JP6037673B2 - SiC single crystal substrate and SiC epitaxial wafer evaluation method, SiC single crystal and SiC epitaxial wafer manufacturing method, and SiC single crystal - Google Patents

Description

  The present invention relates to a method for evaluating a SiC single crystal substrate and a SiC epitaxial wafer, a method for producing a SiC single crystal and a SiC epitaxial wafer, and a SiC single crystal and a SiC epitaxial wafer.

Silicon carbide (SiC) has excellent heat resistance, large breakdown voltage, wide energy band gap, and high thermal conductivity, so it has high power power devices, high-temperature semiconductor devices, Application to radiation semiconductor elements, high-frequency semiconductor elements, and the like is possible. Since silicon is approaching the limit of performance improvement from the physical property limit of the material itself, silicon carbide that can take a physical property limit larger than silicon has attracted attention. In recent years, power electronics technology using silicon carbide materials has been expected as an energy-saving technology to reduce energy loss during power conversion and to counter global warming issues.
Research and development of SiC single crystal growth technology has been vigorously advanced as the basic technology.

As a method for growing a SiC single crystal, a sublimation recrystallization method is widely used. In this method, for example, a seed crystal is attached to a graphite pedestal placed in a graphite crucible, and a silicon carbide raw material powder arranged on the bottom of the crucible is heated to 2000 ° C. or more to generate a sublimation gas, and the sublimation gas is used as a raw material. The SiC single crystal is grown on the seed crystal by recrystallization on the seed crystal that is lower by several tens to several hundreds of degrees C. than the part (for example, Patent Documents 1 to 3).
As another method, a method of manufacturing a SiC single crystal by reacting an evaporation gas from a silicon raw material with a carbon material (Patent Document 4) is also known.

The SiC device is formed on a SiC single crystal substrate obtained by processing from a SiC single crystal (bulk single crystal) manufactured by the method as described above, by chemical vapor deposition (CVD) or the like. In general, it is produced using a SiC epitaxial wafer on which a SiC epitaxial film serving as an active region is grown.
Although silicon carbide has many polymorphs (polytypes), practical SiC devices mainly use hexagonal 4H—SiC having high carrier mobility.

  It is known that a SiC single crystal has many crystal defects such as dislocations and stacking faults, and the crystal defects propagate to the epitaxial film. Therefore, it is important to evaluate crystal defects contained in the SiC single crystal.

An X-ray topography method (for example, Patent Document 5) is known as a method capable of nondestructively detecting crystal defects contained in an SiC single crystal. In the X-ray topography method, crystal defects in a single crystal are visualized using an X-ray diffraction phenomenon.
Since it is difficult to predict the dislocation distribution in the ingot, the SiC single crystal is not suitable for sampling inspection for inspecting only a part of the single crystal substrate (wafer), and 100% inspection is desirable. In this case, KOH etching which is a destructive inspection is not suitable. On the other hand, since the X-ray topography method can be inspected nondestructively, it is possible to inspect all the single crystal substrates (wafers).

It is known that SiC single crystals contain three types of dislocations (through screw dislocations, through edge dislocations, and basal plane dislocations) as linear crystal defects. Threading Sc
rew Dislocation (TSD) is a dislocation whose Burgers vector propagating in the c-axis direction is <0001> or twice that. Further, threading edge dislocation (TED) is a dislocation whose Burgers vector propagating in the c-axis direction is 1/3 <11-20>. Furthermore, basal plane dislocation (Basal Plane D
islocation: BPD) is a dislocation whose Burgers vector existing on the c-plane ((0001) plane) is 1/3 <11-20>.

The intensity I of the dislocation image of the X-ray topography is an inner product (g · b) of the diffraction vector (g) and the Burgers vector (b) (Patent Document 6). Therefore, theoretically, a dislocation image can be obtained when the diffraction vector and the Burgers vector have an angular relationship other than orthogonal, and the clearer the dislocation image is obtained, the closer the diffraction vector and Burgers vector are parallel. (See, for example, Patent Document 7).
If a clear dislocation image of the SiC single crystal substrate can be obtained by X-ray topography, the type of dislocation can be identified, and the dislocation density can be measured, only the high-quality SiC single crystal substrate having a low dislocation density can be selected. It becomes possible to manufacture a SiC epitaxial wafer. If dislocations in the SiC epitaxial wafer can be observed by X-ray topography (for example, dislocations at the interface between the substrate and the epitaxial film), only a high-quality SiC epitaxial wafer having a low dislocation density is selected, and an SiC device is selected. Can be manufactured.

In the SiC epitaxial wafer used in the SiC device, as the SiC single crystal on which the SiC epitaxial film is formed, one having an off angle of 10 ° or less in the <11-20> direction from the c-plane is used. Therefore, if a clear dislocation image is obtained, threading screw dislocations (TSD) and threading edge dislocations (TED) having a propagation direction substantially perpendicular to the wafer surface are substantially parallel to the wafer surface. Is observed as a circular image. In contrast, basal plane dislocations (BPD) having a propagation direction substantially parallel to the wafer surface are observed as a linear image.
In the reflected X-ray topography image, if a clear dislocation image that can be discriminated as an image having a different shape between the threading dislocation (threading screw dislocation and threading edge dislocation) and the basal plane dislocation is obtained, It is possible to obtain the dislocation density of each plane dislocation.

International Publication No. 2 00/39372 JP 2010-13296 A JP 2009-23880 A Japanese Patent No. 4199921 Japanese Patent No. 4679975 JP 2010-98262 A JP-A-5-203592

  However, conventionally, in X-ray topography, it has not been easy to obtain a high-resolution topography image so that the dislocation density can be measured. For example, in reflection X-ray topography, it was recognized that a basal plane dislocation (BPD) image could not be obtained unless a four-crystal collimator (monochromator) was used (paragraph [0051] of Patent Document 5). However, when a monochromator is used, the incident X-ray intensity is reduced to about 1/100, and it takes time to obtain an image, and anisotropy occurs in the resolution of the X-ray, thereby obtaining a clear image. There was a problem that it was difficult to get.

In addition, as a conventional X-ray source, when X-ray topography is used in a transmission method, the wavelength is short,
MoKα rays (0.71Å) with strong transmission power are used, and when used in the reflection method, CuKα rays (1.54Å) that have a long wavelength and do not penetrate deeply into crystals have been used (for example, patent documents). 5). That is, MoKα rays have been used to examine the crystal structure inside the sample, whereas CuKα rays have been used to examine the crystal structure on the surface of the sample.
As described above, the X-ray source has been conventionally divided into the transmission method and the reflection method for the MoKα ray and the CuKα ray, respectively.
Conventionally, in a SiC epitaxial wafer having a SiC epitaxial film with a film thickness of about 10 μm, observation of dislocations at the substrate-epitaxial film interface has been sufficient by reflection X-ray topography using CuKα rays.
However, in recent years, it has become possible to form a thick SiC epitaxial film by the progress of SiC epitaxial technology, and the penetration depth of CuKα rays from the sample surface is about 11 μm. Therefore, a thick SiC epitaxial film for high withstand voltage is used. There has been a problem that dislocations at the substrate-epitaxial film interface of a film (for example, a thickness of 30 μm (usually about 10 μm)) cannot be observed.

In such a situation, the present inventors tried to acquire a dislocation image using MoKα rays in reflection X-ray topography by removing the barrier of the X-ray source that has been conventionally divided between the transmission method and the reflection method. We conducted an intensive study. As a result, by using the {1 2 -3 L} plane (L is an integer) as the diffraction plane, the threading screw dislocation and the basal plane dislocation can be identified as images having different shapes without using a monochromator. It was found that a clear dislocation image can be obtained.
Here, when the reflection method is used, since the sample and the film must be arranged so as to be substantially parallel to each other, it is desirable that the diffraction angle is approximately 90 ° with respect to the sample surface. For this reason, it is necessary to use an asymmetric reflection surface having a different incident X-ray intrusion angle and diffraction beam exit angle as the diffraction surface. For example, in Patent Document 5, an asymmetric reflection surface (11-28) is used as a diffraction surface.
The present invention uses a {1 2 -3 L} plane (L is an integer) which is an asymmetric reflection surface.
Transmission X-ray topography is not effective for evaluating dislocation density. In transmission X-ray topography, dislocations that exist in deep positions that do not affect growth are also observed, making it difficult to measure the dislocation density that affects growth, and it is difficult to observe threading screw dislocations due to the diffraction plane. This is because the threading screw dislocation is likely to be counted off. In general, in the transmission method, when the thickness of the sample is 2 mm or more, the defect contrast becomes weak and cannot be used for evaluating a thick crystal.

  The present invention relates to a method for evaluating a SiC single crystal substrate and a SiC epitaxial wafer, which can evaluate the dislocation density of a SiC single crystal substrate and a SiC epitaxial wafer by reflection X-ray topography without using a monochromator, and an X-ray topography image It is intended to provide a method for producing a SiC epitaxial wafer using a SiC single crystal using a seed crystal in which a low dislocation density is confirmed by using an SiC and a SiC single crystal substrate in which a low dislocation density is confirmed by using an X-ray topography image And

  An object of the present invention is to provide a SiC single crystal having a low dislocation density.

The present invention provides the following means in order to solve the above problems.
(1) A method for evaluating dislocations in a SiC single crystal substrate by reflection X-ray topography,
An X-ray topography image of an SiC single crystal substrate is obtained using MoKα rays as an X-ray source and an asymmetric reflection surface as a diffraction surface, and the dislocation density of the SiC single crystal substrate is measured using the X-ray topography image. A method for evaluating a SiC single crystal substrate, comprising:
(2) A {1 2 -3 L} plane (L is an integer) is used as a diffraction plane (1)
The evaluation method of the SiC single crystal substrate of description.
(3) The SiC single crystal substrate according to (2), wherein a crystal polymorph of the SiC single crystal substrate is a 4H type, and the L is any one of 14, 15, 16, or 17. Evaluation method. (4) The crystal polymorph of the SiC single crystal substrate is a hexagonal or trigonal crystal other than the 4H type,
L is 14, 15, 16, and 17 is an index corrected by a ratio of c-axis length of unit cell (c-axis length of polymorphic crystal other than 4H) / (4H crystal c-axis length). (1) The method for evaluating a SiC single crystal substrate according to (2).
(5) A method for evaluating dislocations in a SiC epitaxial wafer in which a SiC epitaxial film is formed on a SiC single crystal substrate by reflection X-ray topography,
Using an MoKα ray as an X-ray source and an asymmetric reflecting surface as a diffraction surface, obtaining an X-ray topography image of the SiC epitaxial wafer, and measuring the dislocation density of the SiC epitaxial wafer using the X-ray topography image A method for evaluating a SiC epitaxial wafer.
(6) A {1 2 -3 L} plane (L is an integer) is used as a diffraction plane (5)
The evaluation method of the SiC epitaxial wafer of description.
(7) The crystal polymorph of the SiC epitaxial wafer is 4H type, and the L is 14, 1
5. The SiC epitaxial wafer evaluation method according to (6), wherein the evaluation method is any one of 5, 16, and 17.
(8) The crystal polymorph of the SiC epitaxial wafer is a hexagonal or trigonal crystal other than 4H type, and the index 14, 15, 16, 17 is a ratio of c-axis lengths of unit cell (polymorph other than 4H) (6) The method for evaluating an SiC epitaxial wafer according to (6), wherein an index corrected by c-axis length of crystal / (4H crystal c-axis length) is used.
(9) In a method for producing a SiC single crystal, a raw material gas is supplied onto a SiC seed crystal arranged in a crucible, and a SiC single crystal is grown on the SiC seed crystal.
Using a MoKα ray as the X-ray source and an asymmetric reflection surface as the diffraction surface, a reflection X-ray topography image of the SiC single crystal plate is obtained, and the dislocation density of the SiC single crystal plate is measured using the X-ray topography image And a SiC single crystal substrate having a dislocation density of a predetermined value or less is used as the SiC seed crystal.
(10) The SiC single crystal according to claim 9, wherein, as the predetermined value, a basal plane dislocation density is 1000 pieces / cm ² or less and a threading screw dislocation density is 500 pieces / cm ² or less. Method.
(11) A method for producing a SiC epitaxial wafer by supplying a silicon-containing gas and a carbon-containing gas on a SiC single crystal substrate to form a SiC epitaxial film,
Using a MoKα ray as the X-ray source and an asymmetric reflection surface as the diffraction surface, a reflection X-ray topography image of the SiC single crystal substrate is obtained, and the dislocation density of the SiC single crystal substrate is measured using the X-ray topography image And using a SiC single crystal substrate having a dislocation density of a predetermined value or less.
(12) The SiC epitaxial wafer according to (11), wherein the predetermined value is a basal plane dislocation density of 1000 / cm ² or less and a threading screw dislocation density of 500 / cm ² or less. Method.
(13) The basal plane dislocation density produced by the method for producing an SiC single crystal according to any one of (9) and (10) is 1000 / cm ² or less, and the threading screw dislocation density is 500 / SiC single crystal characterized by being ² cm ² or less.

According to the SiC single crystal substrate evaluation method or the SiC epitaxial wafer evaluation method of the present invention, the MoKα ray is used as the X-ray source, the asymmetric reflection surface is used as the diffraction surface, and the X-ray topography of the SiC single crystal substrate is used. Since the image is obtained and the dislocation density (area density) of the SiC single crystal substrate is measured using the X-ray topography image, the threading dislocations and the basal plane dislocations have different shapes without using a monochromator. A clear dislocation image that can be discriminated as an image of the above can be obtained, and the dislocation density of the SiC single crystal substrate can be measured using this dislocation image. Also, since the line width of MoKα line is about 1/2 that of CuKα line, the resolution is improved compared to the conventional reflection X-ray topography using CuKα line, and dislocation lines that could not be observed with CuKα line. Can be observed. In addition, since the monochromator is not used, the incident X-ray intensity remains at the generated intensity, so that a topographic image can be obtained in a shorter time than conventional reflection X-ray topography using a monochromator. Further, since the penetration depth of the MoKα ray from the sample surface is as deep as about 55 μm, dislocations (for example, SiC single crystals) existing deeper in the SiC single crystal substrate than in the case of using the conventional reflection X-ray topography. The dislocation near the interface can also be evaluated for a sample having an epitaxial film with a thickness of 10 μm or more on the crystal substrate. In addition, since a monochromator is not used, observation using X-rays with small anisotropy can be performed, and the relationship between the dislocation line direction and the X-ray incident direction as described in Patent Document 5 is considered. There is no need.

  According to the method for producing a SiC single crystal of the present invention, a reflection X-ray topography image of a SiC single crystal plate is obtained using MoKα rays as an X-ray source and an asymmetric reflection surface as a diffraction surface, and the X-ray topography Since the dislocation density of the SiC single crystal plate is measured using an image and the SiC single crystal plate having a dislocation density equal to or lower than a predetermined value is used as the SiC seed crystal, the dislocation is made using the SiC seed crystal having a low dislocation density. It is possible to produce a high-quality SiC single crystal with a small amount.

  According to the method for producing an SiC epitaxial wafer of the present invention, a reflection X-ray topography image of a SiC single crystal substrate is obtained using MoKα rays as an X-ray source and an asymmetric reflection surface as a diffraction surface, and the X-ray topography Since the dislocation density of the SiC single crystal substrate is measured using an image and the structure using the SiC single crystal substrate having a dislocation density equal to or lower than a predetermined value is adopted, high quality with few dislocations using the SiC single crystal substrate having a low dislocation density The epitaxial wafer can be manufactured.

(A) A reflection X-ray topography image of a 4H—SiC single crystal substrate obtained by using MoKα rays as an X-ray source and using a {1 2 −3 16} plane as an asymmetric reflection surface of a diffraction surface. (B) shows SiC obtained by using CuKα rays as the X-ray source and {1 1 −2 8} plane as the asymmetric reflection surface of the diffraction surface for the same location on the same SiC single crystal substrate as in (a). 2 shows a reflection X-ray topography image of a single crystal substrate. (A) It is the reflection X-ray topography image of the 4H-SiC epitaxial wafer obtained by using MoK (alpha) ray as an X-ray source and using {1 2 -3 16} surface as an asymmetrical reflective surface of a diffraction surface. (B) is the SiC epitaxial obtained by using CuKα rays as the X-ray source and {1 1 −2 8} plane as the asymmetric reflection surface of the diffraction surface for the same location of the same SiC epitaxial wafer as in (a). 2 shows a reflected X-ray topography image of a wafer. It is a cross-sectional schematic diagram which shows an example of the single crystal growth apparatus used with the manufacturing method of the SiC single crystal of this invention. It is a cross-sectional schematic diagram which shows an example of the film-forming apparatus of the SiC epitaxial wafer film | membrane used with the manufacturing method of the SiC epitaxial wafer of this invention.

  Hereinafter, a method for evaluating a SiC single crystal substrate to which the present invention is applied, a method for evaluating a SiC epitaxial wafer, a method for manufacturing a SiC single crystal, a method for manufacturing a SiC epitaxial wafer, and a SiC single crystal will be described with reference to the drawings. explain.

[Evaluation method of SiC single crystal substrate]
The method for evaluating a SiC single crystal substrate of the present invention is a method for evaluating dislocations of a SiC single crystal substrate by reflection X-ray topography, using MoKα rays as an X-ray source, using an asymmetric reflection surface as a diffraction surface, An X-ray topography image of the SiC single crystal substrate is obtained, and the dislocation density of the SiC single crystal substrate is measured using the X-ray topography image.

  The X-ray topography used in the method for evaluating a SiC single crystal substrate of the present invention is based on a reflection method, and the usable reflection X-ray topography apparatus is not particularly limited except that MoKα rays are used as an X-ray source.

As the asymmetric reflection surface used as the diffraction surface of the 4H—SiC crystal, it is preferable to use a {1 2 −3 L} plane (L is an integer). This is because the positional relationship between the sample and the film suitable for the reflective topograph is obtained by using this reflective surface. That is, in the reflection topograph, it is suitable to select a lattice plane that satisfies the diffraction condition at a low angle incidence with respect to the sample surface and has a diffraction angle (2θ) of nearly 90 degrees. In particular, it is preferable that L is any one of 14, 15, 16, or 17. This is because a high-intensity dislocation image can be obtained in the {1 2-3 L} plane.
When the crystal polymorph is other than 4H, such as 6H-SiC used as a blue LED substrate, the index L is (c-axis length of polymorphic crystal other than 4H) / (4H crystal c-axis length). If corrected, an appropriate index of the lattice plane can be obtained. For example, the index of 6H-SiC corresponding to (12-3 16) of 4H-SiC is (6H c-axis length 15.12 mm) / (4H crystal c-axis length 10.05 mm) x16 = 24 (12- (12-3 24) corresponding to 3 16) is obtained.
Similarly, in 15R, (15R c-axis length 37.70 mm) / (4H crystal c-axis length 10.05 mm) × 16 = 60, and (12-360) corresponding to (12-316) is obtained.

FIG. 1A shows a reflection X-ray topography apparatus for a SiC single crystal substrate using MoKα rays (0.71Å) as an X-ray source and {1 2 −3 16} plane as an asymmetric reflection surface of a diffraction surface. The reflection X-ray topography image obtained using this is shown. In addition, FIG. 1B shows the asymmetry of the diffraction plane using CuKα rays (1.54 mm) as the X-ray source as in the conventional method except that the monochromator is not used at the same place on the same SiC single crystal substrate. {1 1 -2 as reflection surface
8 shows a reflection X-ray topography image obtained using the 8} plane.

In the topography image shown in FIG. 1 (a), what is obtained as a circular image is confirmed to be a screw dislocation by a topography by radiation light. On the other hand, the same diffraction pattern as that of the synchrotron radiation topograph is obtained also in the reflection topography image by the Cu wavelength using a collimator, and the circular image is confirmed to be a screw dislocation. From the comparison with the reflection topographic image by Cu wavelength using this collimator, it is confirmed that the circular image observed at the Mo wavelength is also a threading screw dislocation. Moreover, what is obtained as a linear (string-like) image is a basal plane dislocation. Dislocation images can be clearly distinguished between circular and linear (string-like) images, and the dislocation density of threading screw dislocations and the dislocation density of basal plane dislocations can be measured.
In the case of this sample, the dislocation density of threading screw dislocations was 468 pieces / cm ² , and the dislocation density of basal plane dislocations was 92 pieces / cm ² .

  On the other hand, in the topographic image shown in FIG. 1B obtained by the conventional method, a dislocation image can hardly be observed. Therefore, the threading screw dislocation image and the basal plane dislocation image cannot be distinguished, and the dislocation density thereof cannot be measured.

[SiC epitaxial wafer evaluation method]
The SiC epitaxial wafer evaluation method of the present invention is a method for evaluating dislocations in a SiC epitaxial wafer in which a SiC epitaxial film is formed on a SiC single crystal substrate by reflection X-ray topography, and using MoKα rays as an X-ray source. The X-ray topography image of the SiC epitaxial wafer is obtained by using an asymmetric reflection surface as the diffraction surface, and the dislocation density of the SiC epitaxial wafer is measured using the X-ray topography image.

  In the method for evaluating an SiC epitaxial wafer according to the present invention, MoKα rays having a penetration depth of about 55 μm from the sample surface are used as an X-ray source. Therefore, information on interface dislocations can be obtained by a conventional method using CuKα rays. This is effective for a SiC epitaxial wafer having a thick SiC epitaxial film that could not be formed. Specifically, since the penetration depth of the CuKα ray from the sample surface is about 11 μm, for SiC epitaxial wafers having SiC epitaxial films thicker than this (for example, 15 μm or more, 20 μm or more, or 30 μm or more) It is effective.

  The X-ray topography used in the method for evaluating a SiC epitaxial wafer of the present invention is based on the reflection method, and the usable reflection X-ray topography apparatus is not particularly limited except that MoKα rays are used as an X-ray source.

It is preferable to use a {1 2 -3 L} plane (L is an integer) as the asymmetric reflecting surface used as the diffractive surface. This is because a high-intensity dislocation image can be obtained. In particular, it is preferable that L is any one of 14, 15, 16, or 17. This is because a higher intensity dislocation image can be obtained. Since these index planes have different incident angles, the penetration depth of X-rays is different as shown in Table 1. Using this, it is possible to analyze the crystallinity of the epi film in the depth direction. In addition, when analyzing the substrate-epi interface, the index plane can be selected according to the film thickness.

FIG. 2A shows a reflection X-ray topography apparatus for a SiC epitaxial wafer using MoKα rays (0.71Å) as an X-ray source and {1 2 −3 16} plane as an asymmetric reflection surface of the diffraction surface. The reflection X-ray topography image obtained by using is shown. The film thickness of the SiC epitaxial film was 30 μm.
FIG. 2 (b) shows an asymmetric reflection of a diffraction surface using CuKα rays (1.54 mm) as an X-ray source as in the conventional method except that a monochromator is not used at the same place on the same SiC epitaxial wafer. The reflection X-ray topography image obtained using {1 1 -2 8} plane as a plane is shown.

In the topography image shown in FIG. 2A, what is obtained as a circular image is a threading screw dislocation, and what is obtained as a linear (string-like) image is a basal plane dislocation. Dislocation images can be clearly distinguished between circular and linear (string-like) images, and the dislocation density of threading screw dislocations and the dislocation density of basal plane dislocations can be measured.
In the case of this sample, the dislocation density of threading screw dislocations was 324 / cm ² , and the dislocation density of basal plane dislocations was 60 / cm ² .

  On the other hand, in the topography image shown in FIG. 2B obtained by the conventional method, a dislocation image can hardly be observed. Therefore, the threading screw dislocation image and the basal plane dislocation image cannot be distinguished, and the dislocation density thereof cannot be measured.

[Method for producing SiC single crystal]
A method for producing a SiC single crystal according to the present invention is a method for producing a SiC single crystal in which a raw material gas is supplied onto a SiC seed crystal disposed in a crucible and a SiC single crystal is grown on the SiC seed crystal. Using a MoKα ray as a radiation source and an asymmetric reflecting surface as a diffraction surface, a reflection X-ray topography image of the SiC single crystal plate is obtained, and the dislocation density of the SiC single crystal plate is measured using the X-ray topography image. An SiC single crystal plate having a dislocation density of a predetermined value or less is used as the SiC seed crystal.

  The method for producing a SiC single crystal of the present invention can be applied to a method for producing a SiC single crystal using a sublimation recrystallization method, a CVD method, or other methods for growing a SiC single crystal using a SiC seed crystal. A case where the recrystallization method is used will be described as an example.

FIG. 3 is a schematic diagram of an example of a single crystal growth apparatus used in the method for producing a SiC single crystal of the present invention.
The single crystal growth apparatus 100 is generally configured by disposing a crucible 3 covered with a heat insulating material 2 inside a vacuum vessel 1, and has a lid 3 a of a crucible 3 composed of a lid 3 a and a body 3 b. A SiC seed crystal W is joined to one surface 4a of the base 4.
The lid portion and the pedestal may be formed of a single material as an integral member, or may be configured by combining separate members.

  The crucible 3 is comprised from the cover part 3a and the main-body part 3b, and is equipped with the cavity part 6 inside the main-body part 3b. The SiC seed crystal W is fixed to the upper part in the cavity 6. The cavity 6 is provided with a sufficient amount of the silicon carbide raw material 5 for growing a SiC single crystal on the SiC seed crystal W in the lower part and necessary for growing the SiC single crystal in the upper part. Secure space. Therefore, a SiC single crystal can be grown on the growth surface W1 of the SiC seed crystal W toward the inner bottom surface 6a by the sublimation recrystallization method.

The heat insulating material 2 is installed so that the whole crucible 3 consisting of the cover part 3a and the main-body part 3b may be covered. At this time, the holes 2a and 2b are formed so that the lower surface and a part of the upper surface of the crucible 3 are exposed. The heat insulating material 2 is for maintaining the crucible 3 stably in a high temperature state, and for example, a material made of carbon fiber can be used. In the case where the crucible 3 can be stably maintained at a high temperature as necessary, the heat insulating material 2 may not be installed.
The crucible 3 around which the heat insulating material 2 is wound is installed on a support rod 10 at the center inside the vacuum vessel 1. The support bar 10 has a cylindrical shape, and the hole 10 a of the support bar 10 is aligned with the hole 2 a provided in the heat insulating material 2. Accordingly, the radiation thermometer 9 disposed under the vacuum vessel 1 can observe the temperature of the lower surface of the crucible 3 through the hole 10a of the support rod 10 and the lower hole 2a of the heat insulating material 2. It is said that. Similarly, the temperature of the upper surface of the crucible 3 can be observed through another hole 2 b on the upper side of the heat insulating material 2 by another radiation thermometer 9 disposed on the vacuum vessel 1.
For gas exchange inside the vacuum vessel 1, first, air inside the vacuum vessel 1 is exhausted using a vacuum pump (not shown) connected to the discharge pipe 8, for example, reduced pressure of 4 × 10 ⁻³ Pa or less. State. For example, a turbo molecular pump can be used as the vacuum pump. Thereafter, high-purity Ar gas is introduced into the vacuum vessel 1 from the introduction tube 7, and the inside of the vacuum vessel 1 is set to an environment of 9.3 × 10 ⁴ Pa in an Ar atmosphere.

A heating unit 11 is disposed outside the vacuum vessel 1. The heating means 11 is, for example, a high-frequency heating coil, and generates a high frequency by passing an electric current to heat the crucible 3 installed in the center of the vacuum vessel 1 to a temperature of, for example, 1900 ° C. or higher. it can. Thereby, silicon carbide source material 5 in crucible 3 is heated to generate sublimation gas from silicon carbide source material 5.

  In the SiC single crystal manufacturing method of the present invention, the SiC seed crystal W is bonded to the one surface 4a of the pedestal 4 using the single crystal growth apparatus 100 schematically configured as described above to manufacture the SiC single crystal.

  As the SiC seed crystal W, a MoKα ray is used as an X-ray source, an asymmetric reflection surface is used as a diffraction surface, a reflection X-ray topography image of an SiC single crystal plate is obtained, and an SiC single crystal is obtained using the X-ray topography image. The dislocation density of the crystal plate is measured, and an SiC single crystal plate having a dislocation density of a predetermined value or less is used. Specifically, for example, a SiC single crystal plate as shown in FIG.

  When MoKα ray is used as the X-ray source and an asymmetric reflection surface is used as the diffraction surface, it becomes possible to obtain a dislocation image that is distinct enough to be discriminated as an image of a different shape between the threading screw dislocation and the basal plane dislocation, It is possible to measure the dislocation density of each threading screw dislocation and basal plane dislocation.

The X-ray topography used in the method for producing a SiC single crystal of the present invention is based on a reflection method, and the usable reflection X-ray topography apparatus is not particularly limited except that MoKα rays are used as an X-ray source.
It is preferable to use a {1 2 -3 L} plane (L is an integer) as the asymmetric reflecting surface used as the diffractive surface. This is because a high-intensity dislocation image can be obtained. In particular, it is preferable that L is any one of 14, 15, 16, or 17. This is because a higher intensity dislocation image can be obtained.

As the upper limit (predetermined value) of the dislocation density, it is preferable that the basal plane dislocation density is 1000 pieces / cm ² or less and the threading screw dislocation density is 500 pieces / cm ² or less. This is because an SiC single crystal that does not hinder the operation of the SiC device can be produced if the value is less than these values.

[SiC epitaxial wafer manufacturing method]
A method for producing a SiC epitaxial wafer according to the present invention is a method for producing a SiC epitaxial wafer by forming a SiC epitaxial film by supplying a silicon-containing gas and a carbon-containing gas on a SiC single crystal substrate. An X-ray topography image of a SiC single crystal substrate is obtained using MoKα rays and an asymmetric reflection surface as a diffraction surface, and the dislocation density of the SiC single crystal substrate is measured using the X-ray topography image. A SiC single crystal substrate having a predetermined value or less is used.

FIG. 4 is a schematic diagram of an example of a film forming apparatus for a SiC epitaxial wafer film used in the method for producing a SiC epitaxial wafer of the present invention.
The SiC epitaxial wafer film forming apparatus 200 penetrates through a reaction chamber 24 provided between a planetary 21 and a heat radiation member 22 that support a plurality of wafer mounting portions 21b, and a central portion of the heat radiation member 22. A gas supply unit 25 for supplying gas into the reaction chamber 24 and a high-frequency coil 26 for heating the planetary 21 and the heat radiation member 22 are provided. The revolution rotary shaft 21 a is disposed directly below the gas supply unit 25.

With this configuration, the SiC single crystal substrate is revolved by the planetary 21 with the gas supply unit 25 as the central axis, and the SiC single crystal substrate itself is rotated by the wafer mounting unit 21b with the center of the SiC single crystal substrate as the axis. It has become.
In this way, the wafer mounting portion 21b and the planetary 21 are allowed to rotate and revolve to improve the in-plane uniformity of the film thickness, carrier concentration, and temperature distribution of the SiC epitaxial wafer.
Moreover, the substrate can be heated to a high temperature by the configuration in which the high-frequency coil 26 is disposed above and below the reaction chamber 24.

As the silicon-containing gas and the carbon-containing gas, for example, silane (SiH ₄ ) gas and propane (C ₃ H ₈ ) gas can be used, respectively.

The SiC epitaxial wafer manufacturing method of the present invention includes a step of polishing a SiC single crystal substrate (polishing step), a dislocation density of the polished SiC single crystal substrate, and a dislocation density of a SiC single crystal substrate having a predetermined value or less. A step of gas-etching the surface of the SiC single crystal substrate (etching step), and a step of forming an SiC epitaxial film on the SiC single crystal substrate (deposition step). About a grinding | polishing process, an etching process, and a film-forming process, it can carry out in the procedure normally performed.

  As the SiC single crystal substrate on which the SiC epitaxial wafer film is formed, a MoKα ray is used as an X-ray source, an asymmetric reflection surface is used as a diffraction surface, a reflection X-ray topography image of the SiC single crystal substrate is obtained, and the X The dislocation density of the SiC single crystal substrate is measured using a line topography image, and the dislocation density is less than a predetermined value.

  When MoKα rays are used as the X-ray source and an asymmetric reflection surface is used as the diffraction surface, it is possible to obtain a clear dislocation image that can be distinguished as an image having different shapes for the threading screw dislocation and the basal plane dislocation. It is possible to measure the dislocation densities of threading screw dislocations and basal plane dislocations.

The X-ray topography used in the manufacturing method of the SiC epitaxial wafer of the present invention is based on a reflection method, and the usable reflection X-ray topography apparatus is not particularly limited except that MoKα rays are used as an X-ray source.
It is preferable to use a {1 2 -3 L} plane (L is an integer) as the asymmetric reflecting surface used as the diffractive surface. This is because a high-intensity dislocation image can be obtained. In particular, it is preferable that L is any one of 14, 15, 16, or 17. This is because a higher intensity dislocation image can be obtained. Since these index planes have different incident angles, the penetration depth of X-rays is different as shown in Table 1. Using this, it is possible to analyze the crystallinity of the epi film in the depth direction. In addition, when analyzing the substrate-epi interface, the index plane can be selected according to the film thickness.

As the upper limit (predetermined value) of the dislocation density, it is preferable that the basal plane dislocation density is 1000 pieces / cm ² or less and the threading screw dislocation density is 500 pieces / cm ² or less. This is because a SiC epitaxial wafer that does not hinder the operation of the SiC device can be manufactured if the value is below these values.

FIG. 2A shows an SiC epitaxial wafer manufactured using a SiC single crystal substrate having a basal plane dislocation density after polishing of (150) / cm ² and a threading screw dislocation density of (230) / cm ² . It is a reflection X-ray topography image.
As described above, the threading screw dislocation density of the SiC epitaxial wafer was 324 / cm ² , and the basal plane dislocation density was 60 / cm ² .
As a result of using an SiC single crystal substrate having a basal plane dislocation density of 1000 pieces / cm ² or less and a threading screw dislocation density of 500 pieces / cm ² or less, a high-quality SiC epitaxial wafer having a low dislocation density can be produced. It was.
As described above, in the X-ray topography used in the method for producing an SiC epitaxial wafer of the present invention, the X-ray (MoKα line) has a penetration depth of about 65 μm, so that not only the 30 μm thick SiC epitaxial film but also the SiC epitaxial film is used. The dislocation information is reflected in the topography image by penetrating into the interface between the film and the SiC single crystal substrate and further into the SiC single crystal substrate. Therefore, the values of the above threading screw dislocation density of 324 / cm ² and the basal plane dislocation density of 60 / cm ² include not only the SiC epitaxial film but also the dislocations in the interface and the SiC single crystal substrate. Therefore, the dislocation density in the SiC epitaxial film is lower than those values.
Some of the basal plane dislocations existing on the growth surface of the SiC single crystal substrate are converted into stacking faults in the SiC epitaxial film, and the basal plane dislocation density in the SiC epitaxial film is reduced, whereas threading dislocations are It is known that the SiC single crystal substrate propagates as it is to the SiC epitaxial film, and the value of the dislocation density reflects it.

[SiC single crystal]
The SiC single crystal of the present invention is produced by the method for producing a SiC single crystal of the present invention, and has a basal plane dislocation density of 1000 / cm ² or less and a threading screw dislocation density of 500 / cm ² or less. Single crystal.

The SiC single crystal shown in FIG. 1 (a) is manufactured by the SiC single crystal manufacturing method of the present invention, and the basal plane dislocation density measured by the SiC single crystal substrate evaluation method of the present invention is the same. The SiC single crystal has 92 pieces / cm ² and a threading screw dislocation density of 468 pieces / cm ² .

DESCRIPTION OF SYMBOLS 1 Vacuum container 3 Crucible 4 Base 5 Silicon carbide raw material 11 Heating means 21 Planetary 21b Wafer mounting part 22 Thermal radiation member
24 Reaction chamber 25 Gas supply unit 100 Single crystal growth apparatus 200 SiC epitaxial wafer film deposition apparatus W SiC seed crystal

Claims (10)

A method for evaluating dislocations in a SiC single crystal substrate by reflection X-ray topography,
An X-ray topography image of a SiC single crystal substrate is obtained using MoKα rays as an X-ray source and a {1 2 -3 L} plane (L is an integer) as an asymmetric reflection surface of the diffraction surface, and the X-ray topography A method for evaluating a SiC single crystal substrate, comprising measuring dislocation density of the SiC single crystal substrate using an image. The crystalline polymorph of the SiC single crystal substrate is a 4H-type, the evaluation method of the SiC single crystal substrate according to claim 1, wherein L is equal to or is either 14, 15, 16 or 17. The SiC single crystal substrate has a polymorphism of hexagonal or trigonal crystals other than the 4H type, and the L is 14, 15, 16, or 17 and the c-axis length ratio of the unit cell (polymorphic crystals other than 4H) 2. The method for evaluating an SiC single crystal substrate according to claim 1 , wherein an index corrected by c-axis length) / (4H crystal c-axis length) is used. A method for evaluating dislocations in a SiC epitaxial wafer in which a SiC epitaxial film is formed on a SiC single crystal substrate by reflection X-ray topography,
An X-ray topography image of a SiC epitaxial wafer is obtained by using MoKα rays as an X-ray source and a {1 2 -3 L} plane (L is an integer) as an asymmetric reflection surface of the diffraction surface. A method for evaluating a SiC epitaxial wafer, comprising measuring the dislocation density of the SiC epitaxial wafer using 5. The method for evaluating an SiC epitaxial wafer according to claim 4 , wherein a crystal polymorph of the SiC epitaxial wafer is a 4H type, and the L is any one of 14, 15, 16 or 17. The SiC epitaxial wafer has a crystal polymorphism of hexagonal or trigonal crystals other than the 4H type, and the L is 14, 15, 16, or 17 is the ratio of c-axis lengths of unit lattices (polymorphic crystals other than 4H). 5. The SiC epitaxial wafer evaluation method according to claim 4 , wherein an index corrected by c-axis length) / (4H crystal c-axis length) is used. In a method for producing a SiC single crystal, a raw material gas is supplied onto a SiC seed crystal arranged in a crucible, and a SiC single crystal is grown on the SiC seed crystal.
Using a MoKα ray as an X-ray source and a {1 2 -3 L} plane (L is an integer) as an asymmetric reflection surface of a diffraction surface , a reflection X-ray topography image of a SiC single crystal plate is obtained, and the X-ray A method for producing a SiC single crystal, wherein a dislocation density of a SiC single crystal plate is measured using a topography image, and a SiC single crystal substrate having a dislocation density of a predetermined value or less is used as the SiC seed crystal. 8. The method for producing a SiC single crystal according to claim 7 , wherein as the predetermined value, a basal plane dislocation density is 1000 pieces / cm ² or less and a threading screw dislocation density is 500 pieces / cm ² or less. A method for producing a SiC epitaxial wafer by supplying a silicon-containing gas and a carbon-containing gas on a SiC single crystal substrate to form a SiC epitaxial film,
Using a MoKα ray as the X-ray source and a {1 2 -3 L} plane (L is an integer) as the asymmetric reflection surface of the diffraction surface , a reflection X-ray topography image of the SiC single crystal substrate is obtained, and the X-ray A method for producing an SiC epitaxial wafer, comprising measuring a dislocation density of a SiC single crystal substrate using a topography image, and using the SiC single crystal substrate having a dislocation density of a predetermined value or less. 10. The method for producing an SiC epitaxial wafer according to claim 9 , wherein the predetermined value is a basal plane dislocation density of 1000 / cm ² or less and a threading screw dislocation density of 500 / cm ² or less.