Silicon carbide wafer and high-accuracy silicon carbide wafer dislocation detection method

Abstract

The invention relates to the technical field of semiconductors, and discloses a silicon carbide wafer and a high-accuracy silicon carbide wafer dislocation detection method. After a silicon carbide wafer is corroded by potassium hydroxide, residues invisible to naked eyes are attached to the surface of the silicon carbide wafer, the residues cannot be removed through water washing and alcohol washing, and even DMF and DMSO solvents which can be mutually soluble with most organic matters cannot effectively remove the residues. In the prior art, when dislocation is detected by combining potassium hydroxide corrosion with an image recognition method, residues still remain on the surface of a wafer due to the fact that cleaning is not in place easily, and then the dislocation number and the dislocation density when dislocation points are misjudged are confirmed as real numerical values. According to the method, after the silicon carbide wafer to be detected is corroded by the molten potassium hydroxide and before dislocation detection, the surface of the silicon carbide wafer is cleaned by the DMAC, so that the dislocation detection result of the silicon carbide wafer is close to the real dislocation result, and the accuracy is relatively high.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a silicon carbide wafer and a high-accuracy silicon carbide wafer dislocation detection method. Background Art

[0002] Silicon carbide (SiC) is a typical representative of the third generation of semiconductor materials. Due to its excellent comprehensive performance, SiC-based devices can work in extreme environments of high temperature, high pressure, and strong radiation, and have broad application prospects in the fields of power electronics and microwave communications. Therefore, SiC materials have important value.

[0003] The quality of SiC crystals has a great impact on the performance of power electronic devices, so the quality of SiC crystal products needs to be controlled and characterized. The production process of silicon carbide crystal products generally includes: crystal growth, forming, cutting, thinning, polishing, packaging, and delivery. Before delivery, samples need to be taken for dislocation detection to characterize and evaluate the quality of the batch of silicon carbide crystal products.

[0004] Dislocation detection for SiC crystals is mainly carried out by potassium hydroxide (KOH) corrosion combined with image recognition. The specific principle is: due to the distortion of the lattice around the dislocation in the silicon carbide single crystal, when the surface of the silicon carbide single crystal is corroded by potassium hydroxide melt, the corrosion rate is faster at the dislocation outcrop on the surface of the silicon carbide single crystal, so it is easy to form corrosion pits with a specific shape composed of certain low-index surfaces, and then observe the shape and size of the corrosion pits by optical microscope, classify the corrosion pits by image recognition technology and calculate the dislocation density. In the prior art, a patent with application publication number CN115896954 A discloses a method for detecting basal plane dislocations in silicon carbide single crystals, which is to identify and determine the dislocation type by corroding the silicon carbide single crystal in molten potassium hydroxide melt, and then observing the shape of the corrosion pits by microscope. However, the dislocation detection method in patent CN115896954A has the following problems: the corrosion residues on the sample surface after corrosion are not fully cleaned, the corrosion residues will affect the identification of dislocations, and the dislocations are only determined by the size and shape of the corrosion pits in the image. The current calculation method is prone to misjudgment. Summary of the invention

[0005] In order to reduce the misjudgment problem of microscopic dislocation identification and improve the accuracy of dislocation detection, more specifically, to solve the problem of low dislocation detection accuracy caused by corrosion residues of potassium hydroxide melt, the present invention provides a silicon carbide wafer and a high-accuracy silicon carbide wafer dislocation detection method.

[0006] The specific technical scheme of the present invention is: On the one hand, the present invention provides a high-accuracy method for detecting dislocations in silicon carbide wafers. Compared with the prior art, the method is outstanding in that after etching with molten potassium hydroxide and before the dislocation detection, the silicon carbide wafer is cleaned with N,N-dimethylacetamide.

[0007] Generally, the dislocation detection of silicon carbide wafers is carried out by using potassium hydroxide melt to corrode the silicon surface of the silicon carbide wafer to make corrosion pits appear at the dislocations, and then the corrosion pits are identified by image method to detect the number of dislocations and the dislocation density, thereby realizing the detection of dislocations. However, according to the above detection method, when the surface of the silicon carbide wafer is corroded by potassium hydroxide melt, corrosion residues are easily left attached to the surface of the wafer. Although there are also prior arts that the corrosion residues on the surface of the sample after the potassium hydroxide melt corrosion will affect the identification of dislocations, most of the prior arts only target the residues visible to the naked eye, or directly perform routine water washing or alcohol washing without targeting.

[0008] The inventors found that when the dislocation detection was realized by the above detection method, after the surface of the silicon carbide wafer was corroded by potassium hydroxide melt, in addition to the residues visible to the naked eye attached to the wafer surface, there were also some residues invisible to the naked eye attached. These residues cannot be removed by washing with organic alcohol solvents such as water and anhydrous ethanol. These residues are similar in size and shape to threading screw dislocation (TSD), threading edge dislocation (TED) or basal plane dislocation (BPD) under a microscope, so they are easily mistakenly identified as one of the above three dislocations, which reduces the accuracy of dislocation detection. Further research has found that the diameter range of these residues invisible to the naked eye is about 1μm~120μm, and more than 50% of the residues have a diameter range of 10μm~80μm. Based on the above findings, in order to overcome the influence of the residues attached to the surface of the silicon carbide wafer caused by the corrosion of potassium hydroxide melt on the accuracy of dislocation detection, the present invention improves the dislocation detection method of the silicon carbide wafer.

[0009] According to the residue attached to the surface of the silicon carbide wafer caused by the corrosion of the molten potassium hydroxide, the present invention attempts to use a variety of solvents to clean the silicon carbide wafer after the silicon carbide wafer is corroded by the molten potassium hydroxide and before the dislocation detection, and finds that only N, N-dimethylacetamide (DMAC) has an effective effect in removing the residue, which is specifically manifested as follows: after the surface of the silicon carbide wafer cleaned by DMAC is cleaned again by DMAC, the number of dislocations per unit field of view measured remains unchanged; while after the surface of the silicon carbide wafer cleaned by acetone, or N, N-dimethylformamide (DMF), or dimethyl sulfoxide (DMSO) is cleaned again by DMAC, the number of dislocations per unit field of view measured decreases, wherein the number of dislocations measured after cleaning with acetone or DMF and then cleaning with DMAC decreases more significantly, which indicates that acetone and DMF have poor removal effects on the residue, and the number of dislocations measured after cleaning with DMSO and then cleaning with DMAC decreases to a certain extent, which indicates that DMSO has a slight effect on removing the residue. The difficulty in improving the accuracy of dislocation detection by potassium hydroxide corrosion combined with image recognition is caused by the following reasons: first, the residue on the wafer surface caused by potassium hydroxide corrosion is invisible to the naked eye and is often ignored, which leads to the misjudgment of the number of dislocations and the dislocation density as the true value; second, the composition of the above-mentioned residues invisible to the naked eye is unknown, and its adhesion performance cannot be determined. It is difficult to remove the above-mentioned residues. Even DMF, which has similar properties to DMAC, cannot effectively remove the above-mentioned residues. Based on the above attempt, the present invention provides a high-accuracy silicon carbide wafer dislocation detection method, that is, after the silicon carbide wafer to be tested is corroded by molten potassium hydroxide and before the dislocation detection, the silicon carbide wafer is cleaned with N,N-dimethylacetamide.

[0010] Specifically, the present invention provides a high-accuracy method for detecting dislocations in silicon carbide wafers, which comprises the following steps: Step S1: placing the silicon carbide wafer in molten potassium hydroxide for etching, then taking it out and cooling it; Step S2: rinsing the cooled silicon carbide wafer; Step S3: using N,N-dimethylacetamide to clean the surface to be tested of the silicon carbide wafer; Step S4: flushing the surface to be tested after being cleaned with N,N-dimethylacetamide; Step S5: using an automatic dislocation tester to test the dislocations on the surface to be tested.

[0011] As a preferred embodiment of the above detection method, in step S1, the corrosion temperature is 480-550°C.

[0012] As a preferred embodiment of the above detection method, in step S1, the corrosion time is 10 to 25 minutes.

[0013] As a preferred embodiment of the above detection method, in step S2, water is used for the rinsing.

[0014] As a preferred embodiment of the above-mentioned detection method, in step S3, the cleaning method is: pouring N,N-dimethylacetamide liquid on the surface to be detected of the silicon carbide wafer to form an N,N-dimethylacetamide liquid pile with a thickness on the surface to be detected, and then placing a cleaning tool on the surface to be detected, applying pressure to the cleaning tool to form a friction force on the surface to be detected, and moving the tool in a circular motion or back and forth friction manner.

[0015] As a preferred embodiment of the above detection method, the tool is selected from dust-free paper, a brush, a sponge, and a dust-free cloth.

[0016] As a preferred embodiment of the above detection method, in step S4, anhydrous ethanol is used for the rinsing.

[0017] As a preferred embodiment of the above detection method, in step S5, the detection field area is not less than 0.01 cm 2 .

[0018] On the other hand, the present invention provides a silicon carbide wafer for dislocation detection, which is outstanding in that, compared with the prior art, after the silicon carbide wafer is etched by molten potassium hydroxide, the diameter of the residue on the surface of the silicon carbide wafer caused by the etching is 1 μm to 120 μm; Furthermore, after the residue on the surface of the silicon carbide wafer is formed due to the corrosion, it is cleaned with N,N-dimethylacetamide.

[0019] Compared with the prior art, the present invention has the following technical effects: After the silicon carbide wafer is corroded by potassium hydroxide, residues invisible to the naked eye will be attached to its surface. The residues cannot be removed by water washing or alcohol washing. Even DMF and DMSO solvents that are miscible with most organic matter cannot effectively remove the above residues. When the prior art uses potassium hydroxide corrosion combined with image recognition to detect dislocations, it is easy to ignore the residues invisible to the naked eye on the wafer surface caused by potassium hydroxide corrosion during the cleaning step, which leads to the misjudgment of the number of dislocations and the dislocation density when the dislocation point is misjudged as the real value. The present invention cleans the surface of the silicon carbide wafer by DMAC after the silicon carbide wafer to be tested is corroded by molten potassium hydroxide and before the dislocation detection, so that the dislocation detection result of the silicon carbide wafer is close to its real dislocation result, and the accuracy rate is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A flow chart of a high-accuracy silicon carbide wafer dislocation detection method provided for an exemplary embodiment; Figure 2 This is a result diagram of dislocation detection per unit field of view of the surface of a silicon carbide wafer cleaned for the first time using DMAC; Figure 3 The surface of the silicon carbide wafer using DMAC for the first cleaning and DMAC for the second cleaning Figure 2 Result diagram of dislocation detection for the same unit field of view; Figure 4 This is a result diagram of dislocation detection per unit field of view of the surface of a silicon carbide wafer cleaned for the first time using DMF; Figure 5 The surface of the silicon carbide wafer was cleaned with DMF for the first cleaning and DMAC for the second cleaning. Figure 4 Result diagram of dislocation detection for the same unit field of view. DETAILED DESCRIPTION

[0021] Here, exemplary embodiments will be described in detail. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with one or more embodiments of the present invention. Instead, they are only examples of devices and methods consistent with some aspects of one or more embodiments of the present invention as detailed in the attached claims.

[0022] To further illustrate the present invention, the following examples are provided: The production process of silicon carbide crystal products generally includes: crystal growth, forming, cutting, thinning, polishing, packaging, and delivery. Before delivery, sampling is required for dislocation detection to characterize and evaluate the quality of the batch of silicon carbide crystal products. The dislocation detection of the present invention is a sampling detection. Therefore, in the present invention, the cleaning step before dislocation detection is different from the cleaning step in the production process such as cutting or polishing. The cleaning step before dislocation detection is only for impurities formed by the corrosion of silicon carbide wafers by potassium hydroxide melt.

[0023] Firstly, the present invention provides a high-accuracy method for detecting dislocations of silicon carbide wafers, which comprises the steps of: after etching with molten potassium hydroxide and before the dislocation detection, the silicon carbide wafer is cleaned with N,N-dimethylacetamide.

[0024] Generally, the dislocation detection of silicon carbide wafers is carried out by using potassium hydroxide melt to corrode the silicon surface of the silicon carbide wafer to make corrosion pits appear at the dislocations, and then the corrosion pits are identified by image method to detect the number of dislocations and the dislocation density, thereby realizing the detection of dislocations. However, according to the above detection method, when the surface of the silicon carbide wafer is corroded by potassium hydroxide melt, corrosion residues are easily left attached to the surface of the wafer. Although there are also prior arts that the corrosion residues on the surface of the sample after the potassium hydroxide melt corrosion will affect the identification of dislocations, most of the prior arts only target the residues visible to the naked eye, or directly perform routine water washing or alcohol washing without targeting.

[0025] The inventors found that when the dislocation detection was realized by the above detection method, after the surface of the silicon carbide wafer was corroded by potassium hydroxide melt, in addition to the residues visible to the naked eye attached to the wafer surface, there were also some residues invisible to the naked eye attached. These residues cannot be removed by washing with organic alcohol solvents such as water and anhydrous ethanol. These residues are similar in size and shape to threading screw dislocation (TSD), threading edge dislocation (TED) or basal plane dislocation (BPD) under a microscope, so they are easily mistakenly identified as one of the above three dislocations, which reduces the accuracy of dislocation detection. Further research has found that the diameter range of these residues invisible to the naked eye is about 1μm~120μm, and more than 50% of the residues have a diameter range of 10μm~80μm. Based on the above findings, in order to overcome the influence of the residues attached to the surface of the silicon carbide wafer caused by the corrosion of potassium hydroxide melt on the accuracy of dislocation detection, the present invention improves the dislocation detection method of the silicon carbide wafer.

[0026] According to the residue attached to the surface of the silicon carbide wafer caused by the corrosion of the molten potassium hydroxide, the present invention attempts to use a variety of solvents to clean the silicon carbide wafer after the silicon carbide wafer is etched with molten potassium hydroxide and before the dislocation detection, and finds that only N,N-dimethylacetamide (DMAC) has an effective effect in removing the residue, which is specifically manifested as follows: after the surface of the silicon carbide wafer cleaned with DMAC is cleaned again with DMAC, the measured number of dislocations per unit field of view remains unchanged, such as Figure 2 and Figure 3 By comparison, the number of dislocations before and after the second DMAC cleaning is the same, which shows that the residue has been removed when the DMAC is used for the first cleaning. After the silicon carbide wafer surface is cleaned with acetone, acetol, N,N-dimethylformamide (DMF), or dimethyl sulfoxide (DMSO), the number of dislocations per unit field of view is reduced after the DMAC cleaning is used again. Figure 4 and Figure 5 By comparison, it can be seen that the first cleaning uses DMF and the second cleaning uses DMAC. At this time, the difference in the number of dislocations detected before and after is large, and the number of dislocations decreases after the second cleaning with DMAC. It can be seen that a large part of the residue was not removed when DMF was used for the first cleaning. Among them, the number of dislocations measured after cleaning with acetone or DMF and then with DMAC decreased significantly, which shows that acetone and DMF have poor removal effects on the residue. The number of dislocations measured after cleaning with DMSO and then with DMAC decreased to a certain extent, which shows that DMSO has a slight effect on the removal of the residue. The difficulty of improving the accuracy of dislocation detection using potassium hydroxide corrosion combined with image recognition is caused by the following reasons: First, the residues on the surface of the chip caused by potassium hydroxide corrosion are invisible to the naked eye and are often ignored, which leads to the number of dislocations and dislocation density when there is a misjudgment of the dislocation point as the true value; second, the composition of the above-mentioned residues that are invisible to the naked eye is unknown, and its adhesion performance cannot be determined. It is difficult to remove the above-mentioned residues. Even DMF, which has similar properties to DMAC, cannot effectively remove the above-mentioned residues. Based on the above attempts, the present invention provides a high-accuracy method for detecting dislocations in silicon carbide wafers, that is, after the silicon carbide wafer to be tested is corroded using molten potassium hydroxide and before the dislocation detection, the silicon carbide wafer is cleaned with N,N-dimethylacetamide.

[0027] Above Figure 4 This is a graph showing the results of dislocation detection per unit field of view on the surface of a silicon carbide wafer that was first cleaned using DMF. Figure 5 The surface of the silicon carbide wafer was cleaned with DMF for the first cleaning and DMAC for the second cleaning. Figure 4 The result diagram of the dislocation detection of the same unit field of view, but due to the normal error of the instrument, the unit field of view point fluctuates. Figure 5 The position of the chip surface corresponding to the unit field of view is Figure 4 The position of the wafer surface corresponding to the unit field of view has a slight displacement, which is within the normal error range. Figure 4 and Figure 5 The sites of real dislocations in the are still largely overlapped.

[0028] The results of trying to use a variety of solvents to clean the above residues indicate the unexpected effect of using DMAC to clean and remove the residues attached to the surface of the silicon carbide wafer caused by the corrosion of the potassium hydroxide melt. DMF and DMAC have similar structures and properties, which are shown in many practical examples that DMF and DMAC have similar solubility. For example, a viscous liquid or solid linear polyester resin is usually difficult to dissolve in water and ethanol, but the linear polyester resin has good solubility in both DMF and DMAC, but the above residues have good solubility in DMAC and poor solubility in DMF. This shows that the present invention has a better effect in dissolving and removing the above residues with DMAC; DMSO is well known for its excellent solubility, and it can dissolve a wide variety of substances, but the above residues have poor solubility in DMF. The solubility in DMSO is poor, while the above residues have good solubility in DMAC, which can explain the better effect of using DMAC to dissolve and remove the above residues in the present invention; acetone and acetol have certain similarities in structure, but acetone and acetol have quite different effects in dissolving and removing the above residues, acetone has a poor dissolving effect on the above residues, while acetol has a certain effect on the dissolution of the above residues, and the dissolution effect of acetol is greater than that of DMSO and DMF, while the dissolution effect of DMAC is greater than that of acetol, which can explain the better effect of using DMAC to dissolve and remove the above residues in the present invention. In summary, the results of cleaning the above residues with a variety of solvents jointly prove that before the present invention was proposed, the use of DMAC to clean and remove the residues attached to the surface of the silicon carbide wafer caused by the corrosion of the potassium hydroxide melt had an unexpected effect.

[0029] Figure 1 1 is a flow chart of a high-accuracy silicon carbide wafer dislocation detection method provided by an exemplary embodiment of the present invention, the dislocation detection method comprising the following steps: Step S1: placing the silicon carbide wafer in molten potassium hydroxide for etching, then taking it out and cooling it; Step S2: rinsing the cooled silicon carbide wafer; Step S3: using N,N-dimethylacetamide to clean the surface to be tested of the silicon carbide wafer; Step S4: flushing the surface to be tested after being cleaned with N,N-dimethylacetamide; Step S5: using an automatic dislocation tester to test the dislocations on the surface to be tested.

[0030] In this embodiment, after the silicon carbide wafer is etched with molten potassium hydroxide, general impurities on the surface of the silicon carbide wafer are removed by washing, and then the residues attached to the surface of the silicon carbide wafer that are difficult to remove due to the corrosion of the molten potassium hydroxide are removed by washing and dissolving with N,N-dimethylacetamide, and then the N,N-dimethylacetamide and the residues dissolved therein are removed by washing, and finally the dislocation status of the surface to be tested is measured by using a dislocation automatic tester, including the number of dislocations and the dislocation density. The dislocation density is: the total number of dislocations in all unit fields of view / the total area of ​​the field of view.

[0031] The general impurities can be understood as impurities on the surface of the silicon carbide wafer that can be removed by clean water or water with a certain flushing force, for example, dust attached to the surface of the silicon carbide wafer, potassium hydroxide, and residues attached to the surface of the silicon carbide wafer caused by corrosion by potassium hydroxide melt with low adhesion, etc., including but not limited to these.

[0032] The automatic dislocation tester can be understood as an automated instrument that counts dislocation types and their numbers based on the shapes of corrosion pits. It can be a common automatic dislocation tester on the market, for example, the FabXLab-LFM series of SiC corrosion wafer defect detectors from Qianshi Technology.

[0033] In one embodiment, in the above step S1, the etching temperature is 480-550° C., and the etching time is 10-25 minutes.

[0034] Etching at a temperature of 480-550°C for 10-25 minutes can expose dislocations on the silicon surface of the silicon carbide wafer according to the theory of selective chemical etching, presenting corrosion pits of certain shapes and sizes, specifically: screw dislocations appear as hexagonal corrosion pits with a diameter of about 100μm-120μm, a sharp bottom and slightly biased to one side; edge dislocations appear as approximately circular corrosion pits with a diameter of about 50μm-80μm, a sharp bottom and slightly biased to one side; basal plane dislocations appear as elliptical corrosion pits with a diameter of about 30μm-80μm, a bottom and severely biased to one side of the ellipse. After the corrosion pits representing dislocations are exposed, they are identified and counted using a dislocation automatic tester.

[0035] In one embodiment, in the above step S2, water is used for the rinsing.

[0036] According to the purpose of the above step S2, it is preferred to use water for rinsing, which can reduce the cost and play a certain cooling effect on the silicon carbide wafer while satisfying the condition of removing general impurities on the surface of the silicon carbide wafer.

[0037] In one embodiment, in the above step S3, the cleaning method is: pouring N,N-dimethylacetamide liquid on the surface to be inspected of the silicon carbide wafer to form an N,N-dimethylacetamide liquid pile with a thickness on the surface to be inspected, and then placing a cleaning tool on the surface to be inspected, applying pressure to the cleaning tool to form a friction force on the surface to be inspected, and moving the tool in a back-and-forth friction manner.

[0038] Specifically, the back-and-forth rubbing can be performed in a circular motion, or in other ways, and the surface formed by the motion trajectory only needs to cover the surface of the wafer.

[0039] Although N,N-dimethylacetamide can dissolve the residues attached to the surface of the silicon carbide wafer caused by the corrosion of the potassium hydroxide melt, and has a good dissolving ability, the residual adhesion of the residues is relatively stubborn and requires certain means to be completely removed. For example, by increasing the use of friction to remove the residues while dissolving N,N-dimethylacetamide, the removal effect is more excellent.

[0040] In one embodiment, the tool is selected from dust-free paper, a brush, a sponge, and a dust-free cloth. The above tools are equivalent to the tools used in step S3.

[0041] In one embodiment, in the above step S4, anhydrous ethanol is used for the rinsing.

[0042] According to the purpose of the above step S4, it is preferred to use anhydrous ethanol for rinsing, which can quickly wash away N,N-dimethylacetamide and the residue dissolved therein, and the drying time is short, so the next step can be quickly performed. The drying can be done by drying, drying naturally, or wiping with dust-free paper or dust-free cloth.

[0043] In one embodiment, in the above step S5, the field of view of the detection is not less than 0.01 cm 2 .

[0044] A larger field of view is selected for dislocation detection, and a larger number of samples are sampled for detection, which can more accurately represent the number of dislocations on the surface of the tested silicon carbide wafer and improve the detection accuracy. The field of view area should be understood as the total field of view area.

[0045] Secondly, the present invention provides a silicon carbide wafer for dislocation detection, which is outstanding in that, compared with the prior art, after the silicon carbide wafer is etched by molten potassium hydroxide, the diameter of the residue on the surface of the silicon carbide wafer caused by the etching is 1 μm to 120 μm; Furthermore, after the residue on the surface of the silicon carbide wafer is formed due to the corrosion, it is cleaned with N,N-dimethylacetamide.

[0046] The present invention has been found in the research that after the silicon carbide wafer is corroded with molten potassium hydroxide, residues invisible to the naked eye will be formed on its surface, and these residues are difficult to remove by conventional water and ethanol washing, and further research has found that the diameter range of these residues invisible to the naked eye is 1μm~120μm. These residues are easily mistaken for dislocations because their size and surface shape are close to the size and shape of the corrosion pits formed by dislocations, which will lead to low accuracy of dislocation testing. Suppressing the influence of these residues can improve the accuracy of dislocation detection. More specifically, since the shape and size of residues greater than 120μm are quite different from the shape and size of the corrosion pits formed by dislocations, they are more obvious under a microscope and have a lower chance of being misjudged, while residues less than 1μm are difficult to be identified by the dislocation automatic tester, and the chance of being misjudged is also low. Therefore, suppressing the influence of residues with a diameter range of 1μm~120μm can further improve the accuracy of dislocation detection.

[0047] Based on the present invention, the above-mentioned "residue" can be defined as a substance other than silicon carbide formed when the silicon carbide wafer is placed in molten potassium hydroxide, which remains on the surface of the silicon carbide wafer and can be formed by the molten potassium hydroxide corroding the silicon carbide wafer.

[0048] The present invention is further described below in conjunction with the embodiments. In the following embodiments, the dislocation automatic tester uses the SiC etching wafer defect detector of the Qianshi Technology FabXLab-LFM series, and the total field of view area of ​​the dislocation detection is 26.88 cm 2 (a total of 1574 test points), the 8-inch silicon carbide wafers used for dislocation detection are from the same batch of silicon carbide single crystal wafers. A person of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are generally only embodiments of a part of the present invention, rather than all of the embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without making creative efforts should fall within the scope of protection of the present invention.

[0049] Example 1 A method for detecting dislocation of a silicon carbide wafer is provided, comprising the following steps: Step S1: placing an 8-inch silicon carbide wafer into molten potassium hydroxide, etching at 500° C. for 20 minutes, taking it out, and cooling it; Step S2: Rinse the cooled silicon carbide wafer with water; Step S3: Pour 5 mL of N,N-dimethylacetamide liquid on the surface to be tested of the silicon carbide wafer to form a N,N-dimethylacetamide liquid pile with a thickness on the surface to be tested, and then place a dust-free paper on the surface to be tested, apply pressure to the dust-free paper to form a friction force on the surface to be tested, and move the dust-free paper in a circular motion so that the surface formed by the movement track of the dust-free paper covers the entire surface to be tested; Step S4: Rinse the surface to be tested after being cleaned in step S3 with anhydrous ethanol, and then wipe it dry with dust-free paper; Step S5: Use the automatic dislocation tester to test the number and dislocation density of screw dislocations, edge dislocations and basal plane dislocations on the test surface. The results of screw dislocations, edge dislocations and basal plane dislocations are shown in Table 1. This test records the first number and first density.

[0050] Example 2 A method for detecting dislocation of a silicon carbide wafer is provided, which differs from the first embodiment only in that step S1 is different and the other steps are the same as those of the first embodiment.

[0051] Step S1 of this embodiment is as follows: An 8-inch silicon carbide wafer was placed in molten potassium hydroxide, etched at 480°C for 25 minutes, taken out, and cooled.

[0052] Example 3 A method for detecting dislocation of a silicon carbide wafer is provided, which differs from the first embodiment only in that step S1 is different and the other steps are the same as those of the first embodiment.

[0053] Step S1 of this embodiment is as follows: An 8-inch silicon carbide wafer was placed in molten potassium hydroxide, etched at 550°C for 10 minutes, taken out, and cooled.

[0054] Example 4 A method for detecting dislocation of a silicon carbide wafer is provided, which differs from the first embodiment only in that the cleaning method in step S3 is different. The other steps are the same as those in the first embodiment.

[0055] Step S3 of this embodiment is as follows: The silicon carbide wafer was completely immersed in N,N-dimethylacetamide for 10 minutes.

[0056] Example 5 A method for detecting dislocation of a silicon carbide wafer is provided, which differs from the first embodiment only in that the cleaning method in step S3 is different. The other steps are the same as those in the first embodiment.

[0057] Step S3 of this embodiment is as follows: The surface to be inspected of the silicon carbide wafer was rinsed with N,N-dimethylacetamide for 12 minutes.

[0058] Example 6 A method for detecting dislocation of a silicon carbide wafer is provided, which differs from Example 1 only in that 10 mL of N,N-dimethylacetamide is used in step S3. The other steps are the same as those in Example 1.

[0059] Step S3 of this embodiment is as follows: Pour 10 mL of N,N-dimethylacetamide liquid on the surface to be tested of the silicon carbide wafer to form a N,N-dimethylacetamide liquid pile with a thickness on the surface to be tested, then place dust-free paper on the surface to be tested, apply pressure to the dust-free paper to form a friction force on the surface to be tested, and move the dust-free paper in a circular motion so that the surface formed by the movement trajectory of the dust-free paper covers the entire surface to be tested.

[0060] Example 7 A method for detecting dislocation of a silicon carbide wafer is provided, which differs from Example 1 only in that 1 mL of N,N-dimethylacetamide is used in step S3. The other steps are the same as those in Example 1.

[0061] Step S3 of this embodiment is as follows: Pour 1 mL of N,N-dimethylacetamide liquid on the surface to be tested of the silicon carbide wafer, then place a dust-free paper on the surface to be tested, apply pressure to the dust-free paper to form a friction force on the surface to be tested, and move the dust-free paper in a circular motion so that the surface formed by the movement trajectory of the dust-free paper covers the entire surface to be tested.

[0062] Example 8 A method for detecting dislocation of a silicon carbide wafer is provided, which differs from Example 1 only in that 5 mL of acetol is used in step S3. The other steps are the same as those in Example 1.

[0063] Step S3 of this embodiment is as follows: Pour 5 mL of acetol liquid on the surface to be tested of the silicon carbide wafer to form a thick N,N-dimethylacetamide liquid pile on the surface to be tested, then place a dust-free paper on the surface to be tested, apply pressure to the dust-free paper to form a friction force on the surface to be tested, and move the dust-free paper in a circular motion so that the surface formed by the movement trajectory of the dust-free paper covers the entire surface to be tested.

[0064] Example 9 A method for detecting dislocation of a silicon carbide wafer is provided, which differs from Example 1 only in that 10 mL of acetol is used in step S3. The other steps are the same as those in Example 1.

[0065] Step S3 of this embodiment is as follows: Pour 10 mL of acetol liquid on the surface to be tested of the silicon carbide wafer to form a thick N,N-dimethylacetamide liquid pile on the surface to be tested, then place a dust-free paper on the surface to be tested, apply pressure to the dust-free paper to form a friction force on the surface to be tested, and move the dust-free paper in a circular motion so that the surface formed by the movement trajectory of the dust-free paper covers the entire surface to be tested.

[0066] Example 10 A method for detecting dislocation of a silicon carbide wafer is provided, which differs from the first embodiment only in that step S4 is different. The other steps are the same as those of the first embodiment.

[0067] Step S4 of this embodiment is as follows: The surface to be inspected after being cleaned in step S3 is rinsed with water, and then wiped dry with dust-free paper.

[0068] Comparative Example 1 A method for detecting dislocation of a silicon carbide wafer is provided, which differs from Example 1 only in that 5 mL of DMF is used in step S3. The other steps are the same as those in Example 1.

[0069] Step S3 of this embodiment is as follows: Pour 5 mL of DMF liquid on the surface to be tested of the silicon carbide wafer to form a thick N,N-dimethylacetamide liquid pile on the surface to be tested, then place a dust-free paper on the surface to be tested, apply pressure to the dust-free paper to form a friction force on the surface to be tested, and move the dust-free paper in a circular motion so that the surface formed by the movement trajectory of the dust-free paper covers the entire surface to be tested.

[0070] Comparative Example 2 A method for detecting dislocation of a silicon carbide wafer is provided, which differs from Example 1 only in that 5 mL of DMSO is used in step S3. The other steps are the same as those in Example 1.

[0071] Step S3 of this embodiment is as follows: Pour 5 mL of DMSO liquid on the surface to be tested of the silicon carbide wafer to form a thick N,N-dimethylacetamide liquid pile on the surface to be tested, then place dust-free paper on the surface to be tested, apply pressure to the dust-free paper to form a friction force on the surface to be tested, and move the dust-free paper in a circular motion so that the surface formed by the movement trajectory of the dust-free paper covers the entire surface to be tested.

[0072] Comparative Example 3 A method for detecting dislocation of a silicon carbide wafer is provided, which differs from Example 1 only in that 5 mL of acetone is used in step S3. The other steps are the same as those in Example 1.

[0073] Step S3 of this embodiment is as follows: Pour 5 mL of acetone liquid on the surface to be tested of the silicon carbide wafer to form a thick N,N-dimethylacetamide liquid pile on the surface to be tested, then place a dust-free paper on the surface to be tested, apply pressure to the dust-free paper to form a friction force on the surface to be tested, and move the dust-free paper in a circular motion so that the surface formed by the movement trajectory of the dust-free paper covers the entire surface to be tested.

[0074] Method accuracy characterization For the silicon carbide wafers after dislocation detection in Examples 1 to 10 and Comparative Examples 1 to 3, all silicon carbide wafers are cleaned on the surface to be detected by step S3 and step S4 of Example 1, and then the number and dislocation density of screw dislocations, edge dislocations and basal plane dislocations on the surface to be detected are detected again by the automatic dislocation tester. The results of screw dislocations, edge dislocations and basal plane dislocations are shown in Tables 1, 2 and 3, respectively, and recorded as the number of repeated tests and the repeated test density, respectively. Among them, the smaller the error rate, the higher the accuracy rate, and the calculation formula of the error rate is: error rate = (first density-repeated test density) / repeated test density.

[0075] Table 1 Detection results of screw dislocation First quantity (pcs) <![CDATA[Initial density (pcs / cm 2 )]]> Number of repeated tests <![CDATA[Repeat test density (pcs / cm 2 )]]> Error rate (%) Example 1 902 34 902 34 0.00 Example 2 917 34 917 34 0.00 Example 3 901 34 901 34 0.00 Example 4 909 34 900 33 1.00 Example 5 906 34 901 34 0.55 Example 6 894 33 894 33 0.00 Example 7 998 37 990 37 0.81 Example 8 1010 38 910 34 10.99 Example 9 1019 38 941 35 8.29 Example 10 934 35 934 35 0.00 Comparative Example 1 1069 40 901 34 18.65 Comparative Example 2 1121 42 972 36 15.33 Comparative Example 3 1106 41 894 33 23.71 Table 2 Detection results of edge dislocation First quantity (pcs) <![CDATA[Initial density (pcs / cm 2 ).]]> Number of repeated tests <![CDATA[Repeat test density (pcs / cm 2 ).]]> Error rate (%) Example 1 50124 1865 50124 1865 0.00 Example 2 50235 1869 50235 1869 0.00 Example 3 50121 1865 50121 1865 0.00 Example 4 50044 1862 49870 1860 0.35 Example 5 50178 1867 50113 1864 0.13 Example 6 50220 1868 50220 1868 0.00 Example 7 50127 1865 50120 1865 0.01 Example 8 50989 1897 50091 1864 1.79 Example 9 50734 1887 50064 1863 1.34 Example 10 50746 1888 50744 1888 0.00 Comparative Example 1 51126 1902 50026 1861 2.20 Comparative Example 2 51124 1902 50017 1861 2.21 Comparative Example 3 51237 1906 50039 1862 2.39 Table 3 Detection results of basal plane dislocation First quantity (pcs) <![CDATA[Initial density (pcs / cm 2 )]]> Number of repeated tests <![CDATA[Repeated test density (pcs / cm 2 )]]> Error rate (%) Example 1 12356 460 12356 460 0.00% Example 2 12098 450 12098 450 0.00% Example 3 12458 463 12458 463 0.00% Example 4 12249 456 12217 455 0.26% Example 5 12147 452 12131 451 0.13% Example 6 12088 450 12088 450 0.00% Example 7 12476 464 12469 464 0.06% Example 8 12457 463 12267 456 1.55% Example 9 12346 459 12222 455 1.01% Example 10 12350 459 12350 459 0.00% Comparative Example 1 13251 493 12794 476 3.57% Comparative Example 2 13156 489 12655 471 3.96% Comparative Example 3 13448 500 12427 462 8.22% From the data analysis in Tables 1 to 3, we can see that: (1) The corrosion of silicon carbide wafers by potassium hydroxide melt will cause residues that are difficult to remove to adhere to the surface of the wafer. The size and shape of these residues are similar to the corrosion pits caused by screw dislocations, edge dislocations or basal plane dislocations, which makes these residues easily misjudged as dislocations, thereby making the number of dislocations and dislocation density at the time of misjudged dislocation points the real values. For example, the initial number and initial density of Comparative Examples 1 to 3 would be misjudged as the real number of dislocations and dislocation density before the present invention.

[0076] (2) It can be seen from Examples 1 to 3 that the present invention can make the number of dislocations and the dislocation density results of repeated dislocation detection completely consistent with the results of the first detection by cleaning the surface of the silicon carbide wafer with DMAC after the silicon carbide wafer to be tested is corroded with molten potassium hydroxide and before the dislocation detection, so that the dislocation detection result of the silicon carbide wafer is almost close to or its real dislocation result, and the accuracy rate is high.

[0077] (3) From the comparative analysis of Example 1 and Comparative Examples 1 to 3, it can be seen that only DMAC has an effective effect in removing the residue, which is specifically manifested as follows: the number of dislocations per unit field of view of the silicon carbide wafer surface cleaned with DMAC remains unchanged after being cleaned again with DMAC; while the number of dislocations per unit field of view of the silicon carbide wafer surface cleaned with DMF (Comparative Example 1), DMSO (Comparative Example 2), or acetone (Comparative Example 3) decreases after being cleaned again with DMAC, among which the number of dislocations measured after being cleaned with acetone or DMF and then cleaned with DMAC decreases more significantly, indicating that acetone and DMF have poor removal effects on the residue, and the number of dislocations measured after being cleaned with DMSO and then cleaned with DMAC decreases to a certain extent, indicating that DMSO has a slight effect on removing the residue. From the comparative analysis of Example 1, Example 8 and Comparative Example 3, it can be seen that the effect of DMAC in removing the above-mentioned residues is greater than that of acetol, and although acetone and acetol have certain similarities in structure, the effects of acetone and acetol in dissolving and removing the above-mentioned residues are quite different. Acetone has a poor dissolving effect on the above-mentioned residues, while acetol has a certain effect on dissolving the above-mentioned residues. From the above analysis, it can be seen that the use of DMAC to clean and remove the residues attached to the surface of the silicon carbide wafer caused by the corrosion of the potassium hydroxide melt has an unexpected effect.

[0078] (4) From the comparative analysis of Example 1 and Examples 4 to 5, it can be seen that the effect of removing the above-mentioned residues can be improved by optimizing the cleaning means, which is specifically reflected in Example 1: by increasing the use of friction to remove the above-mentioned residues under the premise of dissolving N,N-dimethylacetamide, the cleaning effect is more excellent.

[0079] The raw materials and equipment used in the present invention, unless otherwise specified, are all commonly used raw materials and equipment in the art; the methods used in the present invention, unless otherwise specified, are all conventional methods in the art.

[0080] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A high-accuracy method for detecting dislocations in silicon carbide wafers, characterized in that: After etching with molten potassium hydroxide and before the dislocation detection, the silicon carbide wafer was cleaned with N,N-dimethylacetamide.

2. A high-accuracy silicon carbide wafer dislocation detection method as claimed in claim 1, characterized in that: The following steps are involved: Step S1: placing the silicon carbide wafer in molten potassium hydroxide for etching, then taking it out and cooling it; Step S2: rinsing the cooled silicon carbide wafer; Step S3: using N,N-dimethylacetamide to clean the surface to be tested of the silicon carbide wafer; Step S4: flushing the surface to be tested after being cleaned with N,N-dimethylacetamide; Step S5: using an automatic dislocation tester to test the dislocations on the surface to be tested.

3. A high-accuracy silicon carbide wafer dislocation detection method as claimed in claim 2, characterized in that: In step S1, the corrosion temperature is 480-550°C.

4. A high-accuracy silicon carbide wafer dislocation detection method as claimed in claim 2 or 3, characterized in that: In step S1, the corrosion time is 10 to 25 minutes.

5. A high-accuracy silicon carbide wafer dislocation detection method as claimed in claim 2, characterized in that: In step S2, water is used for the rinsing.

6. A high-accuracy silicon carbide wafer dislocation detection method as claimed in claim 2, characterized in that: In step S3, the cleaning method is: pouring N,N-dimethylacetamide liquid on the surface to be tested of the silicon carbide wafer to form a N,N-dimethylacetamide liquid pile with a thickness on the surface to be tested, and then placing a cleaning tool on the surface to be tested, applying pressure to the cleaning tool to form a friction force on the surface to be tested, and moving the tool in a back-and-forth friction manner.

7. A high-accuracy silicon carbide wafer dislocation detection method as claimed in claim 6, characterized in that: The tool is selected from dust-free paper, a brush, a sponge, and a dust-free cloth.

8. A high-accuracy silicon carbide wafer dislocation detection method as claimed in claim 2, characterized in that: In step S4, anhydrous ethanol is used for the washing.

9. A high-accuracy silicon carbide wafer dislocation detection method as claimed in claim 2, characterized in that: In step S5, the field of view of the detection is not less than 0.01 cm 2 .

10. A silicon carbide wafer for dislocation detection, characterized in that: After the silicon carbide wafer is etched using molten potassium hydroxide, the diameter of the residue on the surface of the silicon carbide wafer caused by the etching is 1 μm to 120 μm; Furthermore, after the residue on the surface of the silicon carbide wafer is formed due to the corrosion, it is cleaned with N,N-dimethylacetamide.

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