SiC crystal ingot and method for producing SiC crystal ingot

Abstract

The invention provides a SiC crystal ingot and a manufacturing method of the SiC crystal ingot. The SiC crystal ingot according to the present embodiment determines the value of the dislocation density of the base surface by directly measuring at least one of the Si surface, the C surface, and the side surface.

Description

Technical Field

[0001] The present disclosure relates to a SiC ingot and a method for manufacturing the SiC ingot.

[0002] This application claims priority based on Special Application No. 2023-120078 filed in Japan on July 24, 2023, and Special Application No. 2023-182652 filed in Japan on October 24, 2023, and the contents of which are incorporated herein by reference. Background Art

[0003] Compared with silicon (Si), the insulation breakdown electric field of silicon carbide (SiC) is one order of magnitude larger and the band gap is three times larger. In addition, silicon carbide (SiC) has characteristics such as thermal conductivity being about three times higher than that of silicon (Si). Therefore, it is expected that silicon carbide (SiC) will be applied to power devices, high-frequency devices, high-temperature working devices, etc. Therefore, in recent years, SiC epitaxial wafers are used for substrates of semiconductor devices such as the above.

[0004] SiC epitaxial wafers are obtained by stacking SiC epitaxial layers on the surface of SiC substrates. Hereinafter, the substrate before stacking the SiC epitaxial layer is referred to as SiC substrate, and the substrate after stacking the SiC epitaxial layer is referred to as SiC epitaxial wafer. SiC substrates are made by cutting out SiC ingots. SiC devices such as power devices, high-frequency devices, and high-temperature working devices are obtained by chipping SiC epitaxial wafers after the SiC epitaxial layer of the SiC epitaxial wafer forms the device.

[0005] Basal plane dislocation (BPD) is known as one of the fatal defects of SiC devices in SiC epitaxial wafers. For example, when current flows in the forward direction of a bipolar device, due to the recombination energy of carriers, part of the basal plane dislocation extending from the SiC substrate to the SiC epitaxial layer moves and expands to form a high-resistance stacking fault. The high-resistance part generated in the device becomes the cause of the reduction in device reliability (forward degradation).

[0006] The basal plane dislocation of the SiC epitaxial layer is mostly continued from the basal plane dislocation of the SiC substrate. Therefore, for example, Patent Document 1 and Patent Document 2 disclose methods for evaluating the basal plane dislocation in the SiC substrate. Patent Document 1 discloses the use of the correlation between the contrast of the X-ray topography image and the basal plane dislocation to evaluate the in-plane distribution of the basal plane dislocation of the SiC substrate. Patent Document 2 discloses the classification of the basal plane dislocation according to the X-ray topography image of each defect, and the measurement of the basal plane dislocation density of the SiC single crystal substrate.

[0007] Prior art literature

[0008] Patent Document 1: Japanese Patent No. 6197722

[0009] Patent Document 2: Japanese Patent No. 6037673 Summary of the invention

[0010] Technical problem to be solved by the invention

[0011] The SiC ingot is located upstream of the manufacturing process compared to the SiC substrate. At the stage of the SiC ingot, it is required to evaluate the basal plane dislocation. However, it is difficult to evaluate the SiC ingot directly. For example, in the method described in Patent Document 1, when measuring the basal plane dislocation density of the SiC ingot, the diffraction intensity will deviate due to reasons other than the basal plane dislocation, and it is difficult to accurately measure the basal plane dislocation. This is because the thickness of the SiC ingot is thicker than the SiC substrate. When using X-ray morphology to evaluate a thick SiC ingot, it is necessary to use a reflected X-ray morphology image. However, due to the influence of the deviation of the penetration length of the X-ray, the signal intensity of the reflected X-ray will deviate greatly. In the case of measuring the basal plane dislocation density from the X-ray morphology image, the basal plane dislocation density is measured based on the correlation between the X-ray intensity and the basal plane dislocation density. In this case, when the signal intensity of the reflected X-ray deviates, the basal plane dislocation density cannot be accurately measured.

[0012] Therefore, the following process is performed: a part of the SiC ingot is cut out as an evaluation substrate, and an X-ray topography image of the evaluation substrate is measured. However, in this case, the object of measurement is the evaluation substrate, and the reliability is poor in terms of ensuring the quality of the entire SiC ingot. In addition, when the evaluation substrate is cut out, the part that can be used for the product will be reduced accordingly from the SiC ingot, and there is a problem of reduced product yield.

[0013] The present disclosure has been made in view of the above-mentioned problems, and an object of the present disclosure is to provide a SiC ingot and a method for manufacturing the SiC ingot, which are easy to ensure in quality and have a high yield.

[0014] Technical solutions to solve problems

[0015] As a result of intensive research, the inventors have found that by extracting the correlation between the image of the entire surface of the measurement area and the basal plane dislocation density instead of using only the intensity of the X-ray topography image, even for SiC ingots, the basal plane dislocation density can be measured. Even if the intensity of the X-ray topography image varies, the pattern of the image of the entire surface of the measurement area does not change, so the basal plane dislocation density can be measured.

[0016] (1) In the SiC ingot according to the first aspect, the value of the basal plane dislocation density is determined by directly measuring at least one of the Si plane, the C plane, and the side surface.

[0017] (2) In the SiC ingot according to the above aspect, the value of the basal plane dislocation density may be an output value obtained based on a measurement result of the entire surface of at least one of the Si plane and the C plane.

[0018] (3) In the SiC ingot according to the above technical solution, the value of the basal plane dislocation density may be an output value obtained based on the measured value of the side surface or the measured value of the side surface and the measured value other than the side surface.

[0019] (4) In the SiC ingot involved in the above-mentioned technical solution, the value of the basal plane dislocation density may also be a value obtained according to a correspondence table, wherein the correspondence table is a correspondence table representing the correlation between the reflected X-ray morphology image of at least one of the Si plane, the C plane and the side surface and the basal plane dislocation density obtained through prior research.

[0020] (5) In the SiC ingot involved in the above technical solution, the value of the basal plane dislocation density can also be an estimated value estimated based on the learning results of deep learning according to the reflected X-ray morphology image of at least one of the Si plane, the C plane and the side surface.

[0021] (6) The method for manufacturing a SiC ingot according to the second technical solution comprises: a measurement step for directly measuring at least one of the Si face, C face and side face of the SiC ingot; and an evaluation step for calculating the basal plane dislocation density based on the correlation between the measurement result of the measurement step and the basal plane dislocation density of the SiC ingot.

[0022] (7) In the measuring step of the method for manufacturing a SiC ingot according to the above-mentioned technical solution, at least one of the Si plane and the C plane may be measured.

[0023] (8) In the measuring step of the method for manufacturing a SiC ingot according to the above-mentioned technical solution, at least the side surface may be measured.

[0024] (9) In the method for manufacturing a SiC ingot according to the above technical solution, the reflected X-ray topography image may be measured in the measuring step.

[0025] (10) In the method for manufacturing a SiC ingot according to the above technical solution, in the evaluation step, the basal plane dislocation density of the SiC ingot may be estimated based on a learning result of deep learning.

[0026] Effects of the Invention

[0027] The quality assurance of the SiC ingot involved in the above technical solution is high in precision. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a perspective view of a SiC ingot according to the present embodiment.

[0029] Figure 2 It is an explanatory diagram of a measurement jig for evaluating the SiC ingot according to the present embodiment.

[0030] Description of Reference Numerals

[0031] 1Si surface

[0032] 2C side

[0033] 3 Side

[0034] 10SiC Ingot

[0035] 11 Support

[0036] 12 Driving mechanism

[0037] 13 Measurement Agency DETAILED DESCRIPTION

[0038] Hereinafter, the SiC ingot and the method for manufacturing the SiC ingot according to the present embodiment will be described in detail with appropriate reference to the accompanying drawings. In order to facilitate the understanding of the features of the present embodiment, the accompanying drawings used in the following description may enlarge the characteristic parts for the sake of convenience, and the dimensional ratios of the various components may be different from the actual ones. The materials, dimensions, etc. illustrated in the following description are examples, and the present disclosure is not limited thereto, and may be implemented with appropriate changes within the scope of the purpose.

[0039] In this specification, individual orientations are indicated by [], and collective orientations are indicated by <>. Regarding negative indices, "-" (bar) is placed above the numbers in crystallography, but in this specification, a minus sign is placed before the numbers.

[0040] "SiC Ingot"

[0041] Figure 1 1 is a perspective view of a SiC ingot 10 according to the present embodiment. The SiC ingot 10 is a cylindrical SiC single crystal. The SiC ingot 10 is processed into a cylindrical shape to cut out a SiC substrate.

[0042] The diameter R of the SiC crystal ingot 10 is, for example, 145 mm or more, preferably 149 mm or more, more preferably 155 mm or less, and further preferably 151 mm or less. The diameter R of the SiC crystal ingot 10 is, for example, 195 mm or more, preferably 199 mm or more, more preferably 205 mm or less, and further preferably 201 mm or less. The SiC crystal ingot 10 can be, for example, a crystal ingot that can obtain a 6-inch substrate or a crystal ingot that can obtain an 8-inch substrate.

[0043] The thickness T of SiC ingot 10 is, for example, 10 mm or more, preferably 20 mm or more, more preferably 30 mm or more, and further preferably 40 mm or more. The thicker SiC ingot 10 is, the more SiC substrates can be obtained.

[0044] The SiC ingot 10 has, for example, a Si face 1, a C face 2, and a side face 3. The Si face 1 is the (0001) face of the SiC ingot 10, and is a face whose surface atoms are Si atoms. The C face 2 is the (000-1) face of the SiC ingot 10, and is a face whose surface atoms are C atoms. The side face 3 is a face connecting the Si face 1 and the C face 2, and is a side face of a cylinder. The Si face 1 and the C face 2 of the SiC ingot 10 may also have an offset angle in the <11-20> direction. For example, the Si face 1 and the C face 2 may also be faces having an offset angle of greater than 0.1 degrees and less than 8 degrees in the <11-20> direction, and having no offset angle in the <1-100> direction. In addition, the offset angle of the SiC ingot 10 is not limited to this example.

[0045] The Si surface 1 is, for example, mirror-finished, mechanically polished, or chemically mechanically polished (CMP). The surface roughness (Ra) of the Si surface 1 is, for example, less than 5 nm. The surface to be measured for the X-ray topography image is required to be a mirror surface. If the Si surface 1 is a mirror surface, the X-ray topography image of the Si surface 1 can be measured.

[0046] The C surface 2 is, for example, mirror-finished, mechanically polished, or chemically mechanically polished (CMP). The surface roughness (Ra) of the C surface 2 is, for example, 5 nm or less. If the C surface 2 is a mirror surface, an X-ray topography image of the C surface 2 can be measured.

[0047] In addition, the side surface 3 is, for example, mirror-polished. The surface roughness (Ra) of the side surface 3 is, for example, less than 5 nm. For the surface roughness (Ra) of the side surface 3, the same position in the circumferential direction is measured in the Z direction. If the side surface 3 is a mirror surface, the X-ray topography image of the side surface 3 can be measured. In addition, the side surface 3 may also be mirror-polished only at least in a part of the measurement area. In this case, the side surface 3 includes a portion with a surface roughness (Ra) of less than 5 nm. The details will be described later, but the side surface 3 is sometimes only measured in a predetermined range. In this case, it is sufficient as long as the predetermined range is a mirror surface. The side surface 3 may also be a mirror surface in its entirety, and the surface roughness (Ra) is less than 5 nm in the entirety.

[0048] The value of the basal plane dislocation density is determined for the SiC ingot 10. The "value" is the average basal plane dislocation density in a predetermined area. The value of the basal plane dislocation density is determined as information to ensure the quality of the SiC ingot 10. For example, the value of the basal plane dislocation density is handled together with the SiC ingot 10 as an inspection report or an analysis certificate. The inspection report and the analysis certificate can be either actual documents or data. For the basal plane dislocation density, the basal plane dislocation density is calculated by dividing the number of basal plane dislocations by the area of ​​the region. For example, when the measuring surface is Si surface 1, it is the average basal plane dislocation density of the entire surface of Si surface 1. For example, when the measuring surface is C surface 2, it is the average basal plane dislocation density of the entire surface of C surface 2. For example, when the measuring surface is side surface 3, it is the average basal plane dislocation density of the measuring area of ​​side surface 3.

[0049] The value of the basal plane dislocation density of the SiC ingot 10 is obtained using the result obtained by directly measuring at least one of the Si face 1, the C face 2 and the side face 3. For the SiC ingot 10, the evaluation is not performed on an evaluation substrate cut out from the SiC ingot, but on the SiC ingot 10 itself, so the accuracy of quality assurance is high. The quality of the SiC ingot 10 is guaranteed by processing the SiC ingot 10 and the inspection report or analysis certificate (for example, data marked with quality assurance values) in a set. The person in charge of the post-process of processing the SiC ingot 10 confirms the quality using a SiC ingot data set. The SiC ingot data set, for example, has data on the SiC ingot 10 and the value of the basal plane dislocation density of the SiC ingot 10.

[0050] The value of the basal plane dislocation density is an output value (estimated value) estimated from the result obtained by directly measuring at least one of Si plane 1, C plane 2 and side surface 3. The value of the basal plane dislocation density can be an output value (estimated value) estimated from the result obtained by directly measuring Si plane 1, or an output value (estimated value) estimated from the result obtained by measuring C plane 2, or an output value (estimated value) estimated from the result obtained by directly measuring side surface 3, or an output value (estimated value) estimated from the result obtained by measuring Si plane 1 and C plane 2, or an output value (estimated value) estimated from the result obtained by measuring Si plane 1 and side surface 3, or an output value (estimated value) estimated from the result obtained by measuring C plane 2 and side surface 3, or an output value (estimated value) estimated from the result obtained by measuring Si plane 1, C plane 2 and side surface 3.

[0051] First, the method of obtaining the measured value is described. When obtaining the measured value, a preliminary step, a measurement step, and an evaluation step are performed.

[0052] In a preliminary step, a correspondence table is prepared to show the correlation between the X-ray topography image of the SiC ingot and the basal plane dislocation density of the SiC ingot. The SiC ingot to be evaluated here is a SiC ingot different from the SiC ingot to be measured. In a preliminary step, the correlation between the X-ray topography image and the basal plane dislocation density of the SiC ingot is derived from a plurality of data to prepare a correspondence table.

[0053] In the preliminary step, an evaluation substrate is cut out from the SiC ingot, and the evaluation substrate is used to evaluate the basal plane dislocation density of the SiC ingot. The preliminary step is a step for making a correspondence table. Therefore, in order to improve the accuracy of the correspondence table, time may be spent in the preliminary step, and some loss may be generated in the SiC ingot. Once the correspondence table is made, the preliminary step may not be performed in the subsequent evaluation of the SiC ingot.

[0054] The X-ray topography image measured in the previous step is a macroscopic overall image of the measured surface. For example, in the case of measuring Si surface 1, it is a whole image of Si surface 1. For example, in the case of measuring C surface 2, it is a whole image of C surface 2. For example, in the case of measuring side surface 3, it is a whole image of the set measurement area. The measurement area can be the entire circumference of side surface 3, an area of ​​a specific width in the circumferential direction of side surface 3, or an area of ​​a predetermined range set arbitrarily. By using a macroscopic overall image instead of a local image of a defective portion, the estimation process in the estimation step does not require the evaluation of a local image, and the time spent on the estimation of the basal plane dislocation density can be shortened.

[0055] In addition, the X-ray topography image measured in the preliminary step is not the intensity distribution of the X-ray topography image, but an overall image. The overall image of the X-ray topography includes not only dislocations, but also overall strain information. For the intensity distribution of the X-ray topography image, sometimes it is affected by the measurement deviation of the penetration length of the X-rays, etc., and the signal intensity will be biased. Since the evaluation substrate measured in the preliminary step is thin, the influence of the deviation of the penetration length of the X-rays is small, but in the SiC ingot measured in the measurement step, the influence is large. Therefore, when only the intensity distribution of the X-ray topography image is used, the correlation between the intensity distribution of the X-ray topography image and the basal plane dislocation density obtained in the preliminary measurement is mostly inconsistent with the correlation between the intensity distribution of the X-ray topography image of the SiC ingot and the basal plane dislocation density. In contrast, the overall image of the X-ray topography is an image of the surface pattern measured, and unlike the case where the intensity distribution is used as the evaluation object, it is not easily affected by the deviation of the penetration length.

[0056] The X-ray topography image measured in the preliminary step may be a diffraction image including diffraction vectors in the <11-20> direction or a diffraction image including diffraction vectors in the <1-100> direction.

[0057] The number of basal plane dislocations contained in the SiC substrate measured in the preliminary step can be obtained from an X-ray topography image, a photoluminescence method, a mirror electron microscope, or by measuring etch pits after KOH etching. In the preliminary step, in order to improve the accuracy of the correspondence table, it is preferred to evaluate the etch pits after KOH etching to classify the basal plane dislocations.

[0058] In order to improve the accuracy of the correspondence table, it is preferable to evaluate a sufficient number of SiC ingots in the preliminary step. For example, it is preferable to measure the relationship between the X-ray topography images and the basal plane dislocation density of 100 or more SiC ingots.

[0059] In addition, deep learning can also be used to create the correspondence table. The data collected in the previous step corresponds to the teacher data of deep learning. The teacher data can be stored in the memory of the evaluation device or in a server located outside the evaluation device. The learning program learns the correlation between the X-ray morphology image of each SiC ingot and the basal plane dislocation density through deep learning.

[0060] The X-ray morphology image stored as the teacher data can be the image directly taken or compressed. For example, it can be stored compressed to a pixel size of 0.1mm 2The pixel size indicates the size of one pixel. For example, an image obtained by compressing a captured X-ray topography image to 250×250 pixels may be used as the teacher data.

[0061] The more teacher data there are, the higher the estimation accuracy of the basal plane dislocation density. The number of teacher data representing the relationship between the X-ray morphology image and the basal plane dislocation density is preferably greater than 100. In the case where a sufficient number of SiC ingots cannot be prepared, an image obtained by inverting or rotating the X-ray morphology image of a SiC ingot may be used as part of the teacher data. For example, a combination of an X-ray morphology image of an evaluation substrate cut from the first SiC ingot and the basal plane dislocation density of the evaluation substrate may be used as the first data, an image obtained by inverting the X-ray morphology image of the evaluation substrate and the basal plane dislocation density of the evaluation substrate may be used as the second data, and an image obtained by rotating the X-ray morphology image of the evaluation substrate and the basal plane dislocation density of the evaluation substrate may be used as the third data.

[0062] The diameters of the plurality of SiC ingots measured in the preliminary step do not necessarily have to be the same. For example, the plurality of SiC ingots measured in the preliminary step may include both an ingot with a diameter of 6 inches and an ingot with an 8-inch substrate.

[0063] By performing the preliminary step as described above, a correspondence table representing the correlation between the X-ray topography image of the SiC ingot and the basal plane dislocation density of the SiC ingot is obtained. The preliminary step is preferably performed using deep learning. By performing deep learning, a large amount of data can be processed efficiently.

[0064] Next, in the measurement step, an X-ray topography image of the SiC ingot is obtained. The X-ray topography image measured here is also an overall image of the macroscopic measurement surface. In the case where the correspondence table in the previous step is prepared based on the measurement result of Si surface 1, the measurement surface measured in the measurement step is Si surface 1. In the case where the correspondence table is prepared using C surface 2 and side surface 3, the same surface as the surface measured when the correspondence table is prepared is also measured. The surface of the X-ray topography image of the SiC ingot obtained in the measurement step can be only Si surface 1, only C surface 2, only surface 3, Si surface 1 and C surface 2, Si surface and side surface 3, or all of Si surface 1, C surface 2 and side surface 3. In the measurement step, it is preferred to measure at least one of Si surface 1 and C surface 2, or side surface 3. In addition, the measured image is preferably a reflection X-ray topography image. The reflection X-ray topography image has information on the surface of the measurement surface, and is less likely to generate noise compared to the transmission X-ray topography image whose image changes according to the penetration depth of the X-ray.

[0065] The basal plane dislocation density of the SiC ingot to be actually evaluated is preferably 10000 / cm 2 Below, more preferably 5000 / cm 2 Below, more preferably 2500 / cm 2 Below, more preferably 1000 / cm 2 Below, particularly preferably 500 / cm 2 Below. When the basal plane dislocation density is too low, it is difficult to measure the basal plane dislocation density based on the intensity of the X-ray topography image. This is because when there is no basal plane dislocation, the X-ray signal intensity has no shades and is easily affected by noise. In addition, when the basal plane dislocation density is estimated based on the overall image of the X-ray topography, the basal plane dislocation density can be estimated even if the basal plane dislocation density is low.

[0066] The diameter R of the SiC ingot that is actually the object of evaluation may be the same as or different from the diameter of the SiC substrate measured in the previous step. For example, the diameter of the SiC ingot that is actually the object of evaluation may be larger than the diameter of the SiC ingot measured in the previous step. When the diameter of the SiC ingot that is actually the object of evaluation is the same as the diameter of the SiC ingot measured in the previous step, the evaluation accuracy is high.

[0067] In the measuring step, for example, the predetermined surface of the SiC ingot 10 is directly measured using an X-ray topography method. The surface measured in the measuring step may be only the Si surface 1, only the C surface 2, only the side surface 3, the Si surface 1 and the C surface 2, the Si surface and the side surface 3, or all of the Si surface 1, the C surface 2, and the side surface 3. In the measuring step, it is preferred to measure at least one of the Si surface 1 and the C surface 2 or the side surface 3. However, since the SiC ingot 10 has shape deviations for each sample, a predetermined measuring fixture is used to perform direct measurement of the SiC ingot 10.

[0068] Figure 2 This is an explanatory diagram of a measuring fixture for measuring SiC ingots. The measuring fixture has a support body 11 that supports the SiC ingot 10, a driving mechanism 12 that changes the height position of the support body 11, and a measuring mechanism 13 that measures the height position of a measuring surface S. The thickness of the SiC ingot 10 varies for each sample. In addition, the flatness deviation is also large within the SiC ingot 10. The measuring fixture can align the position of the measuring surface S for each measurement or during the measurement. The driving mechanism 12 moves the support body 11 in the up and down directions to align the position of the measuring surface S of the SiC ingot 10. The measuring mechanism 13 confirms the position of the measuring surface S. The measuring mechanism 13 is, for example, a camera.

[0069] For example, when X-ray topography is used in the measurement step, by using a measurement fixture for measuring SiC ingots, X-rays can be irradiated to an appropriate position from an appropriate angle. In order to utilize the correlation created in the previous step, it is important that the irradiation angle of the X-ray relative to the SiC ingot 10 does not deviate. In addition, when X-ray topography is used in the measurement step, it is preferred to use reflection X-ray topography. For thick SiC ingots, X-rays do not penetrate, or even if they penetrate, the signal is weak, so it is difficult to measure by transmission X-ray topography.

[0070] For example, when measuring the basal plane dislocation of Si surface 1, the whole image of Si surface is obtained. When measuring the basal plane dislocation density of C surface 2, the whole image of C surface is obtained. When measuring the basal plane dislocation density of side surface 3, the measurement area is first set. The measurement area can be the entire circumference of side surface 3, or a region of a specific width in the circumferential direction of side surface 3, or a region of a predetermined range set arbitrarily. Then, the whole image of the entire surface of the measurement area is obtained.

[0071] The X-ray topography image measured in the measuring step may be a diffraction image including diffraction vectors in the <11-20> direction or a diffraction image including diffraction vectors in the <1-100> direction. The X-ray topography image measured in the measuring step is set to be a diffraction image including diffraction vectors in the same direction as the X-ray topography image measured in the previous step.

[0072] When an X-ray topography image compressed in a previous step is stored as teacher data, the measured X-ray topography image may be compressed. For example, image compression is performed so that the pixel size of the X-ray topography image becomes 0.1 mm. 2 When the diameter of the SiC ingot measured in the previous step is different from the diameter of the SiC ingot actually evaluated, the X-ray topography images obtained by measuring the respective SiC ingots are compressed to the same size (eg, 250×250 pixels).

[0073] The resolution of each X-ray topography image is reduced by performing image compression. When image compression is performed, the calculation in the estimation step can be performed based on the low-resolution image, and the calculation load of the evaluation device can be reduced.

[0074] Next, an evaluation step is performed. In the evaluation step, based on the correspondence table, the basal plane dislocation density is estimated from the X-ray topography image measured in the measurement step. In the case of deep learning, the X-ray topography image of the entire measurement surface of the SiC ingot is used as input, and the basal plane dislocation density at the position corresponding to the measurement surface of the SiC ingot is output. The correlation between the X-ray topography image and the basal plane dislocation density is learned by deep learning, so the evaluation device can estimate the basal plane dislocation density of the predetermined surface of the SiC ingot to be evaluated with high accuracy.

[0075] As described above, the output value (estimated value) output based on the X-ray topography image using the correspondence table created in the previous step or the result of learning in the previous step becomes the output value of the basal plane dislocation density.

[0076] The value of the basal plane dislocation density assigned to the SiC ingot 10 may be an output value based on the measured value of the Si face 1, an output value based on the measured value of the C face 2, an output value based on the measured value of the side face 3, an output value based on the measured values ​​of the Si face 1 and the C face 2, an output value based on the measured values ​​of the Si face and the side face 3, or an output value based on all the measured values ​​of the Si face 1, the C face 2, and the side face 3. The value of the basal plane dislocation density assigned to the SiC ingot 10 preferably includes, for example, an output value based on the measured value of the side face 3 or the measured value of the side face 3 and the measured values ​​other than the side face 3. The value of the side face 3 includes information in the thickness direction of the SiC ingot 10. It is difficult to obtain information in the thickness direction of the SiC ingot 10 in a non-destructive manner, and the value of the basal plane dislocation density of the side face 3, which includes a part of the information in the thickness direction, becomes important information in the processing of the subsequent steps. In the case where the basal plane dislocation density in the length direction of the ingot varies greatly, if only the Si face or the C face is measured, the quality of the inside of the ingot cannot be reflected. In this case, by taking the side surface 3 as the measurement object, the basal plane dislocation density of the part away from the Si plane and the C plane in the length direction of the ingot can be measured. In addition, it is also possible to measure multiple parts in the Z direction. In this way, the distribution information of the basal plane dislocation in the length direction of the ingot can be reflected in the value.

[0077] In addition, the value of the basal plane dislocation density given to the SiC ingot 10 is preferably an output value based on the value measured on the entire surface of at least one of the Si surface 1 and the C surface 2. In most cases, the basal plane dislocation is continued in the stacking direction. Therefore, in order to obtain information on the in-plane direction of the SiC ingot 10, the data on the entire in-plane surface of the Si surface 1 or the C surface 2 becomes important information. For example, by confirming the data on the entire in-plane surface of the Si surface 1 or the C surface 2, the position of the area where the basal plane dislocation is concentrated can be grasped.

[0078] As described above, the SiC ingot involved in the present embodiment is given a value (data) of the basal plane dislocation density obtained from the result of directly measuring the SiC ingot itself. Since the SiC ingot itself is evaluated, the quality assurance accuracy of the SiC ingot involved in the present embodiment is high. In addition, since the SiC ingot itself is evaluated in a non-destructive manner, it is not necessary to cut out an evaluation substrate from the SiC ingot. That is, for the SiC ingot involved in the present embodiment, the yield of the product that can be obtained from the SiC ingot is high.

[0079] In addition, according to the method involved in this embodiment, when determining the value of the SiC ingot, the basal plane dislocation density of the SiC ingot can be estimated using the macroscopic X-ray topography image of the SiC ingot. When the defects are classified one by one to obtain the basal plane dislocation density, it is necessary to classify the defects one by one, and the measurement of the basal plane dislocation density takes time. In contrast, when the SiC ingot is evaluated by this method, the basal plane dislocation density of the SiC substrate can be obtained based on the overall image, so the time spent on the evaluation of the basal plane dislocation density can be shortened.

[0080] In addition, the X-ray topography image of the SiC ingot includes information on defects and strains in the SiC ingot. By performing a preliminary step using an X-ray topography image including both information on defects as microscopic information in the SiC ingot and information on strains as macroscopic information in the SiC ingot, the accuracy of estimating the basal plane dislocation density can be improved.

[0081] In addition, when image compression is performed when calculating the basal plane dislocation density of the SiC ingot, the computational load when estimating the basal plane dislocation density can be reduced. In order to accurately estimate the basal plane dislocation density, the image resolution is generally increased, but in this embodiment, the basal plane dislocation density can be estimated with high accuracy even if the image resolution is reduced.

[0082] In addition, by specifying the pixel size of the image during image compression, even when the diameter of the SiC ingot used for the measurement in the preliminary step is different from the diameter of the SiC ingot of the evaluation object, the basal plane dislocation density of the SiC ingot of the evaluation object can be estimated. For example, SiC ingots with a diameter of more than 8 inches are difficult to produce, and it is difficult to prepare many samples in the preliminary step. Even in this case, the preliminary step can be performed with a SiC ingot with a diameter of 6 inches, and the basal plane dislocation density of the 8-inch SiC ingot can be estimated based on the correspondence table or learning results of the 6-inch SiC ingot.

[0083] "Method for manufacturing SiC ingot"

[0084] The method for manufacturing a SiC ingot according to the present embodiment includes a crystal growth step, a column processing step, a measurement step, and an evaluation step.

[0085] In the crystal growth step, SiC is crystal-grown on one surface of the seed crystal. The crystal growth step can be performed by a well-known method, for example, a sublimation method can be used.

[0086] In the column processing step, the SiC single crystal (SiC boule) after crystal growth is processed into a column shape. Preferably, after the column processing, the Si surface 1, the C surface 2 or the side surface 3 are mirror-polished, mechanically polished or CMP-polished. It is preferred that at least the surface measured in the measurement step of the Si surface 1, the C surface 2 and the side surface 3 is mirror-polished, mechanically polished or CMP-polished.

[0087] In the measuring step and the evaluation step, the basal plane dislocation density of the measuring surface of the SiC ingot 10 is determined. The measuring step and the evaluation step can use the above-mentioned method. In the measuring step, at least one of the Si face 1, the C face 2 and the side face 3 of the SiC ingot 10 is directly measured. In the measuring step, for example, an X-ray morphology image is measured. In the measuring step, for example, at least one of the Si face 1 and the C face 2 can be measured, at least the side face 3 can be measured, the Si face 1 and the C face 2 can be measured, the Si face 1 or the C face 2 and the side face 3 can be measured, or the Si face 1, the C face 2 and the side face 3 can be measured.

[0088] In the evaluation step, the basal plane dislocation density of the SiC ingot is obtained based on the measurement result of the measurement step. The basal plane dislocation density of the SiC ingot is estimated based on the measurement result of the measurement step using the correspondence table or learning result obtained in the previous step.

[0089] The method for manufacturing the SiC ingot according to the present embodiment also includes a step for ensuring the quality of the SiC ingot. Therefore, the quality of the SiC ingot produced using the method for manufacturing the SiC ingot according to the present embodiment is ensured. In addition, the method for manufacturing the SiC ingot according to the present embodiment can ensure the quality in a non-destructive manner, thereby improving the yield rate of the SiC ingot.

[0090] As mentioned above, although the preferred embodiment of the present invention is described in detail, the present invention is not limited to the specific embodiment, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims.

Claims

1. A SiC ingot, The value of the basal plane dislocation density is determined by directly measuring at least one of the Si plane, the C plane, and the side surface.

2. The SiC ingot according to claim 1, The value of the basal plane dislocation density is an output value obtained based on the measurement result of the entire surface of at least one of the Si plane and the C plane.

3. The SiC ingot according to claim 1, The value of the basal plane dislocation density is an output value obtained from the measured value of the side surface or the measured value of the side surface and the measured value other than the side surface.

4. The SiC ingot according to claim 1, The value of the basal plane dislocation density is a value obtained based on a correspondence table, which is a correspondence table that represents the correlation between the reflected X-ray morphology image of at least one of the Si plane, the C plane and the side surface and the basal plane dislocation density obtained through prior research.

5. The SiC ingot according to claim 1, The value of the basal plane dislocation density is an estimated value estimated from a reflection X-ray topography image of at least one of the Si plane, the C plane, and the side surface based on a learning result of deep learning.

6. A method for manufacturing a SiC ingot, comprising: a measuring step of directly measuring at least one of the Si surface, the C surface, and the side surface of the SiC crystal ingot; and The evaluation step is to obtain the basal plane dislocation density based on the correlation between the measurement result of the measurement step and the basal plane dislocation density of the SiC ingot.

7. The method for manufacturing a SiC ingot according to claim 6, In the measuring step, at least one of the Si plane and the C plane is measured.

8. The method for manufacturing a SiC ingot according to claim 6, In the measuring step, at least the side surface is measured.

9. The method for manufacturing a SiC ingot according to claim 6, In the measuring step, the reflected X-ray topography image is measured.

10. The method for manufacturing a SiC ingot according to claim 6, In the evaluation step, a basal plane dislocation density of the SiC ingot is estimated based on a learning result of deep learning.

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