Silicon carbide fine grinding liquid and preparation method thereof

Abstract

The invention discloses a silicon carbide accurate grinding liquid and a preparation method thereof. The accurate grinding liquid comprises the following components in percentage by mass: 0.5-2% of compound diamond abrasive, 0.5-2% of silicon carbide, 0.5-2% of silicon carbide and the balance of water. 6%-12% of a composite dispersant; 2%-5% of a lubricating film-forming agent; 0.5%-2% of a pH regulator; the compound diamond grinding material is prepared by compounding monocrystal diamond micro-powder and polycrystalline diamond, the mass ratio of the monocrystal diamond micro-powder to the polycrystalline diamond is 1: (0.5-2), and the compound dispersing agent is prepared by compounding a polyether amine block copolymer and a phosphate type hyperdispersant. The mass ratio of the polyether amine block copolymer to the phosphate type hyperdispersant is 3: 1; the silicon carbide fine grinding liquid has good dispersion and stability, and the surface roughness of a wafer after fine grinding is smaller than 3 nm while the grinding efficiency is improved; and the preparation method of the fine grinding liquid is simple to operate, reduces the grinding material cost and is suitable for popularization and application.

Description

Technical Field

[0001] The present invention relates to the technical field of precision machining of SIC substrates, and particularly to a silicon carbide fine grinding fluid and a preparation method thereof. Background Art

[0002] Due to the characteristics of high hardness, high brittleness, good wear resistance, and extremely stable chemical properties of SiC crystals, the processing of SiC wafers becomes very difficult.

[0003] The ultra-precision machining process of SiC single crystal wafers, according to its processing sequence, mainly goes through the following processes: directional cutting, rough grinding, fine grinding, polishing, and ultra-precision polishing; among them, fine grinding is carried out with abrasives having a smaller particle size, and the main purpose is to remove the damaged layer left by rough grinding and ensure the surface profile accuracy (WARP, BOW, TTV, LTV, etc.) of the substrate.

[0004] In the fine grinding process, a fine grinding fluid is required, and the fine grinding effect is achieved by the infiltration, lubrication, etc. of the fine grinding fluid; the invention patent with the publication number CN114561187B discloses an environmentally friendly emulsified fine grinding fluid and a preparation method thereof. The raw materials of the fine grinding fluid include the following components in parts by weight: 2-10 parts of fine grinding powder, 1-5 parts of oiliness agent, 1-5 parts of water-soluble acrylic resin, 1-5 parts of tragacanth gum, 1-5 parts of emulsifier, and 80-100 parts of water.

[0005] The above fine grinding fluid can improve the polishing effect and fine grinding rate during use, but the dispersibility and stability of the fine grinding fluid are not good, and it is difficult to ensure the surface roughness of the wafer in the fine grinding process, and the use effect is not ideal. Summary of the Invention

[0006] The purpose of the present invention is to solve the above problems and provide a silicon carbide fine grinding fluid with good dispersion and stability, which can improve the grinding efficiency and make the surface roughness of the wafer after fine grinding < 3 nm, and a preparation method thereof.

[0007] To achieve the above purpose, the technical solution of the present invention is: a silicon carbide fine grinding fluid, which includes the following components in terms of mass fraction: 0.5%-2% of compound diamond abrasive; 6%-12% of composite dispersant; 2%-5% of lubricating film-forming agent; 0.5%-2% of pH regulator; 0.1%-0.5% of chelating agent, and the balance is an environmentally friendly solvent.

[0008] Preferably, the compound diamond abrasive is composed of single crystal diamond micropowder and polycrystalline diamond, the D50 particle size of the single crystal diamond micropowder is 0.2-0.5 μm, the D50 particle size of the polycrystalline diamond is 0.7-0.9 μm, and the mass ratio of the single crystal diamond micropowder to the polycrystalline diamond is 1:0.5-2.

[0009] Preferably, the composite dispersant is a compound of a polyetheramine block copolymer and a phosphate ester hyperdispersant, and the mass ratio of the polyetheramine block copolymer to the phosphate ester hyperdispersant is 3:1.

[0010] Preferably, the lubricating film-forming agent is perfluoropolyether.

[0011] Preferably, the pH regulator is a compound of tetramethylammonium hydroxide and citric acid, and the mass ratio of tetramethylammonium hydroxide to citric acid is 1:1-2.

[0012] Preferably, the chelating agent is disodium ethylenediaminetetraacetate.

[0013] Preferably, the resistivity of the environmental protection solvent is ≥18 MΩ·cm, and the environmental protection solvent is a compound of glycerol and ultrapure water, and the mass ratio of glycerol to ultrapure water is 3:7. A preparation method of a silicon carbide fine grinding fluid includes the following steps: S1: Pretreatment of compound diamond abrasive; S2: Configuration of a dispersion system. Add glycerol, ultrapure water and disodium ethylenediaminetetraacetate into a nitrogen-protected reaction kettle according to a ratio, and control the temperature at 25±2°C; then sequentially add a polyetheramine block copolymer, a phosphate ester hyperdispersant and perfluoropolyether, and then perform ultrasonic dispersion, with an ultrasonic dispersion frequency of 40 kHz and a time of 30 min; S3: Gradient dispersion and homogenization; S4: Filter with a 5μm PTFE filter element to remove oversized particles to achieve ultra-clean treatment.

[0014] Preferably, the pretreatment in step S1 is the pretreatment of single-crystal diamond micropowder and polycrystalline diamond, and specifically includes the following steps: S101: Calcinate the single-crystal diamond micropowder and polycrystalline diamond in turn under argon protection, with a calcination temperature of 300-700°C and a calcination time of 2 h; S102: Perform supercritical CO2 cleaning after calcination, with a critical pressure of 15 MPa and a critical temperature of 40°C; The supercritical CO2 cleaning includes the following steps: S1021: Load the single-crystal diamond micropowder and polycrystalline diamond to be cleaned into a high-pressure-resistant cleaning container and seal it; S1022: Inject liquid CO2 into the container through a high-pressure pump, and raise the temperature and pressure to the supercritical state; S1023: Perform dynamic cleaning; S1024: The cleaned CO2 is condensed into a liquid after being depressurized to separate pollutants and recycled.

[0015] Preferably, the gradient dispersion and homogenization in step S3 further includes the following steps: S301: Divide the compound diamond abrasive into three equal batches and add it into the dispersion system in step 2; S302: The stirring speed for adding the first batch of compound diamond abrasive is 500 rpm; the second batch is 1000 rpm; the third batch is 1500 rpm; S303: After homogenization, add a pH regulator to adjust the pH of the fine grinding fluid to 10.0±0.2.

[0016] A silicon carbide fine grinding fluid and its preparation method disclosed by the present invention. The fine grinding fluid comprises the following components by mass fraction: compound diamond abrasive 0.5% - 2%; composite dispersant 6% - 12%; lubricating film-forming agent 2% - 5%; pH regulator 0.5% - 2%; chelating agent 0.1% - 0.5%, and the balance is an environmentally friendly solvent. The compound diamond abrasive is composed of single crystal diamond micropowder and polycrystalline diamond compounded, and the mass ratio of single crystal diamond micropowder to polycrystalline diamond is 1:0.5 - 2. The composite dispersant is compounded by a polyetheramine block copolymer and a phosphate ester type hyperdispersant, and the mass ratio of the polyetheramine block copolymer to the phosphate ester type hyperdispersant is 3:1. Compared with the prior art, the silicon carbide fine grinding fluid has good dispersion and stability, improves the grinding efficiency while making the surface roughness of the wafer after fine grinding < 3nm; and the preparation method of the fine grinding fluid is simple in operation, and has the beneficial effect of reducing the abrasive cost. Detailed implementation mode

[0017] A silicon carbide fine grinding fluid, which comprises the following components by mass fraction: compound diamond abrasive 0.5% - 2%; composite dispersant 6% - 12%; lubricating film-forming agent 2% - 5%; pH regulator 0.5% - 2%; chelating agent 0.1% - 0.5%, and the balance is an environmentally friendly solvent.

[0018] Wherein the compound diamond abrasive is composed of single crystal diamond micropowder (D50 = 0.2 - 0.5μm) and polycrystalline diamond (D50 = 0.7 - 0.9um) compounded, the particle size distance of single crystal diamond < 0.85, the particle size distance of polycrystalline diamond < 0.9, and the mass ratio of single crystal diamond micropowder to polycrystalline diamond is 1:0.5 - 2; the composite dispersant is compounded by a polyetheramine block copolymer (PEO-PPO-PEO, MW = 5000 - 10000) and a phosphate ester type hyperdispersant (BYK-190), and the mass ratio of the polyetheramine block copolymer to the phosphate ester type hyperdispersant is 3:1; the lubricating film-forming agent is perfluoropolyether (PFPE); the pH regulator is compounded by tetramethylammonium hydroxide (TMAH) and citric acid, and the mass ratio of tetramethylammonium hydroxide to citric acid is 1:1 - 2; the chelating agent is disodium ethylenediaminetetraacetate (EDTA-2Na); the resistivity of the environmentally friendly solvent ≥ 18MΩ·cm, and the environmentally friendly solvent is compounded by glycerol and ultrapure water, and the mass ratio of glycerol to ultrapure water is 3:7.

[0019] Example 1: The fine grinding fluid comprises the following components by mass fraction: compound diamond abrasive 0.5%; composite dispersant 6%; lubricating film-forming agent 2%; pH regulator 0.5%; chelating agent 0.1%, and the balance is an environmentally friendly solvent.

[0020] In this embodiment, the mass ratio of single-crystal diamond micropowder to polycrystalline diamond is 1:0.5; the mass ratio of polyetheramine block copolymer to phosphate ester hyperdispersant is 3:1; the mass ratio of tetramethylammonium hydroxide to citric acid is 1:1; the mass ratio of glycerol to ultrapure water is 3:7.

[0021] The preparation method of the fine grinding fluid includes the following steps: S1: Pretreatment of compound diamond abrasive; the pretreatment in step S1 is the pretreatment of single-crystal diamond micropowder and polycrystalline diamond, which specifically includes the following steps: S101: Calcine the single-crystal diamond micropowder and polycrystalline diamond successively under argon protection, the calcination temperature is 300 °C, and the calcination time is 2 h; S102: After calcination, perform supercritical CO2 cleaning, the critical pressure is 15 MPa, and the critical temperature is 40 °C; The supercritical CO2 cleaning includes the following steps: S1021: Load the single-crystal diamond micropowder and polycrystalline diamond to be cleaned into a high-pressure-resistant cleaning container and seal it; S1022: Inject liquid CO2 into the container through a high-pressure pump, and heat up and pressurize it to the supercritical state; S1023: Dynamic cleaning; S1024: The cleaned CO2 is condensed into a liquid after being depressurized to separate pollutants and recycled; S2: Configuration of the dispersion system, add glycerol, ultrapure water and disodium ethylenediaminetetraacetate in proportion in a nitrogen-protected reaction kettle, and control the temperature at 23 °C; Then add polyetheramine block copolymer, phosphate ester hyperdispersant and perfluoropolyether in sequence, and then perform ultrasonic dispersion, the ultrasonic dispersion frequency is 40 kHz, and the time is 30 min; S3: Gradient dispersion and homogenization; The gradient dispersion and homogenization in step S3 also include the following steps: S301: Divide the compound diamond abrasive into three batches and add it to the dispersion system in step 2; S302: The stirring speed for adding the first batch of compound diamond abrasive is 500 rpm; the second batch is 1000 rpm; the third batch is 1500 rpm; S303: After homogenization, add a pH regulator to adjust the pH of the fine grinding fluid to 9.8; S4: Filter with a 5 μm PTFE filter element to remove oversized particles to achieve ultra-clean treatment.

[0022] Example 2: The fine grinding fluid includes the following components by mass fraction: compound diamond abrasive 1%; composite dispersant 9%; lubricating film-forming agent 3%; pH regulator 1%; chelating agent 0.3%, and the balance is an environmental protection solvent.

[0023] In this embodiment, the mass ratio of single-crystal diamond micropowder to polycrystalline diamond is 1:1; the mass ratio of polyetheramine block copolymer to phosphate ester hyperdispersant is 3:1; the mass ratio of tetramethylammonium hydroxide to citric acid is 1:1.5; the mass ratio of glycerol to ultrapure water is 3:7.

[0024] The preparation method of the fine grinding fluid includes the following steps: S1: Pretreatment of compound diamond abrasive; the pretreatment in step S1 is the pretreatment of single-crystal diamond micropowder and polycrystalline diamond, which specifically includes the following steps: S101: Calcinate the single-crystal diamond micropowder and polycrystalline diamond successively under argon protection, the calcination temperature is 500 °C, and the calcination time is 2 h; S102: After calcination, perform supercritical CO2 cleaning, the critical pressure is 15 MPa, and the critical temperature is 40 °C; Supercritical CO2 cleaning after calcination can effectively remove organic residues (such as grease, resin) on the surface of the micropowder, avoiding metal corrosion or oxidation caused by traditional pickling; Supercritical CO2 cleaning includes the following steps: S1021: Load the single-crystal diamond micropowder and polycrystalline diamond to be cleaned into a high-pressure-resistant cleaning container and seal it; S1022: Inject liquid CO2 into the container through a high-pressure pump, and raise the temperature and pressure to the supercritical state; S1023: Dynamic cleaning; S1024: The cleaned CO2 is condensed into a liquid state after decompression and separation of pollutants for recycling. S2: Configuration of the dispersion system, add glycerol, ultrapure water and disodium ethylenediaminetetraacetate in proportion in a nitrogen-protected reaction kettle, control the temperature at 25 °C; then add polyetheramine block copolymer, phosphate ester type hyperdispersant and perfluoropolyether in sequence, and then perform ultrasonic dispersion, the ultrasonic dispersion frequency is 40 kHz, and the time is 30 min; S3: Gradient dispersion and homogenization; the gradient dispersion and homogenization in step S3 also include the following steps: S301: Divide the compound diamond abrasive into three batches and add it to the dispersion system in step 2; S302: The stirring speed for adding the first batch of compound diamond abrasive is 500 rpm; the second batch is 1000 rpm; the third batch is 1500 rpm; adding in three equal batches can effectively improve the uniformity of stirring and the dispersion of diamond in the system, avoid abrasive sedimentation or aggregation, and is beneficial to improving the grinding accuracy; S303: After homogenization, add a pH regulator to adjust the pH of the fine grinding fluid to 10; S4: Filter with a 5 μm PTFE filter element to remove oversize particles to achieve ultra-clean treatment.

[0025] Example 3: The fine grinding fluid includes the following components by mass fraction: compound diamond abrasive 2%; composite dispersant 12%; lubricating film-forming agent 5%; pH regulator 2%; chelating agent 0.5%, and the balance is an environmental protection solvent.

[0026] In this example, the mass ratio of single-crystal diamond micropowder to polycrystalline diamond is 1:2; the mass ratio of polyetheramine block copolymer to phosphate ester type hyperdispersant is 3:1; the mass ratio of tetramethylammonium hydroxide to citric acid is 1:2; the mass ratio of glycerol to ultrapure water is 3:7.

[0027] The preparation method of the fine grinding liquid comprises the following steps: S1: pretreatment of compound diamond abrasive; the pretreatment in step S1 is the pretreatment of single crystal diamond micropowder and polycrystalline diamond, and specifically comprises the following steps: S101: calcining the single crystal diamond micropowder and polycrystalline diamond in sequence under argon protection, the calcination temperature is 700°C, and the calcination time is 2h; S102: supercritical CO2 cleaning after calcination, the critical pressure is 15MPa, and the critical temperature is 40°C; Supercritical CO2 cleaning after calcination can effectively remove organic residues (such as grease, resin) on the surface of the powder, avoiding metal corrosion or oxidation caused by traditional acid cleaning; Supercritical CO2 cleaning includes the following steps: S1021: The single crystal diamond powder and polycrystalline diamond to be cleaned are placed in a high-pressure resistant cleaning container and sealed; S1022: Liquid CO2 is injected into the container through a high-pressure pump, and the temperature is increased and pressurized to a supercritical state; S1023: Dynamic cleaning; S1024: The cleaned CO2 is condensed into liquid for recycling after decompression and separation of pollutants; S2: Dispersion system configuration, glycerol, ultrapure water and disodium ethylenediaminetetraacetate are added in proportion in a nitrogen-protected reactor, and the temperature is controlled at 27°C; then polyetheramine block copolymer, phosphate ester type hyperdispersant and perfluoropolyether are added in sequence, and then ultrasonic dispersion is performed, the ultrasonic dispersion frequency is 40kHz, and the time is 30min; S3: Gradient dispersion and homogenization; The gradient dispersion and homogenization in step S3 also includes the following steps: S301: Add the compound diamond abrasive into the dispersion system in step 2 in three equal batches; S302: The stirring speed of the first batch of compound diamond abrasive is 500rpm; the second batch is 1000rpm; the third batch is 1500rpm; adding in three equal batches can effectively improve the uniformity of stirring and the dispersion of diamond in the system, avoid abrasive sedimentation or aggregation, and help improve grinding accuracy; S303: After homogenization, add pH regulator to adjust the pH of the fine grinding liquid to 10.2; S4: Use 5μm PTFE filter element to filter and remove oversized particles to achieve ultra-clean treatment.

[0028] In some embodiments, by compounding different diamond micropowder abrasives, the abrasive cost is reduced while taking into account both processing efficiency and wafer quality; in addition, in the composite dispersion synergistic mechanism, the steric hindrance effect of the polyetheramine block copolymer + the anchoring adsorption of the phosphate ester achieves nanoscale monolayer dispersion; at the same time, during use, PFPE forms a 10-20nm self-healing molecular film at the grinding interface, reducing the friction coefficient to below 0.05.

[0029] The performance data of the polishing liquid in the above embodiment and the polishing liquid available on the market are compared as follows: From the above data, it can be seen that in the present invention, polycrystalline diamond and single-crystal diamond particles are mixed as abrasives in a certain proportion. At the same time, through the cooperation with a dispersant, a film-forming agent and a chelating agent, the fine grinding liquid has good dispersion and stability, improving the grinding efficiency while meeting the condition that the surface roughness (Ra) of the wafer after fine grinding is < 3 nm, solving the problems of low grinding efficiency, long processing cycle and high surface roughness of the wafer after grinding.

[0030] Obviously, the above embodiments are merely examples for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.

Claims

1. A silicon carbide fine grinding fluid, characterized in that, The fine grinding fluid comprises the following components by mass fraction: compound diamond abrasive 0.5%-2%; composite dispersant 6%-12%; lubricating film-forming agent 2%-5%; pH regulator 0.5%-2%; chelating agent 0.1%-0.5%, and the balance is environmental solvent.

2. The silicon carbide fine grinding liquid according to claim 1, wherein, The compound diamond abrasive is composed of single crystal diamond micropowder and polycrystalline diamond. The D50 particle size of the single crystal diamond micropowder is 0.2-0.5 μm, the D50 particle size of the polycrystalline diamond is 0.7-0.9 μm, and the mass ratio of the single crystal diamond micropowder to the polycrystalline diamond is 1:0.5-2.

3. The silicon carbide fine grinding fluid according to claim 1, characterized in that, The composite dispersant is prepared by compounding a polyetheramine block copolymer and a phosphate ester type hyperdispersant, and the mass ratio of the polyetheramine block copolymer to the phosphate ester type hyperdispersant is 3:

1.

4. The silicon carbide fine grinding liquid according to claim 1, characterized in that, The lubricating film-forming agent is perfluoropolyether.

5. The silicon carbide fine grinding liquid according to claim 1, characterized in that, The pH regulator is prepared by compounding tetramethylammonium hydroxide and citric acid, and the mass ratio of tetramethylammonium hydroxide to citric acid is 1:1-2.

6. The silicon carbide fine grinding fluid according to claim 1, characterized in that, The chelating agent is disodium ethylenediaminetetraacetate.

7. The silicon carbide fine grinding liquid according to claim 1, characterized in that, The resistivity of the environmental solvent ≥18 MΩ·cm. The environmental solvent is prepared by compounding glycerol and ultrapure water, and the mass ratio of glycerol to ultrapure water is 3:

7.

8. A preparation method of a silicon carbide fine grinding fluid, characterized in that, It includes the following steps: S1: Pretreatment of the compound diamond abrasive; S2: Configuration of the dispersion system. Glycerol, ultrapure water and disodium ethylenediaminetetraacetate are added into a nitrogen-protected reaction kettle in proportion, and the temperature is controlled at 25±2 °C; then a polyetheramine block copolymer, a phosphate ester type hyperdispersant and perfluoropolyether are added in sequence, and then ultrasonic dispersion is carried out. The ultrasonic dispersion frequency is 40 kHz and the time is 30 min; S3: Gradient dispersion and homogenization; S4: Filter with a 5 μm PTFE filter element to remove oversized particles to achieve ultra-clean treatment.

9. The preparation method of the silicon carbide fine grinding fluid according to claim 8, characterized in that, The pretreatment in step S1 is the pretreatment of the single crystal diamond micropowder and the polycrystalline diamond, and specifically includes the following steps: S101: The single crystal diamond micropowder and the polycrystalline diamond are calcined in sequence under argon protection. The calcination temperature is 300-700 °C and the calcination time is 2 h; S102: After calcination, supercritical CO2 cleaning is carried out. The critical pressure is 15 MPa and the critical temperature is 40 °C; The supercritical CO2 cleaning includes the following steps: S1021: The single crystal diamond micropowder and the polycrystalline diamond to be cleaned are loaded into a high-pressure-resistant cleaning container and sealed; S1022: Liquid CO2 is injected into the container through a high-pressure pump, and the temperature and pressure are increased to the supercritical state; S1023: Dynamic cleaning; S1024: The cleaned CO2 is condensed into a liquid after being depressurized to separate pollutants and recycled.

10. The preparation method of the silicon carbide fine grinding fluid according to claim 8, characterized in that The gradient dispersion and homogenization in step S3 further includes the following steps: S301: The compound diamond abrasive is equally divided into three batches and added into the dispersion system in step 2; S302: The stirring speed for adding the first batch of the compound diamond abrasive is 500 rpm; the second batch is 1000 rpm; the third batch is 1500 rpm; S303: After homogenization, a pH regulator is added to adjust the pH of the fine grinding fluid to 10.0±0.2.

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