JP2020026374A - PASTING METHOD OF SiC SINGLE CRYSTAL, MANUFACTURING METHOD OF SiC INGOT, AND PEDESTAL FOR SiC SINGLE CRYSTAL GROWTH - Google Patents

Abstract

To provide a pasting method of a SiC single crystal capable of reducing curvature on an atomic arrangement plane during growth of the crystal.SOLUTION: A pasting method of a SiC single crystal includes a measurement step for measuring a curvature amount and a curvature direction of an atomic arrangement plane of the SiC single crystal along at least a first direction passing through a plane view center, and a second direction orthogonal to the first direction, a preparation step for preparing a pedestal having a curved plane curved in a reverse direction to the atomic arrangement plane of the SiC single crystal, and a pasting step for opposing and pasting the SiC single crystal to the pedestal so that the curvature direction of the atomic arrangement plane is differentiated from a curvature direction of the curved plane.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for bonding a SiC single crystal, a method for manufacturing a SiC ingot, and a pedestal for growing a SiC single crystal.

  Silicon carbide (SiC) has a breakdown electric field one order of magnitude higher than silicon (Si) and a band gap three times larger. Further, silicon carbide (SiC) has characteristics such as a thermal conductivity that is about three times higher than 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.

  For devices such as semiconductors, an SiC epitaxial wafer having an epitaxial film formed on a SiC wafer is used. An epitaxial film provided on a SiC wafer by a chemical vapor deposition (CVD) becomes an active region of the 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 the warp and undulation of the outer shape of a SiC single crystal used as a seed crystal cause cracks and defects. Patent Document 1 describes that by setting the linear expansion coefficient of the SiC single crystal and the pedestal within a predetermined range, the warpage of the wafer is reduced. Patent Literature 2 discloses that the stress applied to a SiC single crystal during growth can be reduced by making the coefficient of thermal expansion of a seed crystal holding portion smaller than that of other portions of the crucible.

Japanese Patent No. 5398492 JP 2009-102187 A

  As one of the killer defects of the SiC wafer, there is a basal plane dislocation (BPD). Part of the BPD of the SiC wafer is also carried over to the SiC epitaxial wafer, which causes a decrease in the forward characteristics when a current flows in the forward direction of the device. BPD is a defect that is considered to be one of the causes of the occurrence of slip at the basal plane.

  As described in Patent Literatures 1 and 2, BPD cannot be sufficiently suppressed even when controlling the warpage of a SiC single crystal used as a seed crystal during crystal growth. Therefore, reduction of BPD is required.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a method of bonding an SiC single crystal that can reduce the curvature of an atomic arrangement surface during crystal growth.

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

(1) In the method for bonding a SiC single crystal according to the first aspect, the bending amount and the bending direction of the atomic arrangement surface of the SiC single crystal are orthogonal to the first direction passing at least through the center in plan view and the first direction. A measurement step of measuring along a second direction, a preparing step of preparing a pedestal having a curved surface curved in a direction opposite to an atomic arrangement surface of the SiC single crystal, and a bending direction of the atomic arrangement surface and the curvature. And attaching the SiC single crystal and the pedestal to each other so that the direction of curvature of the surface is different.

(2) In the method for bonding a SiC single crystal according to the above aspect, the difference between the absolute value of the amount of curvature of the atomic arrangement surface and the absolute value of the amount of curvature of the curved surface of the pedestal may be any one of the attachment surfaces. May be 10 μm or less.

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

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

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

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

(7) In the method of manufacturing an SiC ingot according to the above aspect, a difference in a 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 pedestal for growing a SiC single crystal according to the third aspect includes a curved surface that is curved in a direction opposite to a direction of curvature of an atomic arrangement surface of the SiC single crystal to be bonded.

(9) In the pedestal for growing a SiC single crystal according to the above aspect, the difference between the absolute value of the amount of curvature of the atomically arranged surface of the SiC single crystal to be attached and the absolute value of the amount of curvature of the curved surface is different from that of the attachment surface. The thickness may be 10 μm or less at any point.

  When the bonding method of the SiC single crystal according to the above embodiment is used, it is possible to flatten an atomic arrangement surface during crystal growth.

FIG. 3 is a schematic view of a cut surface obtained by cutting a SiC single crystal along a straight line extending in a first direction passing through the center in plan view. It is the figure which showed typically an example of the atomic arrangement surface of a SiC single crystal. FIG. 4 is a diagram schematically showing another example of the atomic arrangement plane of the SiC single crystal. FIG. 3 is a diagram for specifically explaining a method for measuring the shape of an atomic arrangement surface. FIG. 3 is a diagram for specifically explaining a method for measuring the shape of an atomic arrangement surface. FIG. 3 is a diagram for specifically explaining a method for measuring the shape of an atomic arrangement surface. FIG. 3 is a diagram for specifically explaining a method for measuring the shape of an atomic arrangement surface. An example in which a radius of curvature of an atomic arrangement surface is obtained from a plurality of XRD measurement points will be described. FIG. 9 is a diagram for specifically explaining another example of the method of measuring the shape of the atomic arrangement plane. FIG. 9 is a diagram for specifically explaining another example of the method of measuring the shape of the atomic arrangement plane. It is a figure which shows the relationship between a SiC single crystal and a pedestal. It is the figure which showed typically the state after sticking a SiC single crystal to a pedestal. It is a schematic diagram of an example of the manufacturing apparatus used for the sublimation method. 4 is a graph showing a relationship between a radius of curvature of an atomic arrangement surface of a SiC single crystal and a BPD density.

  Hereinafter, the present embodiment will be described in detail with reference to the drawings as appropriate. In the drawings used in the following description, a characteristic portion may be enlarged for convenience, and a dimensional ratio of each component may be different from an actual one. The materials, dimensions, and the like illustrated in the following description are merely examples, and the present invention is not limited thereto, and can be implemented with appropriate changes without departing from the scope of the invention.

"SiC single crystal bonding method"
The method for bonding a SiC single crystal according to the present embodiment includes a measurement step, a preparation step, and a bonding step. In the measurement 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. Further, in the attaching step, the SiC single crystal and the pedestal are attached to each other such that the curved direction of the atomic arrangement surface and the curved surface of the pedestal are different from each other. Hereinafter, each step will be specifically described.

<Measurement process>
FIG. 1 is a schematic view of a cut surface obtained by cutting the SiC single crystal 1 along a straight line extending in a first direction passing through the center in plan view. An arbitrary 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 direction in which the carbon plane (C plane, (000-1) plane) appears when cut perpendicularly to the [000-1] direction, that is, the <0001> direction. Hereinafter, a case where the first direction is set to [1-100] will be described as an example.

  Here, the crystal orientation and the plane are indicated using the following parentheses as Miller indices. () And ｛｝ are used to represent a surface. () Is used to represent a specific plane, and ｛｝ is used to represent a generic term (collective plane) of equivalent planes due to crystal symmetry. On the other hand, <> and [] are particularly used to indicate directions. [] Is used to represent a specific direction, and <> is used to represent 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 the cut surface of the SiC single crystal is viewed microscopically, an atomic arrangement surface 2 in which a plurality of atoms A are arranged is formed. The atom arrangement surface 2 in the cutting plane is represented 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 may vary depending on the direction of the cut surface, regardless of the shape of the outermost surface of the SiC single crystal 1. 2 and 3 are diagrams schematically showing the shape of the atomic arrangement plane 2. FIG. The atomic arrangement surface 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 orthogonal to the [1-100] direction have the same bending direction. On the other hand, the atom arrangement surface 2 shown in FIG. 3 has a potato chip type (saddle type) shape having a concave shape on a predetermined cut surface and a convex shape on a different cut surface. Therefore, the bending direction of the atomic arrangement surface 2 shown in FIG. 3 differs between the [1-100] direction and the [11-20] direction orthogonal to the [1-100] direction.

  In other words, in order to accurately grasp the shape of the atomic arrangement plane 2, the atomic arrangement plane of the SiC single crystal must be formed along at least two directions (first direction and second direction) passing through the center in plan view and orthogonal to each other. 2 needs to be measured. The crystal structure of SiC single crystal 1 is hexagonal, and it is preferable to measure the shape of atomic arrangement plane 2 along six directions symmetric with respect to the center. If the shape of the atomic arrangement surface 2 is measured along six directions symmetrical with respect to the center, the shape of the atomic arrangement surface 2 can be determined more precisely.

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

  The X-ray diffraction data is acquired at five points along the predetermined direction: the center, the end, and the midpoint between the center and the end. When the atomic arrangement surface 2 is curved, the reflection direction of the X-ray changes, so that the position of the ω angle of the peak of the X-ray diffraction image output at the center and other portions changes. The bending direction of the atomic arrangement surface 2 can be obtained from the position fluctuation of the diffraction peak. Further, the radius of curvature of the atomic arrangement surface 2 can be obtained from the position fluctuation of the diffraction peak, and the amount of curvature of the atomic arrangement surface 2 can also be obtained. Then, the shape of the atomic arrangement surface 2 can be obtained from the bending direction and the amount of curvature of the atomic arrangement surface 2.

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

  FIG. 4 schematically shows a cut surface cut along a direction of measurement of the atomic arrangement plane, for example, along the [1-100] direction, passing through the center in plan view. Assuming that the radius of the wafer 20 is r, the horizontal length of the cross section is 2r. FIG. 4 also shows the shape of the atomic arrangement plane 22 on the wafer 20. As shown in FIG. 4, the shape of the wafer 20 itself is flat, but the atomic arrangement surface 22 may be curved. The atom arrangement surface 22 shown in FIG. 4 is bilaterally symmetric and concavely curved. This symmetry is due to the fact that the manufacturing conditions of the SiC single crystal (ingot) are usually symmetric with respect to the center. The symmetry does not need to be perfect symmetry, but means symmetry as an approximation that allows blurring caused by fluctuations in manufacturing conditions and the like.

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

  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 circles C that are 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. From FIG. 6, geometrically, the center angle φ of the sector including the arc having the contact at both ends becomes equal to the difference Δθ between the measured X-ray diffraction peak angles. The radius of curvature of the atomic arrangement surface 22 corresponds to the radius R of the arc. The radius R of the arc is obtained by the following relational expression.

  Then, from the radius R of the arc and the radius r of the wafer 20, the amount of curvature d of the atomic arrangement surface 22 is obtained. As shown in FIG. 7, the amount of curvature d of the atomic arrangement surface 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 three-square theorem, and the following equation holds. In this specification, the curvature d when the radius of curvature is positive (concave surface) is defined as a positive value, and the curvature d when the radius of curvature is negative (convex) is defined as a negative value.

  As described above, R can be measured only from the measured value of the outer peripheral edge of the XRD wafer 20. On the other hand, when this method is used, there is a possibility that the shape may be mistaken when local distortion or the like exists at the measurement location. Therefore, the X-ray diffraction peak angles are measured at a plurality of locations, and the curvature per unit length is converted from the following equation.

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 in FIG. 8 is the relative position from the wafer center, and the vertical axis is the relative diffraction peak angle of each measurement point with respect to the wafer center diffraction peak angle. FIG. 8 shows an example in which the wafer is measured in the [1-100] direction and the measurement surface is set to (3-3016). The measurement was performed at five places. The five points are substantially arranged in a straight line, and dθ / dr = 8.69 × 10 ⁻⁴ deg / mm is obtained from the inclination. By applying the result to the above equation, it can be calculated that the concave surface has a radius of curvature R = 66 m. Then, from this R and the radius r (75 mm) of the wafer, the amount of curvature d of the atomic arrangement surface is determined to be 42.6 μm.

  So far, an example has been described in which the shape of the atomic arrangement surface is a concave surface. In the case of a convex surface, R is calculated as minus.

(Explanation of another measurement method (method 2) of the shape of the atomic arrangement plane)
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, along the [1-100] direction, passing through the center in plan view. FIG. 9 illustrates an example in which the shape of the atomic arrangement surface 22 is concavely curved.

  As shown in FIG. 9, the diffraction peaks of the X-ray diffraction are measured at two places, that is, at the center of the wafer 20 and at a distance x from the center of the wafer 20. From the symmetry of the manufacturing conditions of the ingot, it is possible to assume that the shape of the wafer 20 is bilaterally symmetric as an approximation, and that the atomic arrangement surface 22 is flat at the center of the wafer 20. Therefore, assuming that the difference between the inclinations of the atomic arrangement surface 22 at two points measured as shown in FIG. 10 is Δθ, the relative position y of the atomic arrangement surface 22 can be expressed by the following equation.

By changing the position of the distance x from the center and measuring a plurality of points, it is possible to obtain the relative atomic position of the atom arrangement surface 22 at the wafer center and the measurement point at each point.
In this method, the relative positions of the atoms on the atomic arrangement plane are obtained at each measurement point. Therefore, the amount of local curvature of the atomic arrangement plane can be obtained. Further, the relative atomic positions of the atomic arrangement surface 22 in the entire wafer 20 can be shown as a graph, which is useful for intuitively grasping the arrangement of the atomic arrangement surface 22.

  Here, the case where the measurement target is the wafer 20 has been described as an example. In the case where the measurement target is a SiC ingot or a cut body cut from the SiC ingot, the amount of curvature of the atomic arrangement surface can be similarly obtained.

  In the above procedure, the amount of curvature of the atomic arrangement surface 2 of the SiC single crystal is measured in at least two directions (first direction and second direction) passing through the center in plan view and orthogonal to each other. The approximate shape of the atomic arrangement plane 2 as shown in FIGS. 2 and 3 can be obtained by obtaining the amount of bending and the bending direction in each direction.

<Preparation process>
In the preparation step, a pedestal on which the SiC single crystal is to be 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. 11, the pedestal 3 has a curved surface 3A that is curved in a direction opposite to the direction of curvature of the atomic arrangement surface 2 of the SiC single crystal 1. By sticking the SiC single crystal 1 to the pedestal 3 in the sticking step described later, the curvature of the atomic arrangement surface 2 can be eliminated and the atomic arrangement surface 2 can be flattened.

  It is desirable that the amount of curvature of the atomic plane arrangement of the SiC single crystal after performing the attaching 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 absolute value difference of the amount of curvature between the pedestal 3 and the atomic arrangement surface 2 is small, the atomic arrangement surface 2 after pasting can be made flatter. When 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 not zero, the pedestal 3 is not subjected to excessive stress due to deformation to the SiC single crystal. Is preferably smaller than the absolute value of the amount of curvature of the atomic arrangement surface 2. The risk of breaking the SiC single crystal by excessively distorting the SiC single crystal can be reduced.

  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 having different bending directions and bending amounts are prepared in advance. Alternatively, one of them may be selected that can flatten the atomic arrangement surface 2 after being attached.

Further, the thermal expansion coefficient of pedestal 3 is preferably close to the thermal expansion coefficient of SiC single crystal 1. Specifically, the difference in thermal expansion coefficient is preferably 0.3 × 10 ⁻⁶ / ° C. or less. The coefficient of thermal expansion shown here means a coefficient of thermal expansion in a temperature region where a crystal is grown using the SiC single crystal 1 as a seed crystal, and means a temperature near 2000 ° C. For example, the thermal expansion coefficient of the graphite, the processing conditions, the inclusion material and the like, can be selected in the range of ^{4.3 × 10 -6 /℃~7.1×10 -6 / ℃} . Since the difference in thermal expansion coefficient between the pedestal 3 and the SiC single crystal 1 is close, it is possible to prevent the SiC single crystal 1 from warping due to the difference in thermal expansion coefficient during crystal growth, and prevent the atomic arrangement plane 2 from being curved.

<Paste process>
In the attaching step, the SiC single crystal 1 and the pedestal 3 are attached so as to face each other such 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. FIG. 12 is a diagram schematically illustrating a state after the SiC single crystal 1 is attached to the pedestal 3.

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

  The thickness of the SiC single crystal 1 at the time of performing the attaching step is preferably 5 mm or less. If the thickness of the SiC single crystal 10 is large, bending is less likely to occur during sticking. For this reason, it is difficult to attach the SiC single crystal in close contact with the pedestal, and it becomes difficult to arrange the atomic arrangement plane (lattice plane) of the SiC single crystal after the attaching step flat.

  In the attaching step, it is preferable that the load pressing the SiC single crystal 1 against the curved surface 3A of the pedestal 3 is changed according to the relative distance of the atomic arrangement surface 2 to the curved surface 3A of the pedestal 3. For example, when the atomic arrangement surface 2 of the SiC single crystal 1 is convexly curved 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 periphery, the SiC single crystal 1 It is preferable to make the load on the outer peripheral side stronger than that on the inner side. When the atomic arrangement surface 2 of the SiC single crystal 1 is concavely curved 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 that the load on the outer peripheral side be higher than that on the outer peripheral side.

  The attaching step is performed using, for example, an adhesive. As the adhesive, a thermosetting resin or the like can be used.

  After the attaching step, a pressure reducing step of reducing the pressure around the SiC single crystal 1 may be further performed. Even when air bubbles or the like are caught in the bonding surface, degassing can be performed by setting a reduced pressure environment. As a result, thickness unevenness of the adhesive at the time of application can be further suppressed.

  The radius of curvature of the atomic arrangement surface 2 of the SiC single crystal 1 leading to the attaching step is preferably 28 m or more. The larger the radius of curvature, the flatter the atomic arrangement surface 2 becomes. Further, when the diameter of the SiC single crystal is 150 mm or more, it is preferable that the maximum value of the amount of curvature of the atomic arrangement surface is 100 μm or less. If the amount of curvature of the atomic arrangement surface 2 is large, it is necessary to greatly deform the SiC single crystal 1 in the direction opposite to the curving direction of the atomic arrangement surface 2 in order to flatten the atomic arrangement surface 2. By setting the amount of strain of the SiC single crystal 1 within a predetermined range, it is possible to suppress the occurrence of cracks in the SiC single crystal 1 and the accumulation of stress in the SiC single crystal 1.

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

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

  FIG. 13 is a schematic view of an example of a manufacturing apparatus used for the sublimation method. The manufacturing apparatus 200 has a crucible 100 and a 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. SiC single crystal 1 is attached to pedestal 3 according to the above-described attaching method. Further, inside the crucible 100, there is provided a taper guide 102 whose diameter increases from the pedestal 3 toward the raw material G.

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

  SiC ingot I inherits much of the crystal information of SiC single crystal 1. Since the atomic arrangement surface 2 of the SiC single crystal 10 is flattened, generation 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 atomic arrangement plane of the SiC single crystal and the BPD density. As shown in FIG. 14, there is a correspondence between the radius of curvature of the atomic arrangement surface 2 and the BPD density in the SiC ingot I. The BPD density tends to decrease as the radius of curvature of the atomic arrangement surface 2 increases (the amount of curvature of the atomic arrangement surface 2 decreases). It is considered that the crystal in which the stress remains inside induces a slip of the crystal plane, and causes the atomic arrangement plane 2 to be curved with the occurrence of BPD. Alternatively, conversely, it is conceivable that the atomic arrangement surface 2 having a large amount of curvature has a strain and causes BPD. In either case, the BPD density decreases as the radius of curvature of the atomic arrangement surface increases (ie, the amount of curvature of the atomic arrangement surface decreases).

  As described above, in the method of manufacturing the SiC ingot according to the present embodiment, since the atomic arrangement surface 2 of the SiC single crystal 1 used as the seed crystal is flattened, the generation of BPD in the SiC ingot I is suppressed. Have been. Therefore, a high quality SiC ingot I having a low BPD density can be obtained.

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

  Further, when heating the crucible 100 and sublimating the raw material G, it is preferable to rotate the crucible 100 so that circumferential anisotropy does not occur. The rotation speed is preferably set to 0.1 rpm or more. Further, it is preferable to reduce the temperature change on the growth surface during growth.

  As described above, the preferred embodiments of the present invention have been described in detail, but the present invention is not limited to the specific embodiments, and various modifications may be made within the scope of the present invention described in the appended claims. Can be modified and changed.

DESCRIPTION OF SYMBOLS 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 Atomic I SiC ingot G Raw material

Claims (9)

A measurement step of measuring the amount and direction of curvature of the atomic arrangement plane of the 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 preparing step of preparing a pedestal having a curved surface curved in a direction opposite to an atomic arrangement surface of the SiC single crystal;
A bonding step of bonding the SiC single crystal and the pedestal so that the bending direction of the atomic arrangement surface is different from the bending direction of the curved surface, and bonding the SiC single crystal and the pedestal.     2. The SiC according to claim 1, wherein a difference between an absolute value of the amount of curvature of the atomic arrangement surface and an absolute value of the amount of curvature of the curved surface of the pedestal is 10 μm or less at any part of the attachment surface. Single crystal bonding method.   The bonding method of a SiC single crystal according to claim 1 or 2, wherein a radius of curvature of the atomic arrangement surface is 28 m or more.   The bonding method of the SiC single crystal according to any one of claims 1 to 3, wherein when the diameter of the SiC single crystal is 150 mm or more, the maximum value of the amount of curvature of the atomic arrangement surface is 100 µm or less.   The method for bonding a SiC single crystal according to any one of claims 1 to 4, wherein the thickness of the SiC single crystal when performing the bonding step is 5 mm or less.   The method for bonding an SiC single crystal according to any one of claims 1 to 5, wherein a crystal is grown using the SiC single crystal attached to the pedestal as a seed crystal. The method for producing an SiC ingot according to claim ⁶ , wherein a difference in thermal expansion coefficient between the pedestal and the SiC single crystal at a crystal growth temperature is 0.3 ^10-6 / C or less.   A SiC single crystal growth pedestal having a curved surface that is curved in a direction opposite to the direction of the atomic arrangement surface of the SiC single crystal to be attached.   9. 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 attachment surface. 10. Pedestal for growing SiC single crystal.

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