JP7149767B2 - SiC Single Crystal Bonding Method, SiC Ingot Manufacturing Method, and SiC Single Crystal Growth Pedestal - Google Patents

Description

TECHNICAL FIELD The present invention relates to a SiC single crystal bonding method, a SiC ingot manufacturing method, and a SiC single crystal growth pedestal.

Silicon carbide (SiC) has a dielectric breakdown field one order of magnitude larger and a bandgap three times larger than silicon (Si). In addition, silicon carbide (SiC) has properties such as a thermal conductivity that is about three times as high as that of silicon (Si). Silicon carbide (SiC) is expected to be applied to power devices, high frequency devices, high temperature operation devices and the like.

Devices such as semiconductors use SiC epitaxial wafers obtained by forming an epitaxial film on a SiC wafer. An epitaxial film provided on a SiC wafer by chemical vapor deposition (CVD) serves as an active region of a SiC semiconductor device.

Therefore, there is a demand for a high-quality SiC wafer that is free from damage such as cracks and has few defects. In this specification, the SiC epitaxial wafer means a wafer after forming an epitaxial film, and the SiC wafer means a wafer before forming an epitaxial film.

For example, Patent Literature 1 and Patent Literature 2 describe that cracks and defects are caused by external warpage and undulation of SiC single crystals used as seed crystals. Patent Literature 1 describes that by setting the linear expansion coefficients of the SiC single crystal and the pedestal within a predetermined range, the warpage of the wafer is reduced. Further, Patent Document 2 describes that by making the thermal expansion coefficient of the seed crystal holding portion smaller than that of other portions of the crucible, the stress that the SiC single crystal receives during growth can be reduced.

Japanese Patent No. 5398492 JP 2009-102187 A

A basal plane dislocation (BPD) is one of the killer defects of SiC wafers. A part of the BPD of the SiC wafer is also inherited by the SiC epitaxial wafer, and causes deterioration of the forward characteristics when current is passed through the device in the forward direction. BPD is a defect that is considered to be caused by one of the causes of slippage that occurs on the basal plane.

As described in Patent Documents 1 and 2, BPD cannot be sufficiently suppressed even by controlling the warpage of the outer shape of the SiC single crystal used as the seed crystal during crystal growth. Therefore, reduction of BPD is demanded.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for bonding SiC single crystals that can reduce the curvature of the plane of atomic arrangement during crystal growth.

As a result of extensive studies, the present inventors have found that there is a correlation between the amount of curvature of the atomic arrangement plane (lattice plane) of a SiC single crystal and the basal plane dislocation (BPD) density. Therefore, the present inventors have found that the plane of atomic arrangement during crystal growth can be flattened by processing the attachment surface of the pedestal on which the SiC single crystal is placed into a predetermined shape.
That is, the present invention provides the following means in order to solve the above problems.

(1) In the SiC single crystal bonding method according to the first aspect, the bending amount and the bending direction of the atomic arrangement plane of the SiC single crystal are set to a first direction passing through at least the center in a plan view and perpendicular to the first direction. a preparatory step of preparing a pedestal having a curved surface curved in a direction opposite to the atomic arrangement surface of the SiC single crystal; a bending direction of the atomic arrangement surface and the bending and an attaching step of attaching the SiC single crystal and the pedestal so that they are opposed to each other so that the directions of curvature of the surfaces are different from each other.

(2) In the SiC single crystal bonding method according to the aspect described above, the difference between the absolute value of the amount of curvature of the atomic arrangement plane and the absolute value of the amount of curvature of the curved surface of the pedestal is It may also be 10 μm or less at the location.

(3) In the method for bonding SiC single crystals according to the aspect described above, the radius of curvature of the atomic arrangement plane may be 28 m or more.

(4) In the SiC single crystal bonding method according to the aspect described above, when the diameter of the SiC single crystal is 150 mm or more, the maximum amount of curvature of the atomic arrangement plane may be 100 μm or less.

(5) In the SiC single crystal bonding method according to the aspect described above, the SiC single crystal may have a thickness of 5 mm or less when performing the bonding step.

(6) A method for manufacturing a SiC ingot according to a second aspect is the SiC single crystal bonding method according to the above aspect, wherein crystal growth is performed using the SiC single crystal attached to the pedestal as a seed crystal.

(7) In the SiC ingot manufacturing method according to the aspect described above, a difference in thermal expansion coefficient between the pedestal and the SiC single crystal at a crystal growth temperature may be 0.3×10 ⁻⁶ /° C. or less.

(8) The SiC single crystal growth pedestal according to the third aspect has a curved surface curved in a direction opposite to the curved direction of the atomic arrangement plane of the SiC single crystal to be attached.

(9) In the SiC single crystal growth pedestal according to the above aspect, the difference between the absolute value of the amount of curvature of the atomic arrangement plane of the SiC single crystal to be attached and the absolute value of the amount of curvature of the curved surface is It may be 10 μm or less at any point.

By using the SiC single crystal bonding method according to the above aspect, the plane of atomic arrangement during crystal growth can be flattened.

FIG. 2 is a schematic diagram of a cross section of a SiC single crystal cut along a straight line extending in a first direction and passing through the center in a plan view; 1 is a diagram schematically showing an example of an atomic arrangement plane of a SiC single crystal; FIG. FIG. 4 is a diagram schematically showing another example of an atomic arrangement plane of a SiC single crystal; It is a figure for demonstrating concretely the measuring method of the shape of an atomic arrangement plane. It is a figure for demonstrating concretely the measuring method of the shape of an atomic arrangement plane. It is a figure for demonstrating concretely the measuring method of the shape of an atomic arrangement plane. It is a figure for demonstrating concretely the measuring method of the shape of an atomic arrangement plane. An example in which the radius of curvature of an atomic arrangement surface is obtained from a plurality of XRD measurement points is shown. FIG. 5 is a diagram for specifically explaining another example of a method for measuring the shape of an atomic arrangement plane; FIG. 5 is a diagram for specifically explaining another example of a method for measuring the shape of an atomic arrangement plane; It is a figure which shows the relationship between a SiC single crystal and a base. It is the figure which showed typically the state after sticking a SiC single crystal on a base. It is a schematic diagram of an example of the manufacturing apparatus used for the sublimation method. 4 is a graph showing the relationship between the radius of curvature of the atomic arrangement surface of SiC single crystal and BPD density.

Hereinafter, this embodiment will be described in detail with appropriate reference to the drawings. In the drawings used in the following description, characteristic portions may be enlarged for the sake of convenience, and the dimensional ratio of each component may differ from the actual one. The materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited to them, and can be modified as appropriate without changing the gist of the invention.

"Method for Bonding SiC Single Crystals"
The SiC single crystal bonding method according to the present embodiment includes a measurement process, a preparation process, and a bonding process. In the measuring step, the shape of the atomic arrangement plane of the SiC single crystal is measured along at least a first direction passing through the center in plan view and a second direction orthogonal to the first direction. In the preparation step, a pedestal having a curved surface curved in a direction opposite to the atomic arrangement surface of the SiC single crystal is prepared. Furthermore, in the attaching step, the SiC single crystal and the pedestal are attached so that the curved direction of the atomic arrangement surface and the curved surface of the pedestal are different from each other. Each step will be specifically described below.

<Measurement process>
FIG. 1 is a schematic diagram of a cross section obtained by cutting a SiC single crystal 1 along a straight line passing through the center in a plan view and extending in a first direction. Any direction can be set as the first direction. In FIG. 1, the first direction is [1-100]. In FIG. 1, the upper side is the [000-1] direction, that is, the direction in which the carbon plane (C plane, (000-1) plane) appears when cut perpendicular to the <0001> direction. An example in which the first direction is [1-100] will be described below.

Here, crystal orientations and planes are expressed using the following parentheses as Miller indices. ( ) and { } are used when representing faces. ( ) is used to express a specific plane, and { } is used to express a generic term (aggregate plane) of equivalent planes based on crystal symmetry. On the other hand , <> and [ ] are used to indicate direction. [ ] is used to express a specific direction, and <> is used to express an equivalent direction due to crystal symmetry.

As shown in FIG. 1, the SiC single crystal 1 is a single crystal in which a plurality of atoms A are aligned. Therefore, as shown in FIG. 1, when microscopically looking at the cut surface of the SiC single crystal, an atomic arrangement plane 2 in which a plurality of atoms A are arranged is formed. The atomic arrangement plane 2 on the cutting plane is expressed as a line extending in a direction substantially parallel to the cutting direction obtained by connecting the atoms A arranged along the cutting plane.

The shape of the atomic arrangement plane 2 does not depend on the shape of the outermost surface of the SiC single crystal 1, but may vary depending on the direction of the cut surface. 2 and 3 are diagrams schematically showing the shape of the atomic arrangement plane 2. FIG. The atomic arrangement plane 2 shown in FIG. 2 is concave toward the center. Therefore, in the atomic arrangement plane 2 shown in FIG. 2, the [1-100] direction and the [11-20] direction perpendicular to the [1-100] direction are curved in the same direction. On the other hand, the atomic array plane 2 shown in FIG. 3 has a potato chip shape (saddle shape), which is concave on a predetermined cross section and convex on a different cross section. Therefore, the atomic arrangement plane 2 shown in FIG. 3 has different bending directions in the [1-100] direction and in the [11-20] direction orthogonal to the [1-100] direction.

That is, in order to accurately grasp the shape of the atomic arrangement plane 2, the atomic arrangement plane of the SiC single crystal should be measured at least along two directions (first direction and second direction) that pass through the center in plan view and are orthogonal to each other. 2 shapes need to be measured. The crystal structure of the SiC single crystal 1 is hexagonal, and it is preferable to measure the shape of the atomic arrangement plane 2 along six directions symmetrical with respect to the center. By measuring the shape of the atomic arrangement plane 2 along six directions symmetrical with respect to the center, the shape of the atomic arrangement plane 2 can be obtained more precisely.

The shape of the atomic arrangement plane 2 can be measured by X-ray diffraction (XRD). The surface to be measured is determined according to the direction of measurement. Assuming that the measurement direction is [hkil], the measurement surface must satisfy the relationship (mh mk min). Here, m is an integer greater than or equal to 0, and n is a natural number. For example, when measuring in the [11-20] direction, the (0004) plane is selected with m=0 and n=4, and the (22-416) plane with m=2 and n=16. On the other hand, when measuring in the [1-100] direction, the (0004) plane is selected with m=0 and n=4, and the (3-3016) plane with m=3 and n=16. That is, the measurement plane may be a different plane depending on the measurement direction, and the atomic arrangement plane 2 to be measured does not necessarily have to be the same plane. By satisfying the above relationship, it is possible to prevent the lattice curvature in the a-plane or m-plane direction, which has little effect on crystal growth, from being mistaken for the lattice curvature in the c-plane direction. The measurement may be performed on either the C surface or the Si surface, but it is preferable to perform the measurement on the attachment surface (first surface) that is attached to the installation surface of the crucible.

X-ray diffraction data are acquired at five points along a given direction: the center, the edge, and the midpoint between the center and the edge. If the atomic arrangement plane 2 is curved, the X-ray reflection direction changes, so the ω angle position of the peak of the output X-ray diffraction image varies between the center and other portions. The bending direction of the atomic arrangement plane 2 can be determined from the positional variation of the diffraction peak. Also, the radius of curvature of the atomic array surface 2 can be obtained from the positional variation of the diffraction peak, and the amount of curvature of the atomic array surface 2 can also be obtained. Then, the shape of the atomic arrangement plane 2 can be obtained from the bending direction and the amount of bending of the atomic arrangement plane 2 .

(Specific explanation of the method for measuring the shape of the atomic arrangement plane (Method 1))
A method for measuring the bending direction and bending amount of the atomic arrangement surface from the XRD measurement value of the outer peripheral end portion of a sample obtained by slicing a SiC single crystal (hereinafter referred to as a wafer 20) will be described in detail. The measurement method will be described using the wafer 20 as an example, but the same method can be used to measure an ingot-shaped SiC single crystal before slicing.

FIG. 4 schematically shows a cross section cut along the direction of measurement of the atomic arrangement plane, eg, the [1-100] direction, passing through the center in plan view. Assuming that the radius of the wafer 20 is r, the lateral length of the cross section is 2r. 4 also shows the shape of the atomic arrangement surface 22 in the wafer 20. As shown in FIG. As shown in FIG. 4, although the shape of the wafer 20 itself is flat, the atomic arrangement surface 22 may be curved. The atomic arrangement plane 22 shown in FIG. 4 is symmetrical and curved concavely. This symmetry results from the fact that manufacturing conditions for SiC single crystals (ingots) are generally symmetrical about the center. Note that this symmetry does not have to be perfect symmetry, but means symmetry as an approximation that allows fluctuations due to fluctuations in manufacturing conditions and the like.

Next, as shown in FIG. 5, XRD is performed on the outer peripheral edge of the wafer 20 to obtain the difference Δθ between the two measured X-ray diffraction peak angles. This .DELTA..theta. is the difference between the tilts of the atomic arrangement plane 22 at the two points measured. As for the diffraction surface used for the X-ray diffraction measurement, an appropriate surface is selected according to the cut surface as described above.

Next, as shown in FIG. 6, the radius of curvature of the curved atomic arrangement surface 22 is obtained from the obtained Δθ. FIG. 6 shows a circle C which is in contact with two measured atomic arrangement planes, assuming that the curved surface of the atomic arrangement plane 22 of the wafer 20 is a part of a circle. Geometrically from FIG. 6, the central angle φ of the sector containing the circular arc with both ends at the tangent point is equal to the measured X-ray diffraction peak angle difference Δθ. The radius of curvature of the atomic arrangement plane 22 corresponds to the radius R of the arc. The arc radius R is obtained by the following relational expression.

Then, from the radius R of this arc and the radius r of the wafer 20, the amount of curvature d of the atomic array surface 22 is obtained. As shown in FIG. 7, the amount of curvature d of the atomic array plane 22 corresponds to the radius of the arc minus the distance of the perpendicular from the center of the arc to the wafer 20 . The distance of the perpendicular from the center of the arc to the wafer 20 is calculated from the Pythagorean theorem, and the following equation holds. In this specification, the curvature amount d is defined as a positive value when the curvature radius is positive (concave surface), and the curvature amount d is defined as a negative value when the curvature radius is negative (convex surface).

As mentioned above, R can also be measured only from the XRD measurements of the outer edge of the wafer 20 . On the other hand, if this method is used, there is a possibility that the shape may be misunderstood when there is local distortion or the like at the measurement location. Therefore, the X-ray diffraction peak angle is measured at multiple points, and the curvature per unit length is converted from the following formula.

FIG. 8 shows an example in which the radius of curvature of the atomic arrangement surface is obtained from a plurality of XRD measurement points. The horizontal axis of FIG. 8 indicates the relative position from the wafer center, and the vertical axis indicates the diffraction peak angle of each measurement point relative to the wafer center diffraction peak angle. FIG. 8 shows an example in which the [1-100] direction of the wafer is measured and the measurement plane is (3-3016). Measurement was performed at five locations. The five points are arranged substantially on a straight line, and dθ/dr=8.69×10 ⁻⁴ deg/mm can be obtained from this slope. By applying this result to the above formula, it is possible to calculate a concave surface with a curvature radius of R=66 m. Then, from this R and the radius r (75 mm) of the wafer, the amount of curvature d of the atomic array plane is found to be 42.6 μm.

Although the example in which the shape of the atomic arrangement surface is concave has been described so far, the same is required for the convex surface. For convex surfaces, R is calculated as negative.

(Description of another method for measuring the shape of the atomic arrangement plane (Method 2))
The shape of the atomic arrangement plane may be obtained by another method. FIG. 9 schematically shows a cross section cut along the direction of measurement of the atomic arrangement plane, for example, the [1-100] direction, passing through the center in plan view. In FIG. 9, an example in which the shape of the atomic array plane 22 is concavely curved will be described.

As shown in FIG. 9, diffraction peaks of X-ray diffraction are measured at two locations, the center of the wafer 20 and the location separated from the center of the wafer 20 by a distance x. From the symmetry of the ingot manufacturing conditions, the shape of the wafer 20 can be approximately left-right symmetrical, and the atomic arrangement plane 22 can be assumed to be flat at the center of the wafer 20 . Therefore, assuming that the difference in inclination of the atomic arrangement plane 22 at two points measured as shown in FIG.

By performing measurements at a plurality of points while changing the position of the distance x from the center, it is possible to obtain the relative atomic positions of the atomic arrangement plane 22 between the wafer center and the measurement point at each point.
This method obtains the relative positions of atoms on the plane of atomic arrangement at each measurement point. Therefore, the curvature amount of the local atomic arrangement plane can be obtained. Moreover, the relative atomic positions of the atomic arrangement plane 22 in the entire wafer 20 can be shown as a graph, which is useful for intuitively grasping the arrangement of the atomic arrangement plane 22 .

Here, the case where the measurement object is the wafer 20 has been described as an example. When the object to be measured is a SiC ingot or a cut body cut from the SiC ingot, the amount of curvature of the atomic arrangement plane can be obtained in the same manner.

By the above-described procedure, the amount of curvature of the atomic arrangement plane 2 of the SiC single crystal is measured along at least two directions (first direction and second direction) that pass through the center in plan view and are orthogonal to each other. By obtaining the amount of curvature and the direction of curvature in each direction, the schematic shape of the atomic arrangement plane 2 as shown in FIGS. 2 and 3 can be obtained.

<Preparation process>
In the preparatory step, a pedestal on which the SiC single crystal is attached is prepared. FIG. 11 is a diagram showing the relationship between the SiC single crystal 1 and the pedestal 3. As shown in FIG. As shown in FIG. 11, pedestal 3 has a curved surface 3A that curves in a direction opposite to the curved direction of atomic arrangement plane 2 of SiC single crystal 1 . By attaching the SiC single crystal 1 to the pedestal 3 in the attachment step described later, the curvature of the atomic arrangement plane 2 can be eliminated and the atomic arrangement plane 2 can be flattened.

It is desirable that the amount of bending of the atomic plane arrangement of the SiC single crystal after the bonding step is zero. Therefore, the difference between the absolute value of the amount of curvature of the atomic arrangement surface 2 and the absolute value of the amount of curvature of the curved surface 3A of the pedestal 3 is preferably 10 μm or less at any point on the attachment surface. is most preferred. If the difference in the absolute value of the amount of curvature between the pedestal 3 and the atomic array surface 2 is small, the atomic array surface 2 can be made flatter after being attached. If the difference between the absolute value of the amount of curvature of the atomic arrangement plane 2 and the absolute value of the amount of curvature of the curved surface 3A of the pedestal 3 is not 0, the pedestal 3 should be adjusted so as not to apply excessive stress due to deformation to the SiC single crystal. It is preferable that the amount of curvature of the curved surface 3A is smaller than the absolute value of the amount of curvature of the atomic arrangement surface 2 . It is possible to reduce the risk of the SiC single crystal cracking due to excessive distortion of the SiC single crystal.

The curved surface 3A of the pedestal 3 may be processed after measuring the shape of the atomic arrangement surface 2 of the SiC single crystal 1, or a plurality of pedestals 3 with different bending directions and amounts of bending may be prepared in advance. , from which the most planarization of the atomic arrangement surface 2 after application may be selected.

Moreover, the thermal expansion coefficient of the pedestal 3 is preferably close to the thermal expansion coefficient of the SiC single crystal 1 . Specifically, the thermal expansion coefficient difference is preferably 0.3×10 ⁻⁶ /° C. or less. The thermal expansion coefficient used here means a thermal expansion coefficient in a temperature range in which crystals grow using the SiC single crystal 1 as a seed crystal, and means a temperature in the vicinity of 2000.degree. For example, the coefficient of thermal expansion of graphite can be selected within the range of 4.3×10 ⁻⁶ /° C. to 7.1×10 ⁻⁶ /° C. depending on processing conditions, materials contained, and the like. Since the thermal expansion coefficient difference between the pedestal 3 and the SiC single crystal 1 is close, it is possible to prevent the SiC single crystal 1 from warping and the atomic arrangement surface 2 from being curved due to the thermal expansion coefficient difference during crystal growth.

<Affixing process>
In the attaching step, the SiC single crystal 1 and the pedestal 3 are opposed to each other so that the curved direction of the atomic arrangement surface 2 and the curved direction of the curved surface 3A of the pedestal 3 are different from each other. FIG. 12 is a diagram schematically showing the state after the SiC single crystal 1 has been attached to the pedestal 3. As shown in FIG.

As shown in FIGS. 11 and 12, when the SiC single crystal 1 is attached to the pedestal 3 so that the curved direction of the atomic arrangement surface 2 and the curved direction of the curved surface 3A of the pedestal 3 are opposite to each other, the SiC single crystal The atomic array surface 2 of the crystal 1 is flattened compared to before the attachment.

It is preferable that the thickness of the SiC single crystal 1 is 5 mm or less when performing the attaching step. If the thickness of the SiC single crystal 10 is large, it is difficult for the SiC single crystal 10 to bend during attachment. As a result, it becomes difficult to stick the SiC single crystal in close contact with the pedestal, and it becomes difficult to evenly arrange the atomic arrangement plane (lattice plane) of the SiC single crystal after the sticking process.

Moreover, in the attaching step, it is preferable to change the load for pressing SiC single crystal 1 against curved surface 3A of pedestal 3 according to the relative distance of atomic arrangement surface 2 from curved surface 3A of pedestal 3 . For example, when the atomic arrangement surface 2 of the SiC single crystal 1 curves convexly toward the pedestal 3 and the distance between the atomic arrangement surface 2 and the curved surface 3A of the pedestal 3 increases toward the outer circumference, the SiC single crystal 1 It is preferable to make the load on the outer peripheral side stronger than that on the inner side. Further, when the atomic arrangement surface 2 of the SiC single crystal 1 curves concavely toward the pedestal 3 and the distance between the atomic arrangement surface 2 and the curved surface 3A of the pedestal 3 increases toward the inside, the inside of the SiC single crystal 1 It is preferable to make the load on the outer peripheral side stronger than that on the outer peripheral side.

Moreover, the sticking process is performed using an adhesive agent, for example. A thermosetting resin or the like can be used as the adhesive.

Further, after the attaching step, a decompression step of decompressing the surroundings of SiC single crystal 1 may be further performed. Even if air bubbles or the like are caught in the adhesive surface, they can be removed by creating a reduced pressure environment. As a result, thickness unevenness of the adhesive during application can be further suppressed.

Moreover, the radius of curvature of the atomic array surface 2 of the SiC single crystal 1 leading to the bonding step is preferably 28 m or more. The larger the curvature radius, the flatter the atomic arrangement plane 2 becomes. Further, when the diameter of the SiC single crystal is 150 mm or more, the maximum amount of curvature of the atomic arrangement plane is preferably 100 μm or less. If the amount of curvature of atomic arrangement surface 2 is large, SiC single crystal 1 needs to be largely distorted in the direction opposite to the bending direction of atomic arrangement surface 2 in order to flatten atomic arrangement surface 2 . By keeping the strain amount of SiC single crystal 1 within a predetermined range, cracks in SiC single crystal 1 and accumulation of stress in SiC single crystal 1 can be suppressed.

As described above, according to the SiC single crystal bonding method according to the present embodiment, the curvature of the atomic arrangement plane 2 can be reduced.

"Manufacturing method of SiC ingot"
In the SiC ingot manufacturing method according to the present embodiment, crystal growth is performed using the SiC single crystal 1 attached to the pedestal 3 as a seed crystal in the SiC single crystal bonding method described above. A SiC ingot can be manufactured, for example, using a sublimation method. The sublimation method is a method of recrystallizing a raw material gas generated by heating a raw material on a single crystal (seed crystal) to obtain a large single crystal (ingot).

FIG. 13 is a schematic diagram of an example of a manufacturing apparatus used for the sublimation method. Manufacturing apparatus 200 has crucible 100 and coil 101 . Between the crucible 100 and the coil 101, a heating element (not shown) that generates heat by induction heating of the coil 101 may be provided.

The crucible 100 has a pedestal 3 provided at a position facing the raw material G. As shown in FIG. SiC single crystal 1 is attached to pedestal 3 according to the above bonding method. Further, inside the crucible 100, a taper guide 102 that expands in diameter from the pedestal 3 toward the raw material G is provided.

When an alternating current is applied to the coil 101, the crucible 100 is heated, and the raw material G is produced as a raw material gas. The generated raw material gas is supplied to SiC single crystal 1 placed on pedestal 3 along taper guide 102 . By supplying the raw material gas to the SiC single crystal 1 , the SiC ingot I is crystal-grown on the main surface of the SiC single crystal 1 . The crystal growth surface of the SiC single crystal 1 is preferably a carbon surface or a surface with an off angle of 10° or less from the carbon surface.

SiC ingot I inherits most of the crystal information of SiC single crystal 1 . Since the atomic arrangement surface 2 of the SiC single crystal 10 is flattened, the occurrence of BPD in the SiC ingot I can be suppressed.

FIG. 14 is a graph showing the relationship between the radius of curvature of the SiC single crystal atomic arrangement surface and the BPD density. As shown in FIG. 14, the radius of curvature of the atomic array surface 2 and the BPD density in the SiC ingot I have a corresponding relationship. The BPD density tends to decrease as the radius of curvature of the atomic arrangement plane 2 increases (the amount of curvature of the atomic arrangement plane 2 decreases). It is thought that a crystal with residual stress inside induces a slip of the crystal plane and bends the atomic arrangement plane 2 along with the occurrence of BPD. Alternatively, conversely, it is conceivable that the atomic arrangement plane 2 having a large amount of curvature has strain and causes BPD. In any case, the larger the radius of curvature of the atomic arrangement plane (that is, the smaller the amount of curvature of the atomic arrangement plane), the smaller the BPD density.

As described above, in the SiC ingot manufacturing method according to the present embodiment, since the atomic arrangement surface 2 of the SiC single crystal 1 used as the seed crystal is planarized, the occurrence of BPD in the SiC ingot I is suppressed. It is Therefore, a good quality SiC ingot I with a low BPD density is obtained.

Finally, the obtained SiC ingot I is sliced to produce SiC wafers. The cutting direction is perpendicular to <0001> or in a direction with an off angle of 0 to 10° to produce a wafer with a plane parallel to the C plane or at an off angle of 0 to 10° from the C plane. do. The surface of the wafer may be mirror-finished on the (0001) plane side, that is, the Si plane side. The Si face is the face on which epitaxial growth is normally performed. Since the SiC ingot I has less BPD, a SiC wafer with less BPD can be obtained. By using a SiC wafer with less BPD, which is a killer defect, a high-quality SiC epitaxial wafer can be obtained, and the yield of SiC devices can be increased.

Moreover, when the crucible 100 is heated to sublimate the raw material G, it is preferable to rotate the crucible 100 so that anisotropy in the circumferential direction does not occur. The rotation speed is preferably 0.1 rpm or higher. Also, it is preferable to reduce the temperature change on the growth surface during growth.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to specific embodiments, and various can be transformed or changed.

1 SiC single crystal 2, 22 atomic arrangement surface 20 wafer 3 pedestal 3A curved surface 100 crucible 101 coil 102 taper guide 200 manufacturing apparatus A atom I SiC ingot G raw material

Claims (10)

a measuring step of measuring the amount of curvature and the direction of curvature of an atomic arrangement plane of a SiC single crystal along at least a first direction passing through the center in plan view and a second direction orthogonal to the first direction;
a preparation step of preparing a pedestal having a curved surface curved in a direction opposite to the atomic arrangement surface of the SiC single crystal;
and a bonding step of bonding the SiC single crystal and the pedestal so that the direction of curvature of the atomic arrangement surface and the direction of curvature of the curved surface are different from each other. The SiC according to claim 1, wherein a difference between an absolute value of the amount of curvature of the atomic arrangement plane and an absolute value of the amount of curvature of the curved surface of the base is 10 µm or less at any point on the attachment surface. Single crystal lamination method. 3. The method of bonding SiC single crystals according to claim 1, wherein the radius of curvature of said atomic arrangement plane is 28 m or more. 4. The method for bonding SiC single crystals according to claim 1, wherein the maximum amount of curvature of the atomic arrangement plane is 100 μm or less when the SiC single crystal has a diameter of 150 mm or more. The SiC single crystal bonding method according to any one of claims 1 to 4, wherein the SiC single crystal has a thickness of 5 mm or less when performing the bonding step. 6. The method for manufacturing a SiC ingot according to claim 1, wherein said SiC single crystal bonded to said pedestal is used as a seed crystal for crystal growth. 7. The method for producing an SiC ingot according to claim 6, wherein a difference in thermal expansion coefficient between said pedestal and said SiC single crystal at a crystal growth temperature is 0.3×10 ⁻⁶ /° C. or less. A pedestal for adhering the SiC single crystal to which the atomic arrangement plane of the SiC single crystal is curved in a concave direction when the adhering surface of the SiC single crystal to be adhered faces downward, the pedestal being curved in a convex shape. A pedestal for SiC single crystal growth, comprising a curved surface that A pedestal for adhering the SiC single crystal to which the atomic arrangement plane of the SiC single crystal is curved in a convex direction when the adhering surface of the SiC single crystal to be adhered faces downward, the pedestal being curved concavely. A pedestal for SiC single crystal growth, comprising a curved surface that 10. The difference between the absolute value of the amount of curvature of the atomic arrangement surface of the SiC single crystal to be attached and the absolute value of the amount of curvature of the curved surface is 10 μm or less at any point on the attached surface. The pedestal for SiC single crystal growth according to .

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