JP6387895B2 - Method for producing silicon carbide single crystal - Google Patents

Description

  The present invention relates to a method for producing a silicon carbide single crystal.

  In recent years, in order to enable a semiconductor device to have a high breakdown voltage and a low loss, silicon carbide is being adopted as a material constituting the semiconductor device.

  One of the methods for producing a silicon carbide single crystal is a sublimation method. For example, Japanese Unexamined Patent Application Publication No. 2009-120419 (Patent Document 1) describes a method of manufacturing a silicon carbide single crystal by a sublimation method using a graphite crucible.

JP 2009-120419 A

  An object of one embodiment of the present invention is to provide a method for manufacturing a silicon carbide single crystal capable of suppressing the introduction or propagation of crystal defects.

  A method for manufacturing a silicon carbide single crystal according to one embodiment of the present invention includes the following steps. A silicon carbide raw material provided in the accommodating portion and a seed crystal provided to face the silicon carbide raw material and fixed to the first main surface of the pedestal are prepared. By sublimating the silicon carbide raw material, a silicon carbide single crystal grows on the seed crystal. After the silicon carbide single crystal is grown, the silicon carbide single crystal is cooled. The step of growing the silicon carbide single crystal is such that the temperature of the second main surface opposite to the first main surface of the pedestal is lower than the temperature of the surface of the silicon carbide single crystal facing the silicon carbide raw material. A step of growing a silicon carbide single crystal while maintaining. In the step of cooling the silicon carbide single crystal, the silicon carbide single crystal is cooled while maintaining the temperature of the second main surface of the pedestal at or above the surface temperature of the silicon carbide single crystal.

  According to one embodiment of the present invention, it is possible to provide a method for manufacturing a silicon carbide single crystal capable of suppressing the introduction or propagation of crystal defects in the silicon carbide single crystal.

It is a cross-sectional schematic diagram which shows schematically the 1st process of the manufacturing method of the silicon carbide single crystal which concerns on one embodiment of this invention. It is a cross-sectional schematic diagram (left side) and temperature distribution (right side) which show schematically the 2nd process of the manufacturing method of the silicon carbide single crystal which concerns on one embodiment of this invention. It is a cross-sectional schematic diagram (left side) and temperature distribution (right side) which show schematically the 3rd process of the manufacturing method of the silicon carbide single crystal which concerns on one embodiment of this invention. First example of time dependency of temperature of each of surface of silicon carbide single crystal and second main surface of pedestal 2 in the second step of the method for manufacturing a silicon carbide single crystal according to one embodiment of the present invention FIG. It is a figure which shows the time dependence of the pressure in a accommodating part in the 2nd process of the manufacturing method of the silicon carbide single crystal which concerns on one embodiment of this invention. Second example of time dependency of temperature of each surface of silicon carbide single crystal and second main surface of base 2 in the second step of the method for producing a silicon carbide single crystal according to one embodiment of the invention FIG. Third example of time dependency of temperature of each surface of silicon carbide single crystal and second main surface of base 2 in the second step of the method for manufacturing a silicon carbide single crystal according to the embodiment of the invention FIG. Fourth Example of Temperature Dependence of Temperature on Each Surface of Silicon Carbide Single Crystal and Second Main Surface of Pedestal 2 in Second Step of Manufacturing Method of Silicon Carbide Single Crystal According to an Embodiment of the Invention FIG. 5th example of time dependency of temperature of each of surface of silicon carbide single crystal and second main surface of base 2 in second step of method for manufacturing silicon carbide single crystal according to one embodiment of the invention FIG.

[Description of Embodiment of the Present Invention]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated. In the crystallographic description in this specification, the individual orientation is indicated by [], the collective orientation is indicated by <>, the individual plane is indicated by (), and the collective plane is indicated by {}. As for the negative index, “−” (bar) is attached on the number in crystallography, but in this specification, a negative sign is attached before the number.

  As a result of intensive studies on the cause of the introduction or propagation of crystal defects in a silicon carbide single crystal, the inventors obtained the following knowledge and found the present invention.

  Crystal growth of the silicon carbide single crystal by the sublimation method is performed as follows. As shown in FIG. 1, silicon carbide raw material 3 is arranged in housing portion 1. A pedestal 2 is arranged on the upper side of the housing portion 1 so as to close the opening of the housing portion 1. Seed crystal 4 is attached to surface 2 a of pedestal 2 so as to face surface 3 a of silicon carbide raw material 3. The heating source (not shown) is arranged, for example, around the housing part 1 and is configured so that the temperature of each of the housing part 1 and the base 2 can be adjusted to a desired temperature. In the step of growing the silicon carbide single crystal, a temperature gradient is provided so that the temperature decreases along the direction from the silicon carbide raw material 3 toward the seed crystal 4. Therefore, when silicon carbide raw material 3 is heated and sublimated by a heating source, the sublimated silicon carbide is recrystallized on surface 4a of seed crystal 4. As described above, silicon carbide single crystal 5 grows on surface 4a of seed crystal 4 (see FIG. 2).

  After the step of growing silicon carbide single crystal 5 is completed, the silicon carbide single crystal 5 grown is cooled by turning off the power source of the heating source. Immediately before the power source of the heating source is turned off, the temperature of the back surface 2b of the pedestal 2 is lower than the temperature of the surface 5a of the silicon carbide single crystal 5 (see FIG. 2).

  When heating is stopped in this state and cooling of the silicon carbide single crystal 5 is started, the temperature of the back surface 2b of the pedestal 2 decreases while maintaining a state lower than the temperature of the silicon carbide single crystal 5. The pedestal 2 is made of carbon, for example. The thermal expansion coefficient of carbon is larger than the thermal expansion coefficient of silicon carbide. Therefore, when the silicon carbide single crystal 5 is cooled, thermal stress is generated in the silicon carbide single crystal 5 when the thermal contraction amount of the base 2 becomes larger than the thermal contraction amount of the silicon carbide single crystal 5.

  When thermal stress is generated in silicon carbide single crystal 5 at a relatively high temperature (for example, 1000 ° C. or higher), crystal defects such as dislocations are introduced into silicon carbide single crystal 5, or already in silicon carbide single crystal 5 In some cases, crystal defects existing in the silicon oxide propagate through the silicon carbide single crystal 5. Further, when thermal stress is generated in silicon carbide single crystal 5 at a relatively low temperature (for example, 500 ° C. or more and less than 1000 ° C.), cracks are generated in silicon carbide single crystal 5 or silicon carbide single crystal 5 is cracked. There is. These phenomena occur more remarkably in the outer peripheral portion of the silicon carbide single crystal 5, and more significantly occur when the silicon carbide single crystal 5 has a large diameter. In particular, when the difference between the thermal expansion coefficient of the material constituting the pedestal 2 and the thermal expansion coefficient of the silicon carbide single crystal is large, the difference between the thermal contraction amount of the pedestal 2 and the thermal contraction amount of the silicon carbide single crystal is more remarkable. become.

  As a result of intensive studies, the inventors have found that the temperature of the back surface 2b of the pedestal 2 is equal to or higher than the temperature of the surface 5a of the silicon carbide single crystal 5 in the cooling step of the silicon carbide single crystal 5 after the growth of the silicon carbide single crystal 5 is completed. It has been devised to cool the silicon carbide single crystal 5 while maintaining the state. Thereby, silicon carbide single crystal 5 can be cooled while maintaining the amount of thermal contraction of pedestal 2 at the same level as the amount of thermal contraction of silicon carbide single crystal 5. As a result, since the thermal stress in silicon carbide single crystal 5 at the time of cooling silicon carbide single crystal 5 can be reduced, introduction or propagation of crystal defects can be suppressed. In particular, when the difference between the thermal expansion coefficient of the material constituting base 2 and the thermal expansion coefficient of silicon carbide single crystal 5 is large, the thermal stress in silicon carbide single crystal 5 can be further reduced.

  (1) The manufacturing method of the silicon carbide single crystal which concerns on 1 aspect of this invention is equipped with the following processes. A silicon carbide raw material 3 provided in the accommodating portion 1 and a seed crystal 4 provided so as to face the silicon carbide raw material 3 and fixed to the first main surface 2a of the base 2 are prepared. By sublimating silicon carbide raw material 3, silicon carbide single crystal 5 grows on seed crystal 4. After silicon carbide single crystal 5 is grown, silicon carbide single crystal 5 is cooled. In the step of growing silicon carbide single crystal 5, surface 5 a of silicon carbide single crystal 5 in which the temperature of second main surface 2 b opposite to first main surface 2 a of pedestal 2 faces silicon carbide raw material 3 is used. A step of growing silicon carbide single crystal 5 while maintaining a state lower than the temperature of. The step of cooling silicon carbide single crystal 5 is performed by cooling silicon carbide single crystal 5 while maintaining the temperature of second main surface 2b of base 2 equal to or higher than the temperature of surface 5a of silicon carbide single crystal 5. Is done. Thereby, at the time of cooling silicon carbide single crystal 5, introduction or propagation of crystal defects to silicon carbide single crystal can be suppressed.

  (2) Preferably, in the method for producing a silicon carbide single crystal according to (1) above, in the step of cooling silicon carbide single crystal 5, the temperature of surface 5a of silicon carbide single crystal 5 is a temperature of 1800 ° C. or higher and 2000 ° C. or lower. In the region, silicon carbide single crystal 5 is cooled while maintaining the temperature of second main surface 2 b of pedestal 2 equal to or higher than the temperature of surface 5 a of silicon carbide single crystal 5. In the cooling process of silicon carbide single crystal 5 in the temperature range where the temperature of surface 5a of silicon carbide single crystal 5 is not lower than 1800 ° C. and not higher than 2000 ° C., the atoms constituting silicon carbide single crystal 5 tend to move. Therefore, in the temperature range, silicon carbide single crystal 5 is cooled while maintaining the temperature of second main surface 2b of pedestal 2 at or above the temperature of surface 5a of silicon carbide single crystal 5. In addition, introduction or propagation of crystal defects during cooling can be further suppressed.

  (3) Preferably, in the method for producing a silicon carbide single crystal according to (2) above, in the step of cooling silicon carbide single crystal 5, the temperature of surface 5a of silicon carbide single crystal 5 is a temperature of 1000 ° C. or higher and 2000 ° C. or lower. In the region, silicon carbide single crystal 5 is cooled while maintaining the temperature of second main surface 2 b of pedestal 2 equal to or higher than the temperature of surface 5 a of silicon carbide single crystal 5. Thereby, the thermal stress in silicon carbide single crystal 5 can be reduced even in the temperature region where the temperature of surface 5a of silicon carbide single crystal 5 is 1000 ° C. or higher and lower than 1800 ° C. Therefore, basal plane dislocations that are considered to enter silicon carbide single crystal 5 at 1000 ° C. or higher due to thermal stress can be suppressed.

  (4) Preferably, in the method for producing a silicon carbide single crystal according to (3) above, in the step of cooling silicon carbide single crystal 5, the temperature of surface 5a of silicon carbide single crystal 5 is a temperature of 500 ° C. or higher and 2000 ° C. or lower. In the region, silicon carbide single crystal 5 is cooled while maintaining the temperature of second main surface 2 b of pedestal 2 equal to or higher than the temperature of surface 5 a of silicon carbide single crystal 5. Thereby, the thermal stress in silicon carbide single crystal 5 can be reduced even in the temperature region where surface 5a of silicon carbide single crystal 5 has a temperature of 500 ° C. or higher and lower than 1000 ° C. Therefore, cracks entering silicon carbide single crystal 5 or cracking of silicon carbide single crystal 5 due to thermal stress as well as crystal defects can be suppressed.

  (5) Preferably, in the method for producing a silicon carbide single crystal according to any one of (1) to (4) above, the step of cooling silicon carbide single crystal 5 is performed by adjusting the temperature of second main surface 2b of base 2. Before the temperature of the surface 5a of the silicon carbide single crystal 5 becomes higher than the temperature. Thereby, when the temperature of the surface 5a of the silicon carbide single crystal 5 becomes higher than the temperature of the surface 3a of the silicon carbide raw material 3, it can suppress that the grown silicon carbide single crystal 5 sublimates.

  (6) Preferably, in the method for producing a silicon carbide single crystal according to any one of (1) to (5), in the step of cooling silicon carbide single crystal 5, silicon carbide single crystal 5 is heated while pedestal 2 is heated. To be cooled. Thereby, the temperature of the 2nd main surface 2b of the base 2 can be maintained more than the temperature of the surface 5a of the silicon carbide single crystal 5. FIG.

  (7) Preferably in the method for manufacturing a silicon carbide single crystal according to any one of (1) to (6) above, in the step of cooling silicon carbide single crystal 5, the temperature of bottom 1b of housing portion 1 is set to pedestal 2 The silicon carbide single crystal 5 is cooled while being kept lower than the temperature of the second main surface 2b. Thereby, the temperature of second main surface 2b of pedestal 2 can be maintained more reliably than the temperature of surface 5a of silicon carbide single crystal 5, so that the introduction or propagation of crystal defects during cooling can be further improved. Can be suppressed.

  (8) Preferably, in the method for manufacturing a silicon carbide single crystal according to any one of (1) to (7), the step of cooling silicon carbide single crystal 5 is performed by adjusting the temperature of second main surface 2b of base 2. And a step of cooling silicon carbide single crystal 5 while maintaining the temperature of second main surface 2b of base 2 in the step of growing silicon carbide single crystal 5 or higher. Thereby, the temperature of second main surface 2b of pedestal 2 can be maintained more reliably than the temperature of surface 5a of silicon carbide single crystal 5, so that the introduction or propagation of crystal defects during cooling can be further improved. Can be suppressed.

(9) In the method for manufacturing a silicon carbide single crystal according to any one of (1) to (8) above, preferably, after the step of growing silicon carbide single crystal 5, and cooling silicon carbide single crystal 5 Before the step, the method further includes a step of annealing silicon carbide single crystal 5 in a state where the pressure in housing portion 1 is maintained higher than the pressure in the step of growing silicon carbide single crystal 5. Thereby, introduction or propagation of crystal defects to silicon carbide single crystal 5 can be further suppressed.
[Details of the embodiment of the present invention]
A configuration of a silicon carbide single crystal manufacturing apparatus according to an embodiment of the present invention will be described.

  As shown in FIG. 1, the silicon carbide single crystal manufacturing apparatus 10 mainly includes a housing 1, a pedestal 2, a heating source (not shown), and a thermometer (not shown). Yes. Accommodating portion 1 is configured to accommodate silicon carbide raw material 3 therein. Base 2 is configured to be able to hold seed crystal 4 made of a silicon carbide single crystal. The pedestal 2 has, for example, a cylindrical shape, and includes a first main surface 2a and a second main surface 2b opposite to the first main surface 2a. The seed crystal 4 is fixed to the first main surface 2a of the base 2 with, for example, an adhesive. The pedestal 2 is disposed on the upper portion of the housing portion 1 so as to close the opening of the housing portion 1. The accommodating part 1 and the base 2 are made of a material containing, for example, porous graphite.

  The heat source is arranged outside the housing part 1 so as to surround the housing part 1, for example. The heating source may be a high frequency induction heating type coil or a resistance heating type heater. The heat source may be arranged at a position facing the second main surface 2 b of the base 2. The heat source may be arranged at a position facing the bottom 1 b of the housing 1. The thermometer is, for example, a radiation thermometer. The thermometer may be configured to be able to measure the temperature of each of the second main surface 2b of the pedestal 2, the side surface 1a of the accommodating portion 1, and the bottom portion 1b, for example. The thermometer may be configured to be able to measure the temperature inside the housing unit 1.

Next, the manufacturing method of the silicon carbide single crystal which concerns on one embodiment of this invention is demonstrated.
As shown in FIG. 1, silicon carbide raw material 3 is provided in housing portion 1. Silicon carbide raw material 3 is, for example, polycrystalline silicon carbide powder. Seed crystal 4 is fixed to first main surface 2a of pedestal 2 using, for example, an adhesive. Seed crystal 4 is made of, for example, a polytype 4H hexagonal silicon carbide single crystal. The diameter of the surface of seed crystal 4 is, for example, 100 mm or more, and preferably 150 mm or more. The surface of seed crystal 4 is, for example, a surface that is off by about 8 ° or less from the {0001} plane. Seed crystal 4 is arranged such that the surface of seed crystal 4 faces surface 3 a of silicon carbide raw material 3. As described above, silicon carbide raw material 3 provided in housing portion 1 and seed crystal 4 provided so as to face silicon carbide raw material 3 and fixed to first main surface 2a of pedestal 2 are provided. Be prepared.

  Next, silicon carbide raw material 3 provided in housing portion 1 is heated to a temperature of, for example, about 2000 ° C. or higher and 2400 ° C. or lower. While the temperature of the silicon carbide raw material 3 is increasing, the pressure of the atmospheric gas in the housing portion 1 is maintained at about 80 kPa, for example. The atmospheric gas contains an inert gas such as argon gas, helium gas or nitrogen gas. Next, the pressure of the atmospheric gas in the housing part 1 is reduced to, for example, 1.7 kPa. Thereby, the silicon carbide raw material 3 in the accommodating part 1 starts sublimation, and recrystallizes on the surface of the seed crystal 4 arrange | positioned in the position facing the surface of the silicon carbide raw material 3, and thereby seed crystal 4 The silicon carbide single crystal 5 begins to grow on the surface of. While the silicon carbide single crystal is growing, the pressure in housing portion 1 is maintained for about 10 hours at a pressure of about 0.5 kPa to 5 kPa, for example. As described above, silicon carbide single crystal 5 grows on seed crystal 4 by sublimating silicon carbide raw material 3.

  As shown in FIG. 2, in the step of growing the silicon carbide single crystal, the surface temperature of seed crystal 4 is maintained to be lower than the temperature of surface 3 a of silicon carbide raw material 3. Specifically, in the direction perpendicular to the second main surface 2b of the pedestal 2, the temperature of the bottom 1b of the housing portion 1 is the highest and the temperature of the second main surface 2b of the pedestal 2 is the lowest. Thus, the temperature of each of the accommodating part 1 and the base 2 is controlled. The temperature of bottom portion 1 b of housing portion 1 is higher than the temperature of the bottom surface of silicon carbide raw material 3. The temperature of the bottom surface of silicon carbide raw material 3 may be higher than the temperature of surface 3 a of silicon carbide raw material 3. The temperature gradient between bottom portion 1b of housing portion 1 and the bottom surface of silicon carbide raw material 3 may be larger than the temperature gradient between the bottom surface of silicon carbide raw material 3 and surface 3a. The temperature of surface 3 a of silicon carbide raw material 3 is higher than the temperature of surface 5 a of silicon carbide single crystal 5. However, the temperature distribution between surface 3a of silicon carbide raw material 3 and surface 5a of silicon carbide single crystal 5 may not be specified. When there is a temperature gradient between surface 3a of silicon carbide raw material 3 and surface 5a of silicon carbide single crystal 5, the temperature gradient between the bottom surface of silicon carbide raw material 3 and surface 3a is the same as that of surface 3a of silicon carbide raw material 3 and carbonized. The temperature gradient with respect to the surface 5a of the silicon single crystal 5 may be larger.

  As shown in FIG. 2, in the step of growing the silicon carbide single crystal, the temperature of surface 5 a of silicon carbide single crystal 5 is higher than the temperature of first main surface 2 a of pedestal 2. The temperature distribution between surface 3a of silicon carbide raw material 3 and surface 5a of silicon carbide single crystal 5 may not be particularly specified. When there is a temperature gradient between surface 3a of silicon carbide raw material 3 and surface 5a of silicon carbide single crystal 5, the temperature gradient between surface 3a of silicon carbide raw material 3 and surface 5a of silicon carbide single crystal 5 is silicon carbide. The temperature gradient between the surface 5a of the single crystal 5 and the first main surface 2a of the pedestal 2 may be smaller. The temperature of the first main surface 2a of the pedestal 2 is higher than the temperature of the second main surface 2b of the pedestal 2. The temperature gradient between surface 5a of silicon carbide single crystal 5 and first main surface 2a of pedestal 2 is greater than the temperature gradient between first main surface 2a and second main surface 2b of pedestal 2. Also good. As described above, in the step of growing silicon carbide single crystal 5, the temperature of second main surface 2 b of pedestal 2 is higher than the temperature of surface 5 a of silicon carbide single crystal 5 facing surface 3 a of silicon carbide raw material 3. The silicon carbide single crystal 5 is grown while maintaining a low state.

  Next, after the crystal growth of silicon carbide single crystal 5 is completed, silicon carbide single crystal 5 is cooled. The step of cooling silicon carbide single crystal 5 is performed by cooling silicon carbide single crystal 5 while maintaining the temperature of second main surface 2b of base 2 equal to or higher than the temperature of surface 5a of silicon carbide single crystal 5. The process is included. Preferably, silicon carbide single crystal 5 is cooled while base 2 is heated. For example, with the heating source facing the second main surface 2b of the pedestal 2 turned on, the heating source facing the side surface 1a of the housing portion 1 is turned off to turn off the silicon carbide single unit while heating the pedestal 2. Crystal 5 is cooled. Alternatively, the silicon carbide single crystal 5 is actively cooled without heating the second main surface 2b of the pedestal 2, so that the temperature of the second main surface 2b of the pedestal 2 becomes the silicon carbide single crystal. Silicon carbide single crystal 5 may be cooled while maintaining a temperature equal to or higher than the temperature of surface 5a of crystal 5.

  As shown in FIG. 3, in the step of cooling the silicon carbide single crystal, the temperature of the bottom portion 1 b of the housing portion 1 is the lowest in the direction perpendicular to the second main surface 2 b of the pedestal 2, and the pedestal The temperature of each of the accommodating portion 1 and the base 2 is controlled so that the temperature of the second second main surface 2b is the highest. That is, in the step of cooling silicon carbide single crystal 5, silicon carbide single crystal 5 is cooled while maintaining the temperature of bottom portion 1 b of housing portion 1 lower than the temperature of second main surface 2 b of pedestal 2. . The temperature of bottom portion 1 b of housing portion 1 is lower than the temperature of the bottom surface of silicon carbide raw material 3. The temperature of the bottom surface of silicon carbide raw material 3 is lower than the temperature of surface 3 a of silicon carbide raw material 3. The temperature gradient between bottom portion 1b of housing portion 1 and the bottom surface of silicon carbide raw material 3 may be larger than the temperature gradient between the bottom surface of silicon carbide raw material 3 and surface 3a. The temperature of surface 3 a of silicon carbide raw material 3 may be lower than the temperature of surface 5 a of silicon carbide single crystal 5. The temperature distribution between surface 3a of silicon carbide raw material 3 and surface 5a of silicon carbide single crystal 5 may not be particularly specified. When there is a temperature gradient between surface 3a of silicon carbide raw material 3 and surface 5a of silicon carbide single crystal 5, the temperature gradient between the bottom surface of silicon carbide raw material 3 and surface 3a is the same as that of surface 3a of silicon carbide raw material 3 and carbonized. The temperature gradient with respect to the surface 5a of the silicon single crystal 5 may be larger.

  As shown in FIG. 3, in the step of cooling the silicon carbide single crystal, the temperature of surface 5 a of silicon carbide single crystal 5 is lower than the temperature of first main surface 2 a of pedestal 2. The temperature distribution between surface 3a of silicon carbide raw material 3 and surface 5a of silicon carbide single crystal 5 may not be particularly specified. When there is a temperature gradient between surface 3a of silicon carbide raw material 3 and surface 5a of silicon carbide single crystal 5, the temperature gradient between surface 3a of silicon carbide raw material 3 and surface 5a of silicon carbide single crystal 5 is silicon carbide. The temperature gradient between the surface 5a of the single crystal 5 and the first main surface 2a of the pedestal 2 may be smaller. The temperature of the first main surface 2a of the pedestal 2 is lower than the temperature of the second main surface 2b of the pedestal 2. The temperature gradient between surface 5a of silicon carbide single crystal 5 and first main surface 2a of pedestal 2 is greater than the temperature gradient between first main surface 2a and second main surface 2b of pedestal 2. Also good. As described above, in the step of cooling silicon carbide single crystal 5, the temperature of second main surface 2b of base 2 is equal to or higher than the temperature of surface 5a of silicon carbide single crystal 5 facing surface 3a of silicon carbide raw material 3. The process of cooling the silicon carbide single crystal 5 is included, maintaining this state. It should be noted that the temperature of second main surface 2b of pedestal 2 may be lower than surface 5a of silicon carbide single crystal 5 in a part of the temperature range in which there is a step of cooling silicon carbide single crystal 5.

  The temperature at each surface is the temperature at the center of each surface. For example, the temperature of the second main surface 2 b of the pedestal 2 is the temperature at the center of the second main surface 2 b of the pedestal 2. Preferably, the step of cooling silicon carbide single crystal 5 maintains a state where the average value of the temperature of second main surface 2b of pedestal 2 is equal to or higher than the average value of the temperature of surface 5a of silicon carbide single crystal 5. However, the silicon carbide single crystal 5 is cooled. More preferably, in the step of cooling silicon carbide single crystal 5, carbonization is performed while maintaining the average value of the temperature of bottom portion 1 b of housing portion 1 lower than the average value of the temperature of second main surface 2 b of pedestal 2. The silicon single crystal 5 is cooled. In addition, the average value of the temperature in each said surface is an average value of the temperature of all the measurement points at the time of measuring several different positions (for example, five positions including a center) of each surface. More preferably, in the step of cooling silicon carbide single crystal 5, the maximum value of the temperature at the plurality of measurement positions on second main surface 2 b of pedestal 2 is set at a plurality of measurement positions on surface 5 a of silicon carbide single crystal 5. Silicon carbide single crystal 5 is cooled while maintaining a state of not less than the minimum value of temperature. More preferably, in the step of cooling silicon carbide single crystal 5, the maximum value of the temperatures at the plurality of measurement positions on bottom 1 b of housing portion 1 is set to the temperature at the plurality of measurement positions on second main surface 2 b of pedestal 2. The silicon carbide single crystal 5 is cooled while being kept lower than the minimum value.

  In addition, the temperature in each surface can be measured, for example with a radiation thermometer. When it is difficult to directly measure the temperature of the surface 5a of the silicon carbide single crystal 5 growing in the housing portion 1, the surface of the housing portion 1 in a plane along the surface of the seed crystal 4 in contact with the silicon carbide single crystal 5 The temperature at the position 1a1 of the side surface 1a can be used as a reference (see FIG. 1). Since the temperature at the position 1a1 is higher than the temperature at the center of the surface 5a of the silicon carbide single crystal 5, if the temperature at the center of the second main surface 2b of the pedestal 2 is higher than the temperature at the position 1a1, the pedestal 2 It can be estimated that the temperature at the center of the second main surface 2 b is higher than the temperature at the center of the surface 5 a of the silicon carbide single crystal 5. That is, the temperature at the center of the surface 5a of the silicon carbide single crystal 5 can be read as the temperature at the position 1a1 to determine the cooling conditions.

  As shown in FIG. 4 and FIGS. 6 to 9, the time change of the temperatures of the surface 5 a of the silicon carbide single crystal 5 and the second main surface 2 b of the base 2 will be described. 4 and 6 to 9, the broken line 11 indicates the temperature of the surface 5 a of the silicon carbide single crystal 5, and the solid line 12 indicates the temperature of the second main surface 2 b of the pedestal 2. 4 and 6 to 9, the period from time T0 to time T1 is a step of substantially growing the silicon carbide single crystal.

  As shown in FIG. 4, in the step of growing the silicon carbide single crystal, the temperature of surface 5 a of silicon carbide single crystal 5 is maintained higher than the temperature of second main surface 2 b of pedestal 2. . In the step of growing the silicon carbide single crystal, the temperature A1 of the surface 5a of the silicon carbide single crystal 5 is not less than 2100 ° C. and not more than 2400 ° C., for example, and the temperature A2 of the second main surface 2b of the base 2 is, for example, 2000 ° C. The temperature is 2300 ° C. or lower. After time T1, silicon carbide single crystal 5 and pedestal 2 are cooled. The cooling rate of silicon carbide single crystal 5 may be larger than the cooling rate of pedestal 2. At time T2, the temperature of surface 5a of silicon carbide single crystal 5 becomes equal to the temperature of second main surface 2b of pedestal 2. After time T2, the temperature of second main surface 2b of pedestal 2 is maintained at or above the temperature of surface 5a of silicon carbide single crystal 5.

  Preferably, in the temperature region where the temperature of surface 5a of silicon carbide single crystal 5 is not lower than 1800 ° C. and not higher than 2000 ° C., the temperature of second main surface 2b of pedestal 2 is equal to or higher than the temperature of surface 5a of silicon carbide single crystal 5. While maintaining a certain state, silicon carbide single crystal 5 is cooled. For example, in FIG. 4, the temperature A3 is 2000 ° C., and the temperature A4 is 1800 ° C. When the temperature of surface 5a of silicon carbide single crystal 5 is higher than 2000 ° C. and lower than 1800 ° C., the temperature of second main surface 2b of pedestal 2 is the same as that of surface 5a of silicon carbide single crystal 5. It may be lower than the temperature.

  Preferably, in the temperature range where surface 5a of silicon carbide single crystal 5 is not lower than 1000 ° C. and not higher than 2000 ° C., the temperature of second main surface 2b of pedestal 2 is equal to or higher than the temperature of surface 5a of silicon carbide single crystal 5. While maintaining a certain state, silicon carbide single crystal 5 is cooled. More preferably, the temperature of the second main surface 2b of the pedestal 2 is equal to or higher than the temperature of the surface 5a of the silicon carbide single crystal 5 in the temperature range where the temperature of the surface 5a of the silicon carbide single crystal 5 is 500 ° C. or higher and 2000 ° C. or lower. While maintaining this state, silicon carbide single crystal 5 is cooled.

  As FIG. 5 shows, the time change of the pressure of the accommodating part 1 is demonstrated. As shown in FIG. 5, pressure P2 between time T0 and time T1 during which silicon carbide single crystal 5 is substantially grown is, for example, not less than 0.5 kPa and not more than 5 kPa. Cooling of the silicon carbide single crystal 5 is started at time T1 after the crystal growth of the silicon carbide single crystal 5 is substantially finished. Preferably, after the time T1 when the cooling of the silicon carbide single crystal 5 is started, the time is higher than the time T2 when the temperature of the second main surface 2b of the base 2 is equal to or higher than the temperature of the surface 5a of the silicon carbide single crystal 5. Before, the pressure in the accommodating part 1 is raised. Specifically, for example, the pressure P1 in the housing part 1 at time T2 is 30 kPa. For example, by introducing an inert gas such as argon into the storage unit 1, the pressure in the storage unit 1 is increased. Before the cooling of the silicon carbide single crystal 5 is started, the pressure in the housing portion 1 may be raised above the pressure during crystal growth.

As shown in FIG. 6, after the cooling of the silicon carbide single crystal 5 is started, after a predetermined time has elapsed, the temperature of the second main surface 2 b of the base 2 is maintained for a predetermined time, and then the second of the base 2 is again formed. The main surface 2b may be cooled. As shown in FIG. 6, each of silicon carbide single crystal 5 and pedestal 2 is cooled after time T1 when crystal growth of silicon carbide single crystal 5 is substantially completed. From time T2 to time T4, the second main surface 2b of the base 2 is maintained at the temperature A3. On the other hand, the temperature of surface 5a of silicon carbide single crystal 5 monotonously decreases from time T2 to time T4. At time T3, the temperature of second main surface 2b of pedestal 2 becomes equal to the temperature of surface 5a of silicon carbide single crystal 5. Between time T3 and time T4, the temperature of second main surface 2b of pedestal 2 is maintained at or above the temperature of surface 5a of silicon carbide single crystal 5.

  As shown in FIG. 7, in the step of cooling silicon carbide single crystal 5, the temperature of second main surface 2 b of pedestal 2 is set to the second main surface of pedestal 2 in the step of growing silicon carbide single crystal 5. Silicon carbide single crystal 5 may be cooled while maintaining the temperature at 2b or higher. As shown in FIG. 7, the temperature of surface 5a of silicon carbide single crystal 5 monotonously decreases after time T1 when the crystal growth of silicon carbide single crystal 5 is substantially completed. On the other hand, the second main surface 2b of the pedestal 2 maintains the temperature A2 during crystal growth from time T1 to time T3. At time T2, the temperature of second main surface 2b of pedestal 2 becomes equal to the temperature of surface 5a of silicon carbide single crystal 5. Between time T2 and time T3, the temperature of second main surface 2b of pedestal 2 is maintained at or above the temperature of surface 5a of silicon carbide single crystal 5.

  As shown in FIG. 8, pedestal 2 may be heated while cooling silicon carbide single crystal 5 after time T <b> 1 when crystal growth of silicon carbide single crystal 5 is substantially completed. In this case, after time T1, the temperature of surface 5a of silicon carbide single crystal 5 decreases monotonously. On the other hand, the temperature of second main surface 2b of base 2 becomes higher than the temperature at the time of crystal growth once after time T1, and becomes equal to the temperature of surface 5a of silicon carbide single crystal 5 at time T2. At time T2, temperature A3 of second main surface 2b of pedestal 2 is higher than the temperature of second main surface 2b of pedestal 2 during crystal growth, and surface 5a of silicon carbide single crystal 5 during crystal growth. The temperature may be lower. The temperature of the second main surface 2b of the pedestal 2 may further increase after the time T2 and shows a maximum value, and then start to decrease.

  As shown in FIG. 9, the step of annealing silicon carbide single crystal 5 may be performed after the step of growing silicon carbide single crystal 5 and before the step of cooling silicon carbide single crystal 5. . For example, the time from time T0 to time T1 is the crystal growth process of silicon carbide single crystal 5, the time from time T1 to time T3 is the annealing process for silicon carbide single crystal 5, and the time after time T3 is the cooling of silicon carbide single crystal 5. It is a process. After the time T1 when the crystal growth of the silicon carbide single crystal 5 is substantially completed, the silicon carbide single crystal is maintained in a state where the pressure in the housing portion 1 is maintained higher than the pressure in the step of growing the silicon carbide single crystal 5. 5 is annealed. Specifically, after time T1, the temperature of surface 5a of silicon carbide single crystal 5 rises from temperature A1 to temperature A5 in a state where an inert gas such as argon is introduced into housing portion 1. Between time T2 and time T3, the temperature of surface 5a of silicon carbide single crystal 5 is maintained at temperature A5. Second main surface 2b of base 2 is maintained at a temperature higher than temperature A1, for example. After time T3, each of silicon carbide single crystal 5 and pedestal 2 is cooled. The temperature difference between the surface of silicon carbide single crystal 5 and second main surface 2b of pedestal 2 during crystal growth may be larger than the temperature difference during annealing.

Next, the effect of the method for manufacturing a silicon carbide single crystal according to the present embodiment will be described.
According to the method for manufacturing a silicon carbide single crystal according to the present embodiment, silicon carbide raw material 3 provided in housing portion 1, provided so as to face silicon carbide raw material 3, and the first of pedestal 2 is provided. A seed crystal 4 fixed to the main surface 2a is prepared. By sublimating silicon carbide raw material 3, silicon carbide single crystal 5 grows on seed crystal 4. After silicon carbide single crystal 5 is grown, silicon carbide single crystal 5 is cooled. In the step of growing silicon carbide single crystal 5, surface 5 a of silicon carbide single crystal 5 in which the temperature of second main surface 2 b opposite to first main surface 2 a of pedestal 2 faces silicon carbide raw material 3 is used. A step of growing silicon carbide single crystal 5 while maintaining a state lower than the temperature of. The step of cooling silicon carbide single crystal 5 is performed by cooling silicon carbide single crystal 5 while maintaining the temperature of second main surface 2b of base 2 equal to or higher than the temperature of surface 5a of silicon carbide single crystal 5. Is done. Thereby, when silicon carbide single crystal 5 is cooled, introduction or propagation of crystal defects to silicon carbide single crystal 5 can be suppressed.

  According to the method for manufacturing a silicon carbide single crystal according to the present embodiment, in the step of cooling silicon carbide single crystal 5, the temperature of surface 5a of silicon carbide single crystal 5 is in the temperature range of 1800 ° C. or higher and 2000 ° C. or lower. The silicon carbide single crystal 5 is cooled while maintaining the temperature of the second main surface 2b of the base 2 equal to or higher than the temperature of the surface 5a of the silicon carbide single crystal 5. In the cooling process of silicon carbide single crystal 5 in the temperature range where the temperature of surface 5a of silicon carbide single crystal 5 is not lower than 1800 ° C. and not higher than 2000 ° C., the atoms constituting silicon carbide single crystal 5 tend to move. Therefore, in the temperature range, silicon carbide single crystal 5 is cooled while maintaining the temperature of second main surface 2b of pedestal 2 at or above the temperature of surface 5a of silicon carbide single crystal 5. The introduction or propagation of crystal defects during cooling can be suppressed.

  Furthermore, according to the method for manufacturing silicon carbide single crystal according to the present embodiment, in the step of cooling silicon carbide single crystal 5, the temperature of surface 5a of silicon carbide single crystal 5 is in the temperature range of 1000 ° C. or higher and 2000 ° C. or lower. The silicon carbide single crystal 5 is cooled while maintaining the temperature of the second main surface 2b of the base 2 equal to or higher than the temperature of the surface 5a of the silicon carbide single crystal 5. Thereby, the thermal stress in silicon carbide single crystal 5 can be reduced even in the temperature region where the temperature of surface 5a of silicon carbide single crystal 5 is 1000 ° C. or higher and lower than 1800 ° C. Therefore, basal plane dislocations that are considered to enter silicon carbide single crystal 5 at 1000 ° C. or higher due to thermal stress can be suppressed.

  Furthermore, according to the method for manufacturing a silicon carbide single crystal according to the present embodiment, in the step of cooling silicon carbide single crystal 5, the temperature of surface 5a of silicon carbide single crystal 5 is in the temperature range of 500 ° C. or higher and 2000 ° C. or lower. The silicon carbide single crystal 5 is cooled while maintaining the temperature of the second main surface 2b of the base 2 equal to or higher than the temperature of the surface 5a of the silicon carbide single crystal 5. Thereby, the thermal stress in silicon carbide single crystal 5 can be reduced even in the temperature region where surface 5a of silicon carbide single crystal 5 has a temperature of 500 ° C. or higher and lower than 1000 ° C. Therefore, cracks entering silicon carbide single crystal 5 or cracking of silicon carbide single crystal 5 due to thermal stress as well as crystal defects can be suppressed.

  Furthermore, according to the method for manufacturing a silicon carbide single crystal according to the present embodiment, the step of cooling silicon carbide single crystal 5 is performed such that the temperature of second main surface 2b of base 2 is the surface 5a of silicon carbide single crystal 5. A step of increasing the pressure in the accommodating portion 1 before the temperature becomes equal to or higher than the temperature. Thereby, when the temperature of the surface 5a of the silicon carbide single crystal 5 becomes higher than the temperature of the surface 3a of the silicon carbide raw material 3, it can suppress that the grown silicon carbide single crystal 5 sublimates.

  Furthermore, according to the method for manufacturing a silicon carbide single crystal according to the present embodiment, in the step of cooling silicon carbide single crystal 5, silicon carbide single crystal 5 is cooled while pedestal 2 is heated. Thereby, the temperature of the 2nd main surface 2b of the base 2 can be maintained more than the temperature of the surface 5a of the silicon carbide single crystal 5. FIG.

  Furthermore, according to the method for manufacturing a silicon carbide single crystal according to the present embodiment, in the step of cooling silicon carbide single crystal 5, the temperature of bottom portion 1b of housing portion 1 is set to the temperature of second main surface 2b of pedestal 2. The silicon carbide single crystal 5 is cooled while being kept lower. Thereby, the temperature of second main surface 2b of pedestal 2 can be maintained more reliably than the temperature of surface 5a of silicon carbide single crystal 5, so that the introduction or propagation of crystal defects during cooling can be further improved. Can be suppressed.

  Furthermore, according to the method for manufacturing a silicon carbide single crystal according to the present embodiment, the step of cooling silicon carbide single crystal 5 causes the temperature of second main surface 2b of base 2 to grow silicon carbide single crystal 5. The process includes cooling the silicon carbide single crystal 5 while maintaining the temperature of the second main surface 2b of the base 2 of the pedestal 2 in the process. Thereby, the temperature of second main surface 2b of pedestal 2 can be maintained more reliably than the temperature of surface 5a of silicon carbide single crystal 5, so that the introduction or propagation of crystal defects during cooling can be further improved. Can be suppressed.

  Furthermore, according to the method for manufacturing a silicon carbide single crystal according to the present embodiment, after the step of growing silicon carbide single crystal 5 and before the step of cooling silicon carbide single crystal 5, The method further includes the step of annealing the silicon carbide single crystal 5 in a state where the pressure is maintained higher than the pressure in the step of growing the silicon carbide single crystal 5. Thereby, introduction or propagation of crystal defects to silicon carbide single crystal 5 can be further suppressed.

  The embodiment disclosed this time is to be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Storage part 1a Side surface 1a1 Position 1b Bottom part 2 Base 2a 1st main surface (surface)
2b Second main surface (back surface)
3 Silicon carbide raw material 3a, 4a, 5a Surface 4 Seed crystal 5 Silicon carbide single crystal 10 Silicon carbide single crystal manufacturing apparatus 11 Temperature of surface of silicon carbide single crystal 12 Temperature of second main surface of pedestal A1, A2, A3 , A4, A5 Temperature P1, P2 Pressure T0, T1, T2, T3, T4 Time

Claims (9)

Preparing a silicon carbide raw material provided in the housing portion and a seed crystal provided to face the silicon carbide raw material and fixed to the first main surface of the pedestal;
Growing a silicon carbide single crystal on the seed crystal by sublimating the silicon carbide raw material;
After the step of growing the silicon carbide single crystal, the step of cooling the silicon carbide single crystal,
In the step of growing the silicon carbide single crystal, the temperature of the second main surface opposite to the first main surface of the pedestal is the temperature of the surface of the silicon carbide single crystal facing the silicon carbide raw material. A step of growing the silicon carbide single crystal while maintaining a lower state,
The step of cooling the silicon carbide single crystal includes cooling the silicon carbide single crystal while maintaining the temperature of the second main surface of the pedestal at or above the temperature of the surface of the silicon carbide single crystal. The manufacturing method of the silicon carbide single crystal including the process to do.   In the step of cooling the silicon carbide single crystal, the temperature of the second main surface of the pedestal is set in the temperature range of the surface of the silicon carbide single crystal of 1800 ° C. or more and 2000 ° C. or less. The method for producing a silicon carbide single crystal according to claim 1, wherein the silicon carbide single crystal is cooled while maintaining a temperature equal to or higher than the temperature of the surface of the crystal.   In the step of cooling the silicon carbide single crystal, the temperature of the second main surface of the pedestal is set in the temperature range where the surface temperature of the silicon carbide single crystal is 1000 ° C. or more and 2000 ° C. or less. The method for producing a silicon carbide single crystal according to claim 2, wherein the silicon carbide single crystal is cooled while maintaining a temperature equal to or higher than the temperature of the surface of the crystal.   In the step of cooling the silicon carbide single crystal, the temperature of the second main surface of the pedestal is set in the temperature range of the surface of the silicon carbide single crystal of 500 ° C. or more and 2000 ° C. or less. The method for producing a silicon carbide single crystal according to claim 3, wherein the silicon carbide single crystal is cooled while maintaining a temperature equal to or higher than the temperature of the surface of the crystal.   The step of cooling the silicon carbide single crystal includes the step of increasing the pressure in the housing portion before the temperature of the second main surface of the pedestal becomes equal to or higher than the temperature of the surface of the silicon carbide single crystal. The manufacturing method of the silicon carbide single crystal of any one of Claims 1-4.   The method for producing a silicon carbide single crystal according to claim 1, wherein in the step of cooling the silicon carbide single crystal, the silicon carbide single crystal is cooled while heating the pedestal.   The silicon carbide single crystal is cooled in the step of cooling the silicon carbide single crystal while maintaining the temperature of the bottom of the housing portion lower than the temperature of the second main surface of the pedestal. The manufacturing method of the silicon carbide single crystal of any one of Claims 1-6.   The step of cooling the silicon carbide single crystal is performed while maintaining the temperature of the second main surface of the pedestal at or above the temperature of the second main surface of the pedestal in the step of growing the silicon carbide single crystal. The manufacturing method of the silicon carbide single crystal of any one of Claims 1-7 including the process of cooling the said silicon carbide single crystal.   After the step of growing the silicon carbide single crystal and before the step of cooling the silicon carbide single crystal, the pressure in the housing portion is maintained higher than the pressure in the step of growing the silicon carbide single crystal. The method for manufacturing a silicon carbide single crystal according to claim 1, further comprising a step of annealing the silicon carbide single crystal in a state.

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