Method for identifying threading dislocations in silicon carbide

Abstract

The application provides a method for identifying penetrating dislocations in silicon carbide, and the method comprises the following steps: performing preliminary etching on a silicon carbide sample to be identified; selecting a suitable diffraction vector; calculating relevant parameters corresponding to X-ray topography detection under the selected diffraction vector by using Bragg diffraction principle, the relevant parameters containing an incident angle; observing TSD and TED etch pits of the preliminary etched silicon carbide sample; recording an included angle between a line connecting the highest point and the lowest point of the selected etch pit and a horizontal line; obtaining an average value of the included angle of the selected etch pit; multiplying the average value of the included angle by a fixed coefficient to obtain a coefficient included angle; comparing the coefficient included angle with the incident angle of the selected diffraction vector; if the coefficient included angle is greater than the incident angle, directly performing X-ray topography detection; otherwise, etching again; and identifying by using an image of the X-ray topography detection. The application can effectively realize positioning and counting of different types of dislocations in silicon carbide.

Description

Technical Field

[0001] This invention belongs to the field of defect characterization technology of silicon carbide single crystal materials, specifically relating to a method for identifying through dislocations in silicon carbide. Background Technology

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

[0003] Silicon carbide (SiC), as a prominent representative of third-generation semiconductor materials, has brought revolutionary breakthroughs to the field of power semiconductor devices due to its superior properties such as a wider bandgap, a higher critical breakdown electric field, and higher thermal conductivity, making it suitable for applications requiring high frequency, high temperature, and high power. However, compared to silicon single crystals, the dislocation density in silicon carbide single crystals is still relatively high, which to some extent limits the performance of subsequent device fabrication. Among these, screw dislocations (TSDs) and edge dislocations (TEDs) have different degrees of impact on device performance and reliability. Therefore, the ability to accurately identify defects in silicon carbide substrates is of great significance for the further development of the silicon carbide field.

[0004] Currently, there are many methods for characterizing dislocations in silicon carbide, such as alkaline etching, transmission electron diffraction (TEM), photoluminescence spectroscopy (PL), and X-ray morphology detection (XRT). Among these, alkaline etching is commonly used for dislocation detection on whole substrates. The principle of alkaline etching is to utilize the greater lattice distortion and stress in the dislocation region during etching, thereby revealing dislocations by forming anisotropic etching pits. This method can obtain information such as the dislocation density and distribution pattern in silicon carbide by identifying the size and morphology of the etching pits. However, this method still has certain problems. For example, in the existing KOH etching method, both TSD and TED are hexagonal, and they can only be distinguished by observing the size of the etching pits under a microscope. However, the size of the etching pits is affected by factors such as sample doping concentration and etching conditions, making it impossible to completely and accurately distinguish between TSD and TED. Some studies have shown that observing the cross-section of the etching pit and identifying TSD and TED by the pit tilt angle can be used, but this method is too complex and cannot be used for dislocation identification on large-size substrates.

[0005] XRT (Extreme Dislocation Recognition) utilizes the principle of imaging different types of defects using specific diffraction vectors. By selecting different diffraction vectors, various defects in silicon carbide substrates can be effectively located and statistically analyzed. However, XRT also has certain limitations in identifying dislocations, such as TED (Dislocation Traceability), due to its Pareto vector... The small size results in weak imaging and overlaps with BPD, so it is currently impossible to accurately identify TED using XRT technology. Summary of the Invention

[0006] To address the aforementioned problems, this invention proposes a method for identifying penetrating dislocations in silicon carbide. This invention can effectively locate and statistically analyze different types of dislocations in silicon carbide.

[0007] According to some embodiments, the present invention adopts the following technical solution:

[0008] A method for identifying through-dislocations in silicon carbide includes the following steps:

[0009] (1) Perform preliminary etching on the silicon carbide sample to be identified;

[0010] (2) Select a suitable diffraction vector Using the Bragg diffraction principle, the selected diffraction vector is calculated. The incident angle is included in the X-ray topography inspection. Relevant parameters;

[0011] (3) Observe the corrosion pits of the silicon carbide sample with preliminary corrosion by TSD and TED, and record the angle between the line connecting the highest and lowest points of the selected corrosion pit and the horizontal plane. And obtain the average value of the selected corrosion pit angle. The average value of the included angle Multiply by the selected fixed coefficient Obtain the coefficient angle , the angle between the coefficients The incident angle of the selected diffraction vector In comparison, if > If the X-ray morphology is detected, proceed directly to step (5); otherwise, proceed to step (4) for further etching.

[0012] (4) The silicon carbide sample was etched again until the coefficient included angle was observed. Angle of incidence greater than the selected diffraction vector ;

[0013] (5) According to the diffraction vector angle calculated in step (2), X-ray morphology detection is performed on the silicon carbide sample 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, which are used as the final dislocation density and distribution on the silicon carbide sample.

[0014] As an alternative implementation, step (1) includes the process of preliminary etching of the silicon carbide sample to be identified, which includes: putting solid potassium hydroxide into the etching furnace, heating and keeping it at a predetermined etching temperature, then putting in the selected silicon carbide sample and performing preliminary etching after preheating, and ending the etching and taking out the silicon carbide sample after etching for a predetermined time.

[0015] As an alternative implementation, in step (1), the minimum resistivity of the silicon carbide sample to be identified is not less than 10 mΩ·cm.

[0016] As an alternative implementation, 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.

[0017] As an alternative implementation, in step (1), the silicon carbide sample after preliminary etching is cleaned sequentially with a weak acid solution, ethanol and deionized water.

[0018] As an alternative implementation, in step (2), the diffraction vector It is 0008, 00012 or 00016.

[0019] As an alternative implementation, in step (3), corrosion pits are observed using a laser confocal microscope. If the difference in diameter between TSD and TED exceeds a set value, and TSD and TED can be clearly distinguished by the size of the corrosion pit diameter, then 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 diameter between TSD and TED is less than a threshold, and TSD and TED cannot be clearly distinguished by the size of the corrosion pit diameter, then a certain number of corrosion pits that can be observed within the microscope field of view are selected.

[0020] As an alternative implementation, the number of corrosion pits selected in step (3) is 3 to 100.

[0021] As an alternative implementation, in step (3), the fixed coefficient The range is any value between 1.2 and 2.0.

[0022] In practice, a fixed coefficient is selected. The significance lies in correcting the angle between the line connecting the highest and lowest points of the corrosion pit and the horizontal plane. and the corresponding average included angle The angle between the line connecting the highest and lowest points and the horizontal. It is not the maximum angle between the sidewall of the corrosion pit and the horizontal plane, because the sidewall of the corrosion pit is often slightly concave into the crystal, so the corresponding maximum angle is not... It is often compared to the angle between the line connecting the highest and lowest points and the horizontal. big.

[0023] As an optional implementation, the duration of the second corrosion in step (4) is between 1 min and 10 min, and the corrosion temperature of the second corrosion is the same as that of the initial corrosion.

[0024] As an alternative implementation, in step (5), the scanning speed for X-ray morphology detection of the silicon carbide sample is 1 mm / min-150 mm / min.

[0025] In step (5), during image recognition, the morphology of the eroded TSD is a half-black and half-white dot, with the half-black part having a higher gray value; the morphology of the eroded TED is a half-black and half-white dot, with the half-black part having a slightly lower gray value.

[0026] As an alternative implementation, in step (5), the Si surface of the silicon carbide sample is tested first.

[0027] As an alternative implementation, step (5) further includes testing the basal plane dislocations of the silicon carbide sample using etching or XRT.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. This invention cleverly utilizes the principle that the concave structure of corrosion pits exhibits different morphologies from normal surfaces under XRT measurements. The corrosion pits of TSD and TED can be divided into two parts: one near the incident radiation direction and the other away from it. The part away from the incident radiation direction, due to the micro-concave structure of the corrosion pits, causes X-rays to focus after incidence, resulting in a larger grayscale value in the image measured under the selected diffraction vector, appearing as a semi-black structure of dislocation dots; this is because the maximum angle formed between the sidewall of the corrosion pit and the horizontal plane... With the angle of incidence There is a comparative relationship; if the maximum included angle... greater than the angle of incidence When light is reflected, the portion of the corrosion pit near the incident light beam is blocked, resulting in reduced light intensity received by the detector. This leads to a smaller grayscale value in the image measured using the diffraction vector, manifesting as a half-white structure of dislocation dots. By identifying these half-black and half-white dots in XRT, the density and distribution of TSD and TED dislocations can be effectively determined. Compared to traditional corrosion methods that differentiate dislocation types based on pit size, this invention provides a more accurate identification method.

[0030] 2. This invention takes into account the imaging of dislocations and extinction conditions. TSD itself appears as a dark black dot under the selected diffraction vector, while TED itself does not form an image under the selected diffraction vector. Therefore, the one with a larger gray value is TSD, and the one with a smaller gray value is TED. By comparing the gray values, TSD and TED in the half-black and half-white dots can be effectively distinguished. This solves the problem that TED cannot be accurately identified due to the small Burgh's vector of TED when using XRT testing in the conventional way, which results in unclear imaging contrast.

[0031] 3. This invention utilizes the principle of X-ray diffraction to identify dislocation corrosion pits. Compared with the traditional alkaline etching method, it can accurately identify different types of dislocations in substrates with a wider range of doping concentrations. Moreover, compared with the traditional etching method, which requires a long etching time to etch the dislocations to a sufficient size, this invention uses a shorter etching time in the etching process, which can effectively improve the etching efficiency.

[0032] 4. The method described in this invention utilizes XRT detection to identify dislocations after etching. Compared to traditional methods that simply use optical microscopy to detect and identify etching pits, this method allows for a reduction in etching time, resulting in shallower etching pits (not exceeding 15 μm) and thus minimizing the destructive impact of etching on the substrate. Since the standard thickness tolerance for substrates in the market is typically ±25 μm, the wafer samples etched using this method can be further polished, enabling substrate reuse and effectively reducing costs.

[0033] 5. This invention utilizes a combination of XRT testing and etching testing to achieve accurate identification, density measurement, and distribution recognition of different types of dislocations on silicon carbide samples.

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0035] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0036] Figure 1 This describes the imaging and dislocation identification of TSD and TED corrosion pits under XRT in Embodiment 1 of the present invention.

[0037] Figure 2 This is a schematic diagram of the XRT corrosion pit morphology in Embodiment 1 of the present invention;

[0038] Figure 3 This is a cross-sectional view of the corrosion pit in Comparative Example 1 of the present invention;

[0039] Figure 4This is a schematic diagram of the XRT corrosion pit morphology in Comparative Example 2 of the present invention;

[0040] Figure 5 This is a flowchart of Embodiment 1 of the present invention. Detailed Implementation

[0041] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0042] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0043] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0044] Where there is no conflict, the embodiments and features described in this application may be combined with each other.

[0045] Example 1

[0046] This embodiment uses a silicon carbide substrate as an example to illustrate a method for identifying through-dislocations in silicon carbide, such as... Figure 5 As shown, it includes the following steps:

[0047] (1) Add solid potassium hydroxide to the corrosion furnace, heat the furnace to 500℃ and hold for 4 hours. Then select the thickness. ,diameter The minimum resistivity is An N-type silicon carbide substrate was loaded into a nickel blue bath and preheated for 10 minutes. Then, the substrate was immersed in an etching solution for 10 minutes for preliminary etching. After the preliminary etching was completed and the substrate was allowed to cool, it was removed and cleaned sequentially with a weak acid solution, ethanol, and deionized water.

[0048] In other embodiments, in step (1), the minimum resistivity of the selected substrate is not less than 10 mΩ·cm, preferably 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 suitable doping concentration range, the substrate can normally etch hexagonal and shell-shaped corrosion 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.

[0049] 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.

[0050] (2) Select As the diffraction vector, it is calculated using the Bragg diffraction principle. The X-ray incident angle corresponding to the lower XRT ( ), X-ray emission angle ( ) and rotation angle ( Test parameters such as )

[0051] In other embodiments, the diffraction vector selected in step (2) It can also be 00012 or 00016.

[0052] (3) Place the initially etched substrate under a laser confocal microscope to observe and record the corrosion pits of TSD and TED. Select a certain number of small corrosion pits that can be observed within the microscope field of view, corresponding to the corrosion pits of TED.

[0053] In other embodiments, in step (3), when distinguishing between TSD and TED, the larger hexagonal corrosion pit corresponds to TSD, and the smaller hexagonal corrosion pit corresponds to TED.

[0054] Optionally, the number of corrosion pits selected in step (3) can be 3 to 100, preferably 20 to 50.

[0055] In practice, the number of corrosion pits selected determines the average value of the corrosion pit angle. The accuracy of the measurement depends on the number of corrosion pits selected. The better it represents the actual situation of dislocations on the substrate.

[0056] (4) Use a laser confocal microscope to test and record the angle between the line connecting the highest and lowest points of each selected small corrosion pit and the horizontal plane. And obtain the average value of the selected corrosion pit angle. Then, the average angle was calculated. Multiply by the selected fixed coefficient Obtain the coefficient angle .Will The incident angle of the selected diffraction vector In comparison, it was discovered > .

[0057] In other embodiments, the fixed coefficient multiplied by the incident angle during the comparison in step (4) The value can be any value between 1.2 and 2.0, preferably between 1.45 and 1.65.

[0058] In practice, a fixed coefficient is selected. The significance lies in correcting the angle between the line connecting the highest and lowest points of the corrosion pit and the horizontal plane. and the corresponding average included angle The angle between the line connecting the highest and lowest points and the horizontal. It is not the maximum angle between the sidewall of the corrosion pit and the horizontal plane, because the sidewall of the corrosion pit is often slightly concave into the crystal, so the corresponding maximum angle is not... It is often compared to the angle between the line connecting the highest and lowest points and the horizontal. big.

[0059] (5) The substrate was placed under XRT to test the silicon surface of the substrate, and a complete image of the substrate under the selected diffraction vector was obtained. The specific morphology of the etched TSD is half black and half white dots, with the half black part having a higher gray value; the specific morphology of the etched TED is half black and half white dots, with the half black part having a slightly lower gray value. Then, the density values ​​and distribution trends of TSD and TED in the substrate were obtained using the existing automatic identification program. The imaging and dislocation identification of the obtained TSD and TED etch pits under XRT are as follows. Figure 1 As shown, the XRT morphology of the corrosion pits is as follows: Figure 2 As shown.

[0060] In other embodiments, the re-corrosion time in step (5) can be between 1 min and 10 min, preferably between 3 min and 5 min.

[0061] (6) The density value and distribution trend of shell-shaped BPDs are automatically identified by using a substrate defect tester.

[0062] (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 used as the final dislocation density and distribution on silicon carbide substrate.

[0063] In other embodiments, when performing XRT testing, it is preferable to test the Si surface of the silicon carbide substrate. This is because KOH etching exhibits anisotropic etching rates on the Si surface, allowing for the acquisition of identifiable dislocation corrosion pits.

[0064] In practice, a prolonged etching time is not required for subsequent etching. The etch pits on the substrate have already reached or are close to the standard after the initial etching. > If the substrate is subjected to a similar prolonged etching process as the initial etching, it may result in excessively large etch pits, with some pits overlapping and affecting measurements. However, the etching temperature for the second etching should be consistent with the initial etching temperature to ensure consistent etching conditions.

[0065] Optionally, the scanning speed during XRT testing can be 1 mm / min to 150 mm / min, preferably 20 mm / min to 40 mm / min.

[0066] Figure 1 (a) shows the XRT test results of a small area of ​​the sample in Example 1. Figure 1 (b) shows the automatic identification of dislocations. For conductive substrates with normal doping concentration, the TSD identified by this method is a half-black, half-white dot with a stronger grayscale value, displayed as... Figure 2 In (a), the magnified area shows a half-black, half-white dot. Figure 1 In (b), the dots are automatically identified as red; TED represents a half-black, half-white dot with a slightly weaker grayscale value, displayed as... Figure 2 In (b), the magnified area shows a half-black, half-white dot. Figure 1 In (b), the dots are automatically identified as green dots. This confirms that the method described in this invention can effectively identify the density and distribution of TSD and TED dislocations.

[0067] The substrate was tested after KOH etching. The depth of the etched pits was 8 μm. After polishing for 10 μm, the substrate thickness was 340 μm, which still met the requirements for conventional substrate thickness and can be reused.

[0068] Example 2

[0069] A method for identifying through-dislocations in silicon carbide includes the following steps:

[0070] (1) Add solid potassium hydroxide to the corrosion furnace, heat the furnace to 550 ℃ and hold for 4 hours. Then select the thickness. ,diameter The minimum resistivity is An N-type silicon carbide substrate was loaded into a nickel blue bath and preheated for 10 minutes. Then, the substrate was immersed in an etching solution for 30 minutes for preliminary etching. After the preliminary etching was completed and the substrate was allowed to cool, it was removed and cleaned sequentially with a weak acid solution, ethanol, and deionized water.

[0071] (2) Select As the diffraction vector, it is calculated using the Bragg diffraction principle. The X-ray incident angle corresponding to the lower XRT ( ), X-ray emission angle ( ) and rotation angle ( Test parameters such as )

[0072] (3) Place the initially etched substrate under a laser confocal microscope to observe and record the corrosion pits of TSD and TED. Select a certain number of small corrosion pits that can be observed within the microscope field of view, corresponding to the corrosion pits of TED.

[0073] (4) Use a laser confocal microscope to test and record the angle between the line connecting the highest and lowest points of each selected small corrosion pit and the horizontal plane. And obtain the average value of the selected corrosion pit angle. Then, the average angle was calculated. Multiply by the selected fixed coefficient Obtain the coefficient angle .Will The incident angle of the selected diffraction vector In comparison, it was discovered ≤ .

[0074] (5) Place the substrate back into the etching furnace for etching at a temperature of 525°C for 4 minutes. After etching, remove the substrate and clean it using the same steps as the initial etching. Then repeat step (4) and record the etching results. ,Discover > .

[0075] (6) The substrate was placed under XRT to test the Si surface of the substrate, and a complete image of the substrate under the selected diffraction vector was obtained. The specific morphology of the etched TSD was half black and half white dots, with the half black part having a higher gray value; the specific morphology of the etched TED was half black and half white dots, with the half black part having a slightly lower gray value. Then, the density values ​​and distribution trends of TSD and TED in the substrate were obtained using an automatic identification program, and the morphology of the TSD and TED etch pits and the dislocation identification were obtained under XRT.

[0076] (7) The density value and distribution trend of shell-shaped BPDs are automatically identified by using a substrate defect tester.

[0077] (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 silicon carbide substrate.

[0078] For heavily doped N-type silicon carbide substrates, the TSD identified by this method is a half-black and half-white dot with a slightly stronger gray value, while the TSD is a half-black and half-white dot with a slightly weaker gray value. This indicates that this method can effectively identify the density and distribution of TSD and TED dislocations in substrates with a wider range of doping concentrations.

[0079] The substrate was tested after KOH etching. The depth of the etched pits was 5μm. After polishing to 8μm, the substrate thickness was 492μm, which still met the requirements for conventional substrate thickness and can be reused.

[0080] Example 3

[0081] A method for identifying through-dislocations in silicon carbide includes the following steps:

[0082] (1) Add solid potassium hydroxide to the corrosion furnace, heat the furnace to 600 ℃ and hold for 4 hours. Then select the thickness. ,diameter The minimum resistivity is 10. 10 A semi-insulating silicon carbide substrate with an Ω·cm content was loaded into a nickel blue bath and preheated for 10 min. The substrate was then immersed in an etching solution for preliminary etching for 15 min. After the preliminary etching was completed and the substrate was allowed to cool, it was removed and cleaned sequentially with a weak acid solution, ethanol, and deionized water.

[0083] (2) Select As the diffraction vector, it is calculated using the Bragg diffraction principle. The X-ray incident angle corresponding to the lower XRT ( ), X-ray emission angle ( ) and rotation angle ( Test parameters such as )

[0084] (3) Place the initially etched substrate under a laser confocal microscope to observe and record the corrosion pits of TSD and TED. Select a certain number of small corrosion pits that can be observed within the microscope field of view, corresponding to the corrosion pits of TED.

[0085] (4) Use a laser confocal microscope to test and record the angle between the line connecting the highest and lowest points of each selected small corrosion pit and the horizontal plane. And obtain the average value of the selected corrosion pit angle. Then, the average angle was calculated. Multiply by the selected fixed coefficient Obtain the coefficient angle .Will The incident angle of the selected diffraction vector In comparison, it was discovered ≤ .

[0086] (5) Place the substrate back into the etching furnace for etching at a temperature of 525°C for 4 minutes. After etching, remove the substrate and clean it using the same steps as the initial etching. Then repeat step (4) and record the etching results. ,Discover > .

[0087] (6) The substrate was placed under XRT to test the Si surface of the substrate, and a complete image of the substrate under the selected diffraction vector was obtained. The specific morphology of the etched TSD was half black and half white dots, with the half black part having a higher gray value; the specific morphology of the etched TED was half black and half white dots, with the half black part having a slightly lower gray value. Then, the density values ​​and distribution trends of TSD and TED in the substrate were obtained using an automatic identification program, and the morphology of the TSD and TED etch pits and the dislocation identification were obtained under XRT.

[0088] (7) The density value and distribution trend of shell-shaped BPDs are automatically identified by using a substrate defect tester.

[0089] (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 silicon carbide substrate.

[0090] For semi-insulating silicon carbide substrates, the TSD identified by this method is a half-black and half-white dot with a slightly stronger gray value, while the TSD is a half-black and half-white dot with a slightly weaker gray value. This indicates that this method can effectively identify the density and distribution of TSD and TED dislocations in substrates with a wider range of doping concentrations.

[0091] The substrate was tested after KOH etching. The depth of the etched pits was 12 μm. After polishing for 15 μm, the substrate thickness was 485 μm, which still met the requirements for conventional substrate thickness and can be reused.

[0092] Comparative Example 1

[0093] The difference between this comparative example and Example 1 is that the initial corrosion time was 60 minutes, and the selected constant coefficient was [missing value]. The rest is the same as in Example 1. Figure 3 (a) shows the morphology of the corrosion pit. Figure 3 (b) is a schematic diagram of the cross-section of the corrosion pit. Due to the long corrosion time, some dislocation pits overlap in the substrate. At the same time, the maximum depth of the corrosion pit exceeds 25 μm, making it impossible to reuse the substrate through subsequent polishing.

[0094] Comparative Example 2

[0095] The difference between this comparative example and Example 1 is that the initial corrosion time was 8 minutes, and the selected constant coefficient was [missing value]. The rest is the same as in Example 1. Figure 4 The XRT morphology of the corrosion pits shows that, due to the short corrosion time, the TSD corrosion pits appear as pure black dots, while the TED corrosion pits are not imaged, making it impossible to properly identify the density and distribution of TED dislocations. This is because selecting a fixed coefficient smaller than the appropriate range cannot reflect the maximum angle formed between the actual corrosion pit sidewall and the horizontal plane. The large error during comparison resulted in the corrosion pits not reaching the required angle, and the dislocations could not present a half-black and half-white morphology in XRT, ultimately making it impossible to accurately identify the density and distribution of dislocations.

[0096] Comparative Example 3

[0097] The difference between this comparative example and Example 1 is that, in step (4), it was found that... ≤ No further etching in step (5) is performed. The rest is the same as in Example 1. In this comparative example, due to the short etching time, the selected etching pits did not reach the required angle, and the dislocations could not show a half-black and half-white morphology in the XRT test. Therefore, the density and distribution of TSD and TED dislocations could not be accurately identified.

[0098] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art without creative effort within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for identifying through-dislocations in silicon carbide, characterized in that, Includes the following steps: (1) Perform preliminary etching on the silicon carbide sample to be identified; (2) Selecting appropriate diffraction vector , using the principle of Bragg diffraction, the selected diffraction vector X-ray topography corresponding to the detection of the relevant parameters containing the angle of incidence ; (3) Observe the corrosion pits of the silicon carbide sample with preliminary corrosion by TSD and TED, and record the angle between the line connecting the highest and lowest points of the selected corrosion pit and the horizontal plane. And obtain the average value of the selected corrosion pit angle. The average value of the included angle Multiply by the selected fixed coefficient Obtain the coefficient angle , the angle between the coefficients The incident angle of the selected diffraction vector In comparison, if > If the X-ray morphology is detected, proceed directly to step (5); otherwise, proceed to step (4) for further etching. (4) the silicon carbide sample is etched again until the observed coefficient angle is greater than the incident angle of the selected diffraction vector ; (5) According to the diffraction vector angle calculated in step (2), X-ray morphology detection is performed on the silicon carbide sample 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, which are used as the final dislocation density and distribution on the silicon carbide sample.

2. The method of claim 1, wherein the step of identifying the threading dislocations in the silicon carbide is characterized by, In step (1), the process of preliminary etching of the silicon carbide sample to be identified includes: putting solid potassium hydroxide into the etching furnace, heating and keeping it at a predetermined etching temperature, then putting in the selected silicon carbide sample and performing preliminary etching after preheating, and ending the etching and taking out the silicon carbide sample after etching for a predetermined time.

3. The method of claim 2, wherein the step of identifying the threading dislocations in the silicon carbide is characterized by, The initial corrosion temperature in step (1) is set between 450℃ and 600℃, and the initial corrosion time is between 10 min and 50 min.

4. The method of claim 3, wherein the step of identifying the threading dislocations in the silicon carbide is characterized by, The initial corrosion temperature in step (1) is set between 500℃ and 550℃, and the initial corrosion time is between 15 min and 30 min.

5. The method of claim 4, wherein the step of identifying the threading dislocations in the silicon carbide is characterized by, In step (1), the silicon carbide sample after preliminary corrosion is cleaned sequentially with a weak acid solution, ethanol and deionized water.

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

7. The method of claim 1 wherein the step of identifying the threading dislocations in the silicon carbide is characterized by, In the step (2), the diffraction vector is 0008, 00012 or 00016.

8. The method of claim 1 wherein the step of identifying the threading dislocations in the silicon carbide is characterized by, In step (3), the corrosion pits are observed using a laser confocal microscope. If the difference in diameter between the corrosion pits of TSD and TED exceeds a set value, and TSD and TED can be clearly distinguished by the size of the corrosion pit diameter, then 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 diameter between the corrosion pits of TSD and TED is less than a threshold, and TSD and TED cannot be clearly distinguished by the size of the corrosion pit diameter, then a certain number of corrosion pits that can be observed within the microscope field of view are selected.

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

0.

10. The method of claim 1 wherein the step of identifying the threading dislocations in the silicon carbide is characterized by, In step (4), the duration of the second corrosion is between 1 min and 10 min, and the corrosion temperature of the second corrosion is the same as that of the initial corrosion.

11. The method for identifying through-dislocations in silicon carbide as described in claim 1, characterized in that, In step (5), the scanning speed for X-ray morphology detection of silicon carbide samples is 1 mm / min-150 mm / min.

12. The method of claim 1 wherein the method is for identifying a threading dislocation in silicon carbide, and wherein the method further comprises: In step (5), during image recognition, the morphology of the eroded TSD is a half-black and half-white dot, with the half-black part having a higher gray value; the morphology of the eroded TED is a half-black and half-white dot, with the half-black part having a slightly lower gray value. ​ Alternatively, in step (5), the Si surface of the silicon carbide sample is tested first.

13. The method for identifying through-dislocations in silicon carbide as described in claim 1, characterized in that, Step (5) also includes testing the basal plane dislocations of the silicon carbide sample using etching or XRT.

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