A diamond polishing fluid, its preparation method and application

Abstract

This invention relates to a stable and dispersed diamond polishing slurry, its preparation method, and its application, belonging to the field of ultra-precision machining technology. The polishing slurry comprises diamond micropowder, a dispersant, a suspending agent, a lubricant, a defoamer, a pH adjuster, and a dispersion medium. The pH adjuster stabilizes the pH value of the system at 7-10. During preparation, the components are first premixed to form an initial slurry, followed by high-speed mechanical stirring and ultrasonic treatment. The synergistic effect of mechanical and ultrasonic treatment achieves deep deagglomeration and uniform dispersion of the diamond micropowder. This method effectively solves the problems of easy agglomeration and sedimentation in diamond polishing slurries. The resulting polishing slurry exhibits good dispersion stability and storage performance. After standing for one week, the average particle size and zeta potential change very little. When applied to 6-inch silicon carbide wafers, it can significantly reduce the surface roughness of the workpiece.

Description

Technical Field

[0001] This invention relates to a diamond polishing fluid, its preparation method, and its application, belonging to the field of ultra-precision machining technology. Background Technology

[0002] Diamond polishing slurry is a polishing material formed by dispersing diamond micro powder as the core abrasive and adding auxiliary components such as dispersants and suspending agents into a liquid medium. It is widely used in the ultra-precision machining of hard and brittle materials such as sapphire substrates, precision ceramics, semiconductor wafers, and optical glass.

[0003] Diamond micropowder (especially nano-diamond) is prone to agglomeration due to its large specific surface area and high surface energy, leading to sedimentation and stratification of the polishing slurry during storage and use, which seriously affects the uniformity and quality of the processed surface. Existing technologies still have the following shortcomings: (1) limited surface modification effect, making it difficult to completely prevent the aggregation of nano-diamond particles; (2) short duration of dispersion stability, requiring the polishing slurry to be remixed before use, which is inconvenient; (3) complex composition, potentially introducing difficult-to-remove contaminants that affect the purity of the final product. Especially in the ultra-precision processing fields such as third-generation semiconductor silicon carbide wafers and diamond substrates, higher requirements are placed on the dispersion uniformity, stability, and surface damage control of the polishing slurry. Therefore, developing a diamond polishing slurry preparation method that can achieve long-term stable dispersion of diamond micropowder, has a simple preparation process, and strong environmental adaptability has significant industrial application value. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a diamond polishing fluid, its preparation method and application, which can overcome the technical defects of existing diamond polishing fluids such as poor dispersion stability, easy agglomeration and sedimentation, and complex formulation, and provide a stable and dispersed diamond polishing fluid.

[0005] The technical solution of this invention is:

[0006] A diamond polishing slurry, the raw materials of which include diamond micro powder, dispersant, suspending agent, lubricant, defoamer, pH adjuster, and dispersion medium; Based on a total mass of 100 parts for the diamond polishing slurry, the mass fractions of each component are as follows: Diamond micro powder 0.3 ~ 25 parts Dispersant 1 to 10 parts 0.1 to 5 parts of suspension Lubricant 0.1 ~ 5 parts Defoamer 0.1 to 5 parts pH adjuster 0.5 ~ 5 parts Dispersion medium balance The average particle size of the diamond micropowder ranges from 0.01 μm to 10 μm; The dispersant is a mixture of one or more of the following: octadecylamine, octadecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, sodium oleate, sodium tripolyphosphate, sodium hexametaphosphate, sodium borohydride, hydroxyethylidene diphosphonic acid, sodium dodecylbenzenesulfonate, carboxymethyl vitamin, Tween-80, OP-10, fatty alcohol polyoxyethylene ether, bentonite, and bentonite derivatives. The suspending agent is a mixture of one or more of the following: low molecular weight polyacrylamide, gelatin, coconut oil ethanolamide, calcium lignosulfonate, and polyvinylpyrrolidone. The lubricant is a mixture of one or more of polyethylene glycol (PEG, molecular weight 200-10000), glycerin, triethyl phosphate, diethylene glycol, dimer acid, isopropanol, and lauryl alcohol. The defoamer is a mixture of one or more of the following: dimethyl silicone oil, emulsified silicone oil, polyether-modified organosilicon, amine ether polyether, EO / PO block copolymer, GP type glycerol polyether, and fatty alcohol polyether. The pH adjuster is used to stabilize the pH value of the grinding slurry in a weakly alkaline range of 7 to 10, and is preferably a mixture of one or more of citric acid, ethylenediamine, ammonia, sodium hydroxide solution, hydrochloric acid, triethanolamine, and amine base. The dispersion medium is preferably deionized water.

[0007] A method for preparing a diamond polishing slurry includes the following steps: S1 premix is ​​a mixture of diamond micron powder, dispersant, suspending agent, lubricant, defoamer, pH adjuster and dispersion medium to form an initial slurry; S2 Mechanical dispersion involves high-speed mechanical stirring of the initial slurry obtained in step S1, with a stirring speed of 1000~10000 rpm and a stirring time of 10~120 min, using high-intensity shear force to initially break up the soft agglomerates of diamond micro powder. S3 Ultrasonic dispersion: The slurry after mechanical dispersion in step S1 is subjected to ultrasonic treatment. The ultrasonic power is 500~1500 W, the frequency is 20~40 kHz, and the treatment time is 3~60 min. This step utilizes the cavitation effect and vibration of ultrasound to further dissociate hard agglomerates and make the particles uniformly and stably dispersed in the medium to obtain a uniform and stable diamond grinding fluid. S4 Post-processing and testing (optional): Perform particle size distribution, zeta potential and long-term static stability tests on the grinding slurry obtained in step S3 to ensure that it meets the usage requirements.

[0008] The application of a diamond polishing fluid includes the following steps: The diamond polishing slurry prepared by this invention is particularly suitable for ultra-precision grinding and polishing of hard and brittle materials such as silicon carbide (SiC), sapphire, single crystal silicon, and optical glass. When using it, it can be adapted by dilution or pH adjustment according to specific process requirements.

[0009] Beneficial effects This invention relates to a stable and dispersed diamond polishing slurry, its preparation method, and its application, belonging to the field of ultra-precision machining technology. The polishing slurry comprises, by weight, 0.3-25 parts diamond micropowder, 1-10 parts dispersant, 0.1-5 parts suspending agent, 0.1-5 parts lubricant, 0.1-5 parts defoamer, 0.5-5 parts pH adjuster, and the balance being a dispersion medium. The pH adjuster stabilizes the pH of the system at 7-10. In preparation, the components are first premixed to form an initial slurry, then sequentially subjected to high-speed mechanical stirring (1000-10000 rpm, 10-120 min) and ultrasonic treatment (500-1500 W, 20-40 kHz, 3-60 min). Ultrasonic synergy enables deep deagglomeration and uniform dispersion of diamond micropowder. This method effectively solves the problems of easy agglomeration and sedimentation in diamond polishing slurries. The resulting slurry exhibits good dispersion stability and storage performance, with minimal changes in average particle size and zeta potential after one week of standing. When applied to 6-inch silicon carbide wafers, it significantly reduces workpiece surface roughness. The preparation method of the diamond polishing slurry of this invention is simple, operates under mild conditions, and is easily scalable for mass production. The diamond polishing slurry of this invention is applicable to the ultra-precision grinding and polishing of hard and brittle materials, especially semiconductor wafers (such as silicon carbide wafers). Attached Figure Description

[0010] Figure 1 The initial particle size distribution of grinding slurry #1; Figure 2 Particle size distribution diagram after #1 grinding slurry has been left to stand for one week; Figure 3 The initial morphology of a 6-inch SiC wafer; Figure 4 The morphology of the SiC wafer after grinding with No. 1 polishing slurry; Figure 5 The initial particle size distribution of grinding slurry #2; Figure 6 The particle size distribution after the No. 2 grinding slurry has been left to stand for one week; Figure 7 AFM morphology of SiC wafer after grinding with No. 2 polishing slurry. Detailed Implementation

[0011] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0012] Example 1 Take 0.3g of commercially available diamond micron powder with a particle size of 1μm by weight. The dispersants selected were 2g sodium dodecylbenzenesulfonate and 0.5g sodium hexametaphosphate. The suspending agent selected was 0.5g of methyl polyacrylamide; The lubricant selected is 1g of polyethylene glycol (molecular weight 6000) and 0.5g of glycerin; The defoamer selected is 2.5g of dimethyl silicone oil; 92.7g of deionized water; A 5% sodium hydroxide solution is used as a pH adjuster; Mix the raw materials and adjust the pH of the system to 9.5; Then mechanically stir for 30 minutes at a speed of 5000 rpm; After mechanical stirring, ultrasonic dispersion with a power of 1000W and a frequency of 40kHz was performed for 30 minutes to obtain a uniform and stable No. 1 grinding slurry.

[0013] The particle size and potential of the grinding slurry were measured using a Zetasizer Pro nanoparticle size potentiometer. The initial particle size distribution is shown in the figure below. Figure 1 As shown, the average particle size is 979.2 nm, the PDI is 0.2035, and the Zeta potential is -30.45 mV. The particle size distribution after standing for one week is shown in the figure. Figure 2 As shown, the average particle size is 988.6 nm, the PDI is 0.2523, and the Zeta potential is -31.63 mV, indicating that the suspension is very stable. When the No. 1 polishing slurry was applied to a 6-inch SiC wafer, the morphology before polishing was as follows. Figure 3 As shown, the morphology after using #1 polishing slurry is as follows. Figure 4 As shown, the roughness is greatly reduced.

[0014] Example 2 Take 0.5g of commercially available diamond micron powder with a particle size of 200nm by weight. Dispersed with 1g of sodium dodecylbenzenesulfonate and 1g of sodium borohydride; The suspending agent is 0.5g of gelatin; The lubricant selected is 1.5g of polyethylene glycol (molecular weight 6000) and 0.5g of isopropanol; The defoamer selected is 1g of emulsified silicone oil; 94g of deionized water; A 5% sodium hydroxide solution is used as a pH adjuster; Adjust the pH of the system to 10; Mechanical stirring for 30 minutes at a speed of 5000 rpm; After stirring, ultrasonic dispersion was performed for 30 minutes using an ultrasonic wave with a power of 1000W and a frequency of 40kHz to obtain a uniform and stable No. 2 grinding slurry.

[0015] The particle size and potential of the grinding slurry were measured using a Zetasizer Pro nanoparticle size potentiometer. The initial particle size distribution is shown in the figure below. Figure 5 As shown, the average particle size is 157.6 nm, the PDI is 0.1085, the Zeta potential is -35.47 mV, and the particle size distribution after standing for one week is shown in the figure. Figure 6 As shown, the average particle size is 160.5 nm, the PDI is 0.1423, and the Zeta potential is -36.73 mV, indicating that the suspension is very stable. The 6-inch SiC wafer, already ground with polishing slurry #1, was then polished using polishing slurry #2. The resulting morphology is shown below. Figure 7 As shown, the roughness is further reduced.

[0016] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A diamond polishing fluid, characterized in that: The raw materials for this diamond polishing slurry include diamond micro powder, dispersant, suspending agent, lubricant, defoamer, pH adjuster, and dispersion medium; Based on a total mass of 100 parts for the diamond polishing fluid raw material, the mass fractions of each component are as follows: Diamond micro powder 0.3 ~ 25 parts Dispersant 1 to 10 parts 0.1 to 5 parts of suspension Lubricant 0.1 ~ 5 parts Defoamer 0.1 to 5 parts pH adjuster 0.5 ~ 5 parts Dispersion medium balance.

2. The diamond polishing fluid according to claim 1, characterized in that: The average particle size of the diamond micropowder ranges from 0.01 μm to 10 μm.

3. The diamond polishing fluid according to claim 1, characterized in that: The dispersant is a mixture of one or more of the following: octadecylamine, octadecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, sodium oleate, sodium tripolyphosphate, sodium hexametaphosphate, sodium borohydride, hydroxyethylidene diphosphonic acid, sodium dodecylbenzenesulfonate, carboxymethyl vitamin, Tween-80, OP-10, fatty alcohol polyoxyethylene ether, bentonite, and bentonite derivatives.

4. The diamond polishing fluid according to claim 1, characterized in that: The suspending agent is a mixture of one or more of the following: low molecular weight polyacrylamide, gelatin, coconut oil ethanolamide, calcium lignosulfonate, and polyvinylpyrrolidone. The lubricant is a mixture of one or more of polyethylene glycol, glycerin, triethyl phosphate, diethylene glycol, dimer acid, isopropanol, and lauryl alcohol; the molecular weight of polyethylene glycol is 200-10000.

5. The diamond polishing fluid according to claim 1, characterized in that: The defoamer is a mixture of one or more of the following: dimethyl silicone oil, emulsified silicone oil, polyether-modified organosilicon, amine ether polyether, EO / PO block copolymer, GP type glycerol polyether, and fatty alcohol polyether.

6. The diamond polishing fluid according to claim 1, characterized in that: The pH adjuster is used to stabilize the pH value of the grinding slurry within a weakly alkaline range of 7 to 10. The pH adjuster is a mixture of one or more of the following: citric acid, ethylenediamine, ammonia, sodium hydroxide solution, hydrochloric acid, triethanolamine, and amine base.

7. The diamond polishing fluid according to claim 1, characterized in that: The dispersion medium is deionized water.

8. A method for preparing the diamond polishing fluid according to claim 1, characterized in that... Includes the following steps: S1, diamond micro powder, dispersant, suspending agent, lubricant, defoamer, pH adjuster and dispersion medium are mixed to form an initial slurry; S2, the initial slurry formed in step S1 is subjected to high-speed mechanical stirring at a speed of 1000~10000 rpm for a time of 10~120 min; S3. The slurry after high-speed mechanical stirring in step S2 is subjected to ultrasonic treatment. The ultrasonic power is 500~1500 W, the frequency is 20~40 kHz, and the treatment time is 3~60 min to obtain diamond grinding fluid.

9. The method for preparing a diamond polishing slurry according to claim 8, characterized in that: In step S1, the initial slurry has a pH value range of 7-10.

10. An application of a diamond polishing fluid, characterized in that: The grinding fluid described in claim 1 is used for ultra-precision grinding and polishing.

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