Diamond wire cutting cooling liquid for silicon carbide wafer cutting

Abstract

The invention provides diamond wire cutting cooling liquid for silicon carbide wafer cutting, and particularly relates to the field of silicon carbide cutting liquid. The cutting coolant comprises the following components in parts by weight: 5-20 parts of polyol ester, 10-30 parts of fatty alcohol polyoxyethylene polyoxypropylene ether, 0.5-15 parts of poly (4-vinyl benzyl-tri (2-cyanoethyl) phosphonium chloride, 1-5 parts of a catalyst, 1-5 parts of a defoaming agent and 1-5 parts of an antioxidant. The cleaning agent is prepared from the following components in parts by weight: 0.01 to 1 part of aromatic acid, 0.05 to 2 parts of macromolecular viscosity modifier, 0.05 to 5 parts of zinc dialkyl dithiophosphate, 2 to 20 parts of alkynediol gemini surfactant, 0.1 to 2 parts of pH regulator, 0 to 20 parts of organic solvent, 0.02 to 2 parts of organic silicon defoaming agent and 10 to 50 parts of deionized water. The diamond wire cooling liquid for silicon carbide wafer cutting provided by the invention has the characteristics of large boundary lubricating film thickness and high boundary lubricating film strength. The cutting mode of the silicon carbide wafer from the diamond powder abrasive mortar and the steel wire is replaced by the diamond wire cutting mode, and the purposes of improving the cutting efficiency, reducing TTV, improving surface line marks and reducing the smudginess rate are achieved.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide wafer cutting technology, and in particular to a diamond wire cutting coolant for silicon carbide wafer cutting. Background Technology

[0002] Silicon carbide, with its wide bandgap, high breakdown field strength, and high thermal conductivity, offers advantages such as high efficiency, high frequency, and high temperature operation, and has become a third-generation semiconductor material. However, its Mohs hardness is 9.2-9.5, and its Vickers hardness (kg / mm²) is... 2 The hardness is 2500-3500, which is greater than the Mohs hardness of silicon and the Vickers hardness (kg / mm²). 2 The silicon carbide (SiC) single-crystal substrate has a thickness of 1000-1150 mm and is brittle, making it very difficult to cut. This makes the slicing process of SiC single-crystal substrates quite challenging. Currently, the mainstream cutting method is free abrasive slurry wire sawing. This suspended grinding method suffers from low efficiency, large TTV (total thickness deviation, the absolute difference between the maximum and minimum thickness measured on the entire wafer surface), and surface defects such as wire marks. Furthermore, using recycled diamond powder abrasive slurry for cutting also leads to an increase in contamination rate.

[0003] In the photovoltaic field, the cutting method of silicon wafers has evolved from free abrasive slurry wire saw cutting to water-based cutting fluid and diamond wire cutting. Diamond wire cutting involves using fixed wire saws at equal intervals on the surface of silicon carbide ingots. By stretching the diamond wire and moving it in a unidirectional or reciprocating cycle, a relative grinding motion is formed between the diamond wire and the object being cut, thereby cutting out silicon carbide wafers.

[0004] CN117946784A discloses a silicon carbide cutting fluid additive composition, a modified silicon carbide cutting fluid, its preparation method, and its application. The silicon carbide cutting fluid additive composition contains oleic acid diethanolamide borate, silicate, and proanthocyanidins in a mass ratio of 18-22:1-4:1, which can improve various properties of the silicon carbide cutting fluid, reduce the contamination rate and wire mark rate when cutting silicon carbide crystals, and improve the yield. At the same time, it can also improve the reusability of silicon carbide cutting fluid. This invention mainly adopts the slurry wire spacing cutting method.

[0005] CN102433191A discloses a silicon carbide cutting fluid containing one of polyethylene glycol cutting fluid, diethylene glycol cutting fluid, and polyamine alcohol cutting fluid, as well as polyphenolic compounds. Compared to commercially available silicon carbide cutting fluids, this silicon carbide cutting fluid has improved its anti-impurity performance to some extent; however, this performance still needs further improvement.

[0006] CN118725952A proposes a diamond wire multi-wire cutting fluid for large-size thin silicon wafers. The cutting fluid includes: 10%~15% wetting agent, 20%~25% dispersing lubricant, and deionized water as the balance. It has excellent lubrication performance, which can significantly reduce the spindle motor torque during the cutting process. In particular, it can significantly improve and eliminate the difficulty of retracting and lifting the cutting tool on large-size thin silicon wafers and the scratches and marks on the surface caused by lifting the cutting tool.

[0007] CN118879391A describes a silicon wafer cutting fluid, which is a silicon wafer cutting fluid with low conductivity, low viscosity, and excellent rust prevention effect, improving silicon wafer cutting efficiency and finished product quality. It comprises the following components by weight percentage: 20-30% wetting agent, 2-5% solubilizer, 20-30% lubricant, 1.5-3.5% coolant, 1.0-2.0% rust inhibitor, 0.3-0.7% bactericide, 0.3-0.7% chelating agent, 0.1-0.5% charge adjuster, and the balance being water. The lubricant includes any one or a combination of Air Dynol 607 surfactant, polyether PE6400, and 465 wetting agent; the coolant includes any one or a combination of isohexanediol, polyethylene glycol 200, diethylene glycol, and triethylene glycol; and the rust inhibitor includes any one or a combination of water-based rust-inhibiting surfactant, triethanolamine borate, and phytic acid.

[0008] However, current diamond wire cutting coolants for monocrystalline / polycrystalline silicon wafers primarily focus on dispersion and wetting, with generally poor performance in terms of boundary lubrication film thickness and strength. When applied to diamond wire cutting of silicon carbide wafers, this has resulted in large wire bowing and significant wire wear, sometimes preventing the cutting process from being completed. Wire bowing refers to the arc height formed when the cutting wire, due to cutting resistance, no longer maintains a straight line and bends inwards into the material. Summary of the Invention

[0009] To achieve the above objectives, the technical solution of the present invention provides a diamond wire cutting coolant for silicon carbide wafer cutting, so as to realize the iteration of the cutting method of silicon carbide wafer from diamond powder abrasive slurry and steel wire to diamond wire cutting method, thereby improving cutting efficiency, reducing TTV, improving surface wire marks and reducing contamination rate.

[0010] A diamond wire cutting coolant for silicon carbide wafer dicing comprises, by weight, the following components: 5-20 parts of polyol ester, 10-30 parts of fatty alcohol polyoxyethylene polyoxypropylene ether, 0.5-15 parts of poly(4-vinylbenzyl-tris(2-cyanoethyl))phosphonium chloride, 0.01-1 parts of aromatic acid, 0.05-2 parts of polymer viscosity modifier, 0.05-5 parts of zinc dialkyl dithiophosphate, 2-20 parts of acetylenic diol gemini surfactant, 0.1-2 parts of pH adjuster, 0-20 parts of organic solvent, 0.02-2 parts of silicone defoamer, and 10-50 parts of deionized water.

[0011] Furthermore, the polyol ester is one of the full-fat polyol esters, preferably trimethylolpropane oleate.

[0012] Furthermore, the fatty alcohol polyoxyethylene polyoxypropylene ether is a fatty alcohol with 6-18 carbon atoms as the starting alcohol, with 5-20 additions of ethylene oxide and 1-8 additions of propylene oxide, preferably a fatty alcohol with 7-11 carbon atoms, with 8-12 additions of ethylene oxide and 2-5 additions of propylene oxide.

[0013] Further, the poly(4-vinylbenzyl-tris(2-cyanoethyl))phosphonium chloride is synthesized in two steps: first, 4-vinylbenzyl-tris(2-cyanoethyl)phosphonium chloride is obtained by reacting tris(2-cyanoethyl)phosphine with 4-vinylbenzyl chloride; second, poly(4-vinylbenzyl-tris(2-cyanoethyl))phosphonium chloride is obtained by controlled free radical polymerization of 4-vinylbenzyl-tris(2-cyanoethyl)phosphonium chloride, preferably with a molecular weight of 2500-6000, and the synthesis reaction equation is as follows: .

[0014] Furthermore, the aromatic acid is one or more of benzoic acid, phthalic acid, terephthalic acid, and p-tert-butylbenzoic acid.

[0015] Furthermore, the polymer viscosity modifier is one or more of polyvinyl alcohol, sodium carboxymethyl cellulose, or polyacrylamide.

[0016] Furthermore, the dialkyl dithiophosphate zinc is di-n-butyl dithiophosphate zinc.

[0017] Furthermore, the acetylenic diol gemini surfactant has an ethylene oxide molar number of 0-30, preferably 3-10, added to the acetylenic diol molecule.

[0018] Furthermore, the organic solvent is an alcohol ether solvent, such as one or more of ethylene glycol methyl ether, ethylene glycol butyl ether, diethylene glycol butyl ether, triethylene glycol butyl ether, propylene glycol methyl ether, and dipropylene glycol methyl ether.

[0019] Furthermore, the pH adjuster is one or more of ethanolamine, diethanolamine, triethanolamine, or N,N-dimethylethanolamine.

[0020] Furthermore, the aforementioned silicone defoamer is any silicone substance known to those skilled in the art capable of eliminating or reducing bubble formation; for example, it can be selected from brands such as TEGO. ® Foamex 810, SAG ® 30. AFE-3183, and TEGO Airex901W, TSILCOLAPSE ® One or more of 502.

[0021] This invention also provides a method for preparing a diamond wire cutting coolant for silicon carbide wafer dicing. The specific experimental steps are as follows: the polyol ester, fatty alcohol polyoxyethylene polyoxypropylene ether, poly(4-vinylbenzyl-tris(2-cyanoethyl))phosphonium chloride, aromatic acid, high molecular viscosity regulator, zinc dialkyl dithiophosphate, acetylacetonate gemini surfactant, pH adjuster, organic solvent, organosilicon defoamer, and deionized water are mixed at once or in steps.

[0022] Compared with existing technologies, such as the cutting fluids in disclosed inventions CN117946784A, CN119795405A, CN118879391A, and CN118725952A, the present invention has the following beneficial effects: (1) It has good dispersion and wetting properties for silicon carbide powder, and can be cut with diamond wire. Using polyol ester as base oil can form a dense lubricating film on the friction interface, which is formed by a combination of physical adsorption and chemical reaction, thereby reducing heat generation and material damage caused by high friction. The selected fatty alcohol polyoxyethylene polyoxypropylene ether has strong tensile strength and excellent emulsification properties, which allows droplets to penetrate deeper into the micro-capillary structure and maintain efficient lubrication and heat dissipation even without electrostatic assistance.

[0023] (2) Poly(4-vinylbenzyl-tris(2-cyanoethyl))phosphonium chloride was introduced. As a water-soluble polyelectrolyte material, it is rich in self-lubricating cyanoethyl groups. Firstly, it has a large molecular weight and has the characteristic of thicker physical adsorption film. Secondly, it contains a P+ structure, which can form chemical bonds with SiC- at the cutting interface, and the strength of the boundary lubrication film formed is much higher than that of the physical adsorption molecular film. Thirdly, it contains phosphorus and chlorine extreme pressure properties. Combined with the other components, it has good dispersion and wetting performance for silicon carbide powder.

[0024] (3) The system based on deionized water combined with low-toxicity additives meets the requirements of green manufacturing, effectively avoids the volatile organic compounds and environmental pollution problems of traditional oil-based coolants, and improves operational safety and health risks.

[0025] (4) The synergistic effect of polyol ester and fatty alcohol polyoxyethylene polyoxypropylene ether can form a uniform and dense lubricating film at the cutting interface. At the same time, the high specific heat capacity of the aqueous phase can be used to quickly absorb and disperse the cutting heat, thereby effectively reducing the temperature rise and crack generation risk of the wafer surface. It also makes the diamond wire cutting coolant for silicon carbide wafer cutting have the characteristics of thick boundary lubricating film and high boundary lubricating film strength. It can realize the iteration of the cutting method of silicon carbide wafer from diamond powder abrasive slurry and steel wire to diamond wire cutting, thereby improving cutting efficiency, reducing TTV, improving surface marks and reducing contamination rate. Detailed Implementation

[0026] The following specific embodiments illustrate the present invention. It should be noted that the following embodiments are only for further explanation of the present invention and do not represent the scope of protection of the present invention. Non-essential modifications and adjustments made by others based on the description of the present invention still fall within the scope of protection of the present invention.

[0027] Example 1 This embodiment provides a diamond wire cutting fluid for silicon carbide wafers, specifically comprising the following components by weight percentage: 10 parts trimethylolpropane oleate, 15 parts fatty alcohol polyoxyethylene polyoxypropylene ether, 10 parts poly(4-vinylbenzyl-tris(2-cyanoethyl))phosphonium chloride, 0.5 parts aromatic acid, 1 part polymeric viscosity modifier, 3 parts zinc dialkyl dithiophosphate, 18 parts acetylenol gemini surfactant, 0.2 parts pH adjuster, 7 parts organic solvent, 0.05 parts silicone defoamer, and 35.25 parts deionized water. These are sequentially added to a high-shear emulsifier and sheared emulsified for 30 minutes.

[0028] Example 2 12 parts of polyol ester, 13 parts of fatty alcohol polyoxyethylene polyoxypropylene ether, 8 parts of poly(4-vinylbenzyl-tris(2-cyanoethyl))phosphonium chloride, 0.3 parts of aromatic acid, 0.8 parts of polymer viscosity modifier, 3 parts of zinc dialkyl dithiophosphate, 20 parts of acetylenol gemini surfactant, 0.12 parts of pH adjuster, 5 parts of organic solvent, 0.04 parts of silicone defoamer, and 37.74 parts of deionized water are added sequentially to a high-shear emulsifier and shear emulsified for 30 minutes.

[0029] Example 3 14 parts of polyol ester, 14 parts of fatty alcohol polyoxyethylene polyoxypropylene ether, 5 parts of poly(4-vinylbenzyl-tris(2-cyanoethyl))phosphonium chloride, 0.2 parts of aromatic acid, 0.7 parts of polymer viscosity modifier, 4 parts of zinc dialkyl dithiophosphate, 15 parts of acetylenol gemini surfactant, 0.08 parts of pH adjuster, 8 parts of organic solvent, 0.02 parts of silicone defoamer, and 37.74 parts of deionized water are added sequentially to a high-shear emulsifier and shear emulsified for 30 minutes.

[0030] Example 4 18 parts of polyol ester, 16 parts of fatty alcohol polyoxyethylene polyoxypropylene ether, 4 parts of poly(4-vinylbenzyl-tris(2-cyanoethyl))phosphonium chloride, 0.7 parts of aromatic acid, 1 part of polymer viscosity modifier, 4 parts of zinc dialkyl dithiophosphate, 17 parts of acetylenol gemini surfactant, 0.28 parts of pH adjuster, 12 parts of organic solvent, 0.02 parts of silicone defoamer, and 27 parts of deionized water are added sequentially to a high-shear emulsifier and shear emulsified for 30 minutes.

[0031] Comparative Example 1 The cutting fluid and cutting method described in CN117946784A shall be used.

[0032] Comparative Example 2 The cutting fluid and cutting method described in CN119795405A shall be used.

[0033] Comparative Example 3 As described in CN116333804A: The composition of the diamond wire cutting fluid for monocrystalline silicon rods, calculated by weight in parts, includes: 45 parts of propylene glycol polyoxyethylene polyoxypropylene ether, 0.4 parts of sodium carboxymethyl cellulose, 3 parts of molybdenum disulfide emulsion, 32 parts of acetylacetonate diol gemini surfactant, 5 parts of triethylene glycol monobutyl ether, and 14.6 parts of deionized water, which are added sequentially to a high-shear emulsifier and sheared and emulsified for 30 minutes.

[0034] Performance testing The cutting fluids prepared in Examples 1-4 and Comparative Example 3 were tested on 8-inch silicon carbide wafers using a GC700XL diamond wire silicon slicing machine manufactured by Qingdao Gaocheng Technology Co., Ltd., 140-micron diamond wire manufactured by Qingdao Gaocheng Technology Co., Ltd., and the same cutting process conditions. Comparative Examples 2 and 3 used the diamond powder abrasive slurry and steel wire cutting method described in the patent document. The results of the core indicators are shown in Table 1. As can be seen from Table 1, the TTV, wire marks, and contamination rate of the cutting fluids provided in Examples 1-5 are all better than those of Comparative Examples 1 and 2.

[0035] Table 1 Bowing during the dicing process is closely related to the contamination rate. Contamination is essentially the agglomeration and deposition of SiC microparticles generated during dicing on the wafer surface in the cutting fluid. During dicing, when the cutting resistance exceeds the tension of the diamond wire, the diamond wire bends to form bowing.

[0036] The fatty alcohol polyoxyethylene polyoxypropylene ether in the cutting coolant of this invention possesses strong tensile strength and excellent emulsifying properties, enabling deeper penetration into the micro-capillary structure. Even without electrostatic assistance, it can enter the kerf formed by diamond wire grinding in silicon carbide ingots. The synergistic effect of the polyol ester and the fatty alcohol polyoxyethylene polyoxypropylene ether forms a uniform and dense lubricating film at the cutting interface. Simultaneously, the high specific heat capacity of the aqueous phase rapidly absorbs and disperses cutting heat, effectively reducing the temperature rise and crack formation risk on the wafer surface. Furthermore, it gives the diamond wire cutting coolant for silicon carbide wafer cutting the characteristics of a thick and strong boundary lubricating film. Poly(4-vinylbenzyl-tris(2-cyanoethyl))phosphonium chloride, as a water-soluble polyelectrolyte material, is rich in self-lubricating cyanoethyl groups and contains phosphorus and chlorine extreme pressure properties. Combined with the other components, it possesses good dispersion and wetting properties for silicon carbide powder, reducing the fouling rate.

Claims

1. A diamond wire cutting coolant for silicon carbide wafer dicing, characterized in that, The raw material composition of this silicon carbide wafer diamond wire cutting fluid, calculated by weight in parts, includes: 5-20 parts of polyol ester, 10-30 parts of fatty alcohol polyoxyethylene polyoxypropylene ether, 0.5-15 parts of poly(4-vinylbenzyl-tris(2-cyanoethyl))phosphonium chloride, 0.01-1 parts of aromatic acid, 0.05-2 parts of polymer viscosity modifier, 0.05-5 parts of zinc dialkyl dithiophosphate, 2-20 parts of acetylenic diol gemini surfactant, 0.1-2 parts of pH adjuster, 0-20 parts of organic solvent, 0.02-2 parts of silicone defoamer, and 10-50 parts of deionized water.

2. The diamond wire cutting coolant for silicon carbide wafer dicing according to claim 1, characterized in that, The polyol ester is one of the full-fat polyol esters, preferably trimethylolpropane oleate.

3. The diamond wire cutting coolant for silicon carbide wafer dicing according to claim 1, characterized in that, The starting alcohol of the fatty alcohol polyoxyethylene polyoxypropylene ether is a fatty alcohol with 6-18 carbon atoms, the number of additions of ethylene oxide is 5-20, and the number of additions of propylene oxide is 1-8. Preferably, it is a fatty alcohol with 7-11 carbon atoms, the number of additions of ethylene oxide is 8-12, and the number of additions of propylene oxide is 2-5.

4. The diamond wire cutting coolant for silicon carbide wafer dicing according to claim 1, characterized in that, The aromatic acid is one or more of benzoic acid, phthalic acid, terephthalic acid and p-tert-butylbenzoic acid.

5. The diamond wire cutting coolant for silicon carbide wafer dicing according to claim 1, characterized in that, The aforementioned polymer viscosity modifier is one or more of polyvinyl alcohol, sodium carboxymethyl cellulose, or polyacrylamide.

6. The diamond wire cutting coolant for silicon carbide wafer dicing according to claim 1, characterized in that, The acetylenic diol gemini surfactant has an addition of ethylene oxide to the acetylenic diol molecule in a molar number of 0-30, preferably 3-10.

7. The diamond wire cutting coolant for silicon carbide wafer dicing according to claim 1, characterized in that, The organic solvent is an alcohol ether solvent, such as one or more of ethylene glycol methyl ether, ethylene glycol butyl ether, diethylene glycol butyl ether, triethylene glycol butyl ether, propylene glycol methyl ether, and dipropylene glycol methyl ether.

8. The diamond wire cutting coolant for silicon carbide wafer dicing according to claim 1, characterized in that, The pH adjuster is one or more of ethanolamine, diethanolamine, triethanolamine or N,N-dimethylethanolamine.

9. The diamond wire cutting coolant for silicon carbide wafer dicing according to claim 1, characterized in that, The aforementioned silicone defoamer is any silicone substance known to those skilled in the art that can eliminate or reduce the generation of bubbles. For example, it may be selected from one or more of the brands TEGO® Foamex 810, SAG® 30, AFE-3183, TEGOAirex901W, and TSILCOLAPSE® 502.

10. A method for preparing a diamond wire cutting coolant for silicon carbide wafer dicing, characterized in that, The polyol ester, fatty alcohol polyoxyethylene polyoxypropylene ether, poly(4-vinylbenzyl-tris(2-cyanoethyl))phosphonium chloride, aromatic acid, high molecular viscosity regulator, zinc dialkyl dithiophosphate, acetylacetonate gemini surfactant, pH adjuster, organic solvent, organosilicon defoamer, and deionized water are mixed at once or in steps.

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