Aggregated diamond, its preparation methods and applications

Abstract

This invention provides an agglomerated diamond, its preparation method, and its applications. The method includes preparing SiC precursor-diamond composite powder using a solution impregnation method with SiC precursor and diamond as raw materials; modifying the SiC precursor-diamond composite powder; ball milling and granulating the modified composite powder; and then sorting the granulated particles to obtain agglomerated diamond. The agglomerated diamond prepared by this method exhibits high hardness and high wear resistance, and the processed wafers possess excellent surface quality. Under the same wafer surface roughness conditions, it demonstrates higher processing efficiency and longer service life.

Description

Technical Field

[0001] This invention relates to the field of diamond, and more specifically, to an aggregated diamond, its preparation method, and its application. Background Technology

[0002] Third-generation semiconductor materials, represented by SiC, possess wider bandgap, higher thermal conductivity, and greater radiation resistance, making them more suitable for fabricating high-temperature, high-frequency, radiation-resistant, and high-power devices. The processing precision of SiC substrates directly affects device performance. Currently, SiC wafer processing can be broadly categorized into dicing, rough grinding, fine grinding, and polishing. Grinding aims to remove scratches and damage layers on the SiC surface caused during dicing. Due to the high hardness of SiC, high-hardness abrasives must be used during grinding. To achieve high grinding efficiency, polycrystalline diamond or agglomerated diamond grinding slurries are commonly used for SiC single-crystal substrates. Agglomerated diamond uses a binder to bond fine abrasive particles together, resulting in spherical or near-spherical shapes with uniformly distributed cutting edges.

[0003] For example, the invention patent with publication number CN117003581A discloses an agglomerated diamond, its preparation method, and its application. This method ensures the sphericity of the agglomerated diamond through a special suspension dispersion granulation and suspension dispersion sintering method. This avoids the poor sphericity caused by ordinary crushing granulation, and the problems of poor dispersion and agglomeration during sintering due to ordinary static sintering and accumulation in a container. The agglomerated diamond prepared by this method has excellent sphericity, which is beneficial for grinding and polishing. However, this method still directly uses a ceramic binder as the binder raw material and employs a sol-gel method for mixing. Due to the difference in hardness and wear resistance between the ceramic binder and SiC, the service life of the ceramic-bonded diamond and the grinding efficiency of the workpiece under the same surface roughness conditions still need to be improved. Summary of the Invention

[0004] To achieve high hardness and wear resistance in the prepared agglomerated diamond, and to ensure excellent surface quality of wafers processed using agglomerated diamond as an abrasive, thereby achieving higher processing efficiency and abrasive lifespan under the same wafer surface roughness conditions, the technical solution adopted in this invention is: a method for preparing agglomerated diamond, comprising the following steps:

[0005] The composite powder was prepared by using SiC precursor and diamond as raw materials and by using a solution impregnation method to prepare SiC precursor diamond composite powder.

[0006] Modification treatment was carried out on SiC precursor diamond composite powder;

[0007] Ball milling granulation involves ball milling the modified composite powder and then granulating it.

[0008] Sintering involves burying the granulated particles in sand and vacuum sintering, followed by sorting to obtain agglomerated diamond.

[0009] Based on the above, the steps for preparing the composite powder include:

[0010] Polycarbosilane is dissolved in toluene, xylene, n-hexane, acetone, or ethanol. Diamond with a median particle size of 0.25 μm to 3.5 μm is then added to the solvent and stirred and kept warm in an oil bath. The mixture is then dried in an oven to obtain SiC precursor diamond composite powder, wherein the mass percentage of diamond is 70% to 90% and the mass percentage of polycarbosilane is 10% to 30%.

[0011] Specifically, the median diamond particle size can be selected from 0.25μm, 0.5μm, 1μm, 1.5μm, 2.5μm, 3μm, and 3.5μm. The oil bath temperature is 90℃~130℃, and the holding time is 8h~12h. The oven temperature is 150℃~180℃, and the drying holding time is 4h~7h.

[0012] Based on the above, the modification steps include: modifying the SiC precursor diamond composite powder in a vacuum furnace at a temperature of 400℃~600℃ for 3h~4h.

[0013] Based on the above, the ball milling granulation step includes:

[0014] The modified sample was ball-milled for 48 to 72 hours and then dried.

[0015] The dried ball mill powder is mixed with ultrapure water to prepare a ceramic slurry with a viscosity of 150 mPa·s to 300 mPa·s. Then, a temporary binder is added to the ceramic slurry, and after mixing, it is granulated using a granulator. The mass of the temporary binder added accounts for 1% to 5% of the mass of the ceramic slurry.

[0016] The temporary adhesive can be one or more of PVA, PEG, dextrin, etc., with a mass fraction of 0.5% to 1%.

[0017] Based on the above, the sintering step includes:

[0018] The granulated particles are subjected to sand embedding treatment, followed by sintering treatment in a vacuum furnace or atmosphere furnace at a temperature of 1100℃~1700℃ and a holding time of 200min~500min. After cooling, they are sorted to obtain agglomerated diamond. The sand embedding treatment uses one or more materials such as SiC, diamond, BN, and alumina, with the added mass accounting for 25%~50% of the mass of the granulated particles. The atmosphere can be an inert gas such as argon or helium.

[0019] The present invention also provides an aggregated diamond, which is prepared by the preparation method described above. The aggregated diamond includes a ceramic binder and diamond dispersed in the ceramic binder. The ceramic binder is obtained by the transformation of SiC precursor during diamond sintering.

[0020] Based on the above, the mass percentage of diamond in the aggregated diamond is 70% to 90%.

[0021] The present invention also provides an application of agglomerated diamond as an abrasive for grinding SiC wafers.

[0022] This invention represents a substantial advancement over existing technologies. Specifically, the agglomerated diamond, its preparation method, and its applications provided by this invention involve preparing SiC precursor-diamond composite powder using a solution impregnation method with SiC precursor and diamond as raw materials. After modification treatment, spherical agglomerated diamond is prepared using spray granulation technology. SiC precursor-converted ceramics are then grown in situ on the diamond surface using sintering technology. This results in a high-hardness binder within the agglomerated diamond, making it less prone to breakage during grinding, thereby improving the lifespan and grinding efficiency of the abrasive wheels prepared from it.

[0023] Furthermore, by controlling the particle size and content of diamond in the agglomerated diamond, the prepared agglomerated diamond is made into a near-spherical shape, with the vast majority of particles having a good spherical morphology. The near-spherical agglomerated diamond particles are encapsulated and bonded together by a glassy phase, with a large number of diamond particles exposed and semi-embedded on the surface. This ensures that during the abrasive's machining process, multiple exposed and semi-embedded diamond particles can play a grinding role, greatly increasing the number of grinding edges, effectively improving grinding efficiency and reducing workpiece surface roughness. At the same time, because the diamond particles are bonded together by the in-situ generated SiC phase, this structure also has good self-sharpening and impact resistance.

[0024] Furthermore, during the preparation of agglomerated diamond, modification treatment allows the polycarbosilane to undergo thermal decomposition and morphological transformation before pelletizing, enabling the gradual removal of organic groups such as -H and -CH during the modification step. Simultaneously, the heating and cooling processes during modification pre-explode bubbles generated during thermal decomposition, effectively preventing foaming during subsequent pelletizing and sintering, thereby improving the material's density and hardness.

[0025] Furthermore, thermodynamic analysis reveals that during granulation and sintering after modification, the microstructure undergoes further changes based on the composition generated after the modified pyrolysis, rather than requiring a further transformation from polycarbosilane. This reduces the difficulty of the microstructure transformation, lowers the entropy that the material needs to overcome for the transformation, and improves the bonding quality between materials. Consequently, it promotes the subsequent granulation and sintering process and microstructure changes, enabling the material to completely decompose and transform into amorphous SiC, and then further transform into crystalline β-SiC. This ensures that the agglomerated diamond possesses the advantages of high temperature resistance, high hardness, high strength, corrosion resistance, and oxidation resistance.

[0026] Therefore, the agglomerated diamond prepared by the preparation method provided by the present invention has high hardness and high wear resistance, and the processed wafer has excellent surface quality. Under the same surface roughness conditions, it has high processing efficiency and abrasive life. Attached Figure Description

[0027] Figure 1 and Figure 2 This is a SEM image of aggregated diamond provided in Embodiment 1 of the present invention.

[0028] Figure 3 This is an EDS image of aggregated diamond provided in Embodiment 1 of the present invention. Detailed Implementation

[0029] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0030] Example 1

[0031] This embodiment provides a method for preparing aggregated diamond, including the following steps:

[0032] Step 1: Weigh 30g of polycarbosilane and dissolve it in ethanol solvent. Then weigh 70g of diamond with a median particle size of 1.5μm and add the weighed diamond to the above solution and mix evenly. Then place it in an oil bath at 130℃ and stir and keep warm for 8 hours. Finally, place it in an oven and dry it at 180℃ for 7 hours.

[0033] Step 2: Modify the dried sample in a vacuum furnace at 600℃ for 4 hours.

[0034] Step 3: The modified sample is ball-milled in a planetary ball mill or a drum ball mill for 72 hours, and then dried.

[0035] Step 4: Mix the dried ball-milled powder with ultrapure water to prepare a ceramic slurry with a viscosity of 200 mPa·s. Then, add one or more of the following as a temporary binder at a mass fraction of 0.5%: PVA, PEG, dextrin, etc. The amount of temporary binder added is 1% of the mass of the ceramic slurry. After mixing evenly, granulate the mixture using a centrifugal, spray, or fluidized bed granulator.

[0036] Step 5: The granulated particles are subjected to sand embedding treatment. The sand type is SiC, and the amount of sand added is 30% of the mass of the granulated particles. Then, the particles are sintered in a vacuum furnace at a temperature of 1600℃ for a holding time of 200min to 500min. Finally, the cooled sample is sorted to separate the sand and granulated particles to obtain agglomerated diamond.

[0037] This embodiment also provides an aggregated diamond prepared by the same method.

[0038] Example 2

[0039] This embodiment provides a method for preparing agglomerated diamond. The main difference from Embodiment 1 is that, in this embodiment, the median particle size of the diamond in the raw material for agglomerated diamond is 3.5 μm.

[0040] This embodiment also provides an aggregated diamond prepared by the same method.

[0041] Example 3

[0042] This embodiment provides a method for preparing aggregated diamond. The main difference from Embodiment 1 or Embodiment 2 is that in this embodiment, the mass of polycarbosilane is 10g and the mass of diamond with a median particle size of 1.5μm is 90g.

[0043] This embodiment also provides an aggregated diamond prepared by the same method.

[0044] Example 4

[0045] This embodiment provides a method for preparing aggregated diamond. The main difference from Embodiment 1 or Embodiment 2 is that in this embodiment, the mass of polycarbosilane is 20g and the mass of diamond with a median particle size of 1.5μm is 80g.

[0046] This embodiment also provides an aggregated diamond prepared by the same method.

[0047] Example 5

[0048] This embodiment provides an application of agglomerated diamond prepared by embodiment 1, 2, 3, or 4, which is used as an abrasive to grind SiC wafers.

[0049] Comparative Example 1

[0050] Comparative Example 1 provides a method for preparing aggregated diamond, comprising the following steps:

[0051] Step 1: First, weigh 70g of diamond with a median particle size of 1.5μm and 30g of ceramic binder with a median particle size of 1.5μm. Add the weighed diamond and ceramic binder to 50g of deionized water and mix evenly. Then, add one or more dispersants such as sodium hexametaphosphate, sodium dodecylbenzenesulfonate, and hexadecyl ammonium chloride. The amount of dispersant added is 0.5% of the diamond mass. Stir evenly to obtain ceramic slurry.

[0052] Step 2: Add one or more of PVA, PEG, dextrin, etc., at a mass fraction of 0.5% to the ceramic slurry as a temporary binder. The amount added is 1% of the ceramic slurry. After mixing evenly, granulate the mixture using a centrifugal, spray, or fluidized bed granulator.

[0053] Step 3: The granulated particles are then subjected to sand embedding treatment. The type of sand is diamond, and the added mass of the selected sand is between 30% and the mass of the granulated particles. Subsequently, the particles are sintered in a muffle furnace at a sintering temperature of 700℃ for a holding time of 300min. Finally, the cooled sample is sorted to separate the sand and granulated particles, thus obtaining agglomerated diamond.

[0054] Comparative Example 2

[0055] Comparative Example 2 provides a method for preparing agglomerated diamond. The difference between Comparative Example 1 and Comparative Example 2 is that the median particle size of the ceramic binder in the raw material of agglomerated diamond is 1.5 μm, and the median particle size of the diamond is 3.5 μm.

[0056] SiC wafer grinding test

[0057] Processing efficiency testing: The agglomerated diamonds obtained in Examples 1, 2, 1, and 2 were weighed at a mass fraction of 1% and mixed with 500 ml of deionized water. 1 g of carboxymethyl cellulose was added to prepare a polishing solution. The SiC wafers were ground using a double-end grinder. The thickness of the samples before and after grinding was measured, and the processing efficiency was calculated.

[0058] Surface roughness measurement method: The surface roughness of the ground SiC wafer sample was measured using a white light interferometer, and the average was calculated. The specific test results are shown in Table 1 below.

[0059] Table 1. Grinding effect of different aggregated diamonds on SiC wafers

[0060]

[0061] As shown in Table 1, when using the agglomerated diamond prepared in Examples 1 and 2 of this invention to grind SiC wafers, the processing efficiency of this invention is higher under the same wafer surface roughness conditions. Furthermore, testing revealed that, compared to Comparative Examples 1 and 2, the agglomerated diamond prepared in this invention also possesses advantages such as high hardness and high wear resistance, thereby improving the service life of the agglomerated diamond when grinding SiC wafers.

[0062] Meanwhile, the microstructure and composition of the agglomerated diamond prepared in the examples were analyzed, and the results are as follows: Figure 1 , Figure 2 , Figure 3 As shown.

[0063] from Figure 1 As can be seen, the agglomerated diamond prepared by this invention is spherical, with the vast majority of particles exhibiting excellent spherical morphology and a particle size of less than 50 μm, and very few large lumps of material adhering to each other. Furthermore, it is evident that the spherical agglomerated diamond particles are encapsulated and bonded together by a glassy phase, with a large number of diamond particles exposed or semi-embedded on the surface. This ensures that during workpiece machining, multiple exposed and semi-embedded diamond particles can all play a grinding role, greatly increasing the number of grinding edges, effectively improving grinding efficiency, and reducing workpiece surface roughness. Simultaneously, because the diamond particles are bonded together by the in-situ generated SiC phase, this structure also possesses good self-sharpening and impact resistance.

[0064] from Figure 2 , Figure 3 As can be seen, the aggregated diamond structure prepared by this invention contains a SiC phase, and the SiC phase is widely distributed. This indicates that the preparation process provided by this invention can promote the thermal decomposition and morphological transformation of polycarbosilane. The generated silicon carbide can coat the surface of diamond particles and fill the pores, thereby improving the density and hardness of the abrasive. At the same time, the β-SiC and α-SiC converted from polycarbosilane have good wettability with diamond particles and can effectively inhibit the graphitization of diamond particles.

[0065] More importantly, the present invention performs a modification step before pelletizing. The SiC precursor diamond composite powder is heated in a vacuum furnace at a temperature of 400℃~600℃ for 3h~4h. This allows the polycarbosilane to undergo thermal decomposition and morphological transformation before pelletizing, enabling it to gradually remove organic groups such as -H and -CH during the modification step.

[0066] Meanwhile, the heating and cooling processes after the modification steps can also pre-explode the bubbles generated during the thermal decomposition process, effectively avoiding the formation of foams during the subsequent sintering process, thereby improving the density and hardness of the material.

[0067] Furthermore, thermodynamic analysis reveals that during granulation and sintering after modification, the microstructure undergoes further changes based on the composition generated after the modified pyrolysis, rather than requiring a further transformation from polycarbosilane. This reduces the difficulty of the microstructure transformation, lowers the entropy that the material needs to overcome for the transformation, and improves the bonding quality between materials. Consequently, it promotes the subsequent granulation and sintering process and microstructure changes, enabling the material to completely decompose and transform into amorphous SiC, and then further transform into crystalline β-SiC. This ensures that the agglomerated diamond possesses the advantages of high temperature resistance, high hardness, high strength, corrosion resistance, and oxidation resistance.

[0068] That is, the present invention actually divides the thermal decomposition and morphological transformation of polycarbosilane into two stages, prolonging the process of thermal decomposition and morphological transformation, so that it can fully carry out thermal decomposition and morphological transformation.

[0069] Furthermore, after modifying the SiC precursor diamond composite powder, the wetting angle and compatibility of polycarbosilane with water can be changed, making it more compatible with water and easier to granulate, thus ensuring the morphology of the granulated particles and the density of the particles during subsequent sintering.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A method for preparing aggregated diamond, comprising the following steps: To prepare the composite powder, polycarbosilane was dissolved in toluene, xylene, n-hexane, acetone, or ethanol. Diamond with a median particle size of 0.25 μm to 3.5 μm was then added to the solvent and stirred and kept warm in an oil bath. The mixture was then dried in an oven to obtain SiC precursor diamond composite powder, wherein the mass percentage of diamond was 70% to 90%, and the mass percentage of polycarbosilane was 10% to 30%. The SiC precursor diamond composite powder was modified in a vacuum furnace at a temperature of 400℃~600℃ for 3 h~4 h. Ball milling granulation involves ball milling the modified composite powder and then granulating it. Sintering involves sintering the granulated particles with sand, followed by sorting to obtain agglomerated diamond.

2. The method for preparing aggregated diamond according to claim 1, characterized in that: The ball milling granulation step includes: The modified SiC precursor diamond composite powder was ball-milled for 48 h to 72 h and then dried. The dried ball mill powder is mixed with ultrapure water to prepare a ceramic slurry with a viscosity of 150 mpa.s to 300 mpa.s. Then, a temporary binder is added to the ceramic slurry, and after mixing, it is granulated using a granulator. The mass of the temporary binder added accounts for 1% to 5% of the mass of the ceramic slurry.

3. The method for preparing aggregated diamond according to claim 1 or 2, characterized in that: The sintering step includes: burying the granulated particles in sand, then sintering them in a vacuum or inert atmosphere at a temperature of 1100℃~1700℃ for a holding time of 200 min~500 min, and then sorting them after cooling to obtain agglomerated diamond.

4. An aggregated diamond, characterized in that: The agglomerated diamond is prepared by the preparation method according to any one of claims 1 to 3, wherein the agglomerated diamond comprises a ceramic binder and diamond dispersed within the ceramic binder, and the ceramic binder is obtained by the transformation of SiC precursor during diamond sintering.

5. The aggregated diamond according to claim 4, characterized in that: In the aggregated diamond, the mass percentage of diamond is 70% to 90%.

6. An application of the aggregated diamond according to claim 4 or 5, characterized in that: The aggregated diamond was used as an abrasive to grind SiC wafers.

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