A silicon carbide abrasive sheet and a method for nondestructively detecting a wear layer of the abrasive sheet
Raman spectroscopy was used to perform non-destructive testing on silicon carbide polishing wafers, solving the problem of detecting polishing damage layers, optimizing the polishing and grinding process, and improving the production efficiency and quality of silicon carbide devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SICC CO LTD
- Filing Date
- 2023-06-15
- Publication Date
- 2026-05-29
AI Technical Summary
In the existing technology, it is difficult to effectively detect and remove the grinding damage layer during the grinding process of silicon carbide grinding discs, which leads to the complexity of the subsequent polishing process and the consumption of manpower and resources. In addition, the traditional KOH etching method is a destructive detection method and cannot detect the damage layer in time during the grinding stage.
Raman spectroscopy was used to perform non-destructive testing on the surface of silicon carbide grinding discs. By measuring the stress distribution map, the presence and degree of removal of the grinding damage layer were determined, which guided the improvement of grinding and polishing processes.
This technology enables non-destructive testing of silicon carbide grinding discs, saves processing steps, improves the quality and yield of grinding discs, and reduces material waste and processing costs.
Smart Images
Figure CN119141432B_ABST
Abstract
Description
Technical Field
[0001] This application relates to a silicon carbide grinding disc and a method for grinding damaged layers on a non-destructive testing grinding disc, belonging to the field of silicon carbide production and processing technology. Background Technology
[0002] Silicon carbide crystals are cut and separated using multi-wire dicing to obtain silicon carbide wafer substrates. However, due to the presence of numerous wire marks and dicing damage layers on the surface after dicing, grinding is required to remove these damage layers and obtain polished wafers. During the grinding process, the abrasive material and the silicon carbide substrate are subjected to hard contact friction under pressure through a grinding disc to achieve the purpose of thickening and removing the dicing damage layer. However, this process inevitably introduces grinding damage layers again. Therefore, polished wafers generally require a further polishing process to further remove the grinding damage layers.
[0003] The introduction of a grinding damage layer affects the surface roughness and other physical properties of silicon carbide substrates. Currently, the KOH etching method is often used to verify the presence of a grinding damage layer on wafers. By etching the wafer with a hot KOH solution, the damage on the polished surface can be confirmed. In addition to normal dislocation etching pits, the presence of a large number of densely packed teardrop-shaped etching pits indicates that a grinding damage layer remains after polishing. If only dislocation etching pits are visible under an optical microscope after etching, and other areas are smooth, it indicates that the grinding damage layer has been largely removed. Since the surface of the polished wafer is not mirror-like, the etching process does not reveal any defects. Therefore, this method is only applicable to polished samples. Furthermore, this is a destructive method; if the damage layer is not completely removed, rework to the grinding stage is required for secondary removal, further consuming manpower and resources. Summary of the Invention
[0004] To address the aforementioned issues, a method for non-destructive testing of the grinding damage layer on a grinding disc is provided. Raman spectroscopy allows direct testing of the grinding damage layer on the grinding disc, characterizing the surface stress and thus reflecting the size of the grinding damage layer. This testing method is non-destructive, and the test results can guide improvements in the grinding process to reduce the introduction of grinding damage stress, and also guide subsequent polishing processes to further remove the grinding damage layer.
[0005] According to one aspect of this application, a method for nondestructively testing the damaged layer of a grinding wheel is provided, comprising the following steps:
[0006] (1) Extend 20-30 μm from the surface of the grinding disc to perform Raman testing on the surface layer of the grinding disc to obtain the stress distribution map of the surface layer of the grinding disc.
[0007] (2) Divide the stress distribution map into a first square region and a second square region, both with a side length of 100 μm. The first square region is a region with an absolute stress value greater than 35 MPa, and the second square region is a region with an absolute stress value less than or equal to 30 MPa. If the overall proportion of the stress distribution map in the first square region is greater than 3.5% and is randomly distributed, it indicates that the grinding damage layer has not been completely removed. If the overall proportion of the stress distribution map in the first square region is less than or equal to 3.5% and there is no obvious abnormal random distribution, it indicates that the grinding damage layer can be easily completely removed.
[0008] This Raman spectroscopy method allows for non-destructive testing of polished wafers, eliminating the need to wait until polishing before testing. It provides a more direct reflection of the quality of the polishing process. If the test results show that the polishing damage layer is not completely removed, the method can determine whether to rework to the polishing stage or proceed directly to the polishing stage based on the state of the damage layer. Since polishing removes damage at a slower rate than polishing, when the detection method detects minimal residual polishing damage, polishing can be performed directly to remove the excess damage. However, if the residual damage is severe, polishing alone may not be sufficient, requiring a second polishing process to reduce the damage layer before final polishing. Therefore, this method saves on wafer processing steps and avoids issues such as wafer thinning or unevenness caused by secondary polishing and polishing.
[0009] Optionally, the stress distribution diagram is calculated as follows:
[0010] Coefficient determination: Before Raman testing, calculate the peak position shift and stress conversion coefficient of the polishing disc;
[0011] Test calculation: Based on the peak value and peak offset of the wafer obtained by Raman test, the stress on the surface of the polishing wafer is calculated by the peak offset and the stress conversion coefficient in step S1, thus obtaining the stress distribution map.
[0012] Optionally, the diameter of the grinding disc is 150 mm or more, preferably 200 mm or more.
[0013] Optionally, the calculation steps for the peak position offset and stress conversion coefficient are as follows:
[0014] S1: The interplanar spacing dx and interplanar spacing difference Δd at different positions of the grinding disc are tested and calculated using a testing instrument. The stress values at different positions are calculated using Hooke's law or stress-strain formula.
[0015] S2: Using Raman testing of the peak position value of the grinding disc, calculate the peak position offset at different positions. The ratio of the peak position offset to the stress value is the peak position offset to stress conversion coefficient.
[0016] Optionally, the testing instrument in S1 is selected from any one or more of the following: XRD diffractometer, synchrotron radiation tester, white light tester, neutron diffractometer, scanning electron microscope, and transmission electron microscope.
[0017] When testing the substrate using an XRD diffractometer, the interplanar spacing dx at different locations on the substrate is calculated using the Bragg diffraction formula.
[0018] In the above-mentioned substrate surface stress test and substrate body stress test, the peak position value and peak position offset in step S2 are obtained by fitting, and the fitting function includes Gaussian, Lorentz, GaussLor, AGAuss, Aloren and AgaussLor.
[0019] Optionally, in the Raman test of step (1), an equal-spacing focusing mode is used, wherein the distance between the Raman laser spot at each test point and the surface of the grinding plate is equal, and the peak position value and peak position offset are obtained after fitting.
[0020] The automatic focusing function of the Raman tester ensures that the laser spot hits the surface of the grinding disc, so that the test is not affected by the surface undulation of the grinding disc, thus accurately measuring the stress condition of the grinding disc surface.
[0021] Optionally, the grinding disc is a silicon carbide grinding disc;
[0022] Preferably, the silicon carbide polishing disc has a crystal form of 2H-SiC, 4H-SiC, 6H-SiC, 3C-SiC, or 15R-SiC.
[0023] According to another aspect of this application, a silicon carbide polishing disc is provided, wherein the silicon carbide polishing disc is obtained by cutting and polishing silicon carbide crystals, and the silicon carbide polishing disc includes a first main surface and a second main surface opposite to the first main surface;
[0024] The silicon carbide polishing sheet is divided into a first square region with an absolute surface stress greater than 35 MPa and a length of 100 μm, and a second square region with an absolute surface stress less than or equal to 30 MPa and a length of 100 μm. The ratio of the number of the first square region to the number of the second square region is 1:(30-100), preferably 1:(31-100), and more preferably 1:(67-100).
[0025] The absolute value of the surface stress is the absolute value of the stress detected in a region extending inward from the first main surface or the second main surface for 20-30 μm.
[0026] The smaller the ratio of the number of first square regions to the number of second square regions, the larger the proportion of the second square regions. This means a smaller proportion of the silicon carbide polishing disc contains unremoved polishing damage layers, resulting in better quality of the silicon carbide polishing disc and making it more suitable for subsequent polishing and processing. Preferably, the ratio of the number of first square regions to the number of second square regions is 1:100.
[0027] Due to the limitations of the shape of the silicon carbide polishing disc, there may be cases where the area of the first square region and the second square region at the edge of the silicon carbide polishing disc does not meet the requirement of one first square region or one second square region. Therefore, the number of first square regions and second square regions does not have to be an integer. For example, if the edge of the silicon carbide polishing disc can only be divided into a 50μm region, but the absolute value of the surface stress in this region is less than or equal to 20MPa, then it is calculated as 0.25 second square regions according to the area ratio.
[0028] Optionally, at any plane parallel to the first main surface and / or the second main surface, S1 represents the average absolute value of surface stress in all the first square regions, and S2 represents the average absolute value of surface stress in any of the first square regions, with 0.79 ≤ S1 / S2 ≤ 1.35.
[0029] Optionally, the diameter of the silicon carbide polishing disc is 150 mm or more, preferably 200 mm or more.
[0030] Optionally, at any plane parallel to the first main surface and / or the second main surface, S3 represents the average absolute value of surface stress in all the second square regions, and S4 represents the average absolute value of surface stress in any second square region, with 0.21≤S3 / S4≤1.50;
[0031] Preferably, 1.5≤S1 / S3≤10.
[0032] More preferably, 1.5≤S1 / S3≤9.9.
[0033] Multi-point stress testing is performed on the silicon carbide polishing wafer. The average value of the absolute surface stress in the first square region or the second square region refers to the sum of the absolute surface stress values at all test points in the region and then divided by the number of test points. This multi-point stress testing can be performed by selecting multiple points at different locations in the region, or by performing a mapping test on the substrate.
[0034] The ratio of S1 / S2 mentioned above represents the difference between any one first square region and the average value of all first square regions in the radial direction. The closer the ratio is to 1, the smaller the difference in surface stress among all first square regions in the radial direction, that is, the smaller the regional difference of the polishing damage layer, which means that the polishing damage layer on the silicon carbide polishing disc is more uniformly distributed.
[0035] Similarly, the S3 / S4 ratio represents the difference between any second square region and the average value of all second square regions in the radial direction. The closer the ratio is to 1, the smaller the difference in surface stress among all second square regions in the radial direction, and the more uniform the stress distribution of the silicon carbide polishing disc, i.e., the better the quality of the silicon carbide polishing disc. The S1 / S3 ratio represents the ratio of the average radial internal stress of the silicon carbide substrate with and without a polishing damage layer in the radial direction. It represents the difference between all first square regions and second square regions. The more residual polishing damage layer in the first square region, the greater the stress value of the first square region, and the larger the S1 / S3 ratio, which means the greater the stress difference of the silicon carbide polishing disc, i.e., the worse the quality, and the less conducive it is to subsequent polishing and production processing.
[0036] Optionally, at any plane parallel to the first main surface and / or the second main surface, S max1 Let S be the maximum surface stress in any of the first square regions. min1 Let S be the minimum surface stress in any of the first square regions, ΔS1 = S max1 -S min1 , 10MPa≤△S1≤20MPa.
[0037] Preferably, 10.9MPa≤△S1≤20MPa.
[0038] Optionally, S max2 Let S be the maximum internal stress value in any second square region. min2 Let S be the minimum surface stress in the second square region, ΔS2 = S max2 -S min2 , 10MPa≤△S2≤30MPa.
[0039] Preferably, 10.2MPa≤△S2≤30MPa
[0040] Because the interplanar spacing *d* of a silicon carbide polishing wafer undergoes corresponding stretching and contraction due to tensile and compressive stress, Raman peak intensity will shift towards lower or higher frequencies when using Raman spectroscopy to test the stress. When the silicon carbide polishing wafer is subjected to tensile stress, the Raman peak shifts to lower frequencies, resulting in a positive stress value. When the silicon carbide polishing wafer is subjected to compressive stress, the Raman peak shifts to higher frequencies, resulting in a negative stress value. Therefore, the positive or negative sign before the stress value in this application represents the direction of force on the silicon carbide polishing wafer, and the absolute value of the value represents the magnitude of the stress. For example, if the surface stress in the first square region is -20 MPa and the surface stress in the second square region is -10 MPa, it means that the surface stress in both the first and second square regions is compressive stress, and the surface stress in the first square region is greater than that in the second square region.
[0041] The above S max1 S min1 S max2 and S min2 The meaning is the true value of radial surface stress, which distinguishes between compressive stress and tensile stress in the radial direction. For example, at any plane parallel to the first main surface and / or the second main surface, the radial surface stress of the first square region is -10 to 5 MPa. Then the maximum value of the radial surface stress is 5 MPa, and the minimum value of the radial surface stress is -10 MPa. △S1 is 15 MPa. △S1 and △S2 represent the degree of change between the interplanar spacing of the silicon carbide polishing wafer in the radial direction in the first square region and the second square region, respectively. The smaller △S1 and △S2 are, the smaller the change in interplanar spacing of the silicon carbide polishing wafer in the radial direction, which means that the stress distribution of the silicon carbide polishing wafer is more uniform and the quality of the silicon carbide polishing wafer is better.
[0042] The aforementioned stresses include absolute stress and relative stress. Absolute stress reflects the difference between a wafer and a defect-free, perfect SiC crystal, and is used to determine the stress level of the SiC wafer. However, since it is difficult to achieve a perfectly defect-free wafer with current technology, relative stress can be used to determine the relative stress distribution within the wafer plane.
[0043] For example, if the absolute stress of the wafer is large and the relative stress is small, it indicates that the in-plane lattice distortion causes the stress to be large, but the stress distribution is uniform, the crystal quality is poor, and the stress quality is relatively uniform in all regions of the wafer; if the absolute stress is small and the relative stress is large, the overall wafer quality is good, but there are abnormal stress quality deviations in some areas.
[0044] In this application, the reference value of absolute stress is the reference stress calculated based on the standard Raman peak position obtained from the SiC perfect lattice parameters, and is marked as 0; the relative stress is obtained by taking a reference value on the entire test plane and performing relevant numerical calculations on the value of each test point with the reference value. The reference value includes, but is not limited to, any one of the results calculated by the median, mean, mode or other statistical functions of all stress values on the entire test plane.
[0045] The beneficial effects of this application include, but are not limited to:
[0046] 1. According to the detection method for the grinding damage layer of the grinding disc in this application, the grinding disc is directly tested, which not only directly represents the degree of removal of the grinding damage layer by the grinding process, but also realizes non-destructive testing. Appropriate post-processing procedures can be selected according to the degree of residual grinding damage layer, saving testing time and avoiding waste of grinding discs.
[0047] 2. According to the method for detecting the grinding damage layer of the grinding disc in this application, the results obtained by the detection method can, on the one hand, guide the improvement of the grinding process to reduce the introduction of grinding damage stress, and on the other hand, guide the subsequent polishing process to further remove the grinding damage layer of the grinding disc.
[0048] 3. The silicon carbide polishing disc according to this application has a low residual surface damage layer, which is beneficial for subsequent polishing and processing. Using it to prepare silicon carbide devices can improve the performance and yield of silicon carbide devices, facilitate mass production and processing, and save processing costs of silicon carbide devices.
[0049] 4. According to the silicon carbide polishing disc of this application, the first square region and the second square region have small radial differences, and based on the ratio of the number of all first square regions and all second square regions to the surface stress, it can be seen that the proportion of the first square region is small, thus proving that the silicon carbide polishing disc has good quality. Attached Figure Description
[0050] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:
[0051] Figure 1 This is a flowchart illustrating the calculation of peak position offset and stress conversion coefficient in Embodiment 1 of this application.
[0052] Figure 2 This is a flowchart of the Raman test stress involved in Embodiment 1 of this application.
[0053] Figure 3This is a schematic diagram of the test for surface stress on a Raman equidistant focusing mode abrasive disc.
[0054] Figure 4 This is a Raman spectroscopy image of the grinding disc.
[0055] Figure 5 This is a schematic diagram of a polished disc after being etched with KOH solution. Detailed Implementation
[0056] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0057] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.
[0058] Example 1
[0059] This embodiment relates to a method for detecting the grinding damage layer of a grinding disc, including the following steps:
[0060] (1) Calculation of peak position offset and stress conversion coefficient
[0061] refer to Figure 1 First, a single-crystal XRD diffractometer was used to test silicon carbide wafers, and the parameters of the standard silicon carbide wafers were calculated and compared with the standard parameters based on the reciprocal lattice spatial resolution substrate. Then, according to the Bragg diffraction equation: 2dsinθ=nλ, where d is the interplanar spacing, θ is the diffraction half-angle, n is the diffraction order, and λ is the wavelength, θ and d were tested for different silicon carbide wafers. It was found that the tensile and compressive stresses inside the wafer caused corresponding stretching and contraction changes in the interplanar spacing d. Based on different interplanar spacings d0 and d... x d x The interplanar spacing is divided into d1 and d2, where d0 is the theoretical interplanar spacing, d1 is the interplanar spacing after tensile stress (d1 is greater than d0), and d2 is the interplanar spacing after compressive stress (d2 is less than d0). The difference in interplanar spacing Δd at different positions is calculated, where Δd = d1 - d0 or Δd = d0 - d2.
[0062] Based on the actual peak position of the silicon carbide wafer obtained by Raman testing, the peak position offset Δv at different test points is calculated compared with the standard peak position. The stress value σ of the silicon carbide wafer at different test points is calculated by combining Hooke's law or stress-strain formula. The ratio of the peak position offset to the stress value at different test points is the peak position offset to stress conversion coefficient μ, which ranges from -125 to -2500.
[0063] Hooke's Law is calculated as σ / S = E × (Δd / d0), where S is the area under the action of σ, which is a fixed value; E is the Young's modulus of the substrate, which is a fixed parameter of the substrate; Δd is the difference in interplanar spacing at different locations; d0 is the theoretical interplanar spacing; and σ is the stress value to be calculated.
[0064] The formula for calculating stress and strain is σ=E×△d, where E is the Young's modulus of the substrate, which is a fixed parameter of the substrate, △d is the difference in interplanar spacing at different locations, and σ is the stress value to be calculated.
[0065] (2) Raman test of the grinding disc
[0066] refer to Figure 2 First, the Raman test points are set. Single-point testing or mapping scanning of the entire polished wafer can be performed. Therefore, single-point testing involves setting up scattered coordinate points, while mapping scanning involves 10x10 to 50x50 points or more. The appropriate test method can be selected according to the properties of the substrate to determine the Raman test coordinate diagram of the polished wafer.
[0067] The test results are then output, including but not limited to editable peak positions, peak intensity data, and mapping.
[0068] The output data is then fitted with peak positions using functions including but not limited to Gaussian, Lorentz, GaussLor, AGAuss, Aloren, and AGAussLor, to obtain accurate peak position values and peak position offsets, with the peak position accurate to more than one decimal place.
[0069] Finally, based on the peak position shift and stress conversion coefficient μ calculated in (1) and the peak position shift Δv obtained from the Raman test, the stress value of silicon carbide is calculated. The calculation formula is: σ (MPa)=μ×Δv (cm -1 ).
[0070] The Raman test employs an equidistant focusing method, the testing principle of which is as follows: Figure 3 As shown, Figure 3 (b) Schematic diagram of the Raman laser focusing on the damaged layer on the substrate surface. Figure 3 (a) is a schematic diagram of the test principle. Under this test method, the focusing depth (d) of the Raman laser on the damaged layer on the surface of the grinding disc remains unchanged at different test points.
[0071] By adjusting the parameters of the Raman spectrometer and using the autofocus function to focus the laser onto the surface of the polishing wafer, the surface damage layer of the wafer falls within the laser spot range. This allows for equidistant focused testing at different test points on the polishing wafer, meaning the distance between the focusing plane and the substrate surface remains constant. This method is unaffected by the bending or warping of the polishing wafer surface, ensuring that the obtained Raman peak intensity always remains at the maximum axial value at the test point. Based on the above quantitative stress testing method, the stress test image of the polishing wafer is obtained as follows: Figure 4 As shown, Figure 4 (a) is a schematic diagram showing that the damaged layer of the grinding disc was not completely removed. Figure 4 (b) is a schematic diagram showing the complete removal of the grinding damage layer from the grinding disc.
[0072] Polished discs obtained by etching with hot KOH solution using the same grinding process and then polishing are shown in the following figures. Figure 5 As shown, under an optical microscope, Figure 5 (a) A large number of densely packed, teardrop-shaped corrosion pits are present, which is a schematic diagram of the incomplete removal of the grinding damage layer from the grinding disc. Figure 5 (b) Only dislocation corrosion pits are visible, while other areas are flat and smooth, which is a schematic diagram of the complete removal of the grinding damage layer of the grinding disc.
[0073] Example 2
[0074] This embodiment relates to a grinding process for silicon carbide wafers. The cut silicon carbide wafers are placed in a grinding machine, and a mixed abrasive material consisting of nanofluid, abrasive particles, and a polishing slurry is added to grind the wafers. The grinding process uses a polishing pad with diamond-encrusted particles of size W5. The specific grinding process is as follows:
[0075] 1. First, prepare the nanofluid. Select dispersant-modified SiO2, Si, or SiC as nanoparticles with a concentration of 1.5%-3.5% and a particle size of 10-1000 nm. Use heat-conducting oil or a mixture of ethylene glycol and water as the carrier liquid for the nanofluid. In addition, add 10%-11% dispersant and 3%-5% modifier. Use an ultrasonic stirrer to ultrasonically stir the above solution until the nanoparticles are evenly dispersed in the carrier liquid. Finally, use diluted HCl and NaOH as pH adjusters to adjust the pH to 7.5-9 to obtain the nanofluid.
[0076] In the preparation of nanofluids, the "%" mentioned above refers to the weight percentage of the added substance in the nanofluid carrier liquid.
[0077] Next, the abrasive material is prepared, using nanofluid as the abrasive carrier. 20%-30% of boron carbide and diamond powder are added to the nanofluid, with a weight ratio of boron carbide to diamond powder of 1.5-4:1, a boron carbide particle size of 5-6 μm, and a diamond particle size of 6-8 μm. Then, 1-3% of a suspending agent is added, followed by a dispersant, to achieve a suspending agent to dispersant volume ratio of 1:20-25 in the overall system, thus obtaining the abrasive material.
[0078] In the preparation of abrasive materials, the above "%" refers to the weight percentage of the added substance relative to the nanofluid.
[0079] The dispersants mentioned above include, but are not limited to, glycerol, polyethylene glycol, sodium hexametaphosphate, sodium pyrophosphate, and sodium orthophosphate; the modifiers include, but are not limited to, sodium soft alkylbenzene sulfonate and taurine; and the suspending agents include, but are not limited to, polyvinyl alcohol and BYK.
[0080] 2. Next, the SiC wafers are coarsely ground to remove surface scratches. Diamond powder with a particle size of W7 is selected, and the pressure is 30 g / cm³. 2 The internal and external gear rings were rough ground at a speed ratio of 1:2 for 1 hour.
[0081] 3. After coarse grinding, intermediate grinding is performed to remove micro-cracks under the cutting lines and thin the cutting damage layer. The process used is to select W5 diamond powder and adjust the pressure to 70 g / cm. 2 The intermediate grinding was carried out with the internal and external gear rings rotating at a speed ratio of 1:2, and the grinding time was 1 hour.
[0082] 4. Finally, the sample is finely ground to remove as much of the damage layer introduced by the previous grinding as possible, in order to further remove this layer for subsequent polishing. Diamond powder with a particle size of W3.5 and a pressure of 50 g / cm³ are selected. 2 The internal and external gear rings were precision ground at a speed ratio of 1:4 for 3 hours to obtain silicon carbide grinding discs.
[0083] Using the above grinding process, silicon carbide grinding discs 1#-8# are prepared, wherein steps 2-4 use the above process, and the specific differences in step 1 are as follows:
[0084] Silicon carbide grinding disc #1
[0085] First, the nanofluid was prepared using sodium hexametaphosphate-modified SiC as the nanoparticle, with a concentration of 3.5% and a particle size of 300 nm. A mixture of ethylene glycol and water was used as the carrier liquid for the nanofluid grinding slurry, with a ratio of ethylene glycol to water of 3:5. In addition, 10% glycerol and 0.1% sodium hexametaphosphate were added as dispersants, and 5% soft alkylbenzene sulfonate was added as a modifier. The above solution was ultrasonically stirred until the nanoparticles were uniformly dispersed in the carrier liquid. Finally, diluted HCl and NaOH were used as pH adjusters to adjust the pH to 8 to obtain the nanofluid.
[0086] Next, the abrasive is prepared using nanofluid as the abrasive carrier. 25% boron carbide and diamond powder are added to the nanofluid, with a boron carbide to diamond powder weight ratio of 3:1, a boron carbide particle size of 6 μm, and a diamond particle size of 7 μm. Then, 1.4% BYK is added as a suspending agent, and glycerol is added again as a dispersant, resulting in a suspending agent to dispersant volume ratio of 1:25 in the entire system, thus obtaining abrasive material 1#. The abrasive material 1# is then used to grind the cut wafer in steps 2-4 to obtain silicon carbide abrasive wafer 1#.
[0087] Silicon carbide grinding disc #2
[0088] First, the nanofluid was prepared using sodium pyrophosphate-modified SiO2 as the nanoparticle, with a concentration of 3.5% and a particle size of 10 nm. A mixture of ethylene glycol and water was used as the carrier liquid for the nanofluid grinding slurry, with a ratio of ethylene glycol to water of 3:5. In addition, 10% glycerol and 0.1% sodium pyrophosphate were added as dispersants, and 3% soft alkylbenzene sulfonate was added as a modifier. The above solution was ultrasonically stirred until the nanoparticles were uniformly dispersed in the carrier liquid. Finally, diluted HCl and NaOH were used as pH adjusters to adjust the pH to 7.5 to obtain the nanofluid.
[0089] Next, the abrasive is prepared using nanofluid as the abrasive carrier. 20% boron carbide and diamond powder are added to the nanofluid, with a boron carbide to diamond powder weight ratio of 4:1, a boron carbide particle size of 5 μm, and a diamond particle size of 8 μm. Then, 3% BYK is added as a suspending agent, and glycerol is added again as a dispersant, resulting in a suspending agent to dispersant volume ratio of 1:20 in the entire system, thus obtaining abrasive material 2#. The abrasive material 1# is then used to grind the cut wafer using steps 2-4 to obtain silicon carbide abrasive wafer 2#.
[0090] Silicon carbide grinding disc #3
[0091] First, the nanofluid was prepared using sodium orthophosphate-modified Si as the nanoparticle, with a concentration of 1.5% and a particle size of 1000 nm. A mixture of ethylene glycol and water was used as the carrier liquid for the nanofluid grinding slurry, with a ratio of ethylene glycol to water of 3:5. In addition, 10% glycerol and 1% sodium orthophosphate were added as dispersants, and 5% taurine was added as a modifier. The above solution was ultrasonically stirred until the nanoparticles were evenly dispersed in the carrier liquid. Finally, diluted HCl and NaOH were used as pH adjusters to adjust the pH to 9 to obtain the nanofluid.
[0092] Next, the abrasive is prepared using nanofluid as the abrasive carrier. 30% boron carbide and diamond powder are added to the nanofluid, with a boron carbide to diamond powder weight ratio of 2:1, a boron carbide particle size of 6μm, and a diamond particle size of 6μm. Then, 1% BYK is added as a suspending agent, and glycerol is added again as a dispersant, resulting in a suspending agent to dispersant volume ratio of 1:25 in the entire system, thus obtaining abrasive material 3#. The abrasive material 1# is then used to grind the cut wafer in steps 2-4 to obtain silicon carbide abrasive wafer 3#.
[0093] Silicon carbide grinding disc #4
[0094] The difference between this silicon carbide grinding disc #4 and silicon carbide grinding disc #1 is that: it uses sodium pyrophosphate surface-modified SiO2 and sodium orthophosphate surface-modified Si as nanoparticles, with concentrations of 2% and 1% respectively. The remaining materials and grinding steps are the same as those of silicon carbide grinding disc #1, thus obtaining silicon carbide grinding disc #4.
[0095] Silicon carbide grinding disc #5
[0096] The difference between this silicon carbide grinding disc #5 and silicon carbide grinding disc #1 is that heat-conducting oil is used as the nanofluid carrier liquid, while the other materials and grinding steps are the same as those of silicon carbide grinding disc #1, thus obtaining silicon carbide grinding disc #5.
[0097] Silicon carbide grinding disc #6
[0098] The difference between this silicon carbide grinding disc #6 and silicon carbide grinding disc #1 is that the particle size of the nanoparticles is 800nm. The other materials and grinding steps are the same as those of silicon carbide grinding disc #1, thus obtaining silicon carbide grinding disc #6.
[0099] Comparison of silicon carbide grinding disc D1#
[0100] The difference between this comparative silicon carbide grinding disc D1# and silicon carbide grinding disc 1# is that the concentration of nanoparticles used is 5%, while the other materials and grinding steps are the same as those of silicon carbide grinding disc 1#, thus obtaining comparative silicon carbide grinding disc D1#.
[0101] Comparison of silicon carbide grinding disc D2#
[0102] The difference between this comparative silicon carbide polishing disc D2# and silicon carbide polishing disc 1# is that the boron carbide particle size is 10μm and the diamond particle size is 3μm. The remaining materials and polishing steps are the same as those of silicon carbide polishing disc 1#, thus obtaining comparative silicon carbide polishing disc D2#.
[0103] The silicon carbide polishing wafer described above was characterized using the detection method of Example 1, and the data are shown in Table 1 below.
[0104] Table 1
[0105]
[0106] The performance parameters of the grinding discs in Table 1 are all calculated using relative stress values. The data in Table 1 are only for grinding discs prepared by combining some of the processing parameters in Example 2. When other processing parameters in the grinding process of Example 2 are used to prepare the grinding discs, and when the performance parameters of the grinding discs in Table 1 are characterized by absolute stress, the grinding discs can still meet the requirements that the ratio of the number of the first square region to the number of the second square region is 1:(30-100); 0.79≤S1 / S2≤1.35; 0.21≤S3 / S4≤1.50; 1.5≤S1 / S3≤10; 10MPa≤△S1≤20MPa; 10MPa≤△S2≤30MPa.
[0107] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.
Claims
1. A method for non-destructive testing of the damaged layer of a grinding wheel, characterized in that, Includes the following steps: (1) Extend 20-30 μm inward from the surface of the grinding disc to perform Raman testing on the surface of the grinding disc to obtain the stress distribution map of the surface of the grinding disc; (2) Divide the stress distribution map into a first square region and a second square region, both with a side length of 100 μm. The first square region is a region with an absolute stress value greater than 35 MPa, and the second square region is a region with a stress value less than or equal to 30 MPa. If the overall proportion of the stress distribution map in the first square region is greater than 3.5% and is randomly distributed, it indicates that the grinding damage layer has not been completely removed. If the overall proportion of the stress distribution map in the first square region is less than or equal to 3.5% and there is no obvious abnormal random distribution, it indicates that the grinding damage layer can be easily completely removed.
2. The method according to claim 1, characterized in that, The method for calculating the stress distribution diagram is as follows: Coefficient determination: Before Raman testing, calculate the peak position shift and stress conversion coefficient of the polishing disc; Test calculation: Based on the peak values and peak offsets of the wafer obtained from Raman testing, the stress on the surface of the polished wafer is calculated using the peak offsets and the stress conversion factor, thus obtaining the stress distribution map; and / or The diameter of the grinding disc is 150 mm or more.
3. The method according to claim 2, characterized in that, The calculation steps for the peak position offset and stress conversion coefficient are as follows: S1: Use a testing instrument to test and calculate the interplanar spacing dx and interplanar spacing difference Δd at different positions on the grinding disc, and use Hooke's law or stress-strain formula to calculate the stress value at different positions. S2: Using Raman testing of the peak position value of the grinding disc, calculate the peak position offset at different positions. The ratio of the peak position offset to the stress value is the peak position offset to stress conversion coefficient.
4. The method according to claim 3, characterized in that, The testing instrument in S1 is selected from any one or more of the following: XRD diffractometer, synchrotron radiation tester, white light tester, neutron diffractometer, scanning electron microscope, and transmission electron microscope.
5. The method according to claim 2, characterized in that, In the Raman test of step (1), an equal-spacing focusing mode is used. The equal-spacing focusing mode controls the distance between the Raman laser spot at each test point and the surface of the grinding plate to be equal. After fitting, the peak position value and peak position offset are obtained.
6. A silicon carbide grinding disc, characterized in that, The silicon carbide polishing disc is obtained by cutting and polishing silicon carbide crystals. The silicon carbide polishing disc includes a first main surface and a second main surface opposite to the first main surface. The silicon carbide polishing sheet is divided into a first square region with an absolute surface stress greater than 35 MPa and a length of 100 μm, and a second square region with an absolute surface stress less than or equal to 30 MPa and a length of 100 μm. The ratio of the number of the first square region to the number of the second square region is 1:(30-100). The absolute value of the surface stress is the absolute value of the stress detected in a region extending inward from the first main surface or the second main surface for 20-30 μm.
7. The silicon carbide grinding disc according to claim 6, characterized in that, At any plane parallel to the first main surface and / or the second main surface, S1 represents the average absolute value of surface stress in all the first square regions, and S2 represents the average absolute value of surface stress in any of the first square regions, 0.79≤S1 / S2≤1.35; The diameter of the silicon carbide polishing disc is 150 mm or more.
8. The silicon carbide grinding disc according to claim 7, characterized in that, At any plane parallel to the first main surface and / or the second main surface, S3 represents the average absolute value of surface stress in all the second square regions, S4 represents the average absolute value of surface stress in any second square region, and 0.21≤S3 / S4≤1.
50.
9. The silicon carbide grinding disc according to claim 8, characterized in that, 1.5≤S1 / S3≤10.
10. The silicon carbide grinding disc according to claim 6, characterized in that, At any point on a plane parallel to the first main surface and / or the second main surface, S max1 Let S be the maximum surface stress in any of the first square regions. min1 Let S be the minimum surface stress in any of the first square regions, ΔS1 = S max1 - S min1 , 10MPa≤△S1≤20MPa.
11. The silicon carbide polishing disc according to claim 10, characterized in that, S max2 Let S be the maximum surface stress value in any of the second square regions. min2 Let S be the minimum surface stress in any of the second square regions, ΔS2 = S max2 -S min2 , 10MPa≤△S2≤30MPa.