JP6971144B2 - Pedestal, SiC single crystal manufacturing equipment and manufacturing method - Google Patents

Description

The present invention relates to a pedestal to which a seed (seed crystal) is attached during crystal growth, and an apparatus and method for producing a SiC single crystal using the pedestal.

It is known that silicon carbide (SiC), which is a semiconductor material, has a wider bandgap than Si (silicon), which is widely used as a substrate for devices at present, and is excellent in pressure resistance and thermal conductivity. Therefore, silicon carbide is expected to be applied to power devices, high frequency devices, high temperature operation devices and the like.

As a semiconductor device using silicon carbide, a SiC epitaxial wafer having an epitaxial film formed on the SiC wafer is used. An epitaxial film provided on a SiC wafer by a chemical vapor deposition (CVD) method becomes an active region of a SiC semiconductor device. The active layer of the epitaxial wafer is affected by the quality of the SiC wafer by taking over the crystal defects of the SiC wafer as they are or converting them into other crystal defects and taking over. Therefore, there is a demand for high-quality SiC wafers with few defects.

For example, Patent Document 1 describes that the epitaxial film formed on a SiC wafer is improved by keeping the amount of warpage of the wafer and the amount of deviation of the crystal orientation within a predetermined range. Further, Patent Document 2 describes that a high-quality epitaxial thin film can be obtained by keeping the deviation of the growth plane orientation in the wafer plane within a predetermined range.

Japanese Unexamined Patent Publication No. 2011-219296 Japanese Unexamined Patent Publication No. 2011-16721

However, it may not be possible to sufficiently suppress the occurrence of basal plane dislocations (BPD) only by controlling the degree of lattice shift in a predetermined direction as described in Patent Documents 1 and 2. The basal plane dislocation is one of the killer defects generated in the SiC wafer, and the slip (dislocation) of the crystal lattice on the basal plane is considered to be one of the causes.

As a result of diligent studies by the present inventor, the number of basal plane dislocations generated during single crystal growth is when the shape of the lattice surface of the crystal constituting the growing single crystal film is a saddle shape in which convex portions and concave portions coexist. It has been found to increase in and decrease in the case of a dome shape with only one of the protrusions or recesses. Further, it has been found that the smaller the amount of curvature of the convex lattice surface, the more the number of basal plane dislocations is suppressed. The shape of the crystal lattice plane of the single crystal film depends on the crystal lattice surface shape of the seed during the growth of the single crystal, that is, in the heated state. Since the seed is heated with one side adhered to the pedestal, it deforms as a rigid body when heated. Therefore, the crystal lattice plane of the seed is deformed according to the change in the shape of the seed. Therefore, by controlling the shape of the seed at the time of heating, the lattice surface shape of the seed at the time of heating is controlled, and the shape of the crystal lattice surface of the SiC single crystal formed is within the range of an appropriate amount of curvature. It is considered possible to make it dome-shaped.

Conventionally, regarding the shape of the seed, the surface shape has been considered from the viewpoint of preventing the occurrence of irregular shape by keeping the growth surface during crystal growth in a convex shape. However, the surface shape of the seed is affected by the temperature distribution near the growth surface and the like, and changes during the sublimation of the seed before growth and the very early growth. On the other hand, the lattice surface shape of the seed does not change during the sublimation of the seed before growth or the very early growth, and affects the subsequent growth. This time, we focused on the method of controlling the seed shape from the viewpoint of controlling the grid surface shape of the seed, not the surface shape of the seed.

The present invention has been made in view of such circumstances, and makes it possible to control the shape of the seed during crystal growth in order to grow a SiC single crystal in which the occurrence of basal dislocations is suppressed. The purpose is to provide a pedestal for seeds.

In order to solve the above problems, the present invention employs the following means.

(1) The pedestal according to one aspect of the present invention is a pedestal of a seed during crystal growth, and a plurality of first pedestals having different coefficients of thermal expansion in a plurality of directions from a predetermined position in a plan view from one side. The members have overlapping portions, and the coefficient of thermal expansion of the first member changes monotonically as the members move away from the predetermined position in the overlapping direction.

(2) In the pedestal according to the above (1), a plurality of the first members may have a portion overlapping in two directions opposite to each other from the predetermined position.

(3) In the pedestal according to any one of (1) or (2), the plurality of first members may have a portion overlapping in a plurality of directions radially extending from the predetermined position. ..

(4) In the pedestal according to any one of (1) to (3), the number of overlapping first members may be constant regardless of the overlapping direction.

(5) In the pedestal according to any one of (1) to (3), the number of overlapping first members may be different from the other directions in a part of the overlapping directions.

(6) In the pedestal according to any one of (3) or (4), the plurality of first members all have a circular shape surrounding the predetermined position in a plan view from one side. You may be doing it.

(7) In the pedestal according to any one of (1) to (6), the coefficient of thermal expansion of the first member monotonically increases as the distance from the predetermined position increases in the overlapping direction. May be good.

(8) In the pedestal according to any one of (1) to (6), the coefficient of thermal expansion of the first member monotonically decreases as the distance from the predetermined position increases in the overlapping direction. May be good.

(9) In the pedestal according to any one of (1) to (8), one side of the plurality of first members may be covered with the second member.

(10) In the pedestal according to (9), the thickness of the second member is preferably 1 times or less the thickness of the first member in the direction perpendicular to the overlapping direction.

(11) In the pedestal according to any one of (1) to (10), the side of the plurality of first members located opposite to the one side may be covered with the third member. ..

(12) In the pedestal according to (11), the thickness of the third member is preferably 1 times or less the thickness of the first member in the direction perpendicular to the overlapping direction.

(13) In the SiC single crystal manufacturing apparatus according to one aspect of the present invention, the pedestal according to any one of (1) to (12) is provided so that one side thereof is the seed growth surface side. I have.

(14) The method for producing a SiC single crystal according to one aspect of the present invention is to produce a SiC single crystal using the SiC single crystal manufacturing apparatus according to (13) above.

In the pedestal of the present invention, when a plurality of first members are stacked so that the coefficient of thermal expansion monotonically increases from the center to the outside in the overlapping direction, the outer first member expands more during heating. It will be. Therefore, in the pedestal of the present invention, the surface parallel to the overlapping direction of the first member has a shape in which the outer side is warped as compared with the center, and the shape of the seed mounted therein follows this and is compared with the center. The outside is curved. The grid surface shape of the seed is deformed in the same manner as the shape of the seed. Then, the SiC single crystal that grows on the seed inherits the shape of the crystal lattice plane of the seed and grows. Therefore, by using an appropriate pedestal for the warp of the original lattice surface of the seed, the shape of the lattice surface of the growing SiC crystal can be corrected in the direction of dome shape and less curvature, and eventually the base. The number of surface dislocations can be suppressed.

It is a vertical sectional view of the single crystal film manufacturing apparatus provided with the pedestal which concerns on 1st Embodiment of this invention. (A) It is a top view of the pedestal which concerns on 1st Embodiment of this invention. (B) It is a side view of the pedestal in the state which is sandwiched between the 2nd member and the 3rd member. (A), (b) is a cross-sectional view before heating and after heating of a pedestal on which a seed is placed on a second member. (A)-(d) It is a plan view of the pedestal which concerns on the 2nd Embodiment of this invention. It is a top view of the pedestal which concerns on the modification of the 2nd Embodiment of this invention. It is a graph which shows the result of 6-direction measurement about the warp amount of the SiC wafer manufactured as the Example of this invention. It is a graph which shows the shape of the crystal lattice plane in the SiC wafer manufactured as the Example of this invention.

Hereinafter, the present invention will be described in detail with reference to the drawings as appropriate. In the figure used in the following description, in order to make the features of the present invention easy to understand, the featured portions may be enlarged for convenience, and the dimensional ratios of each component may differ from the actual ones. There is. Further, the materials, dimensions, etc. exemplified in the following description are examples, and the present invention is not limited thereto, and can be appropriately modified and carried out within the range in which the effect of the present invention is exhibited. ..

<First Embodiment>
[Construction of SiC single crystal manufacturing equipment and pedestal]
FIG. 1 is a vertical sectional view of a SiC single crystal manufacturing apparatus 100 provided with a seed pedestal during crystal growth by a sublimation method according to the first embodiment of the present invention. The SiC single crystal manufacturing apparatus 100 includes at least a crucible 101, a pedestal 102 of a seed (seed crystal) S arranged on one end side of the crucible 101, and a coil 103 surrounding the outer wall of the crucible 101. The raw material G is configured to be accommodated on the other end side of the inside. The SiC single crystal manufacturing apparatus 100 may further include a taper guide 104 that expands in diameter from the pedestal 102 toward the raw material G.

The pedestal 102 has a portion in which a plurality of first members 102A having different coefficients of thermal expansion overlap in a plurality of directions from a predetermined position in a plan view from one side which is the seed growth surface side. FIG. 2A is a plan view of the pedestal 102 as seen from the raw material G side in FIG. In FIG. 2 (a), the pedestal 102, in two directions (right and left) D ₁ opposite each other from the predetermined position (central), the plate-like plurality of first members 102A, each of the width direction (shorter An example shows a case where the parts are overlapped (with the sides facing each other) in the same direction (direction). In other words, a plurality of plate-shaped first members 102A having different coefficients of thermal expansion are arranged in a direction parallel to the surface to which the seed is attached. In the following, for the first member and other members, the size of the first member in the overlapping direction L is referred to as "width", and the size in the direction perpendicular to the overlapping direction L is referred to as "thickness". ..

The first member 102A is a member made of a carbon molding material containing graphite as a main raw material, porous carbon, glassy carbon or other carbon-based material. The thickness of the first member 102A in the direction substantially perpendicular to the overlapping direction (width direction of the first member 102A) L, that _{is, the thickness t 1} of the pedestal 102 is preferably 2 mm or more.

FIG. 2A illustrates a case where the five first members 102A ₁ , 102A ₂ , 102A ₃ , 102A ₄ , and 102A ₅ are stacked in this order, but the number of stacking members is not limited. Further, FIG. 2A assumes a case where the pedestal 102 is cylindrical, but the shape of the pedestal 102 is not limited to this case.

The width of each first member in the overlapping direction L may be appropriately determined according to the size of the pedestal 102 set according to the size of the seed crystal and the number of overlapping. As shown in FIG. 2A, the widths of the first members may be the same as or different from each other in the overlapping direction L.

In the overlapping direction L of the plurality of first members 102A, the coefficient of thermal expansion monotonically changes (increases or decreases) as the distance from the central portion, that is, from the central portion to the outside (direction D _1). The monotonous change means a change that continues to increase or a change that continues to decrease.

It is assumed that the first member 102A of the present embodiment is stacked so that the coefficient of thermal expansion monotonically increases from the central portion to the outside. That is, the coefficient of thermal expansion of each of _{the first member 102A 3} , the first member 102A ₂ , the first member 102A ₁ , the first member 102A ₃ , the first member 102A ₄ , and the first member 102A _{5 becomes monotonous.} It is assumed that it is increasing.

FIG. 2B is a side view when the pedestal 102 of FIG. 2A is sandwiched between the second member 105 and the third member 106. In this case, the pedestal 102 is installed so that the overlapping direction L of the first members 102A is substantially parallel to the ceiling and floor surface of the single crystal film manufacturing apparatus 100.

As shown in FIG. 2B, the surface (seed forming surface) of the raw material G side (one side) of the pedestal 102 is a carbon molding material mainly made of graphite, porous carbon, glassy carbon, or other carbon. It is preferably covered with a second member 105 made of a system material. In this case, the seed L is formed on the integrated second member 105, and the adhesion of the seed L to the pedestal 102 can be improved as compared with the case where the seed L is mounted over the plurality of first members 102A. .. In the direction perpendicular to the overlapping direction L (vertical direction in FIG. 2B), the thickness t ₂ of the second member is preferably 1 times or less of _{the thickness t 1} of the first member, and is 0.5. It is more preferable that it is double or less.

Further, as shown in FIG. 2B, the surface (attachment surface to the crucible 101) on the side opposite to the raw material G of the pedestal 102 (the side located opposite to one side) is also carbon using graphite as the main raw material. It is preferably covered with a third member 106 made of a molding material, porous carbon, glassy carbon, or other carbon-based material. In this case, the pedestal 102 will be attached to the crucible 101 via the third member 106, and the adhesion of the pedestal 102 to the crucible 101 can be improved. In the direction perpendicular to the overlapping direction L, the thickness t ₃ of the third member is preferably 1 times or less, more preferably 0.5 times or less the thickness t _{1 of the first member.} Further, when the second member 105 is provided, the thickness of the third member 106 may exceed the thickness of the second member 105.

3A and 3B are step views of the pedestal 102 before and after heating, respectively. The pedestal 102 is installed so that the overlapping direction L of the first members 102A is substantially parallel to the inner wall 101a of the single crystal film manufacturing apparatus 100.

_{The thickness t 1} of the pedestal 102 before heating is uniformly uniform as shown in FIG. 3A, but by heating, the plurality of first members 102A constituting the pedestal 102 are respectively. Since it expands according to the coefficient of thermal expansion, the pedestal 102 is deformed as shown in FIG. 3 (b).

Since the first member 102A of the present embodiment has a larger coefficient of thermal expansion as it is located on the outer side, the size increases from the central portion to the outer side. As a result, the surface 102a of the pedestal on the raw material G side has a curved shape with a recess in the center, and the second member 105 covering the surface 102a also has a shape following this. Therefore, the seed S formed directly with respect to the pedestal 102 or via the second member 105 also has the same curved shape as the pedestal 102. However, since the surface of the pedestal 102 on the opposite side of the seed forming portion is fixed to the inner wall 101a via the third member 106, expansion in the direction of this surface is suppressed.

From the viewpoint of forming a smooth curved surface in the seed forming portion during heating, the difference in thermal expansion coefficient between adjacent first members 102A ^{is preferably 3 × 10 -6} K- ¹ or less.

When the pedestal 102 is stacked so that the coefficient of thermal expansion of the first member 102A decreases monotonically from the central portion to the outside, the central portion expands more than the outside during heating. Therefore, the outside of the seed S can be bent toward the pedestal 102 side. Therefore, for example, when the outer portion of the seed S has a lattice surface that is excessively warped on the opposite side to the pedestal 102, if such a pedestal is used, the outer portion of the seed S is pulled toward the pedestal 102 side. Therefore, the degree of warpage can be alleviated.

In the pedestal as shown in FIG. 2 above, the seed is warped in the direction in which the first member is overlapped and is not deformed in a method orthogonal to it, so that the lattice plane is convex in one direction and concave in the orthogonal direction. When transforming a seed with a saddle-shaped (potato chips) lattice surface into a dome shape, or when transforming a seed that is dome-shaped and has a large difference in the amount of warpage depending on the orientation, it should be transformed into a dome shape with a small warp. This is especially effective in such cases.

[Manufacturing method of SiC single crystal]
A method for producing a SiC single crystal using the pedestal 102 of the present embodiment will be described.

First, the shape of the lattice plane of the SiC single crystal to be the seed is measured in advance. The lattice plane is an atomic arrangement plane of a SiC single crystal and can be measured by X-ray diffraction (XRD). As the diffraction plane used for the XRD measurement, for example, the (0004) plane can be selected. Since the X-ray diffraction direction of the lattice surface changes according to the curvature of the atomic arrangement surface, the change in the position of the ω angle corresponding to the peak of X-ray diffraction is measured while changing the position along the measurement direction. , Can be calculated from the result. The measurement directions may be two orthogonal directions or six symmetrical directions. Since 4H-SiC is a hexagonal crystal and the c-plane has 6-fold symmetry, measurement in 6 directions is preferable.

Next, an appropriate pedestal is selected in order to correct the shape of the lattice surface based on the shape of the lattice surface obtained by XRD, and the seed crystal is attached in an appropriate direction. For example, when the lattice surface is large in one direction, it may be attached so that the direction in which the warp is large and the direction in which the plurality of plate-shaped first members are overlapped are aligned. When the seeds are cut out from the same single crystal, the lattice plane has the same warp, so that it is not necessary to measure all the seeds, and other known measurement results may be used.

The seed is placed in the crucible with the seed attached to the pedestal, and in the SiC single crystal film manufacturing apparatus 100 shown in FIG. 1, an alternating current is applied to the coil 103 to heat the crucible 101. As a result, the raw material gas is generated from the raw material G, and the raw material gas is supplied to the seed S installed on the pedestal 102 along the taper guide 104. By supplying the raw material gas to the seed S, the SiC single crystal ingot B crystal grows on the main surface of the seed S. The crystal growth surface of the seed S is preferably a carbon surface or a surface provided with an off angle of 10 ° or less from the carbon surface.

The obtained SiC ingot B is sliced to prepare a SiC wafer. Slices perpendicular to <0001> or in a direction with an off angle of 0 to 10 ° to prepare a wafer having a plane parallel to the c-plane or having a plane with an off-angle of 0 to 10 ° from the c-plane. The off angle may be provided in any direction. For example, when it is provided in the <11-20> direction, the angle formed by the main surface and the <11-20> direction is the offset angle. The surface of the wafer may be mirror-treated on the (0001) surface side, that is, the Si surface side. The Si surface is a surface that normally undergoes epitaxial growth.

As described above, in the pedestal 102 according to the present embodiment, when a plurality of first members 102A are stacked so that the coefficient of thermal expansion monotonically increases from the center to the outside in the overlapping direction L, the outer side The first member 102A expands significantly when heated. Therefore, in the pedestal 102 of the present invention, the surface parallel to the overlapping direction L of the first member has a shape in which the outer side is warped as compared with the center, and the shape of the seed S mounted therein follows this shape. The shape is such that the outside is warped compared to the center. Since the lattice surface of the seed during crystal growth is attached so that the shape of the lattice surface becomes appropriate due to this warp, it is possible to form a dome shape with a small curvature, and the single crystal growth formed is that of the seed. It is possible to obtain a single crystal in which the shape of the crystal lattice plane is inherited to an appropriate shape and the number of dislocations on the basal plane is suppressed.

<Second embodiment>
4 (a) to 4 (d) are plan views of the pedestals 112, 122, 132, 142 according to the second embodiment of the present invention, respectively.

Pedestal 112, 122, 132, and 142 of the present embodiment, in a plan view from one side, in a plurality of directions _{D 2} extending radially from a predetermined position (central), the plate-like plurality of first member , Each has an overlapping portion in which the width direction (short direction) is aligned (the sides face each other). That is, the first members 112A, 122A, 132A, 142A constituting each pedestal of the present embodiment have overlapping portions in any direction extending from the central portion, not limited to the two directions opposite to each other. Other configurations of the pedestals 112, 122, 132, 142 are the same as those of the pedestal 102 of the first embodiment. Here, overlapping in an arbitrary direction extending from the central portion means a direction perpendicular to the direction in which the first member overlaps, that is, in a plan view from the side of the surface to which the seed is attached, in an arbitrary direction from the center to the outside. , Means that a plurality of first members are arranged. It may be arranged rotationally symmetrically with respect to the center as shown in FIGS. 4A and 4C, or may be arranged six times symmetrically as shown in FIGS. 4B and 4D. It does not have to have symmetry with respect to the center.

The shape of the first member to be overlapped may be a circular shape all isotropic with respect to the central portion as in the pedestal 112 of FIG. 4 (a), or as in the pedestal 122 of FIG. 4 (b). , Only a part may have another shape such as a hexagon. Further, the first members to be stacked may all have the same thickness as in the pedestal 112 of FIG. 4 (a), or may be the pedestals 132 and 142 of FIGS. 4 (c) and 4 (d). Some may have different thicknesses.

According to these configurations, the inclination of the coefficient of thermal expansion occurs in all directions of the seed forming surface. The surface of the pedestal on the side where the seed is formed has a shape in which the entire circumference is warped compared to the center, and the shape of the seed that grows there also follows this, and the shape is such that the entire circumference is warped compared to the center. Become. Therefore, compared to the case where the inclination in the thermal direction is generated in only one direction, the formed epitaxial film has a substantially isotropic dome shape of the crystal lattice plane, and the number of dislocations on the basal plane is further suppressed. It will be the one that was done.

In particular, in FIG. 4A, the plurality of first members all have a circular shape surrounding the central portion in a plan view from one side in the direction perpendicular to the overlapping direction L. In this case, since the slope of the coefficient of thermal expansion occurs at the same angle in all directions of the seed forming surface, the formed epitaxial film has a more isotropic dome shape of the crystal lattice surface. , The number of basal plane dislocations is further suppressed.

In the case of the type in which the first member is overlapped in all directions extending from the central portion in this plan view, it is easily deformed equally in all directions as described above. It is preferably used to reduce the curvature.

(Modification example)
FIG. 5 is a plan view of the pedestal 152 according to the modified example of the second embodiment. 4 (a) to 4 (d) show an example in which the number of overlapping first members is constant regardless of the overlapping direction, but in FIG. 5, the number of overlapping first members 152A is large. , In some overlapping directions, it is different from other directions. As described above, the first member 152A may have an asymmetrical shape with respect to the central portion in a plan view from one side in the direction perpendicular to the overlapping direction L. The pedestal in which the first member 152A is arranged asymmetrically is effective for correcting the deformation of the lattice surface when it is asymmetrical.

Hereinafter, the effects of the present invention will be further clarified by examples. The present invention is not limited to the following examples, and can be appropriately modified and implemented without changing the gist thereof.

(Example)
Using the pedestal 102 of the first embodiment, a SiC single crystal was produced by a sublimation method. A seed crystal having a diameter of 150 mm was used. Therefore, the pedestal is a cylinder with a diameter of 150 mm. As the pedestal 102 _{, three graphite plates (first member) having a thickness t 1} of 2 mm were stacked (A1 to A3) in the overlapping direction L and bonded to each other. The width of the graphite plate was the same in the overlapping direction L. As the graphite of the first member A2 in the center, a material having a coefficient of thermal expansion smaller than the coefficient of thermal expansion of the graphites of the first members A1 and A3 on both outer sides was used. As the graphite material used, one having a difference in linear expansion coefficient at room temperature of 1 × 10 ^-6 / K was selected. A graphite plate (second member, third member) having a thickness of 2 mm was adhered to one side and the other side in the direction perpendicular to the overlapping direction L of the first member 102A, respectively. When the seed was attached to the pedestal, the overlapping direction of the first member was adjusted to the <1-100> direction in which the warp in the negative direction was large in the state of the seed.

Using this pedestal and seed, SiC single crystal growth was carried out, and a wafer was cut out from the vicinity of the seed of the obtained single crystal. The lattice plane shape of the seed before crystal growth and the lattice plane shape near the seed in the SiC single crystal obtained by crystal growth are shown in the <11-20> direction, the <1-100> direction, and the <1-210> direction. , <01-10> direction, <10-10> direction, and <-2110> direction, XRD measurement was performed, and the warpage amounts d ₁ , d ₂ , d ₃ , d ₄ , d ₅ , and d ₆ were obtained, respectively. rice field. As a result of this experiment, the amount of warpage in the seed before crystal growth was d ₁ = 77.8 μm, d ₂ = -16.7 μm, d ₃ = 30.9 μm, d ₄ = 72.5 μm, d ₅ = 44. It was 4 μm and d ₆ = -7.6 μm. The amount of warpage in the SiC single crystal obtained by crystal growth was d ₁ = 87.5 μm, d ₂ = 24.6 μm, d ₃ = 42.5 μm, d ₄ = 60.5 μm, and d ₅ = 80.1 μm, respectively. , D ₆ = 43.3 μm. Of the six warpage amounts, when the maximum value was d _max and the minimum value was d _{min , the d max} in the seed before crystal growth was d ₁ and the d _min was d ₂ . Further, in the SiC single crystal obtained by crystal growth, the d _max was d ₁ and the d _min was d ₂ . The radius of curvature in each direction and the amount of curvature | d _max −d _min | were calculated. The results are shown in Table 1. It can be seen that the crystal growth reduces the curvature of the lattice plane of the SiC single crystal in the vicinity of the seed after crystal growth (the crystal portion after growth), and the shape of the lattice plane is corrected.

Further, the graph of FIG. 6 shows the result of confirming the shape of the atomic arrangement plane in six directions by X-ray diffraction (XRD) on the SiC single crystal in the vicinity of the seed after crystal growth. In the graph of FIG. 6, the horizontal axis shows the distance (mm) from the central portion in the overlapping direction, and the vertical axis shows the warp amount (curvature amount relative value) (μm). From this graph, it can be seen that in all six directions, the outer side is curved with respect to the central portion, the obtained single crystal film is curved in the same direction, and the lattice surface is dome-shaped.

In addition, the relationship between the angle (angle of rotation) and the amount of warpage in each direction when the <11-20> direction is 0 ° in the seed before crystal growth and the SiC single crystal near the seed after crystal growth is summarized. The results are shown in the graph of FIG. In the graph of FIG. 7, the horizontal axis shows the angle (°) in each direction when the <11-20> direction is 0 °, and the vertical axis shows the amount of warpage (μm).

In the distribution of warpage before single crystal growth, the radius of curvature of a part of the seed is a negative value (the direction of curvature is opposite), whereas in the vicinity of the seed of the SiC single crystal after growth, in any direction. , The radius of curvature has changed to a positive value. From this result, it can be seen that the obtained single crystal film is curved in the same direction because the lattice plane of the seed warped in the saddle shape is corrected to the dome shape.

100 ... SiC single crystal manufacturing equipment 101 ... Crucible 102, 112, 122, 132, 142, 152 ... Pedestal 102A, 102A ₁ , 102A ₂ , 102A ₃ , 102A ₄ , 102A ₅ ... One member 112A, 122A, 132A, 142A, 152A ... First member 102a ... Pedestal surface 103 ... Coil 104 ... Tapered guide 105 ... Second member 106 ... Third member B ... Ingot D ₁ , D ₂ ... Inclined direction of coefficient of thermal expansion G ... Raw material L ... Overlapping direction S ... Seed t ₁ ... Thickness of first member t ₂ ... Thickness of the second member t ₃ ... Thickness of the third member

Claims (13)

The pedestal of the seed during crystal growth,
In plan view from one side
A plurality of first members having different thermal expansion coefficients are overlapped from a predetermined position in a plurality of directions, and the thermal expansion coefficient of the first member changes monotonically as the distance from the predetermined position is increased in the overlapping direction. and,
A pedestal characterized in that one side of the plurality of first members is covered with a second member. The pedestal according to claim 1, wherein the plurality of first members have portions that overlap each other in two directions opposite to each other from the predetermined position. The pedestal according to claim 1, wherein the plurality of first members have portions overlapping in a plurality of directions radially extending from the predetermined position. The pedestal according to any one of claims 1 to 3, wherein the number of overlapping first members is constant regardless of the overlapping direction. The pedestal according to any one of claims 1 to 3, wherein the number of overlapping first members differs from the other directions in a part of the overlapping directions. The pedestal according to claim 3 or 4, wherein the plurality of first members all have a circular shape surrounding the predetermined position in a plan view from one side. .. The pedestal according to any one of claims 1 to 6, wherein the coefficient of thermal expansion of the first member monotonically increases as the distance from the predetermined position increases in the overlapping direction. The pedestal according to any one of claims 1 to 6, wherein the coefficient of thermal expansion of the first member monotonically decreases as the distance from the predetermined position increases in the overlapping direction. The pedestal according to any one of claims 1 to 8, wherein the thickness of the second member is one or less times the thickness of the first member in the direction perpendicular to the overlapping direction. .. The pedestal according to any one of claims 1 to 9 , wherein the side of the plurality of first members located opposite to the one side is covered with the third member. The pedestal according to claim 10 , wherein the thickness of the third member is one or less times the thickness of the first member in the direction perpendicular to the overlapping direction. An apparatus for producing a SiC single crystal, wherein the pedestal according to any one of claims 1 to 11 is provided so that one side thereof is the seed growth surface side. A method for producing a SiC single crystal, which comprises producing a SiC single crystal using the SiC single crystal manufacturing apparatus according to claim 12.

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