WO2017135272A1

WO2017135272A1 - Method for manufacturing sic single crystal and sic seed crystal

Info

Publication number: WO2017135272A1
Application number: PCT/JP2017/003519
Authority: WO
Inventors: 楠　一彦; 和明関; 寛典大黒; 幹尚加渡; 雅喜土井
Original assignee: 新日鐵住金株式会社; トヨタ自動車株式会社
Priority date: 2016-02-04
Filing date: 2017-02-01
Publication date: 2017-08-10

Abstract

Provided is a method for manufacturing an SiC single crystal with a solution growth method, allowing for suppression of solvent inclusion, and an SiC seed crystal. The method for manufacturing an SiC single crystal according to the present embodiment is a manufacturing method based on a solution growth method for growing an SiC single crystal, by contacting a crystal growth face (80) of an SiC seed crystal (8) with an Si-C solution (7). The manufacturing method comprises a preparation step and a growth step. In the preparation step, a starting material is heated and melted to prepare the Si-C solution (7). In the growth step, the crystal growth face (80) is brought into contact with the Si-C solution (7), and a SiC single crystal is grown on the crystal growth face (80). The crystal growth face (80) includes a facet region (81), and the offset angle of the crystal growth face (80) is 0.5° or less. The center of gravity (82) of the facet region (81) is arranged within a distance of 0.40 r from the center of gravity (83) of the crystal growth face (80). The maximum length of a line segment connecting the center of gravity (83) and outer periphery (84) of the crystal growth face (80) is r.

Description

Method for producing SiC single crystal and SiC seed crystal

The present invention relates to a method for producing a SiC single crystal and a SiC seed crystal, and more particularly to a method for producing a SiC single crystal by a solution growth method and a SiC seed crystal used in the solution growth method.

SiC single crystal is a thermally and chemically stable compound semiconductor. The SiC single crystal has excellent physical properties as compared with the Si single crystal. For example, a SiC single crystal has a large band gap, a high breakdown voltage, and a high thermal conductivity, and has a high electron saturation rate compared to a Si single crystal. For this reason, SiC single crystals are attracting attention as next-generation semiconductor materials.

As a method for producing a SiC single crystal, a sublimation recrystallization method (hereinafter also referred to as a sublimation method), a solution growth method (hereinafter also referred to as a solution method), and the like are known. In the sublimation recrystallization method, a SiC single crystal is grown by supplying a raw material on a SiC seed crystal in a gas phase state.

On the other hand, in the solution growth method, a SiC single crystal is grown on the SiC seed crystal by bringing the SiC seed crystal into contact with the Si—C solution. Specifically, a raw material containing Si is put in a crucible and melted to produce a Si—C solution. A SiC single crystal is manufactured by bringing the SiC seed crystal into contact with the Si—C solution and supercooling the Si—C solution in the vicinity of the SiC seed crystal. Here, the Si—C solution refers to a solution in which carbon (C) is dissolved in a melt of Si or Si alloy.

When a SiC single crystal is manufactured, regardless of the manufacturing method, polycrystal generation, mixing of different crystal polymorphs, introduction of crystal defects and dislocations, and the like may occur, and the quality of the SiC single crystal may deteriorate. For this reason, the further improvement of quality is calculated | required by the SiC single crystal.

In order to improve the quality of the SiC single crystal, in the sublimation method, for example, studies have been made to obtain a uniform SiC single crystal by adjusting the position of the facet region generated during crystal growth. For example, JP 2004-323348 A (Patent Document 1), JP 2009-051701 A (Patent Document 2), JP 2010-254520 A (Patent Document 3), and JP 2013-087005 A (Patent Document 2). Document 4) proposes a technique for obtaining a uniform SiC single crystal by adjusting the position of the facet region.

On the other hand, the SiC single crystal manufactured using the solution method has fewer defects such as micropipes and basal plane dislocations than the SiC single crystal manufactured using the sublimation method. Therefore, a method for producing a SiC single crystal by a solution method has been studied.

However, when SiC single crystals are produced using the solution method, solvent inclusion may occur. The solvent inclusion refers to a defect caused by the Si—C solution being confined inside the SiC single crystal. If solvent inclusion occurs, the quality of the SiC single crystal is degraded.

JP-A-2006-117441 (Patent Document 5) proposes a technique for suppressing the occurrence of solvent inclusion in a solution method. Patent Document 5 is characterized in that the Si—C solution is stirred by periodically changing the number of revolutions or the number of revolutions and the direction of rotation of the crucible. Thus, Patent Document 5 describes that even if the diameter is 1 inch or more and the thickness is as large as 5 microns or more, a high-quality SiC single crystal without inclusion can be produced at a high crystal growth rate.

JP 2004-323348 A JP 2009-051701 A JP 2010-254520 A JP 2013-087005 A JP 2006-117441 A

However, even if the technique disclosed in Patent Document 5 described above is used, solvent inclusion may occur in the SiC single crystal.

An object of the present invention is to provide a method for producing a SiC single crystal by a solution growth method and a SiC seed crystal used for the solution growth method, which can suppress the occurrence of solvent inclusion.

The method for producing an SiC single crystal according to the present invention is a production method by a solution growth method in which an SiC single crystal is grown by bringing the crystal growth surface of an SiC seed crystal into contact with an Si—C solution. The manufacturing method includes a preparation process and a growth process. In the preparation step, the raw material is heated and melted to prepare a Si—C solution. In the growth step, the crystal growth surface is brought into contact with the Si—C solution, and an SiC single crystal is grown on the crystal growth surface. The crystal growth surface includes a facet region, and the offset angle of the crystal growth surface with respect to the {0001} plane is 0.5 ° or less. The center of gravity of the facet region is arranged at a distance within 0.40 r from the center of gravity of the crystal growth surface. Here, the length of the longest line segment connecting the center of gravity of the crystal growth surface and the outer periphery of the crystal growth surface is r.

The SiC seed crystal according to the present invention is an SiC seed crystal used in a solution growth method in which a SiC single crystal is grown on an SiC seed crystal by bringing the SiC seed crystal into contact with an Si—C solution. The SiC seed crystal has a crystal growth surface having an offset angle of 0.5 ° or less with respect to the {0001} plane. The crystal growth surface includes a facet region. The center of gravity of the facet region is arranged at a distance within 0.40 r from the center of gravity of the crystal growth surface. Here, the length of the longest line segment connecting the center of gravity of the crystal growth surface and the outer periphery of the crystal growth surface is r.

The method for producing a SiC single crystal and the SiC seed crystal according to the present invention can suppress the occurrence of solvent inclusion.

FIG. 1 is a schematic view of a manufacturing apparatus used in the method for manufacturing a SiC single crystal according to the present embodiment. FIG. 2 is a bottom view (a diagram of a crystal growth surface) of the SiC seed crystal. FIG. 3 is a bottom view of a SiC seed crystal according to another embodiment different from FIG.

The present inventors have made various studies on a method for producing an SiC single crystal by a solution method that can suppress the occurrence of solvent inclusion. As a result, the following knowledge was obtained.

In the crystal growth of the SiC single crystal by the solution method, the SiC single crystal is grown by bringing the crystal growth surface of the SiC seed crystal into contact with the Si-C solution. The SiC seed crystal may include a facet region. A facet region refers to a region having the same crystal structure as other regions and having a higher screw dislocation density and nitrogen concentration than other regions. The screw dislocation has a small step at an atomic level called a step in which crystal growth easily proceeds. The facet region is a source of steps during crystal growth because of the high screw dislocation density. That is, if a facet region is included in the crystal growth surface, crystal growth proceeds preferentially in the facet region compared to other regions.

In the facet region, crystal growth is fast. On the other hand, in regions other than the facet region, the crystal growth is slower as the distance from the facet region increases. Therefore, if there is a facet region at the end of the crystal growth surface, the crystal growth rate differs greatly between the facet region and the region farthest from the facet region. In this case, the thickness at which the SiC single crystal grows greatly differs between the facet region and the region farthest from the facet region. If the crystal growth thickness differs greatly, step bundling called step bunching proceeds. Step bunching promotes three-dimensional growth of SiC single crystal. If the SiC single crystal grows three-dimensionally, a part of the solvent is confined in the SiC single crystal, and solvent inclusion occurs.

In this embodiment, the facet region is arranged at the center of the crystal growth surface. This reduces the distance between the facet area and the area farthest from the facet area. Therefore, the difference in crystal growth rate between the facet region and the region farthest from the facet region is reduced. That is, the variation in the crystal growth thickness is suppressed. This suppresses step bunching and three-dimensional growth of the SiC single crystal. As a result, solvent inclusion can be suppressed.

The SiC single crystal manufacturing method according to the present embodiment completed based on the above knowledge is a manufacturing method by a solution growth method in which the SiC single crystal is grown by bringing the crystal growth surface of the SiC seed crystal into contact with the Si-C solution. . The manufacturing method includes a preparation process and a growth process. In the preparation step, the raw material is heated and melted to prepare a Si—C solution. In the growth step, the crystal growth surface is brought into contact with the Si—C solution, and an SiC single crystal is grown on the crystal growth surface. The crystal growth surface includes a facet region, and the offset angle of the crystal growth surface with respect to the {0001} plane is 0.5 ° or less. The center of gravity of the facet region is arranged at a distance within 0.40 r from the center of gravity of the crystal growth surface. Here, the length of the longest line segment connecting the center of gravity of the crystal growth surface and the outer periphery of the crystal growth surface is r.

In the above manufacturing method, a SiC single crystal is manufactured using a SiC seed crystal in which the facet region is arranged in the center. Therefore, solvent inclusion can be suppressed.

Preferably, the crystal growth surface is a single surface.

In this case, solvent inclusion can be further suppressed.

Preferably, the center of gravity of the facet region is arranged at a distance within 0.25r from the center of gravity of the crystal growth surface.

In this case, solvent inclusion can be further suppressed.

Preferably, the area ratio of the facet region to the crystal growth surface is 0.04 or more.

In this case, solvent inclusion can be further suppressed.

Preferably, the area ratio of the facet region to the crystal growth surface is 0.10 or more.

In this case, solvent inclusion can be further suppressed.

In the growth step, a SiC single crystal may be grown by 2 mm or more.

In this case, the yield of the SiC single crystal can be increased.

The SiC seed crystal and the SiC single crystal may have a 4H polymorphic crystal structure.

The SiC seed crystal according to the present embodiment is an SiC seed crystal used in a solution growth method in which an SiC single crystal is grown on an SiC seed crystal by bringing the SiC seed crystal into contact with an Si—C solution. The SiC seed crystal has a crystal growth surface having an offset angle of 0.5 ° or less with respect to the {0001} plane. The crystal growth surface includes a facet region. The center of gravity of the facet region is arranged at a distance within 0.40 r from the center of gravity of the crystal growth surface. Here, the length of the longest line segment connecting the center of gravity of the crystal growth surface and the outer periphery of the crystal growth surface is r.

The SiC single crystal produced using the seed crystal can suppress solvent inclusion.

Preferably, the crystal growth surface is a single surface.

In this case, solvent inclusion can be further suppressed.

Hereinafter, this embodiment will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[Manufacturing equipment]
FIG. 1 is a schematic diagram of an example of a manufacturing apparatus 1 used in the method for manufacturing a SiC single crystal according to the present embodiment.

The manufacturing apparatus 1 includes a chamber 2, a crucible 5, a heat insulating member 4, an induction heating device 3, a rotating device 20, and a seed shaft 6.

Chamber 2 is a casing. The chamber 2 accommodates the heat insulating member 4 and the induction heating device 3. The chamber 2 can further accommodate a crucible 5. When the SiC single crystal is manufactured, the chamber 2 is cooled with a cooling medium.

The crucible 5 is housed in a casing-shaped heat insulating member 4. The crucible 5 is a housing whose upper end is open. The crucible 5 may be provided with a top plate. In this case, evaporation of the Si—C solution 7 can be suppressed. The crucible 5 accommodates the Si—C solution 7.

The Si-C solution 7 is produced by melting the raw material by heating. The raw material may be only Si, or may contain Si and another metal element. For example, the metal element contained in the raw material of the Si-C solution 7 is selected from the group consisting of titanium (Ti), manganese (Mn), chromium (Cr), cobalt (Co), vanadium (V), and iron (Fe). 1 type, or 2 or more types. The Si—C solution 7 is generated by further dissolving carbon (C) in these raw materials. When carbon is supplied to the Si—C solution 7 from the added carbon source, the raw material of the Si—C solution 7 contains carbon (C).

When supplying carbon to the Si—C solution 7 by melting the crucible 5, the crucible 5 preferably contains carbon. More preferably, the material of the crucible 5 is graphite. When supplying carbon from the added carbon source to the Si—C solution 7, the crucible 5 may be any material that is stable at the crystal growth temperature. In this case, the material of the crucible 5 may be ceramics or a high melting point metal. When the crucible 5 is made of a material other than graphite, a film containing graphite may be formed on the inner surface of the crucible 5.

The heat insulating member 4 surrounds the crucible 5. The heat insulating member 4 is made of a well-known heat insulating material. The heat insulating material is, for example, a fiber-based or non-fiber-based molded heat insulating material.

The induction heating device 3 surrounds the heat insulating member 4. The induction heating device 3 includes a high frequency coil. The high frequency coil is disposed coaxially with the seed shaft 6. The induction heating device 3 induction-heats the crucible 5 by electromagnetic induction and melts the raw material stored in the crucible 5 to generate the Si—C solution 7. The induction heating device 3 further maintains the Si—C solution 7 at the crystal growth temperature.

Rotating device 20 is a shaft extending in the height direction of chamber 2. The upper end of the rotating device 20 is disposed inside the chamber 2. The crucible 5 is disposed on the upper surface of the rotating device 20. The rotation device 20 is connected to a drive source 21 and rotates around the central axis of the rotation device 20 by the drive source 21. When the rotating device 20 rotates, the crucible 5 rotates. The crucible 5 and the rotating device 20 may rotate or may not rotate.

The seed shaft 6 is a shaft extending in the height direction of the chamber 2. The upper end of the seed shaft 6 is disposed outside the chamber 2. The seed shaft 6 is attached to the drive source 9 outside the chamber 2. The lower end of the seed shaft 6 is disposed inside the crucible 5. An SiC seed crystal 8 is attached to the lower end of the seed shaft 6. The seed shaft 6 can be moved up and down and rotated by a drive source 9. The seed shaft 6 is lowered by the drive source 9, and the SiC seed crystal 8 comes into contact with the Si—C solution 7. The seed shaft 6 is rotated by the drive source 9, and the SiC seed crystal 8 is rotated. The rotation direction of the seed shaft 6 may be the same as the rotation direction of the crucible 5 or may be the opposite direction. The seed shaft 6 may rotate or may not rotate. Preferably, the seed shaft 6 is graphite.

[SiC seed crystal]
The SiC seed crystal 8 has a plate shape and is made of a SiC single crystal. SiC seed crystal 8 may be, for example, a SiC single crystal manufactured by a sublimation method. Preferably, the crystal structure of SiC seed crystal 8 is the same as the crystal structure of the SiC single crystal to be manufactured. For example, when producing a 4H polymorphic SiC single crystal, it is preferable to use a 4H polymorphic SiC seed crystal 8.

[Crystal growth surface]
Of the surface of the SiC seed crystal 8, the surface on which the SiC single crystal grows on the Si-C solution 7 is called a crystal growth surface. The offset angle of the crystal growth surface of the seed crystal of the present invention with respect to the {0001} plane is 0.5 ° or less. In the present specification, the offset angle of the crystal growth surface with respect to the {0001} plane is also simply referred to as “offset angle”. If the offset angle is larger than 0.5 °, the step density is different between a region near the {0001} plane and a region far from the {0001} plane on the crystal growth surface. Specifically, the step density is higher in the region near the {0001} plane on the crystal growth surface than in the region far from the {0001} plane on the crystal growth surface. In this case, step bunching is likely to occur in an area where the step density is high. For this reason, irregularities are generated on the surface of the grown crystal, and solvent inclusion may occur. Therefore, the offset angle of the crystal growth surface of the seed crystal of the present invention with respect to the {0001} plane is 0.5 ° or less. Preferably, the crystal growth surface is a {0001} plane. That is, the offset angle is 0.0 °. More preferably, the crystal growth plane is a (000-1) plane (carbon plane). In this specification, the fact that the offset angle of the crystal growth surface with respect to the {0001} plane is 0.5 ° or less is also referred to as “the crystal growth surface is on axis”.

Preferably, the crystal growth surface of the seed crystal of the present invention is a single surface. In this specification, a single surface means a smooth surface having no ridgeline. The crystal growth surface of the seed crystal of the present invention may have microscopic distortion as long as it does not have a ridgeline. When the crystal growth surface of the seed crystal has a ridge line, unevenness may occur in the ridge line portion of the grown crystal surface. As a result, solvent inclusion may occur. More preferably, the crystal growth surface is a single plane.

FIG. 2 is a bottom view of the SiC seed crystal 8 (a diagram of a crystal growth surface). Referring to FIG. 2, crystal growth surface 80 includes a facet region 81. The crystal growth surface 80 may be circular as shown in FIG. 2 or other shapes. The shape of the crystal growth surface 80 is, for example, a hexagon shown in FIG. The shape of the crystal growth surface 80 may be another polygon (such as a quadrangle and an octagon), or may be an ellipse. The shape of the crystal growth surface 80 is not particularly limited.

[Facet area]
The facet region 81 is a region having the same crystal structure as other regions and having a higher screw dislocation density and nitrogen concentration than the other regions. The facet region 81 can be confirmed by measuring the screw dislocation density and the nitrogen concentration by a known method. The facet area 81 can also be confirmed by the following method. The SiC seed crystal 8 is cut to a thickness of 1 mm or less. The cut piece is placed in front of a light source such as an incandescent bulb to transmit light. A portion (facet region 81) that is more strongly colored than the other regions can be visually confirmed.

[Position of facet area]
Facet region 81 is arranged at the center of crystal growth surface 80. Specifically, the centroid 82 of the facet region 81 is arranged at a distance within 0.40 r from the centroid 83 of the crystal growth surface 80. Here, the length of the longest line segment among the line segments connecting the center of gravity 83 of the crystal growth surface 80 and the outer periphery 84 of the crystal growth surface 80 is r. By disposing facet region 81 in the center of crystal growth surface 80, the distance between facet region 81 and the region farthest from facet region 81 is reduced. Therefore, the difference in crystal growth rate between the facet region 81 and the region farthest from the facet region 81 is reduced. That is, the variation in the crystal growth thickness is suppressed. This suppresses the progress of step bunching during crystal growth. As a result, solvent inclusion can be suppressed.

The closer the position of the center of gravity 82 of the facet region 81 is to the center of gravity 83 of the crystal growth surface 80, the higher the effect of suppressing solvent inclusion. Preferably, the center of gravity 82 of the facet region 81 is arranged at a distance within 0.25 r from the center of gravity 83 of the crystal growth surface 80.

[Area ratio of facet area]
Furthermore, the larger the area ratio of the facet region 81 to the crystal growth surface 80, the higher the effect of suppressing solvent inclusion. This is presumably because the distance between the facet region 81 and the region farthest from the facet region 81 decreases as the area ratio increases. Preferably, the area ratio of facet region 81 to crystal growth surface 80 is 0.04 or more, more preferably 0.10 or more. The upper limit of the area ratio of facet region 81 to crystal growth surface 80 is not particularly limited.

The SiC seed crystal 8 including the crystal growth surface 80 including the facet region 81 in the center is manufactured by being cut out from a SiC single crystal ingot. For example, a well-known method can be adopted as a method for cutting the SiC single crystal ingot. For example, a blade saw method and a wire saw method. When the SiC seed crystal 8 is cut out, the positions of the facet region 81 and the crystal growth surface 80 are appropriately adjusted so as to be as described above.

[Production method]
The manufacturing method of the SiC single crystal according to the present embodiment includes a preparation process and a growth process.

[Preparation process]
In the preparation step, the raw material is heated and melted to prepare the Si—C solution 7. First, the raw material of the Si—C solution 7 having the above composition is stored in the crucible 5. The crucible 5 containing the raw material is disposed on the upper surface of the rotating device 20 in the chamber 2. After the crucible 5 is stored in the chamber 2, the chamber 2 is filled with an inert gas, for example, helium gas. Further, the raw material of the crucible 5 and the Si—C solution 7 is heated by the induction heating device 3 to the melting point or higher of the raw material of the Si—C solution 7. If the crucible 5 containing carbon is heated, carbon melts from the crucible 5 into the melt. As a result, a Si—C solution 7 is generated. As another method, there is a method via a gas phase in which carbon is dissolved from a hydrocarbon gas into the Si—C solution 7. As yet another method, there is a method in which a solid-phase carbon source is charged into the Si—C solution 7 and dissolved. The solid-phase carbon source is, for example, one or more selected from the group consisting of graphite, amorphous carbon raw material, SiC, and carbides of additive elements. These are added to the Si-C solution 7 in the form of blocks, rods, granules and powders. The Si—C solution 7 is generated by heating the raw material containing carbon.

The heating is performed until the Si-C solution 7 reaches the crystal growth temperature. Heating may be continued up to the crystal growth temperature, or a period for holding at a constant temperature may be provided. When holding at a constant temperature, the holding temperature should just be more than the liquidus temperature of a raw material. In this case, the heating is performed until the SiC concentration in the Si—C solution 7 approaches a saturated state. When using a solid carbon source, it is preferable to heat until the carbon source is completely dissolved. The heating time is, for example, 0.5 to 10 hours.

[Growth process]
In the growth step, the crystal growth surface 80 of the SiC seed crystal 8 is brought into contact with the Si—C solution 7 to grow a SiC single crystal on the crystal growth surface 80 of the SiC seed crystal 8.

After the Si—C solution 7 is generated, the seed shaft 6 is lowered, and the crystal growth surface 80 of the SiC seed crystal 8 is brought into contact with the Si—C solution 7 (hereinafter also referred to as a landing liquid). The crystal growth surface 80 is on axis and includes a facet region 81. The facet region 81 includes a screw dislocation. The steps (small steps at the atomic level) possessed by screw dislocations are structures depending on the crystal structure. Therefore, a crystal structure similar to SiC seed crystal 8 grows stably.

The output of the induction heating device 3 is adjusted to maintain the temperature of the Si—C solution 7 at the crystal growth temperature. The crystal growth temperature is, for example, 1850 to 2050 ° C.

By applying a temperature gradient to the Si-C solution 7, a SiC single crystal can be produced efficiently. Specifically, a temperature gradient is applied so that the vicinity of the SiC seed crystal 8 in the Si—C solution 7 is lower in temperature than other portions. Thereby, the supersaturation degree of SiC in the vicinity of SiC seed crystal 8 can be increased. As a result, the growth rate of the SiC single crystal is increased. For example, the output of the induction heating device 3 is adjusted to give a temperature gradient so that the upper part of the Si—C solution 7 becomes a low temperature. Otherwise, the output of the induction heating device 3 is adjusted so that the temperature of the Si—C solution 7 is maintained by heat transfer from the crucible 5. As a result, a temperature gradient is applied so that the center of the Si—C solution 7 has a low temperature. The temperature gradient is preferably in the range of 5 to 50 ° C./cm regardless of the vertical direction or the horizontal direction. If the temperature gradient is 5 ° C./cm or more, the growth rate of the SiC single crystal is increased. If the temperature gradient is 50 ° C./cm or less, spontaneous generation of SiC nuclei in the Si—C solution 7 can be suppressed.

The growth step may be performed while maintaining the temperature of the Si—C solution 7 constant or may be performed while the temperature is increased. By performing crystal growth while raising the temperature of the Si—C solution 7, the degree of supersaturation of the carbon (C) concentration in the Si—C solution 7 can be adjusted to an appropriate range. Therefore, spiral growth proceeds predominantly. As a result, mixing of different crystal polymorphs due to two-dimensional nucleus growth can be further suppressed. When the growth step is performed while raising the temperature of the Si—C solution 7, if the rate of temperature rise is within a certain range, the two-dimensional nucleus growth can be stably suppressed without dissolving the SiC single crystal.

A meniscus may be formed after the landing. In the case of forming a meniscus, the SiC seed crystal 8 in contact with the Si—C solution 7 is pulled upward from the liquid level of the Si—C solution 7. By forming the meniscus, wetting of the Si—C solution 7 can be suppressed. As a result, polycrystals can be suppressed. The meniscus height is, for example, 0.1 to 4.0 mm.

[Other manufacturing methods]
In FIG. 1, the example of the manufacturing apparatus 1 using the crucible 5 is shown. However, a levitation method in which the raw material is levitated and melted by electromagnetic force without using the crucible 5 may be employed. Alternatively, a cold crucible method for generating the Si—C solution 7 levitated by magnetic repulsion in a water-cooled metal crucible may be employed.

The SiC single crystal of this embodiment can be manufactured through the above steps.

The manufacturing apparatus 1 shown in FIG. 1 was used. In the example, the crucible 5 was a graphite crucible, the induction heating device 3 was a high frequency coil, the seed shaft 6 was graphite, and the chamber 2 was a water-cooled stainless steel chamber.

In a graphite crucible, the raw material of the Si—C solution (molar ratio, Si: Cr = 60: 40) was charged. The inside of the production apparatus was replaced with helium gas. The raw material of the graphite crucible and the Si—C solution was heated by a high frequency coil to prepare an Si—C solution.

A temperature gradient was formed so that the upper part of the Si-C solution had a low temperature. The temperature gradient was formed by controlling the positional relationship between the graphite crucible and the high frequency coil. Specifically, the temperature gradient was formed by arranging the Si—C solution so that the center portion is located above the center of the high-frequency coil (heat generation center). The temperature gradient was confirmed by inserting a thermocouple into the Si—C solution in advance and measuring the temperature separately from this example. The temperature gradient in the vicinity of the SiC seed crystal was about 12 ° C./cm. The temperature of the Si-C solution near the SiC seed crystal during crystal growth was measured. The measurement was performed by measuring the temperature of the graphite on the back surface of the SiC seed crystal with an optical thermometer using a seed shaft provided with a temperature measuring hole. The crystal growth temperature was 1940 ° C.

The seed shaft was lowered to allow the SiC seed crystal to land on the Si-C solution. The SiC seed crystal was manufactured by a sublimation recrystallization method and had a circular crystal growth surface with a radius of 37.5 mm. The crystal structure of the SiC seed crystal was 4H—SiC. The crystal growth surface was a single plane and was a (000-1) plane on axis. That is, the offset angle of the crystal growth surface was 0.3 °. Using the method described above, the facet region was visually confirmed. The facet area was circular. Table 1 shows the position of the center of gravity of the facet region, the area of the facet region, and the area ratio of the facet region to the crystal growth surface. In Table 1, “the position of the center of gravity of the facet region” indicates the distance between the center of gravity of the crystal growth surface and the center of gravity of the facet region. For the distance, the length of the longest line segment among the line segments connecting the center of gravity of the crystal growth surface and the outer periphery of the crystal growth surface is described as r (mm).

After landing, the seed shaft was pulled up to form a meniscus. The meniscus height was 0.5 mm. Crystal growth was performed while keeping the temperature of the Si-C solution constant. The crucible and the seed shaft were rotated at 10 rpm in the opposite direction. The time from the landing to the end of crystal growth was 50 hours. After completion of crystal growth, the seed shaft was raised to separate the SiC single crystal from the Si—C solution. After slowly cooling the graphite crucible to room temperature, the SiC single crystal was separated from the seed shaft and collected.

[Growth thickness measurement test]
The SiC seed crystal and SiC single crystal of each test number were cut in the crystal growth direction, and the cross section was polished. The cross section was observed using a Nomarski type differential interference microscope. The thickness of the SiC single crystal in the crystal growth direction was measured and used as the growth thickness. The results are shown in Table 1.

[Inclusion-free thickness measurement test]
In the SiC single crystal of each test number, the thickness of the crystal grown without generating solvent inclusion was measured. Specifically, microscopic observation was performed in the same manner as in the growth thickness measurement test. The crystal growth thickness of the SiC single crystal in which no step bunching or solvent inclusion occurred at the boundary between the facet region and the other region was measured to obtain an inclusion free thickness. The results are shown in Table 1.

[Evaluation results]
In Test No. 1 to Test No. 6, SiC single crystals were produced using appropriate SiC seed crystals. Specifically, the SiC seed crystals of Test No. 1 to Test No. 6 had a center of gravity position of the facet region of 0.40 r or less. For this reason, the SiC single crystals of Test No. 1 to Test No. 6 had an inclusion free thickness of 2.0 mm or more.

Furthermore, the SiC seed crystals of Test No. 1 to Test No. 3 had a center of gravity position of the facet region of 0.25 r or less. Therefore, the SiC single crystals of Test No. 1 to Test No. 3 had a larger inclusion-free thickness than the SiC single crystals of Test No. having the same facet area ratio. Specifically, the inclusion-free thickness of the SiC single crystal of test number 1 was larger than that of the SiC single crystal of test number 4. The SiC single crystal of test number 2 had a larger inclusion-free thickness than the SiC single crystal of test number 5. The SiC single crystal of test number 3 had a larger inclusion-free thickness than the SiC single crystal of test number 6.

Furthermore, comparing SiC single crystals having the same test number with the same center of gravity of the facet region, solvent inclusion was suppressed as the area ratio of the facet region to the crystal growth surface was larger. Specifically, the SiC seed crystals of

test numbers

2 and 3 had an area ratio of 0.04 or more. Therefore, the SiC single crystals of

test numbers

2 and 3 had a larger inclusion-free thickness than the single crystal of test number 1. The SiC seed crystals of

test numbers

5 and 6 had an area ratio of 0.04 or more. Therefore, the SiC single crystals of

test numbers

5 and 6 had a larger inclusion-free thickness than the SiC single crystal of test number 4.

Further, the area ratio of the SiC seed crystal of test number 3 was 0.10 or more. Therefore, the SiC single crystal of test number 3 had a larger inclusion-free thickness than the SiC single crystals of test numbers 1 and 2. The SiC seed crystal of test number 6 had an area ratio of 0.10 or more. Therefore, the SiC single crystal of test number 6 had a larger inclusion-free thickness than the SiC single crystals of

test numbers

4 and 5.

On the other hand, the SiC seed crystals of Test No. 7 to Test No. 9 had a center of gravity position of the facet region larger than 0.40r. For this reason, the SiC single crystals of Test No. 7 to Test No. 9 had an inclusion free thickness of less than 2.0 mm.

The embodiment of the present invention has been described above. However, the above-described embodiment is merely an example for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and can be implemented by appropriately changing the above-described embodiment without departing from the spirit thereof.

DESCRIPTION OF SYMBOLS 1 Manufacturing apparatus 7 Si-C solution 8 SiC seed crystal 80 Crystal growth surface 81 Facet region 82 Center of gravity of facet region 83 Center of gravity of crystal growth surface 84 Perimeter of crystal growth surface

Claims

A method for producing an SiC single crystal by a solution growth method in which an SiC single crystal is grown by bringing a crystal growth surface of an SiC seed crystal into contact with an Si-C solution,
Heating and melting the raw material to prepare the Si-C solution;
The crystal growth surface including a facet region whose center of gravity is disposed at a distance within 0.40 r from the center of gravity of the crystal growth surface and having an offset angle of 0.5 ° or less with respect to the {0001} plane is added to the Si-C solution. And a step of growing the SiC single crystal on the crystal growth surface.
Here, the length of the longest line segment among the line segments connecting the center of gravity of the crystal growth surface and the outer periphery of the crystal growth surface is defined as r.
It is a manufacturing method of the SiC single crystal according to claim 1,
The method for producing a SiC single crystal, wherein the crystal growth surface is a single surface.
A method for producing a SiC single crystal according to claim 1 or 2,
The SiC single crystal manufacturing method, wherein the center of gravity of the facet region is arranged at a distance within 0.25 r from the center of gravity of the crystal growth surface.
A method for producing a SiC single crystal according to any one of claims 1 to 3,
The SiC single crystal manufacturing method, wherein an area ratio of the facet region to the crystal growth surface is 0.04 or more.
It is a manufacturing method of the SiC single crystal according to claim 4,
The manufacturing method of the SiC single crystal whose said area ratio is 0.10 or more.
A method for producing a SiC single crystal according to any one of claims 1 to 5,
In the step of growing the SiC single crystal,
A method for producing a SiC single crystal, wherein the SiC single crystal is grown by 2 mm or more on the crystal growth surface.
A method for producing a SiC single crystal according to any one of claims 1 to 6,
The method for producing a SiC single crystal, wherein the SiC seed crystal and the SiC single crystal have a 4H polymorphic crystal structure.
A SiC seed crystal used in a solution growth method in which a SiC single crystal is grown on the SiC seed crystal by bringing the SiC seed crystal into contact with a Si-C solution,
A crystal growth surface having an offset angle of 0.5 ° or less with respect to the {0001} plane;
The crystal growth surface is a SiC seed crystal including a facet region in which a center of gravity is arranged at a distance within 0.40 r from the center of gravity of the crystal growth surface.
Here, the length of the longest line segment among the line segments connecting the center of gravity of the crystal growth surface and the outer periphery of the crystal growth surface is defined as r.
The SiC seed crystal according to claim 8,
The SiC seed crystal, wherein the crystal growth surface is a single surface.
The SiC seed crystal according to claim 8 or 9, wherein
The SiC seed crystal whose area ratio with respect to the said crystal growth surface of the said facet area | region is 0.04 or more.