FIG. Has been. The surface of the tantalum substrate 15 on the C atom supply substrate 17 side is a surface 15a subjected to tantalum carbide processing, and an SiC single crystal 28 as a seed crystal is formed in advance on the surface 15a. As the SiC single crystal 28, a tantalum carbide surface 15a formed in a thin plate shape by, for example, a vapor phase method (CVD) can be employed. As shown in FIG. 6B, the SiC single crystal 28 is provided at four locations at equal intervals in the circumferential direction in plan view, and each is formed in a circular shape. Since other configurations are substantially the same as those of the first embodiment described above, the corresponding members are denoted by the same reference numerals and description thereof is omitted.

  When the sealed container 16 shown in FIG. 6A is heat-treated by the heat treatment apparatus 1 described above, C atoms of the C atom supply substrate 17 are supplied to the upper surface of the SiC single crystal 28, and the grown crystal is first formed of the SiC single crystal 28. Appears on the top. Then, the metal Si melt as a result of melting the Si substrate 14 wraps around the appearing SiC growth crystal (periphery in the direction perpendicular to the thickness direction of the metal Si melt layer 18). The grown crystal 20 formed on the SiC single crystal (seed crystal) 28 grows not only in the thickness direction but also in the lateral direction. Therefore, similarly to the first embodiment, this single crystal SiC substrate 27 is made of an extremely high quality single crystal SiC having almost no defects such as micropipes at least in the portion other than the SiC single crystal 28 as the seed crystal. it can. In this embodiment, in particular, the single crystal 28 only needs to be partially disposed only at the core of the central portion (the upper surface of the island-like protrusion 15b), so that the manufacturing cost of the single crystal SiC substrate 27 can be significantly reduced. it can.

  Further, in the present embodiment, as shown in FIG. 6A, a plurality of SiC single crystals 28 serving as seed crystals are provided with respect to one C atom supply substrate 17. Therefore, since a plurality of single crystal SiC substrates 27 can be manufactured by a single heat treatment, the manufacturing efficiency can be improved and the manufacturing cost can be reduced. Furthermore, since each SiC single crystal 28 as a seed crystal has a circular shape as shown in FIG. 6, the SiC single crystal 20 can be epitaxially grown uniformly in the lateral direction, and the quality of the single crystal SiC substrate 27 can be improved. In addition, the time required for manufacturing the single crystal SiC substrate 27 can be reduced. Moreover, the SiC single crystal 28 as the initial seed crystal can be made smaller, and the cost of the seed crystal can be greatly reduced.

[Third Embodiment]
In the third embodiment shown in FIG. 8, the single crystal SiC holding plate 5 ′ is made of a circular plate-like member that is entirely made of single crystal SiC, as in the first embodiment. Then, the seed crystal C atom supply substrate 30 is placed so as to face the single crystal SiC holding plate 5 ′.

  The surface of the single crystal SiC holding plate 5 ′ facing the seed crystal C atom supply substrate 30 side is simply a flat surface. On the other hand, in the C atom supply substrate 30 for seed crystal, irregularities are provided in advance on the surface facing the single crystal SiC holding plate 5 ′, such as a concave portion 30 a and a convex portion 30 b. Then, as shown in FIG. 8, the Si substrate 14 is sandwiched between the two plates 5 'and 30, and then stored in the sealed container 16, and high-temperature heat treatment is performed by the heat treatment apparatus 1 of FIG. A metal Si melt 18 is interposed between the holding plate 5 ′ and the seed crystal C atom supply substrate 30. Then, as shown in FIG. 9, on the flat surface of the single-crystal SiC holding plate 5 ′, single-crystal SiC is grown in a liquid phase epitaxial manner only in a portion facing the convex portion 30b of the seed crystal C atom supply substrate 30. As a result, a convex portion 5c is formed on the single crystal SiC holding plate 5 ′. Note that the front end surface 5b (convex portion) of the convex portion 5c functions as a seed crystal in the liquid phase epitaxial growth in the horizontal direction in the next heat treatment.

  As shown in FIG. 10 (b), the convex portions 5c are provided at four positions at equal intervals in the circumferential direction in a plan view, and are each formed in a circular shape. In other words, the concavo-convex shape of the seed crystal C atom supply substrate 30 (specifically, the arrangement and shape of the convex portions 30b) is determined so as to have such an arrangement and shape of the convex portions 5c.

  Then, as shown in FIG. 10A, the sealed container 16 is placed in a state in which a new C atom supply substrate 17 is opposed to the single crystal SiC holding plate 5 ′ formed with the convex portion 5c with the Si substrate 14 interposed therebetween. The high temperature heat treatment is again performed with the heat treatment apparatus of FIG. Then, as shown in FIG. 11, the SiC single crystal 20 is epitaxially grown in a direction substantially perpendicular to the direction facing the C atom supply substrate 17 (the thickness direction of the metal Si melt layer 18), and the single crystal SiC substrate 27 Is obtained. As in the first and second embodiments, this SiC single crystal substrate 27 is defective in the portion grown in the lateral direction other than the portion corresponding to the seed crystal (the portion on the tip surface 5b of the convex portion 5c). It can be made of extremely high quality with almost no

  In particular, in the present embodiment, as shown in FIG. 9, by forming irregularities on the seed crystal C atom supply substrate 30 as shown in FIG. 8 and heat-treating it against the single crystal SiC holding plate 5 ′, as shown in FIG. In a portion corresponding to the convex portion 30b of the C atom supply substrate 30, the convex portion 5c and the tip surface 5b can be formed on the single crystal SiC holding plate 5 ′ by epitaxial growth. Accordingly, it is not necessary to directly process the single crystal SiC holding plate 5 ′ to form the protrusions 5 c and the like, and thus the cost for forming the protrusions 5 c and the tip surface 5 b can be reduced. For example, when a polycrystalline SiC substrate is used as the C atom supply substrate 30 for seed crystal, the uneven processing is considerably easier than the holding plate 5 ′ made of single crystal SiC. Therefore, the formation cost of the seed crystal (tip surface 5b) can be greatly reduced, and this effect is particularly remarkable when it is desired to form a large number of seed crystals at once.

  Further, in this embodiment, as shown in FIG. 10A, a plurality of SiC single crystals serving as seed crystals (in other words, the front end surface 5 b of the convex portion 5 c) are plural with respect to one C atom supply substrate 17. It is installed as follows. Therefore, since a plurality of single crystal SiC substrates 20 can be manufactured by a single heat treatment, the manufacturing efficiency can be improved and the manufacturing cost can be reduced. Furthermore, since each SiC single crystal (tip surface 5b of the convex portion 5c) as a seed crystal has a circular shape as shown in FIG. 10B, the SiC single crystal 20 is epitaxially grown evenly in the lateral direction. The quality of the single crystal SiC substrate 27 can be improved, and the time required for manufacturing the single crystal SiC substrate 27 can be reduced. Moreover, the SiC single crystal (the convex part 5c thru | or the end surface 5b) as an initial seed crystal can be made smaller.

  A plurality of preferred embodiments of the present invention have been described above, but the above embodiments can be implemented with the following modifications, for example.

  (1) Planar shape of single-crystal SiC as a seed crystal before growth (specifically, the planar shape of the flat surface 5b of the first embodiment, the planar shape of the seed crystal of the second embodiment, The planar shape of the front end surface 5b of the convex portion 5c is not limited to the circular shape as in the second embodiment or the third embodiment, for example, depending on the size of the single crystal SiC to be obtained. You can do it. Also, the heat treatment time in the main heating chamber 2 can be appropriately selected so that the generated single crystal SiC has a desired size (area) or thickness.

  (2) Instead of using the Si substrate 14 illustrated in FIGS. 3, 6, 8, or 10 as the Si material supply source for the metal Si melt layer 18, the single crystal SiC holding plate 5 or the like Alternatively, a metal Si film having a thickness of about 50 to 200 μm formed on the surface in advance by the vapor phase method (CVD), a Si powder disposed on the surface of the single crystal SiC holding plate 5 or the like may be used.

  (3) In the above embodiment, the single crystal SiC holding plates 5 and 5 ′ and the tantalum substrate 15 are disposed on the lower side and the C atom supply substrate 17 is disposed on the upper side in the sealed container 16. As long as they are arranged so as to face each other, the positional relationship can be arbitrarily changed. For example, they may be arranged upside down, or both substrates may be arranged to face each other horizontally.

  (4) In order to adjust the thickness of the metal Si melt layer 18 interposed between the single crystal SiC holding plate 5 and the C atom supply substrate 17, the single crystal SiC holding plates 5 and 5 ′ and the C atom supply are provided. For example, a spacer having an appropriate thickness of about 30 to 50 μm may be provided between the substrate 17 and the substrate 17. The number, shape, and arrangement number of the spacers are not particularly limited, and can be appropriately selected and used according to circumstances such as the seed crystal layout. As this spacer, for example, a convex portion provided by machining on the single crystal SiC holding plates 5, 5 ′ or the tantalum substrate 15 or a convex portion bonded by a solid phase reaction can be employed.

The schematic cross section which shows an example of the heat processing apparatus suitable for the manufacturing method of the SiC single crystal substrate of this invention. The figure which removed the upper container and the lower container of the airtight container. In 1st Embodiment, the schematic cross section which shows the mode of the airtight container before heat processing. The schematic cross section which shows the state by which the SiC single crystal grew the liquid phase epitaxially in the seed crystal part. FIG. 5 is a schematic cross-sectional view showing a state in which a SiC single crystal substrate is manufactured by liquid phase epitaxial growth of a SiC single crystal in the lateral direction from the state of FIG. 4. (A) is a schematic cross section which shows the state of the airtight container before heat processing in 2nd Embodiment, (b) is a schematic top view. (A) is a schematic cross section which shows the state which heat-processed from the state of FIG. 6, and the SiC single crystal substrate was manufactured, (b) is a schematic top view. In 3rd Embodiment, the schematic cross section which shows the mode of the airtight container before heat processing. FIG. 9 is a schematic cross-sectional view showing a state in which SiC single crystal islands (convex portions) are partially grown by liquid phase epitaxial growth on the surface of the single crystal SiC holding plate by performing heat treatment from the state of FIG. 8. (A) is a schematic cross section which shows the mode of the airtight container before heat processing in 3rd Embodiment, (b) is a schematic top view. (A) is a schematic cross section which shows the state which heat-processed from the state of FIG. 10, and the SiC single crystal substrate was manufactured, (b) is a schematic top view.

Explanation of symbols

1 Heat treatment apparatus 5,5 'single crystal SiC holding plate (plate member)
5a Concave part 5b Flat surface, tip surface of convex part (convex part, part functioning as seed crystal)
5c Convex (SiC single crystal grown from a single crystal SiC holding plate)
14 Metal Si Plate 15 Tantalum Substrate 15a Tantalum Carbide Surface 16 Sealed Container 17 C Atom Supply Substrate 18 Metal Si Melt 27 Single Crystal SiC Substrate 30 C Crystal Supply Substrate for Seed Crystal 30a Recess 30b Protrusion

Claims (9)

A single crystal silicon carbide serving as a seed crystal is subjected to high-temperature heat treatment in a closed container while facing the C atom supply substrate, thereby interposing a metal silicon melt between the single crystal silicon carbide and the C atom supply substrate. A liquid crystal epitaxial growth method for producing a single crystal silicon carbide substrate, comprising:
The single crystal silicon carbide as the seed crystal has a smaller area than the C atom supply substrate,
The single crystal silicon carbide is subjected to liquid phase epitaxial growth in a direction perpendicular to the direction facing the C atom supply substrate to obtain a single crystal silicon carbide substrate having an area larger than the initial area of the seed crystal, A method for producing a single crystal silicon carbide substrate. A single crystal silicon carbide serving as a seed crystal is subjected to high-temperature heat treatment in a closed container while facing the C atom supply substrate, thereby interposing a metal silicon melt between the single crystal silicon carbide and the C atom supply substrate. A liquid crystal epitaxial growth method for producing a single crystal silicon carbide substrate, comprising:
The metal silicon melt is present around single crystal silicon carbide in a direction perpendicular to the direction facing the C atom supply substrate;
A method for producing a single crystal silicon carbide substrate, comprising subjecting the single crystal silicon carbide to liquid phase epitaxial growth in a direction perpendicular to a direction facing the C atom supply substrate. A method for producing a single crystal silicon carbide substrate according to claim 1 or 2,
The method for producing a single crystal silicon carbide substrate, wherein the single crystal silicon carbide serving as a seed crystal is formed in a circular shape. A method for producing a single crystal silicon carbide substrate according to claim 1 or 2,
A method for producing a single crystal silicon carbide substrate, wherein a plurality of single crystal silicon carbides serving as seed crystals are provided for one C atom supply substrate. A method for producing a single crystal silicon carbide substrate according to any one of claims 1 to 4,
A method for producing a single crystal silicon carbide substrate, comprising growing a single crystal silicon carbide substrate at an area ratio of 2 times or more as compared with an initial seed crystal. A method for producing a single crystal silicon carbide substrate according to any one of claims 1 to 5,
The single crystal silicon carbide to be a seed crystal is configured as a relative convex portion among the irregularities provided on the surface of the plate member made of single crystal silicon carbide facing the C atom supply substrate. A method for producing a single crystal silicon carbide substrate, which is characterized. A method for producing a single crystal silicon carbide substrate according to claim 6,
Opposite to the convex portion of the seed crystal C atom supply substrate by performing liquid phase epitaxial growth with a metal silicon melt interposed between the plate member and the seed crystal C atom supply substrate having an uneven surface. A method for producing a single crystal silicon carbide substrate, wherein the convex portion is formed on the plate member of the portion to be formed. A method for producing a single crystal silicon carbide substrate according to any one of claims 1 to 5,
The method for producing a single crystal silicon carbide substrate, wherein the single crystal silicon carbide serving as a seed crystal is installed as a thin plate-like member on a surface of a tantalum substrate having a tantalum carbide processed surface.   A single crystal silicon carbide substrate manufactured by the manufacturing method according to claim 1.

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