Diamond micro powder specially used for rough grinding of silicon carbide wafers and preparation method thereof

Abstract

The present invention provides a method for preparing diamond micropowder for rough grinding of silicon carbide wafers, which specifically comprises the following steps: (1) taking diamond micropowders of different particle sizes and mixing them; (2) adding the diamond micropowders uniformly mixed in step (1) to a reactor containing a dilute acid solution under stirring conditions to react, and at the same time, adding a hydrogen peroxide solution to the reactor during the entire reaction process until the reaction is completed; (3) washing the diamond micropowder treated with acid in step (2) with pure water until the pH value of the supernatant is between 6 and 7; dispersing the diamond micropowder in pure water to obtain a diamond micropowder dispersion; (4) wet sieving the diamond micropowder dispersion in step (3); and obtaining a diamond micropowder abrasive for rough grinding of silicon carbide wafers. The prepared diamond micropowder is used for rough grinding of silicon carbide wafers, and the removal rate of the rough grinding is high, and the surface of the silicon carbide wafer is not damaged, which significantly improves the processing efficiency and quality.

Description

Technical Field

[0001] The invention belongs to the technical field of silicon carbide processing, and in particular relates to a diamond micro powder specially used for rough grinding of silicon carbide wafers and a preparation method thereof. Background Art

[0002] As a third-generation semiconductor material, silicon carbide crystal has great application prospects in high-temperature, high-frequency, high-power and radiation-resistant devices. However, due to its high hardness, high brittleness and good chemical stability, it is difficult to process. The commonly used processing procedures for silicon carbide crystals are mortar cutting-chamfering-double-sided rough grinding-double-sided fine grinding-double-sided rough polishing-single-sided fine polishing (Si side). There are currently several main processing schemes for rough grinding of silicon carbide wafers. First, the traditional sapphire wafer rough grinding method is used, and boron carbide is used in combination with cast iron discs for processing. This processing method has the following main problems: boron carbide is generally selected with a coarse particle size, so the processing damage layer is deep, and subsequent fine grinding requires a high removal amount to remove the damage layer. In addition, it cannot avoid the scratch problem caused by the inaccurate grading of boron carbide. Second, the resin soft pad is used in combination with agglomerated diamond abrasive grinding liquid for processing. The main problem with this processing method is that due to the soft pad and the high temperature during the processing, the wafer is severely deformed (high Warp value), which ultimately affects the quality of the wafer. Third, using cast iron discs and 2-4μm single crystal diamond grinding fluid for processing, through strict abrasive control, this processing method can achieve high removal rate, no scratches, and high wafer quality. For example, Chinese patent CN114231251A discloses a diamond grinding fluid for rough grinding of silicon carbide wafers and its preparation method. The patent mainly describes the formula of the rough grinding fluid in detail, and does not specifically disclose the specific requirements of diamond micropowder (processing method and factors such as the particle size and distribution width of diamond micropowder) and the influence of the rough grinding fluid on the processing efficiency of silicon carbide wafers and the sub-damage of the wafer surface after processing. Summary of the invention

[0003] In view of the deficiencies in the prior art, the object of the present invention is to provide a high cutting force, low scratch diamond powder for rough grinding of silicon carbide wafers and a preparation method thereof.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for preparing diamond micropowder for rough grinding of silicon carbide wafers, characterized in that it specifically comprises the following steps:

[0006] (1) Mix diamond powders of different particle sizes, and measure the distribution width of the diamond powders after mixing them evenly;

[0007] (2) adding the diamond powder uniformly mixed in step (1) into a reactor containing a dilute acid solution under stirring to carry out a reaction, and simultaneously adding a hydrogen peroxide solution dropwise into the reactor during the entire reaction process until the reaction is completed;

[0008] (3) washing the diamond powder treated with acid in step (2) with pure water until the pH value of the supernatant is between 6 and 7; dispersing the diamond powder in pure water to obtain a diamond powder dispersion;

[0009] (4) wet-sieving the diamond micropowder dispersion in step (3); obtaining a diamond micropowder abrasive specially used for rough grinding of silicon carbide wafers; and testing the particle size, large particles and agglomerates of the diamond micropowder abrasive.

[0010] Furthermore, the diamond micropowders of different particle sizes described in step (1) are selected from several types with a D50 particle size of 2.70-3.30 μm; and after the diamond micropowders are uniformly mixed, the particle size distribution width of the diamond micropowders is 42-50%.

[0011] Furthermore, the diamond micropowders of different particle sizes are three types of diamond micropowders with particle size D502.70 μm and distribution width 38.9%, particle size D503.00 μm and distribution width 38.6%, and particle size D503.30 μm and distribution width 40.1%.

[0012] Furthermore, the weight ratio of the three types of diamond micropowders with a particle size of D502.70 μm and a distribution width of 38.9%, a particle size of D503.00 μm and a distribution width of 38.6%, and a particle size of D503.30 μm and a distribution width of 40.1% is 1-2:1:1-2.

[0013] Furthermore, the mass of the diamond powder in step (2) is 10% of the mass of the dilute acid solution.

[0014] Furthermore, the dilute acid solution described in step (2) is prepared by mixing concentrated sulfuric acid, concentrated nitric acid and pure water in a weight ratio of 3:2:5.

[0015] Furthermore, the mass fraction of the hydrogen peroxide solution in step (2) is 30%; and the amount of hydrogen peroxide added is 5% of the mass of the dilute acid solution.

[0016] Furthermore, the reaction conditions in step (2) are as follows: the temperature is controlled at 80° C. and the reaction time is 6-8 hours.

[0017] Furthermore, the wet screening process described in step (4) uses an ultrasonic vibration screening machine; wherein the upper screen is a 12.5 μm electroforming screen, and the lower screen is a 10 μm electroforming screen.

[0018] The diamond micro powder specially used for rough grinding of silicon carbide wafers is prepared by the method.

[0019] The application of the special diamond micro powder for rough grinding of silicon carbide wafers in the processing of silicon carbide wafers.

[0020] Beneficial Effects

[0021] (1) In the method of the present invention, diamond micropowders of different D50 particle sizes are mixed to control the distribution width of the diamond micropowders, thereby improving the processing efficiency of the diamond micropowders for silicon carbide wafers; breaking the traditional concept that the more concentrated the distribution of diamond micropowders, the higher the removal rate.

[0022] (2) The method of the present invention adopts dilute acid purification treatment to deagglomerate and purify diamonds to improve the dispersibility of diamond particles. Then, by adding a dispersant, ultrasonic dispersion, and wet screening, oversized particles and agglomerates in the diamond micropowder that are prone to scratching are effectively removed, thereby effectively reducing the risk of diamond micropowder scratching the silicon carbide wafer.

[0023] (3) The inventors have experimentally verified that diamond micropowder with a D50 particle size controlled between 2.9-3.2 μm is suitable for rough grinding of silicon carbide wafers; and diamond micropowder with a particle size distribution width of 42-50% is suitable for rough grinding of silicon carbide wafers. DETAILED DESCRIPTION

[0024] The technical scheme of the present invention is described in detail below in conjunction with specific embodiments. The raw materials used in the present invention can be obtained from the market unless otherwise specified; the methods described are conventional methods unless otherwise specified.

[0025] The diamond powder particle size D50 detection, distribution width measurement and large particle and agglomerate detection in the present invention adopt the following methods:

[0026] (1) Particle size D50 detection method

[0027] The particle size distribution of the diamond powder to be tested was measured using the S3500 produced by Microtrac.

[0028] (2) Measurement of diamond powder distribution width

[0029] The KBKL-Ⅱ intelligent particle image analyzer of Zhengzhou Jianbin Electronic Technology Co., Ltd. was used to evaluate the particle size distribution width of diamond micropowder. The specific detection method is as follows: clean the glass slide with pure water and dry it. Take a small amount of diamond micropowder to be tested, put it on the glass slide, add a drop of glycerin, use a toothpick to mix the diamond micropowder to be tested and glycerin evenly, cover the glass slide, and compact it until the diamond micropowder is a single particle and does not move. Use the 40X lens equipped with the KBKL-Ⅱ intelligent particle image analyzer to take pictures, and then perform particle image analysis. The number of analyzed particles is between 1000-1200. The specific particle size distribution width should refer to the particle size width distribution under the equivalent circle diameter.

[0030] (3) Detection of large particles and agglomerates

[0031] The diamond dispersion to be tested (the content of diamond micropowder is less than 10%, and the weight of diamond micropowder is 2000±50ct) is wet screened. The wet screening equipment is the equipment disclosed in Chinese patent CN110918451B, but the upper ultrasonic component is removed, and the upper screen is a 10μm electroforming screen. After the wet screening is completed, the abrasive enriched on the upper screen is flushed into a 100ml glass beaker using a spray pot, and a few drops of potassium pyrophosphate solution are added. The abrasive is evenly dispersed by ultrasound, and the Flowcam8100 equipment is used to detect the coarse end of the diamond micropowder particles in the dispersion. The number of analyzed particles should be no less than 300,000. In the coarse end detection, there are no elongated particles larger than 12.5μm (the aspect ratio is greater than 3:1, which is regarded as elongated) and block particles larger than 10μm. There are no agglomerates larger than 15μm, which are suitable as diamond micropowder for rough grinding of silicon carbide crystals.

[0032] Preparation of dilute acid solution

[0033] Weigh 5 parts of pure water, 3 parts of concentrated sulfuric acid, and 2 parts of concentrated nitric acid, slowly add the concentrated sulfuric acid and concentrated nitric acid into water and disperse them evenly to prepare a dilute acid solution; wherein the parts are parts by weight.

[0034] Example 1

[0035] (1) D502.70 μm, distribution width 38.9%, D503.00 μm, distribution width 38.6%, and D503.30 μm, distribution width 40.1%, were selected and mixed in a mass ratio of 1:1:1. After mixing evenly, the distribution width of the diamond powder was measured to be 42.5%;

[0036] (2) Add the dilute acid solution into a glass reactor, and under stirring, add the diamond powder (the mass of the diamond powder is 10% of the mass of the dilute acid solution) mixed evenly in step (1) into the glass reactor, control the temperature of the glass reactor at 80°C, react for 6-8 hours, and slowly add a 30% hydrogen peroxide solution to the reaction until the reaction is completed. The total amount of hydrogen peroxide added is 5% of the mass of the dilute acid. Control the dripping speed of the hydrogen peroxide until the reaction is completed, and avoid the situation where the reaction is not completed but the hydrogen peroxide has been added;

[0037] (3) washing the diamond micro-powder abrasive treated with acid in step (2) with pure water until the pH value of the supernatant is between 6 and 7;

[0038] (4) Add pure water to the diamond micropowder abrasive dispersion treated in (3) to adjust the solid content of the abrasive to about 10%, and use the equipment disclosed in CN110918451B patent to wet-screen the abrasive. The upper screen is a 12.5 μm electroforming screen, and the lower screen is a 10 μm electroforming screen. The abrasive is screened twice.

[0039] (5) The sieved abrasive in (4) was measured for particle size using S3500, where D50 = 2.99 μm. Large particles and agglomerates were detected using large particle and agglomerate detection methods. The results of large particle and agglomerate detection were: the maximum size of strip particles was 12.5 μm*2.5 μm, the maximum size of granules was 8 μm, and the maximum size of agglomerates was 12.5 μm.

[0040] (6) The diamond micro-powder abrasive processed in (5) is prepared into a grinding liquid for a grinding evaluation experiment to evaluate the removal rate and scratch condition of the diamond micro-powder on the silicon carbide wafer.

[0041] The preparation of the diamond rough grinding liquid described in this embodiment is specifically referred to the Chinese invention patent CN114231251A

[0042] The method described in Example 1. However, the preparation of the diamond rough grinding liquid is not limited to the method described in Example 1 of Chinese invention patent CN114231251A.

[0043] Example 2

[0044] (1) Select D502.70μm, distribution width 38.9%, D503.00μm distribution width 38.6%, D503.30μm distribution width 40.1%, mix them in a mass ratio of 2:1:2, and after mixing evenly, measure the distribution width of the diamond powder to be 49.5%;

[0045] Steps (2) to (4) are the same as in Example 1;

[0046] (5) The sieved abrasive in (4) was measured for particle size using S3500, where D50 = 3.03 μm. Large particles and agglomerates were detected using the large particle and agglomerate detection method. The large particle and agglomerate detection results were: the maximum size of strip particles was 12.5*2.5 μm, the maximum size of granular particles was 8.8 μm, and the maximum size of agglomerates was 12.5 μm.

[0047] (6) The diamond micro-powder abrasive processed in step (5) is prepared into a grinding liquid for a grinding evaluation experiment to evaluate the removal rate and scratch condition of the diamond micro-powder on the silicon carbide wafer.

[0048] The preparation of the diamond grinding liquid described in this embodiment specifically refers to the method described in Example 1 of Chinese invention patent CN114231251A. However, the preparation of the diamond rough grinding liquid is not limited to the method described in Example 1 of Chinese invention patent CN114231251A.

[0049] Example 3

[0050] (1) D502.70μm, distribution width 38.9%, D503.00μm, distribution width 38.6%, D503.30μm, distribution width 40.1%, were selected and mixed in a mass ratio of 2:1:1. After mixing evenly, the distribution width of the diamond powder was measured to be 45.6%;

[0051] Steps (2) to (4) are the same as in Example 1;

[0052] (5) The sieved abrasive in (4) was measured for particle size using S3500, where D50 = 2.95 μm. Large particles and agglomerates were detected using the large particle and agglomerate detection method. The large particle and agglomerate detection results were: the maximum size of strip particles was 12.5*2.5 μm, the maximum size of granular particles was 8.7 μm, and the maximum size of agglomerates was 12.5 μm.

[0053] (6) preparing the abrasive treated in step (5) into a grinding liquid to conduct a grinding evaluation experiment to evaluate the removal rate and scratch condition of the diamond micropowder on the silicon carbide wafer;

[0054] The preparation of the diamond grinding liquid described in this embodiment specifically refers to the method described in Example 1 of Chinese invention patent CN114231251A. However, the preparation of the diamond rough grinding liquid is not limited to the method described in Example 1 of Chinese invention patent CN114231251A.

[0055] Example 4

[0056] (1) D502.70μm, distribution width 38.9%, D503.00μm, distribution width 38.6%, D503.30μm, distribution width 40.1%, were selected and mixed in a mass ratio of 1:1:2. After mixing evenly, the distribution width of the diamond powder was measured to be 46.2%;

[0057] Steps (2) to (4) are the same as in Example 1;

[0058] (5) The sieved abrasive in (4) was measured for particle size using S3500, where D50 = 3.16 μm. Large particles and agglomerates were detected using the large particle and agglomerate detection method. The detection results of large particles and agglomerates were as follows: the maximum size of strip-shaped particles was 12.5*2.5 μm, the maximum size of granular particles was 8.9 μm, and the maximum size of agglomerates was 12.5 μm.

[0059] (6) preparing a grinding liquid with the diamond micro-powder abrasive treated in step (5) to conduct a grinding evaluation experiment to evaluate the removal rate and scratch condition of the diamond micro-powder on the silicon carbide wafer;

[0060] The preparation of the diamond grinding liquid described in this embodiment specifically refers to the method described in Example 1 of Chinese invention patent CN114231251A. However, the preparation of the diamond rough grinding liquid is not limited to the method described in Example 1 of Chinese invention patent CN114231251A.

[0061] Comparative Example 1

[0062] Diamond micropowder with a D50 distribution width of 38.6% was selected, and the abrasive was no longer finely processed, that is, steps (2)-(4) were omitted relative to Example 1, and large particles and agglomerates were detected according to the specified detection method. The detection results of large particles and agglomerates showed that the maximum size of strip particles was 12.5*2.5μm, the maximum size of granules was 10.5μm, and the maximum size of agglomerates was 17.5μm. The diamond micropowder abrasive was prepared into a grinding liquid for a grinding evaluation experiment to evaluate the removal rate and scratch condition of the diamond micropowder on the silicon carbide wafer; wherein, the preparation method of the diamond grinding liquid was the same as that of Example 1.

[0063] Comparative Example 2

[0064] Diamond micro-powder with a distribution width of 38.6% and a D50 of 3.00 μm was selected; the diamond micro-powder abrasive was finely treated according to the steps (2) to (4) of Example 1, and the treated diamond micro-powder abrasive was tested for particle size using S3500, where D50 = 2.99 μm. The large particles and agglomerates were tested using a large particle and agglomerate detection method. The test results of large particles and agglomerates of the treated diamond micro-powder abrasive were as follows: the maximum strip particles were 12.5*2.5 μm, the maximum granular particles were 7.5 μm, and the maximum agglomerates were 12.5 μm. The treated diamond micro-powder abrasive was prepared into a grinding liquid for a grinding evaluation experiment to evaluate the removal rate and scratching of the diamond micro-powder on the silicon carbide wafer; wherein the preparation method of the diamond grinding liquid was the same as that of Example 1.

[0065] Comparative Example 3

[0066] Diamond micropowder with a distribution width of 3.50 μm and 41% is selected, and the abrasive is no longer finely treated, that is, steps (2)-(4) are omitted relative to Example 1. The treated diamond micropowder abrasive is tested for particle size using S3500, where D50=3.49 μm, and large particles and agglomerates are tested according to the specified testing method, wherein the test results of large particles and agglomerates of the abrasive are as follows: the maximum strip particles are 12.5*2.5 μm, the maximum granular particles are 11 μm, and the maximum agglomerates are 15 μm. The treated diamond micropowder abrasive is prepared into a grinding liquid for a grinding evaluation experiment to evaluate the removal rate and scratching of the diamond micropowder on the silicon carbide wafer; wherein the preparation method of the diamond grinding liquid is the same as that of Example 1.

[0067] The abrasives in Examples 1-4 and Comparative Examples 1-3 were verified using the following process conditions:

[0068] The 4-inch silicon carbide wafer was processed using the processing conditions in Table 1. After processing, the wafer was cleaned and the wafer removal rate was measured. The surface scratch condition was observed with the naked eye. The specific conditions of the wafer surface after processing are shown in Table 2.

[0069] Table 1 Grinding fluid processing conditions

[0070]

[0071] Table 2 Removal rate and surface state of silicon carbide wafer corresponding to diamond powder

[0072]

[0073]

[0074] It can be seen from the data in Table 2 that the rough grinding of silicon carbide wafers using the grinding liquid prepared with the diamond powder obtained in Examples 1-4 of the present invention shows a high removal rate and no scratches are left on the surface of the silicon carbide wafers.

[0075] The above embodiments are only preferred specific implementation methods of the present invention, and the protection scope of the present invention is not limited thereto. Any simple changes or equivalent replacements of the technical solutions that can be obviously obtained by any technician familiar with the technical field within the technical scope disclosed in the present invention all fall within the protection scope of the present invention.

Claims

1. A method for preparing diamond micropowder for rough grinding of silicon carbide wafers, characterized in that: The specific steps include: Mix diamond powders of different particle sizes, and measure the distribution width of the diamond powders after mixing evenly; Adding the diamond powder uniformly mixed in step (1) into a reactor containing a dilute acid solution under stirring to react, and simultaneously adding a hydrogen peroxide solution dropwise into the reactor during the entire reaction process until the reaction is complete; Washing the diamond powder treated with acid in step (2) with pure water until the pH value of the supernatant is between 6 and 7; dispersing the diamond powder in pure water to obtain a diamond powder dispersion; Wet-sieving the diamond powder dispersion in step (3); You can get diamond micro-powder abrasives specially used for rough grinding of silicon carbide wafers, and test the particle size, large particles and agglomerates of diamond micro-powder abrasives; After being uniformly mixed in step (1), the particle size distribution width of the diamond micropowder is 42-50%; The diamond micropowders of different particle sizes are three kinds of diamond micropowders with particle size D50 2.70 μm and distribution width 38.9%, particle size D50 3.00 μm and distribution width 38.6%, and particle size D50 3.30 μm and distribution width 40.1%. The weight ratio of the three kinds of diamond micropowders with a particle size D50 of 2.70 μm and a distribution width of 38.9%, a particle size D50 of 3.00 μm and a distribution width of 38.6%, and a particle size D50 of 3.30 μm and a distribution width of 40.1% is 1-2:1:1-2.

2. The method for preparing diamond micropowder for rough grinding of silicon carbide wafers according to claim 1, characterized in that: The mass of the diamond powder in step (2) is 10% of the mass of the dilute acid solution.

3. The method for preparing diamond micropowder for rough grinding of silicon carbide wafers according to claim 1 or 2, characterized in that: The dilute acid solution in step (2) is prepared by mixing concentrated sulfuric acid, concentrated nitric acid and pure water in a weight ratio of 3:2:

5.

4. The method for preparing diamond micropowder for rough grinding of silicon carbide wafers according to claim 1, characterized in that: The mass fraction of the hydrogen peroxide solution is 30%; the amount of hydrogen peroxide added is 5% of the mass of the dilute acid solution.

5. The method for preparing diamond micropowder for rough grinding of silicon carbide wafers according to claim 1, characterized in that: The reaction conditions are as follows: the temperature is controlled at 80° C. and the reaction time is 6-8 hours.

6. The method for preparing diamond micro powder for rough grinding of silicon carbide wafers according to claim 1, characterized in that: The wet screening process adopts an ultrasonic vibration screening machine; wherein, the upper screen mesh is a 12.5 μm electroforming screen, and the lower screen mesh is a 10 μm electroforming screen.

7. Diamond micro powder specially used for rough grinding of silicon carbide wafers prepared by the method according to any one of claims 1 to 6.

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