Method for distinguishing TSD and TMD defects in silicon carbide
By etching the single crystal of silicon carbide and observing the depth of field microscopy, a three-dimensional image is formed to distinguish TSD and TMD defects, which solves the problem of difficult to distinguish TSD and TMD in the prior art, and achieves accurate and fast defect resolution.
Patent Information
- Application Number
- CN202510040516.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-10
- Publication Date
- 2025-04-22
AI Technical Summary
The prior art is difficult to accurately and quickly distinguish similar size TSD and TMD defects in silicon carbide, resulting in difficulties in material quality control and device performance improvement.
The single crystal of silicon carbide is etched by using a corrosive agent, and the width and depth information of the corrosion pit are observed through the depth of field microscope to form a three-dimensional image, and TSD and TMD defects are distinguished by the color depth of the corrosion pit.
Accurate resolution of TSD and TMD defects with similar sizes in silicon carbide is achieved, and the shortcomings of conventional identification methods relying on the relative size of corrosion pits are avoided, and a simple, fast and effective identification method is provided.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to the field of material defect detection, and in particular to a method for distinguishing TSD and TMD defects in silicon carbide. Background Art
[0002] As an important wide-bandgap semiconductor material, silicon carbide is widely used in power electronics, optoelectronics, new energy vehicles, etc. However, defects in silicon carbide (SiC) can have a significant impact on its performance. Therefore, accurately and quickly distinguishing these defects is crucial for quality control of silicon carbide materials and improving device performance.
[0003] Defects in silicon carbide materials are usually divided into: point defects (PD), micropipe defects (MP), basal plane dislocations (BPD), edge dislocations (TED), screw dislocations (TSD), stacking dislocations (SF), and combined dislocations (TMD). At present, when using corrosion methods to identify TSD and TMD in SiC substrates, the shape of the corrosion pits and the relative size of the corrosion pits are used for identification. It is generally believed that screw dislocations (TSD) are larger than combined dislocations (TMD). However, this method cannot be used to distinguish dislocations for TMD and TSD with similar sizes and morphologies. Therefore, there is currently a lack of effective technology for quickly distinguishing TSD and TMD with similar sizes.
[0004] Different types of dislocations in the substrate have different effects on SiC epitaxy and devices. For example, TSD in the SiC substrate will penetrate into the epitaxial layer, causing the reverse leakage current of the device to increase; at the same time, TSD may also cause the epitaxial layer to form morphological defects that are extremely harmful to device performance, such as carrot defects and triangle defects. Therefore, accurate identification of dislocation types is crucial for optimizing epitaxial growth and improving device yield. Accurately identifying dislocation types in SiC single crystal materials is of great significance to improving single crystal growth processes and preparing high-performance devices. Summary of the invention
[0005] In view of this, the present invention provides a method for distinguishing TSD and TMD defects in silicon carbide. The method of the present invention can intuitively and clearly distinguish TSD and TMD defects of similar sizes in silicon carbide single crystals.
[0006] The present invention provides a method for distinguishing TSD and TMD defects in silicon carbide, comprising the following steps:
[0007] A) etching the silicon carbide single crystal using an etchant, and then determining whether the etching is qualified;
[0008] The determination method is as follows:
[0009] Use a microscope to observe the dislocation morphology of the sample and measure the width of the silicon carbide silicon surface defect corrosion pit. If the width is 70-100 μm, it is judged to be qualified for etching;
[0010] B) For the sample to be tested that has passed the corrosion test in step A), the width and depth information of the corrosion pits are observed through a depth of field microscope, and a three-dimensional image is formed using the height difference of the corrosion pits. TSD and TMD defects are distinguished by the color depth of the corrosion pits in the three-dimensional image; wherein, the corrosion pits with darker colors are TSD defects, and the corrosion pits with lighter colors are TMD defects.
[0011] Preferably, in step A), the corrosive agent is KOH.
[0012] Preferably, in step A), the etching method comprises:
[0013] S1. Heating the corrosive agent to make it melt;
[0014] S2, placing the silicon carbide wafer into the molten corrosive obtained in step S1 for etching.
[0015] Preferably, in step S1, the heating temperature is 400-550°C;
[0016] In step S2, the etching time is 1 to 35 minutes.
[0017] Preferably, step S1 specifically includes: pouring the corrosive agent into a container, starting the corrosion furnace, setting the temperature of the corrosion furnace, and stabilizing the corrosion furnace for a period of time after the corrosion furnace reaches the set temperature.
[0018] Preferably, the stabilization time is 0.5 to 2 hours.
[0019] Preferably, the container is a crucible made of a material that does not react with molten KOH.
[0020] Preferably, in step A), after etching is completed, the silicon carbide wafer is taken out and cooled to room temperature in air, and then washed with water.
[0021] Preferably, in step B), the depth-of-field microscope is a VHX depth-of-field microscope.
[0022] Preferably, in step A), when determining whether the etching is qualified, if the silicon carbide silicon surface defect corrosion pits are not completely exposed and the widths of the exposed corrosion pits are all less than 700 μm, it is determined to be under-etched; for the above situation, the etching process is repeated until the etching is qualified.
[0023] In view of the problem that the TSD and TMD in the SiC substrate can be roughly judged by comparing the morphology and relative size of the etching pits, but the dislocation type cannot be accurately judged, the present invention provides a method for distinguishing TSD and TMD defects in silicon carbide, which is a method for distinguishing TSD and TMD defects of similar sizes in silicon carbide based on a 3D image of a depth of field microscope. Specifically, a silicon carbide single crystal is first etched with an etchant, and then whether the etching is qualified is determined by a certain judgment standard; for the silicon carbide single crystal that has qualified the etching, the width and depth information of the etching pits are observed through a depth of field microscope, and a three-dimensional image is formed by using the height difference of the etching pits, and the TSD and TMD defects are distinguished by the depth of the color of the etching pits in the three-dimensional image; wherein, the etching pits with darker colors are TSD defects, and the etching pits with lighter colors are TMD defects. The method of the present invention does not need to evaluate the dislocation type by comparing the relative sizes of the corrosion pits, but observes the three-dimensional image formed by the height difference of the dislocation corrosion pits with the help of a VHX depth of field microscope, and distinguishes TSD and TMD dislocations of similar sizes by the color depth of the etching pits in the image. It can clearly distinguish TSD and TMD of similar sizes, avoiding the problem that conventional identification methods that rely on the relative size of the corrosion pits cannot accurately judge. The present invention provides a simple, fast and effective identification method for distinguishing TSD and TMD of similar sizes and similar morphologies. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.
[0025] Figure 1 Schematic diagram of a 4-inch silicon carbide single crystal etched wafer;
[0026] Figure 2 is a schematic diagram of the corrosion pits in the etching of silicon carbide in Example 1;
[0027] Figure 3 is the 3D image created in the resolution method of Example 1;
[0028] Figure 4 Schematic diagram of a 6-inch silicon carbide single crystal etched wafer;
[0029] Figure 5 is the 3D image created in the resolution method of Example 2;
[0030] Figure 6 It is a schematic diagram of an 8-inch silicon carbide single crystal etching wafer;
[0031] Figure 7 This is the 3D image created in the resolution method of Example 3. DETAILED DESCRIPTION
[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.
[0033] In this article, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.
[0034] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.
[0035] Herein, when it comes to numerical ranges, unless otherwise specified, the numerical ranges are deemed to be continuous and include the minimum and maximum values of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.
[0036] In this article, when referring to the units of a data range, if only the right endpoint is followed by a unit, it means that the units of the left and right endpoints are the same.
[0037] The present invention provides a method for distinguishing TSD and TMD defects in silicon carbide, comprising the following steps:
[0038] A) etching the silicon carbide single crystal using an etchant, and then determining whether the etching is qualified;
[0039] The determination method is as follows:
[0040] Use a microscope to observe the dislocation morphology of the sample and measure the width of the silicon carbide silicon surface defect corrosion pit. If the width is 70-100 μm, it is judged to be qualified for etching;
[0041] B) For the sample to be tested that has passed the corrosion test in step A), the width and depth information of the corrosion pits are observed through a depth of field microscope, and a three-dimensional image is formed using the height difference of the corrosion pits. TSD and TMD defects are distinguished by the color depth of the corrosion pits in the three-dimensional image; wherein, the corrosion pits with darker colors are TSD defects, and the corrosion pits with lighter colors are TMD defects.
[0042] [About Step A]:
[0043] A) A silicon carbide single crystal is etched using an etchant, and then it is determined whether the etching is qualified.
[0044] In the present invention, there is no special limitation on the preparation method of the silicon carbide single crystal, and it can be prepared according to the known preparation methods in the art, such as the liquid phase method, the PVT method (i.e., the physical vapor transport method), etc.; among them, the PVT method is the mainstream method for preparing silicon carbide single crystals and is widely used in large-scale production. The present invention has no special limitation on the process of the PVT method, and it can be carried out according to the conventional process flow in the art.
[0045] In the present invention, after the silicon carbide single crystal is grown, it is preferably cut, ground, polished, cleaned, and then etched. There is no special restriction on the size of the cut, and it can be a conventional single crystal size in the art, such as 4 inches, 6 inches, and 8 inches. The above size means that both the forward and the deflection are the above size. For example, a 4-inch single crystal wafer refers to a single crystal wafer with a forward and deflection of 4 inches. Grinding, polishing, and cleaning are all conventional surface treatment processes in the art, and the present invention has no special restrictions on this.
[0046] In the present invention, the etchant used to etch the silicon carbide single crystal is preferably KOH, and specifically, the etching is performed using molten KOH.
[0047] In the present invention, the etching method preferably includes:
[0048] S1. Heating the corrosive agent to make it melt;
[0049] S2, placing the silicon carbide wafer into the molten corrosive obtained in step S1 for etching.
[0050] Regarding step S1:
[0051] In the present invention, the etchant is preferably KOH. The heating temperature is preferably 400-550° C., specifically 400° C., 410° C., 420° C., 430° C., 440° C., 450° C., 460° C., 470° C., 480° C., 490° C., 500° C., 510° C., 520° C., 530° C., 540° C., 550° C. The etchant is melted by the heating treatment.
[0052] In the present invention, step S1 preferably specifically includes: pouring the corrosive agent into a container, turning on the corrosion furnace, setting the temperature of the corrosion furnace, and stabilizing for a period of time after the corrosion furnace reaches the set temperature. Wherein, the container is preferably a crucible, and more preferably a crucible of a material that does not react with molten KOH, such as a graphite crucible. The corrosion furnace can be a resistance furnace. The temperature of the corrosion furnace is set to the target temperature of heating in the above text, which is 400 to 550°C. When the corrosion furnace reaches the set temperature, stabilize for a period of time to ensure that the water in the crucible is completely volatilized. The stabilization time is preferably 0.5 to 2 hours, and can be specifically 0.5 hours, 1.0 hours, 1.5 hours, or 2.0 hours.
[0053] Regarding step S2:
[0054] In the present invention, the method of placing the silicon carbide wafer into the molten corrosive agent obtained in step S1 can be: placing the silicon carbide wafer in a sample cage made of silver wire, and then slowly placing it into the molten corrosive agent.
[0055] In the present invention, the etching time of the silicon carbide wafer in the molten corrosive agent obtained in step S1 is preferably 1 to 35 minutes, specifically 1 minute, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, or 35 minutes.
[0056] In the present invention, after etching is completed, the silicon carbide wafer is taken out and cooled to room temperature in air, and then washed with water. The number of times of washing with water is preferably 2 to 5 times, and after washing with water, a clean silicon carbide etched wafer is obtained.
[0057] In the present invention, after the above-mentioned etching process, the etching of the silicon carbide wafer is determined to be qualified. In the present invention, the determination method is as follows: observe the dislocation morphology of the sample under a microscope, measure the width of the defect corrosion pit on the silicon surface of the silicon carbide, and if the width is 70 to 100 μm, the etching is determined to be qualified. That is, after etching, the present invention observes the corrosion pit on the silicon surface of the silicon carbide single crystal substrate and records the width of the cross-sectional diagram of the TSD and TMD corrosion pits, and then determines whether the etching is successful. Among them, the microscope is preferably a depth of field microscope, and more preferably a VHX depth of field microscope.
[0058] During the judgment process, unqualified situations may also occur: (1) If the exposed corrosion pits on the silicon carbide silicon surface are small and few, and the specific silicon carbide silicon surface defect corrosion pits are not completely exposed and the width of the exposed corrosion pits are all less than 700μm, it is judged as under-corrosion. In this case, repeat the previous etching process until the etching is qualified. (2) If the silicon carbide silicon surface defect corrosion pits are completely exposed and the width of the corrosion pits are all greater than 100μm, it is judged as over-corrosion. To avoid over-corrosion, the degree of corrosion can be controlled by etching conditions. For example, light etching can be performed first. If it is unqualified, the etching can be repeated many times to gradually qualify it.
[0059] [About step B]:
[0060] B) For the sample to be tested that has passed the corrosion test in step A), the width and depth information of the corrosion pits are observed through a depth of field microscope, and a three-dimensional image is formed using the height difference of the corrosion pits. TSD and TMD defects are distinguished by the color depth of the corrosion pits in the three-dimensional image; wherein, the corrosion pits with darker colors are TSD defects, and the corrosion pits with lighter colors are TMD defects.
[0061] In the present invention, for the qualified silicon carbide single crystal sample to be tested in step A), the width and depth information of the corrosion pits are observed by a depth of field microscope, and a three-dimensional image is formed by using the height difference of the corrosion pits. Wherein, the depth of field microscope is preferably a VHX depth of field microscope, and in some embodiments of the present invention, it is a VHX-X1 depth of field microscope. The present invention observes the width and depth information of the corrosion pits with the help of a depth of field microscope, forms a three-dimensional image (3D image) by using the height difference of the corrosion pits, and then distinguishes TSD and TMD defects of similar size by the color depth of the corrosion pits in the three-dimensional image. Specifically, relatively speaking, the corrosion pits have darker colors for TSD defects, and the corrosion pits have lighter colors for TMD defects. The above-mentioned color depth can also be understood as the depth of the color change of the corrosion pits. The TSD corrosion pits are darker, with obvious color changes or obvious color stratification, while the TMD corrosion pits are lighter, with weaker color changes or unclear color stratification. After etching, the silicon carbide wafer is firstly eliminated by the morphology and size. As for the remaining TSD and TMD, the corrosion pit of TSD is relatively deep. The different colors of the 3D image of the depth of field microscope can characterize its depth. The depth of TMD is much smaller than that of TSD, and the color presentation can clearly distinguish them, thereby distinguishing TSD and TMD.
[0062] The present invention provides a method for distinguishing TSD and TMD defects in silicon carbide. The method is a method for distinguishing TSD and TMD defects of similar sizes in silicon carbide based on a 3D image of a depth of field microscope. Specifically, a silicon carbide single crystal is first etched by an etchant, and then whether the etching is qualified is determined by a certain judgment standard; for the silicon carbide single crystal that has qualified etching, the width and depth information of its corrosion pits are observed by a depth of field microscope, a three-dimensional image is formed by the height difference of the corrosion pits, and the TSD and TMD defects are distinguished by the color depth of the corrosion pits in the three-dimensional image; wherein, the corrosion pits with darker colors are TSD defects, and the corrosion pits with lighter colors are TMD defects. The method of the present invention does not need to evaluate the dislocation type by comparing the relative size of the etching pits, but observes the three-dimensional image formed by the height difference of the dislocation etching pits with the help of a VHX depth of field microscope, and distinguishes TSD and TMD dislocations of similar sizes by the color depth of the etching pits in the image. It can clearly distinguish TSD and TMD of similar sizes, avoiding the problem that conventional identification methods that rely on the relative size of the etching pits cannot accurately judge. The present invention provides a simple identification method for distinguishing TSD and TMD of similar size and similar morphology. In addition, the method of the present invention is combined with the traditional SiC etching process, is simple to operate, and is easy to promote; and can be applied to silicon carbide single crystal wafers of different sizes and conductivity types.
[0063] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.
[0064] Example 1
[0065] 1. Test object n-type 4H-SiC single crystal substrate:
[0066] On a large diameter SiC single crystal furnace, a 4-inch 4H-SiC single crystal was grown by using a free seed crystal fixing method. (000-1) C surface seed crystal was used for growth, the growth temperature was controlled at 2100-2200℃, and the growth pressure was 50-300mbar. During the single crystal growth process, inert gas argon was used for protection and nitrogen was doped. After the single crystal was grown, the positive and biased 4-inch 4H-SiC single crystal wafers were obtained through the SiC wafer processing process.
[0067] 2. Identification method:
[0068] A) Etching and determination:
[0069] S1. Pour 90% pure KOH into a graphite crucible, turn on the resistance furnace, set the corrosion temperature to 400°C, and wait for the resistance furnace to reach the set temperature and stabilize for 2 hours.
[0070] S2. Place the silicon carbide wafer in a sample cage made of silver wire, and then slowly place it in 400°C molten KOH for etching for 30 minutes. After the etching is completed, take out the silicon carbide wafer and cool it to room temperature in the air, then wash it with water twice to obtain an etched wafer. The obtained etched wafer is as follows Figure 1 As shown, Figure 1 Schematic diagram of a 4-inch silicon carbide single crystal etched wafer.
[0071] determination:
[0072] The dislocation morphology of the sample was observed under a microscope, and the width of the silicon carbide silicon surface defect corrosion pit was measured. The results showed that the width was 70-100 μm, so it was determined to be qualified for etching. Figure 2 As shown, Figure 2 Schematic diagram of corrosion pits in silicon carbide in Example 1.
[0073] B) For the sample to be tested that has passed the corrosion test in step A), the width and depth information of the corrosion pits are observed through a VHX-X1 depth of field microscope, and a three-dimensional image is formed using the height difference of the corrosion pits. TSD and TMD defects are distinguished by the color depth of the corrosion pits in the three-dimensional image; wherein, the corrosion pits with darker colors are TSD defects, and the corrosion pits with lighter colors are TMD defects.
[0074] The three-dimensional image formed is Figure 3 As shown, Figure 3 This is a 3D image created in the resolution method of Example 1. It can be seen that there are darker corrosion pits (with obvious color changes, or obvious color stratification, and green in the center), which are TSD defects; and lighter corrosion pits (i.e., weaker color changes, or unclear color stratification), which are TMD corrosion pits.
[0075] Example 2
[0076] 1. Test object n-type 4H-SiC single crystal substrate:
[0077] On a large diameter SiC single crystal furnace, a 6-inch 4H-SiC single crystal was grown by using a free seed crystal fixing method. (000-1) C-plane seed crystal was used for growth, the growth temperature was controlled at 2100-2200°C, and the growth pressure was 50-300mbar. During the single crystal growth process, inert gas argon was used for protection and nitrogen was doped. After the single crystal was grown, the positive and biased 6-inch 4H-SiC single crystal wafers were obtained through the SiC wafer processing process.
[0078] 2. Identification method:
[0079] A) Etching and determination:
[0080] S1. Pour 90% KOH into a graphite crucible, turn on the resistance furnace, set the corrosion temperature to 400°C, and wait for the resistance furnace to reach the set temperature and stabilize for 2 hours.
[0081] S2. Place the silicon carbide wafer in a sample cage made of silver wire, and then slowly place it in 400°C molten KOH for etching for 30 minutes. After the etching is completed, take out the silicon carbide wafer and cool it to room temperature in the air, then wash it with water twice to obtain an etched wafer. The obtained etched wafer is as follows Figure 4 As shown, Figure 4 Schematic diagram of a 6-inch silicon carbide single crystal etched wafer.
[0082] determination:
[0083] The sample dislocation morphology was observed under a microscope and the width of the defect corrosion pit on the silicon carbide surface was measured. The results showed that the width was 70 to 100 μm, so the etching was judged to be qualified.
[0084] B) For the sample to be tested that has passed the corrosion test in step A), the width and depth information of the corrosion pits are observed through a VHX-X1 depth of field microscope, and a three-dimensional image is formed using the height difference of the corrosion pits. TSD and TMD defects are distinguished by the color depth of the corrosion pits in the three-dimensional image; wherein, the corrosion pits with darker colors are TSD defects, and the corrosion pits with lighter colors are TMD defects.
[0085] The three-dimensional image formed is Figure 5 As shown, Figure 5 This is a 3D image created in the resolution method of Example 2. It can be seen that there are darker corrosion pits (with obvious color changes, or obvious color stratification, and red in the center), which are TSD defects; and lighter corrosion pits (i.e., weaker color changes, or unclear color stratification), which are TMD corrosion pits.
[0086] Example 3
[0087] 1. Test object n-type 4H-SiC single crystal substrate:
[0088] On a large-diameter SiC single crystal furnace, 8-inch 4H-SiC single crystals were grown using a free seed crystal fixing method. (000-1)C surface seed crystals were used for growth, the growth temperature was controlled at 2100-2200°C, and the growth pressure was 50-300mbar. During the single crystal growth process, inert gas argon was used for protection and nitrogen was doped. After the single crystal was grown, the positive and biased 8-inch 4H-SiC single crystal wafers were obtained through the SiC wafer processing process.
[0089] 2. Identification method:
[0090] A) Etching and determination:
[0091] S1. Pour 90% KOH into a graphite crucible, turn on the resistance furnace, set the corrosion temperature to 400°C, and wait for the resistance furnace to reach the set temperature and stabilize for 2 hours.
[0092] S2. Place the silicon carbide wafer in a sample cage made of silver wire, and then slowly place it in 400°C molten KOH for etching for 30 minutes. After the etching is completed, take out the silicon carbide wafer and cool it to room temperature in the air, then wash it with water twice to obtain an etched wafer. The obtained etched wafer is as follows Figure 6 As shown, Figure 6 Schematic diagram of an 8-inch silicon carbide single crystal etched wafer.
[0093] determination:
[0094] The sample dislocation morphology was observed under a microscope and the width of the defect corrosion pit on the silicon carbide surface was measured. The results showed that the width was 70 to 100 μm, so the etching was judged to be qualified.
[0095] B) For the sample to be tested that has passed the corrosion test in step A), the width and depth information of the corrosion pits are observed through a VHX-X1 depth of field microscope, and a three-dimensional image is formed using the height difference of the corrosion pits. TSD and TMD defects are distinguished by the color depth of the corrosion pits in the three-dimensional image; wherein, the corrosion pits with darker colors are TSD defects, and the corrosion pits with lighter colors are TMD defects.
[0096] The three-dimensional image formed is Figure 7 As shown, Figure 7 This is a 3D image created in the resolution method of Example 3. It can be seen that there are darker corrosion pits (i.e., the corrosion pits circled in red on the right side of the figure, whose colors have obvious changes, or obvious color stratification, and the center is blue), which are TSD defects; and lighter corrosion pits (i.e., the corrosion pits circled in red on the left side of the figure, whose colors have weaker changes, or the color stratification is not obvious), which are TMD corrosion pits.
[0097] In summary, it can be seen that with the help of VHX depth of field microscope, TSD and TMD of similar size can be clearly distinguished, among which the one with obvious color stratification is TSD, and the one with unclear color stratification is TMD. This method provides a simple method to distinguish TSD and TMD of similar size and morphology.
[0098] Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enable any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal expression of the claims, or if they include equivalent structural elements that are not substantially different from the literal expression of the claims, then these other embodiments should also be included in the scope of the claims.
Claims
1. A method for distinguishing TSD and TMD defects in silicon carbide, characterized in that: The following steps are involved: A) etching the silicon carbide single crystal using an etchant, and then determining whether the etching is qualified; The determination method is as follows: Use a microscope to observe the dislocation morphology of the sample and measure the width of the silicon carbide silicon surface defect corrosion pit. If the width is 70-100 μm, it is judged to be qualified for etching; B) For the sample to be tested that has passed the corrosion test in step A), the width and depth information of the corrosion pits are observed through a depth of field microscope, and a three-dimensional image is formed using the height difference of the corrosion pits. TSD and TMD defects are distinguished by the color depth of the corrosion pits in the three-dimensional image; wherein, the corrosion pits with darker colors are TSD defects, and the corrosion pits with lighter colors are TMD defects.
2. The method according to claim 1, characterized in that In step A), the etching agent is KOH.
3. The method according to claim 1 or 2, characterized in that In step A), the etching method comprises: S1. Heating the corrosive agent to make it melt; S2, placing the silicon carbide wafer into the molten corrosive obtained in step S1 for etching.
4. The method according to claim 3, characterized in that In step S1, the heating temperature is 400-550°C; In step S2, the etching time is 1 to 35 minutes.
5. The method according to claim 3, characterized in that Step S1 specifically includes: pouring the corrosive agent into a container, starting the corrosion furnace, setting the temperature of the corrosion furnace, and stabilizing the corrosion furnace for a period of time after the corrosion furnace reaches the set temperature.
6. The method according to claim 5, characterized in that The stable time is 0.5 to 2 hours.
7. The method according to claim 5, characterized in that The container is a crucible made of a material that does not react with molten KOH.
8. The method according to claim 1, characterized in that In step A), after etching is completed, the silicon carbide wafer is taken out and cooled to room temperature in air, and then washed with water.
9. The method according to claim 1, characterized in that In step B), the depth-of-field microscope is a VHX depth-of-field microscope.
10. The method according to claim 1, characterized in that In step A), when determining whether the etching is qualified, if the silicon carbide silicon surface defect corrosion pits are not completely exposed and the widths of the exposed corrosion pits are all less than 700 μm, it is determined to be under-etched; for the above situation, the etching process is repeated until the etching is qualified.