Method for identifying penetration dislocation in silicon carbide

Abstract

The invention provides a method for identifying penetration dislocation in silicon carbide, which comprises the following steps of: preliminarily corroding a silicon carbide sample to be identified, selecting a proper diffraction vector, and calculating relevant parameters containing an incidence angle # imgabs0 # corresponding to X-ray morphology detection under the selected diffraction vector by utilizing a Bragg diffraction principle; carrying out TSD and TED corrosion pit observation on the silicon carbide sample subjected to preliminary corrosion, recording an included angle # imgabs1 # between a connecting line between the highest point and the lowest point of the selected corrosion pit and the horizontal plane, obtaining an average value # imgabs2 # of the included angles of the selected corrosion pit, multiplying the average value # imgabs3 # of the included angles by a selected fixed coefficient # imgabs4 # to obtain a coefficient included angle # imgabs5 #, and carrying out TSD and TED corrosion pit observation on the coefficient included angle # imgabs5 #; the coefficient included angle # imgabs6 # is compared with the incidence angle # imgabs7 # of the diffraction vector, if # imgabs8 # is larger than # imgabs9 #, X-ray morphology detection is directly carried out, and otherwise, corrosion is carried out again; and carrying out identification by using an image detected by the X-ray morphology. According to the method, positioning and statistics of different kinds of dislocations in silicon carbide can be effectively realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of defect characterization of silicon carbide single crystal materials, and particularly relates to a method for identifying threading dislocations in silicon carbide. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Silicon carbide (SiC), a prominent representative of third-generation semiconductor materials, has revolutionized the field of power semiconductor devices with its superior properties, including a wider bandgap, higher critical breakdown electric field, and higher thermal conductivity. It is suitable for applications requiring high frequency, high temperature, and high power. However, compared to silicon single crystals, the dislocation density in SiC single crystals remains relatively high, which to some extent limits the performance of subsequent devices. Screw dislocations (TSDs) and edge dislocations (TEDs) have varying degrees of impact on device performance and reliability. Therefore, the ability to accurately identify defects in SiC substrates is crucial for the further development of the SiC field.

[0004] Currently, there are many methods for characterizing dislocations in silicon carbide, including alkaline etching, transmission electron diffraction (TEM), photoluminescence spectroscopy (PL), and X-ray morphology (XRT). Among these, alkaline etching is the most commonly used method for dislocation detection on whole substrates. The principle of alkaline etching is to exploit the greater lattice distortion and stress in dislocated regions during the etching process, thereby revealing dislocations through the formation of anisotropic etch pits. This method, by identifying the size and morphology of etch pits, can reveal information about the density and distribution of dislocations in silicon carbide. However, this method still has certain limitations. For example, in the existing KOH etching method, both TSD and TED are hexagonal, and can only be distinguished by microscopic observation of etch pit size. However, pit size is affected by factors such as sample doping concentration and etching conditions, making it difficult to accurately distinguish between TSD and TED. Studies have shown that observing etch pit cross-sections and using pit inclination to distinguish TSD and TED is feasible, but this method is too complex to be applicable to dislocation identification on large-scale substrates.

[0005] The XRT method uses the principle that different types of defects are imaged at specific diffraction vectors. By selecting different diffraction vectors, various defects in silicon carbide substrates can be effectively located and counted. However, there are certain limitations in using XRT to identify dislocations. For example, for the identification of TED, the Burger vector The smaller size results in weak imaging and there is a problem of overlapping with BPD. Therefore, it is currently impossible to accurately identify TED using XRT technology. Summary of the Invention

[0006] In order to solve the above problems, the present invention proposes a method for identifying threading dislocations in silicon carbide. The present invention can effectively locate and count different types of dislocations in silicon carbide.

[0007] According to some embodiments, the present invention adopts the following technical solutions: A method for identifying threading dislocations in silicon carbide comprises the following steps: (1) Perform preliminary corrosion on the silicon carbide sample to be identified; (2) Select a suitable diffraction vector , using the Bragg diffraction principle, calculate the selected diffraction vector The incident angle corresponding to the X-ray topography detection is Related parameters of (3) Observe the corrosion pits of the initially corroded silicon carbide sample by TSD and TED, and record the angle between the line connecting the highest point and the lowest point of the corrosion pit and the horizontal. , and get the average value of the selected corrosion pit angle , the average value of the angle Multiply by the selected fixed coefficient Get the coefficient angle , the coefficient angle The incident angle of the selected diffraction vector In comparison, if > , then directly proceed to step (5) for X-ray morphology detection, otherwise, proceed to step (4) for corrosion again; (4) The silicon carbide sample is etched again until the coefficient angle is observed. Greater than the incident angle of the selected diffraction vector ; (5) According to the diffraction vector angle calculated in step (2), the silicon carbide sample is subjected to X-ray morphology detection to obtain a complete image of the silicon carbide sample under the selected diffraction vector. The density values and distribution trends of TSD and TED in the silicon carbide sample are obtained by image recognition as the final dislocation density and distribution on the silicon carbide sample.

[0008] As an optional embodiment, in step (1), the process of performing preliminary corrosion on the silicon carbide sample to be identified includes: placing solid potassium hydroxide into the corrosion furnace, heating and keeping it warm to reach a predetermined corrosion temperature, then placing the selected silicon carbide sample and performing preliminary corrosion after preheating, and ending the corrosion after the predetermined corrosion time and taking out the silicon carbide sample.

[0009] As an optional embodiment, in step (1), the minimum resistivity of the silicon carbide sample to be identified is not less than 10 mΩ·cm.

[0010] As an optional embodiment, the initial corrosion temperature in step (1) is set between 450°C and 600°C, preferably between 500°C and 550°C, and the initial corrosion time can be between 10 min and 50 min, preferably between 15 min and 30 min.

[0011] As an optional embodiment, in step (1), the silicon carbide sample after preliminary etching is cleaned using a weak acid solution, ethanol and deionized water in sequence.

[0012] As an optional embodiment, in step (2), the diffraction vector is 0008, 00012, or 00016.

[0013] As an optional embodiment, in step (3), the corrosion pits are observed using a laser confocal microscope. If the difference in corrosion pit diameters between TSD and TED exceeds a set value, and TSD and TED can be clearly distinguished by the size of the corrosion pit diameters, a certain number of corrosion pits smaller than the predetermined value that can be observed within the microscope field of view are selected; if the difference in corrosion pit diameters between TSD and TED is smaller than a threshold value, and TSD and TED cannot be clearly distinguished by the size of the corrosion pit diameters, a certain number of corrosion pits that can be observed within the microscope field of view are selected.

[0014] As an optional implementation, the number of corrosion pits selected in step (3) is 3-100.

[0015] As an optional implementation, in step (3), the fixed coefficient The range is any value between 1.2-2.0.

[0016] In actual operation, select the fixed coefficient The purpose is to correct the angle between the line connecting the highest and lowest points of the corrosion pit and the horizontal And the corresponding average angle The angle between the line connecting the highest point and the lowest point and the horizontal It is not the maximum angle between the side wall of the corrosion pit and the horizontal, because the side wall of the corrosion pit is often slightly recessed into the crystal, so the corresponding maximum angle It is often greater than the angle between the line connecting the highest point and the lowest point and the horizontal big.

[0017] As an optional embodiment, the duration of the re-corrosion in step (4) is between 1 min and 10 min, and the corrosion temperature of the re-corrosion is the same as the corrosion temperature of the initial corrosion.

[0018] As an optional embodiment, in step (5), the scanning speed when performing X-ray morphology detection on the silicon carbide sample is 1 mm / min-150 mm / min.

[0019] In the step (5), in the image recognition, the specific morphology of the TSD after corrosion is a half-black and half-white dot, wherein the gray value of the half-black part is higher; the specific morphology of the TED after corrosion is a half-black and half-white dot, wherein the gray value of the half-black part is slightly lower.

[0020] As an optional embodiment, in step (5), the Si surface of the silicon carbide sample is preferentially tested.

[0021] As an optional embodiment, the step (5) further includes testing the basal plane dislocation of the silicon carbide sample by etching or XRT.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention cleverly utilizes the principle that different parts of the concave structure of the corrosion pit show different morphologies from the normal surface under XRT measurement. The corrosion pits of TSD and TED can be divided into two parts, one close to the incident line and the other away from the incident line. The part away from the incident line is focused by the X-ray after the incident due to the slightly concave structure of the corrosion pit, and shows a larger gray value in the image measured under the selected diffraction vector, which appears as a semi-black structure of the dislocation dot; because the maximum angle between the side wall of the corrosion pit and the horizontal is and the angle of incidence There is a comparative relationship, if the maximum angle Greater than the angle of incidence , the portion of the etch pit closest to the incident beam is blocked, and after reflection, the intensity of the corresponding portion of light received by the detector is reduced. The image measured using the selected diffraction vector exhibits a lower grayscale value, manifesting as a half-white structure of dislocation dots. By identifying these half-black, half-white dots in XRT, the density and distribution of TSD and TED dislocations can be effectively identified. Compared to traditional etching methods that use etch pit size to distinguish dislocation types, the identification method of this invention is more accurate.

[0023] 2. The present invention takes into account the imaging and extinction conditions of dislocations. The TSD itself appears as a dark black dot under the selected diffraction vector, while the TED itself does not form an image under the selected diffraction vector. Therefore, the one with a larger grayscale value is the TSD, and the one with a smaller grayscale value is the TED. By comparing the grayscale values, the TSD and TED in the half-black and half-white dots can be effectively distinguished. This solves the problem of unclear imaging contrast and inability to accurately identify TED due to the small Burger vector of TED during conventional XRT testing.

[0024] 3. The present invention uses the principle of X-ray diffraction to identify dislocation etching pits. Compared with the traditional alkaline etching method, it can accurately identify different types of dislocations in a substrate with a larger doping concentration range. Compared with the traditional etching method that requires a long etching time to etch the dislocations to a sufficient size, the etching time used in the etching step of the present invention is shorter, which can effectively improve the etching efficiency.

[0025] 4. The method described in this invention utilizes XRT to detect dislocations after etching. Compared with traditional methods that rely solely on optical microscopy to identify etching pits, this method can shorten the etching time and reduce the pit depth to less than 15μm, thereby reducing the damage to the substrate. Since the thickness tolerance of substrates in the field is generally ±25μm, the wafer samples after etching can be further polished, enabling the reuse of the substrate and effectively reducing costs.

[0026] 5. The present invention utilizes a method combining XRT testing with corrosion testing to achieve accurate identification of different types of dislocations on silicon carbide samples, density measurement, and distribution identification.

[0027] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0029] Figure 1 This is the imaging and dislocation identification of TSD and TED corrosion pits under XRT in Example 1 of the present invention; Figure 2 Schematic diagram of the XRT corrosion pit morphology in Example 1 of the present invention; Figure 3 is a cross-sectional view of the corrosion pit in Comparative Example 1 of the present invention; Figure 4 Schematic diagram of the XRT corrosion pit morphology in Comparative Example 2 of the present invention; Figure 5 It is a flow chart of Example 1 of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0031] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0032] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0033] In the absence of conflict, the embodiments and features in the embodiments of this application can be combined with each other.

[0034] Example 1 This embodiment takes a silicon carbide substrate as an example to illustrate a method for identifying threading dislocations in silicon carbide. Figure 5 As shown, the following steps are included: (1) Place solid potassium hydroxide into the corrosion furnace, heat the corrosion furnace to 500℃ and keep it warm for 4 hours. Then select the thickness ,diameter , the minimum resistivity is An N-type silicon carbide substrate was loaded into nickel blue and preheated for 10 minutes. The substrate was then immersed in an etching solution for a 10-minute initial etching. After the initial etching, the substrate was cooled, removed, and cleaned in a weak acid solution, ethanol, and deionized water.

[0035] In other embodiments, in step (1), the minimum resistivity of the selected substrate is not less than 10 mΩ·cm, and preferably, the minimum resistivity value is not less than 15 mΩ·cm. In actual operation, the resistivity of the selected silicon carbide substrate reflects the doping concentration of the substrate. Within a certain appropriate doping concentration range, the substrate can be normally etched into hexagonal and shell-shaped etching pits after etching. If the resistivity of the substrate is too low, it indicates that the doping concentration in the substrate is too high, and traditional KOH etching cannot normally etch pits. Therefore, when selecting a substrate, a substrate with a minimum resistivity of not less than 10 mΩ·cm should be selected.

[0036] In other embodiments, the initial corrosion temperature in step (1) can be set between 450°C and 600°C, preferably between 500°C and 550°C, and the initial corrosion time can be between 10 min and 50 min, preferably between 15 min and 30 min.

[0037] (2) Selection As the diffraction vector, using the Bragg diffraction principle, we can calculate The X-ray incident angle corresponding to the XRT below ( )、X-ray exit angle( ) and the rotation angle ( ) and other test parameters.

[0038] In other embodiments, the diffraction vector selected in step (2) It can also be 00012, 00016.

[0039] (3) Place the initially corroded substrate under a laser confocal microscope to observe and record the corrosion pits of TSD and TED, and select a certain number of small corrosion pits that can be observed within the microscope field of view, which correspond to the corrosion pits of TED.

[0040] In other embodiments, when distinguishing TSD from TED in step (3), large hexagonal etching pits correspond to TSD, and small hexagonal etching pits correspond to TED.

[0041] Optionally, the number of corrosion pits selected in step (3) may be 3-100, preferably 20-50.

[0042] In actual operation, the number of corrosion pits selected determines the average value of the corrosion pit angle. The more corrosion pits are selected, the higher the accuracy. The better it can represent the actual situation of dislocations on the substrate.

[0043] (4) Use a laser confocal microscope to test and record the angle between the line connecting the highest point and the lowest point of each selected small corrosion pit and the horizontal line. , and get the average value of the selected corrosion pit angle Then the average angle Multiply by the selected fixed coefficient Get the coefficient angle .Will The incident angle of the selected diffraction vector In comparison, it was found > .

[0044] In other embodiments, the fixed coefficient by which the incident angle is multiplied when making the comparison in step (4) is The range can be any value between 1.2-2.0, preferably 1.45-1.65.

[0045] In actual operation, select the fixed coefficient The purpose is to correct the angle between the line connecting the highest and lowest points of the corrosion pit and the horizontal And the corresponding average angle The angle between the line connecting the highest point and the lowest point and the horizontal It is not the maximum angle between the side wall of the corrosion pit and the horizontal, because the side wall of the corrosion pit is often slightly recessed into the crystal, so the corresponding maximum angle It is often greater than the angle between the line connecting the highest point and the lowest point and the horizontal big.

[0046] (5) Place the substrate under XRT to test the silicon surface of the substrate and obtain a complete image of the substrate under the selected diffraction vector. The specific morphology of the TSD after corrosion is a half-black and half-white dot, in which the gray value of the half-black part is higher; the specific morphology of the TED after corrosion is a half-black and half-white dot, in which the gray value of the half-black part is slightly lower. Then, the density value and distribution trend of TSD and TED in the substrate are obtained using the existing automatic recognition program. The imaging and dislocation recognition of the TSD and TED corrosion pits under XRT are shown as follows: Figure 1 As shown, the XRT morphology of the corrosion pit is as follows Figure 2 shown.

[0047] In other embodiments, the duration of the re-corrosion in step (5) may be between 1 min and 10 min, preferably between 3 min and 5 min.

[0048] (6) Use the substrate defect meter test to automatically identify the density value and distribution trend of shell-shaped BPD.

[0049] (7) The density values and distribution trends of TSD and TED recorded by XRT test and the density values and distribution trends of BPD recorded by substrate defect instrument test are taken as the final dislocation density and distribution on the silicon carbide substrate.

[0050] In other embodiments, when performing XRT testing, it is preferred to test the Si surface of the silicon carbide substrate. This is because the KOH etching rate on the Si surface is anisotropic, and discernible dislocation etching pits can be obtained.

[0051] In actual operation, it is not necessary to etch for too long when re-etching. After the initial etching, the etching pits on the substrate have reached or are close to the standard > If the substrate is etched again for a similarly long time as the initial etch, the etch pits may become too large and some etch pits may overlap, affecting the measurement. However, the etch temperature of the second etch should be consistent with the etch temperature of the initial etch to ensure consistent etch conditions.

[0052] Optionally, the scanning speed during the XRT test may be 1 mm / min-150 mm / min, preferably 20 mm / min-40 mm / min.

[0053] Figure 1 (a) is the XRT test of a small area of the sample in Example 1, Figure 1 (b) shows the automatic identification of dislocations. For a conductive substrate with normal doping concentration, the TSD identified by this method is a half-black and half-white dot with a stronger grayscale value, which is displayed as Figure 2 The half-black and half-white dots in the enlarged area of (a) are Figure 1 In (b), it is automatically identified as a red dot; TED is a half-black and half-white dot with a slightly weaker grayscale value, which is displayed as Figure 2 The half-black and half-white dots in the enlarged area of (b) are Figure 1 The green dots are automatically identified in (b), which proves that the method of the present invention can effectively identify the density and distribution of TSD and TED dislocations.

[0054] After testing the substrate with KOH corrosion, the corrosion pit depth was 8 μm. After grinding and polishing for 10 μm, the substrate thickness was 340 μm, which still met the conventional substrate thickness requirements and could be reused.

[0055] Example 2 A method for identifying threading dislocations in silicon carbide comprises the following steps: (1) Place solid potassium hydroxide into the corrosion furnace, heat the corrosion furnace to 550℃ and keep it warm for 4 hours. Then select the thickness ,diameter , the minimum resistivity is An N-type silicon carbide substrate was loaded into nickel blue and preheated for 10 minutes. The substrate was then immersed in an etchant for a 30-minute initial etching. After the initial etching, the substrate was cooled, removed, and cleaned sequentially with a weak acid solution, ethanol, and deionized water.

[0056] (2) Selection As the diffraction vector, using the Bragg diffraction principle, we can calculate The X-ray incident angle corresponding to the XRT below ( )、X-ray exit angle( ) and the rotation angle ( ) and other test parameters.

[0057] (3) Place the initially corroded substrate under a laser confocal microscope to observe and record the corrosion pits of TSD and TED, and select a certain number of small corrosion pits that can be observed within the microscope field of view, which correspond to the corrosion pits of TED.

[0058] (4) Use a laser confocal microscope to test and record the angle between the line connecting the highest point and the lowest point of each selected small corrosion pit and the horizontal line. , and get the average value of the selected corrosion pit angle Then the average angle Multiply by the selected fixed coefficient Get the coefficient angle .Will The incident angle of the selected diffraction vector In comparison, it was found ≤ . (5) Place the substrate in the etching furnace again for etching. The etching temperature is 525℃ and the etching time is 4 minutes. After etching, take out the substrate and perform the same cleaning steps as the initial etching. Then perform step (4) again and record the results after the second etching. ,Discover > .

[0059] (6) The substrate is placed under XRT to test the Si surface of the substrate and obtain a complete image of the substrate under the selected diffraction vector. The specific morphology of the TSD after etching is a half-black and half-white dot, in which the half-black portion has a higher grayscale value; the specific morphology of the TED after etching is a half-black and half-white dot, in which the half-black portion has a slightly lower grayscale value. Then, an automatic recognition program is used to obtain the density value and distribution trend of TSD and TED in the substrate, and the morphology and dislocation identification of the TSD and TED corrosion pits under XRT are obtained.

[0060] (7) The density value and distribution trend of shell-shaped BPD are automatically identified using the substrate defect meter test.

[0061] (8) The density values and distribution trends of TSD and TED recorded by XRT test and the density values and distribution trends of BPD recorded by substrate defect instrument test are used as the final dislocation density and distribution on the silicon carbide substrate.

[0062] For N-type silicon carbide substrates with a high doping concentration, the TSD identified by this method is a half-black and half-white dot with a slightly stronger grayscale value, and the TSD is a half-black and half-white dot with a slightly weaker grayscale value, indicating that this method can effectively identify the TSD of substrates with a larger doping concentration range and the density and distribution of TED dislocations.

[0063] After testing the substrate with KOH corrosion, the corrosion pit depth was 5μm. After grinding and polishing for 8μm, the substrate thickness was 492μm, which still met the conventional substrate thickness requirements and can be reused.

[0064] Example 3 A method for identifying threading dislocations in silicon carbide comprises the following steps: (1) Place solid potassium hydroxide into the corrosion furnace, heat the corrosion furnace to 600℃ and keep it warm for 4 hours. Then select the thickness ,diameter , the minimum resistivity is 10 10 A 1.5-1.5-cm semi-insulating silicon carbide substrate was placed in nickel blue and preheated for 10 minutes. The substrate was then immersed in an etchant for a 15-minute initial etching. After the initial etching, the substrate cooled and was removed and cleaned sequentially with a weak acid solution, ethanol, and deionized water.

[0065] (2) Selection As the diffraction vector, using the Bragg diffraction principle, we can calculate The X-ray incident angle corresponding to the XRT below ( )、X-ray exit angle( ) and the rotation angle ( ) and other test parameters.

[0066] (3) Place the initially corroded substrate under a laser confocal microscope to observe and record the corrosion pits of TSD and TED, and select a certain number of small corrosion pits that can be observed within the microscope field of view, which correspond to the corrosion pits of TED.

[0067] (4) Use a laser confocal microscope to test and record the angle between the line connecting the highest point and the lowest point of each selected small corrosion pit and the horizontal line. , and get the average value of the selected corrosion pit angle Then the average angle Multiply by the selected fixed coefficient Get the coefficient angle .Will The incident angle of the selected diffraction vector In comparison, it was found ≤ . (5) Place the substrate in the etching furnace again for etching. The etching temperature is 525℃ and the etching time is 4 minutes. After etching, take out the substrate and perform the same cleaning steps as the initial etching. Then perform step (4) again and record the results after the second etching. ,Discover > .

[0068] (6) The substrate is placed under XRT to test the Si surface of the substrate and obtain a complete image of the substrate under the selected diffraction vector. The specific morphology of the TSD after etching is a half-black and half-white dot, in which the half-black portion has a higher grayscale value; the specific morphology of the TED after etching is a half-black and half-white dot, in which the half-black portion has a slightly lower grayscale value. Then, an automatic recognition program is used to obtain the density value and distribution trend of TSD and TED in the substrate, and the morphology and dislocation identification of the TSD and TED corrosion pits under XRT are obtained.

[0069] (7) The density value and distribution trend of shell-shaped BPD are automatically identified using the substrate defect meter test.

[0070] (8) The density values and distribution trends of TSD and TED recorded by XRT test and the density values and distribution trends of BPD recorded by substrate defect instrument test are used as the final dislocation density and distribution on the silicon carbide substrate.

[0071] For semi-insulating silicon carbide substrates, the TSD identified by this method is a half-black and half-white dot with a slightly stronger grayscale value, and the TSD is a half-black and half-white dot with a slightly weaker grayscale value, indicating that this method can effectively identify the TSD of substrates with a larger doping concentration range and the density and distribution of TED dislocations.

[0072] After testing the substrate with KOH corrosion, the corrosion pit depth was 12 μm. After grinding and polishing for 15 μm, the substrate thickness was 485 μm, which still met the conventional substrate thickness requirements and could be reused.

[0073] Comparative Example 1 The difference between this comparative example and Example 1 is that the corrosion time of the initial corrosion is 60 min, and the fixed coefficient is selected as The rest is the same as in Example 1. Figure 3 (a) is the morphology of the corrosion pit. Figure 3 (b) is a schematic diagram of the cross-section of the etching pit. Due to the long etching time, some dislocation pits overlap in the substrate. At the same time, the maximum depth of the etching pit exceeds 25μm, and the substrate cannot be reused through subsequent grinding and polishing.

[0074] Comparative Example 2 The difference between this comparative example and Example 1 is that the corrosion time of the initial corrosion is 8 min, and the fixed coefficient is selected as The rest is the same as in Example 1. Figure 4 This is the XRT morphology of the corrosion pit. It can be seen that due to the short corrosion time, the TSD corrosion pit morphology is a pure black spot, and the TED corrosion pit is not imaged. The density and distribution of TED dislocations cannot be properly identified because the smaller fixed coefficient outside the appropriate range cannot reflect the maximum angle formed between the side wall of the corrosion pit and the horizontal. , the error is large when comparing, resulting in the corrosion pits not reaching the required angle, and the dislocations cannot appear as a half-black and half-white morphology in XRT, which ultimately makes it impossible to accurately identify the density and distribution of dislocations.

[0075] Comparative Example 3 The difference between this comparative example and Example 1 is that in step (4) ≤ The etching in step (5) is not repeated. The rest is the same as in Example 1. In this comparative example, due to the short etching time, the etching pit does not reach the required angle, and the dislocation cannot show a half-black and half-white morphology in the XRT test. Therefore, the density and distribution of TSD and TED dislocations cannot be accurately identified.

[0076] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made by those skilled in the art that fall within the spirit and principles of the present invention and do not require creative effort are intended to be within the scope of protection of the present invention.

Claims

1. A method for identifying threading dislocations in silicon carbide, characterized in that: The following steps are involved: (1) Perform preliminary corrosion on the silicon carbide sample to be identified; (2) Select a suitable diffraction vector , using the Bragg diffraction principle, calculate the selected diffraction vector The incident angle corresponding to the X-ray topography detection is Related parameters of (3) Observe the corrosion pits of the initially corroded silicon carbide sample by TSD and TED, and record the angle between the line connecting the highest point and the lowest point of the corrosion pit and the horizontal. , and get the average value of the selected corrosion pit angle , the average value of the angle Multiply by the selected fixed coefficient Get the coefficient angle , the coefficient angle The incident angle of the selected diffraction vector In comparison, if > , then directly proceed to step (5) for X-ray morphology detection, otherwise, proceed to step (4) for corrosion again; (4) The silicon carbide sample is etched again until the coefficient angle is observed. Greater than the incident angle of the selected diffraction vector ; (5) According to the diffraction vector angle calculated in step (2), the silicon carbide sample is subjected to X-ray morphology detection to obtain a complete image of the silicon carbide sample under the selected diffraction vector. The density values and distribution trends of TSD and TED in the silicon carbide sample are obtained by image recognition as the final dislocation density and distribution on the silicon carbide sample.

2. The method for identifying threading dislocations in silicon carbide according to claim 1, wherein: In the step (1), the process of performing preliminary corrosion on the silicon carbide sample to be identified includes: placing solid potassium hydroxide into the corrosion furnace, heating and keeping it warm until it reaches a predetermined corrosion temperature, then placing the selected silicon carbide sample and performing preliminary corrosion after preheating, and ending the corrosion after the predetermined corrosion time and taking out the silicon carbide sample; Alternatively, the initial corrosion temperature in step (1) is set between 450°C and 600°C, preferably between 500°C and 550°C, and the initial corrosion time can be between 10 min and 50 min, preferably between 15 min and 30 min; Alternatively, in step (1), the silicon carbide sample after preliminary etching is cleaned in sequence using a weak acid solution, ethanol, and deionized water.

3. The method for identifying threading dislocations in silicon carbide according to claim 1, wherein: In the step (1), the minimum resistivity of the silicon carbide sample to be identified is not less than 10 mΩ·cm.

4. The method for identifying threading dislocations in silicon carbide according to claim 1, wherein: In step (2), the diffraction vector is 0008, 00012, or 00016.

5. The method for identifying threading dislocations in silicon carbide according to claim 1, wherein: In the step (3), the corrosion pits are observed using a laser confocal microscope. If the difference in diameter between the TSD and TED corrosion pits exceeds a set value, and the TSD and TED can be clearly distinguished by the size of the corrosion pit diameters, a certain number of corrosion pits smaller than the predetermined value that can be observed in the field of view of the microscope are selected; if the difference in diameter between the TSD and TED corrosion pits is smaller than a threshold value, and the TSD and TED cannot be clearly distinguished by the size of the corrosion pit diameters, a certain number of corrosion pits that can be observed in the field of view of the microscope are selected.

6. The method for identifying threading dislocations in silicon carbide according to claim 1, wherein: In step (3), the number of corrosion pits selected is 3 to 100; Or, in step (3), the fixed coefficient The range is any value between 1.2-2.

0.

7. The method for identifying threading dislocations in silicon carbide according to claim 1, wherein: The duration of the re-corrosion in step (4) is between 1 min and 10 min, and the corrosion temperature of the re-corrosion is the same as the corrosion temperature of the initial corrosion.

8. The method for identifying threading dislocations in silicon carbide according to claim 1, wherein: In the step (5), the scanning speed when performing X-ray morphology detection on the silicon carbide sample is 1 mm / min-150 mm / min.

9. The method for identifying threading dislocations in silicon carbide according to claim 1, wherein: In the step (5), in the image recognition, the specific morphology of the TSD after corrosion is a half-black and half-white dot, wherein the gray value of the half-black part is higher; the specific morphology of the TED after corrosion is a half-black and half-white dot, wherein the gray value of the half-black part is slightly lower; Alternatively, in step (5), the Si surface of the silicon carbide sample is tested preferentially.

10. The method for identifying threading dislocations in silicon carbide according to claim 1, wherein: The step (5) further includes testing the basal plane dislocation of the silicon carbide sample by etching or XRT.

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