JP2018090823A - Water-soluble cutting fluid composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cutting fluid being well suited for use with a diamond wire saw for cutting silicon ingots.SOLUTION: An aqueous cutting fluid comprises water and a water-soluble polyalkylene glycol (PAG) having a cloudy point of 30°C to 80°C. The cutting fluid is an aqueous fluid, thus it comprises at least 50 wt.% of water. The cutting fluid exhibits one or more of low hydrogen generation, no wafer cleaning issues, good lubricity, good cooling efficiency, good swarf suspension and dispersion, and low foaming. The cutting fluid is generally non-sensitive to metal ions, and is nonflammable.SELECTED DRAWING: None

Description

  The present invention relates to a cutting fluid. In one aspect, the invention relates to a water soluble cutting fluid, while in another aspect, the invention relates to a water soluble cutting fluid for use with a diamond wire saw.

  Diamond wire slicing is a technique for being employed in photovoltaic (PV) silicon wafer manufacturing. Unlike the coarse-polishing wire saw technology, the diamond wire uses a resin layer or by electric plating to place abrasive grains on the core wire and perform a cutting operation through the installed abrasive grains. Slicing methods include moving a diamond wire saw against a workpiece, such as a silicon ingot, while cutting fluid or coolant is dispensed from a storage tank onto a wire web. The liquid film formed on the wire web or wire moves with the moving wire to the contact front surface of the workpiece, providing cooling and lubricity. The cutting fluid then returns to the storage layer with the workpiece powder or fines generated by the slicing method. The cutting fluid mixture is cooled and circulated for continued use until the cutting fluid is depleted or the amount of powder reaches a certain level. The temperature of the cutting fluid or the mixture of cutting fluid and powder is kept at a temperature slightly below room temperature, for example 25 ° C. At the contact surface between the wire and the silicon ingot, the temperature is usually in the range of 50 ° to 80 ° C. due to friction between the ingot and the wire. In addition to the main functions of cooling and lubricity, the cutting fluid also provides the interrupting and conveying (dispersing) function of the workpiece powder (debris), and if foam is present, its generation is negligible. is there.

  Aqueous cutting fluids are desirable for diamond wire wafer slicing because aqueous cutting fluids provide excellent cooling efficiency and low environmental impact, and aqueous cutting fluids offer the potential for cost savings. However, there are technical problems that prevent practical acceptance of aqueous cutting fluids. The main problems include difficulty in cleaning the wafer surface, and hydrogen generation, which are usually associated with the newly generated silicon surface and water reaction. In addition, the lubricity of aqueous cutting fluid is inferior to polyalkylene glycol (PAG) based on cutting fluid.

  The advantage of those skilled in the art of diamond wire cutting technology is that, especially for those who use this technology to cut silicon ingots, aqueous cutting fluids that exhibit excellent lubricity and dispersion capability still minimize hydrogen generation and wafer cleaning problems. It is to suppress.

  In one embodiment, the present invention relates to water and a cloud point of 30 ° C to 80 ° C, more typically a cloud point of 40 ° C to 70 ° C, and even more typically 40 ° C to 60 ° C. An aqueous cutting fluid containing a water-soluble polyalkylene glycol (PAG).

In one embodiment, the present invention is a cutting fluid,
(A) a water-soluble PAG having a cloud point of 30 ° C to 80 ° C;
(B) water and
(C) a wetting agent,
(D) a dispersant,
(E) antifoaming agent,
(F) a corrosion inhibitor,
(G) a complexing agent, and (H) at least one of a biocide.

  In certain embodiments of the present invention, the cutting fluid includes two, three, four, five, or all six of the optional components. The cutting fluid is aqueous, that is, includes at least 50, typically at least 60, more typically at least 80, and even more typically at least 90 weight percent (wt%) water. Typically, the cutting fluid comprises less than 98, more typically less than 97% by weight water. Water sources are diverse and typically water is free of particulates or other contaminants. Typically, the water is demineralized and / or deionized.

  The cutting fluid of the present invention has low viscosity, excellent cooling efficiency, excellent work scrap interruption and dispersibility, excellent work dust fineness wettability (especially silicon fine dust), excellent diamond wire saw cleaning, Excellent wafer surface cleaning, low foaming, generally insensitive to metal ions and non-flammable. The cutting fluid of the present invention is also extremely stable at high temperatures and relatively long-lasting, for example, typically the fluid can be used to cut several workpieces before they need to be replaced. In addition, the remaining cutting fluid on the silicon processing waste can be easily removed and can be easily used for recycling of the processing waste.

In one embodiment, the present invention is a method of cutting a hard and brittle material using a wire saw used in combination with an aqueous cutting fluid, the method comprising cutting the material into the wire saw and cutting under cutting conditions. Contacting the fluid, the cutting fluid comprising:
(A) a water-soluble PAG having a cloud point of 30 ° C to 80 ° C;
(B) water
(C) a wetting agent,
(D) a dispersant,
(E) antifoaming agent,
(F) a corrosion inhibitor,
(G) a complexing agent, and (H) at least one of a biocide.

  Cutting fluid is typically applied to a wire saw, typically a diamond wire saw, at or just before the contact point of the workpiece and the wire saw, ie, at the interface.

In one embodiment, the present invention is a cutting fluid premix,
(A) a water-soluble PAG having a cloud point of 30 ° C to 80 ° C;
(B) water and
(C) a wetting agent,
(D) a dispersant,
(E) antifoaming agent,
(F) a corrosion inhibitor,
(G) a complexing agent, and (H) at least one of a biocide.

  In this embodiment, the premix is converted to a cutting fluid by adding water.

It is a bar graph showing the result of a wear test of four balls. 6 is a bar graph showing hydrogen production by newly generated silicon surfaces, mimicking a method of cutting silicon ingots using a wire diamond saw and various coolants.

Definitions Unless stated to the contrary, implicit from the context, or customary in the art, all parts and percentages are based on weight. For the purposes of US patent conventions, any reference patent, patent application, or public notice content is particularly subject to disclosure of definitions (to the extent not inconsistent with any definitions specifically provided in this disclosure) and general in the art. Knowledge is incorporated by reference in its entirety (or its equivalent US version is so incorporated by reference).

  The numerical range includes all values from the lower limit value to the upper limit value in units of one unit, provided that there is a separation of at least 2 units between any lower limit value and upper limit value. . By way of example, if a property such as molecular weight is 100-1,000, such as compositional, physical, or other, all individual values such as 100, 101, 102, and 100-144, 155-170 Subranges such as 197-200, etc. are explicitly listed. For ranges containing values that are fractions less than 1 or greater than 1 (eg, 1.1, 1.5, etc.), 1 unit is 0.0001, 0.001, 0.01 or 0.1, as appropriate, Is considered. For ranges containing single-digit values that are less than 10 (eg, 1-5), one unit is usually considered 0.1. These are only examples explicitly mentioned, and it is believed that all possibilities in combinations of numerical ranges between the lower and upper limits listed should be explicitly described in this disclosure. . Numerical ranges are provided, among other things, for the amount of polyglycol in the coolant within the present disclosure.

  A word such as “compatible with other components of the cutting fluid” refers to certain components of the cutting fluid, such as wetting agents, dispersing agents, antifoaming agents, corrosion inhibitors, etc. It means that it does not interfere with or significantly hinder the ability of other components.

  The cloud point of the PAG is the temperature at which the first PAG solution, which was clear, becomes opaque due to the second separation. The cloud point measurement was performed according to ASTM D 2024. This opacity reduces the transmittance of light that passes through the specimen and reaches the detector. Permeability is measured using a Mettler FP90 Cloud Point System and softened with benzophenone and / or benzoic acid. The specimen is prepared with 1% by weight surfactant in deionized water. The Cloud Point System gradually increased the temperature from the estimated cloud point of less than about 15 ° C. to the estimated cloud point of more than 10 ° C. (usually 3 ° C./min). F factor (light transmittance reduction standard) is set to 4% to 28%.

Overview During slicing of an ingot to a silicon wafer, the local temperature, ie the wire / ingot contact area, or in other words, the surface temperature of the ingot at the point where the wire contacts the ingot, is higher than the cloud point of the polyglycol in the coolant. In that case, the polyglycol “exits” the coolant as an oil. The resulting polyglycol forms an oil layer on both the diamond wire and the surface of the ingot, providing effective lubricity. At the same time, and particularly with respect to silicon ingots, the oil film on the surface of the ingot can provide a protective layer for suppressing hydrogen production due to the reaction of water with the surface of newly generated ingot, wafer or processing waste. As the wire moves forward, the oil layer on the silicon surface (including the powder surface) returns to the coolant volume when the coolant temperature falls below the cloud point of the polyglycol. This allows continuous circulation and continuous use of the coolant.

Polyalkylene glycol (PAG)
The polyalkylene glycols used in the practice of this invention are known as compounds and are alkylene oxide monomers or alkylene oxide monomers by reaction of one or more water and monovalent, divalent or polyvalent compounds. Made from the polymerization of the mixture and promoted by a catalyst under reaction conditions known in the art (see, for example, “Alkyrene Oxides and Ther Polymers”, Surfactant Science Series, Vol 35).

In one embodiment, the initiator is ethylene or propylene glycol, or one oligomer therein. In one embodiment, the initiator is
R ¹ O— (CHR ² CH ₂ O) _m —R ³
A compound of the formula: wherein R ¹ and R ³ independently have a linear or branched structure and may contain one or more unsaturated bonds C ₁ -C ₂₀ aliphatic group or aromatic Or a hydrogen, provided that at least one of R ¹ and R ³ is hydrogen, each R ² is independently hydrogen, methyl, or ethyl, m Is an integer of 0-20. In one embodiment, the starting compound is a hydrocarbon compound containing three or more hydroxyl groups, such as glycerin or sorbit.

  In one embodiment, the catalyst is at least one of a base, usually an alkali or alkaline earth metal hydroxide or carbonate, an aliphatic amine, an aromatic amine, or a heterocyclic amine. In one embodiment, the sodium or potassium hydroxide is a base catalyst.

The alkylene oxide used as monomers in the polymerization are ethylene oxide, propylene oxide, butylene oxide, hexene oxide, or the like octene oxide, a C ₂ -C ₈ oxide. In one embodiment, the alkylene oxide is ethylene or propylene oxide. When the polymerization is complete, the reaction mixture is discharged and then neutralized with one or more acids. The neutralized polyalkylene glycol product has a pH value of 4.0 to 8.5.

  In one embodiment of the invention, the polyalkylene oxide is polyethylene oxide or a water soluble or dispersible copolymer of ethylene oxide (EO) and propylene oxide (PO), or one of them monomethyl, ethyl, propyl or butyl ether, Alternatively, polyethylene oxide initiated with glycerol or a copolymer of EO and PO. In one embodiment, the polyalkylene glycol has a molecular weight of 100 to 1,000, more typically 200 to 600.

  The amount of PAG in the cutting fluid is typically based on the total weight of the fluid, typically at least 0.01 weight percent (wt%), more typically at least 0.05 wt%, and even more typically at least 0.1% by weight. The maximum amount of PAG in the cutting fluid is largely a matter of economic benefit and convenience, but typically does not exceed 20 wt%, more typically does not exceed 10 wt%, and even more Typically not more than 5% by weight. The PAG used in the practice of this invention can partially serve as a wetting agent and / or a dispersing agent. Typically, PAGs are used alone or as a combination of two or more, but PAGs can be used in combination with one or more other optional ingredients.

Wetting agent Good compatibility with other components of the cutting fluid, for example, can effectively reduce the surface tension of water-soluble preparations such as cutting fluid, effectively moistening the surfaces of workpieces and wire saws Any compound that can be used can be used in the practice of this invention. Water-soluble or water-dispersible wetting agents are surfactants or surfactant mixtures and are typically predominantly anionic, nonionic or zwitterionic.

  Examples of anionic wetting agents are carboxylate surfactants such as sodium, potassium or amine salts of fatty acids, acrylated amino acids, acrylated polypeptides and polyoxyalkylenated fatty alcohol carboxylates; alkylbenzene sulfonates Petroleum sulfonate, α-olefin sulfonate, paraffin sulfonate, secondary n-alkane sulfonate, N-acyl-n-alkyl taurate, aryl alkane sulfonate, alkyl diphenyl ether (di) sulfonate, sulfosuccinate ester, alkylnaphthalene sulfonic acid Sulfonate surfactants such as salts and isethionates; sulfated alcohols, sulfated polyoxyalkylenated alcohols, sulfated triglyceride oils, fatty acid monoethanolamides Rufeto, including silicone-based surfactants, such as polyoxyalkylenated fatty acid monoethanolamide sulfate, sulfate-based surfactants, and phosphoric acid or polyphosphoric acid ester, a. In the anionic surfactant, the hydrophobizing agent is a linear or branched hydrocarbon chain, a linear or branched alkylaryl, or a linear or branched alkylphenol, and the hydrocarbon chain contains a carbon-carbon unsaturated bond It may be partially or fully fluorinated.

  Examples of non-ionic surfactants suitable for use as wetting agents include block copolymerization, random copolymerization of propylene oxide (PO), butylene oxide (BO), or higher alkylene oxide units. Linear or branched, which may be included in different forms, such as end capping, hydrocarbon chains may contain carbon-carbon unsaturated bonds, and may be partially or fully fluorinated Primary or secondary alcohol ethoxylate or alkoxylate; amine alkoxylate; alkylphenol ethoxylate; block copolymer of ethylene and propylene oxide or butylene oxide; fatty acid glyceryl and fatty acid polyglyceryl ester, sorbit or polyoxyethylene sorbite ester Which, long chain carboxylic acid esters; including and siloxane surfactant, a; alkylpolyglycosides; ethoxylated acetylenic diols. In nonionic surfactants, as a partially or fully “capped” surfactant, the terminal hydroxyl group is replaced by chlorine, alkyl ether, allyl ether, benzyl ether, acetate, or acetal. Also good.

  Examples of zwitterionic surfactants suitable for use as wetting agents include alkyl betaines, cocamidopropyl betaines, hydroxysultyans, lecithins and sodium lauroamphoacetate. Additional zwitterionic surfactants are described in US Pat. No. 4,301,044 and references described therein.

  Preferred surfactants or combinations of surfactants provide application of surface tension to the cutting fluid below 45 mN / m. Typically, the choice of surfactant or surfactant combination results in no foaming, low foaming, or improper foaming of the formulation. Preferably, the surfactant is readily biodegradable as judged by the OECD 301 method. Surfactants having a low surface tension based on secondary alcohols or highly branched secondary ethoxylates (SAE) are preferred.

  The amount of wetting agent in the cutting fluid is typically at least 0.01 wt%, more typically 0.1 wt%, based on the total weight of the cutting fluid. The maximum amount of wetting agent in the cutting fluid is mostly a matter of economic effectiveness and convenience, but typically does not exceed 5 wt%, more typically does not exceed 3 wt%, and even more Typically not more than 2% by weight.

Dispersants Dispersing agents, or simply “dispersants”, used in the practice of this invention are water-soluble polymers that contain one or more groups that are negatively charged after being dissolved in water. Examples of negatively charged groups include carboxyl, sulfonic acid, sulfinic acid and phosphoric acid. Examples of polymers include homopolymers and copolymers of acrylic acid, methacrylic acid, alkenyl sulfonic acid, aromatic alkenyl sulfonic acid, acrylamide sulfonic acid, and maleic acid, collectively known as polycarboxylates. The polymer may have styrene or hydrogen on the alkyl group replaced with fluorine, chlorine, hydroxyl, or other atoms or groups, and the alkyl contains one or more oxygen, sulfur, or silicon atoms. Contains units from water-insoluble comonomers, such as alkyl styrene, alkyl acrylate and alkyl methacrylate, and an amount of aryl acrylate or methacrylate that can maintain sufficient water solubility of the polymer May be. Among the polycarboxylic acid-based polymer compounds defined above, particularly suitable compounds include acrylic acid homopolymers and / or alkali metal salts and / or onium salts of acrylic acid and maleic acid copolymers. . The weight average molecular weight (Mw) of the polycarboxylic acid polymer compound and / or salt is typically 1,000 to 1,000,000, more typically 1,000 to 100,000, and More typically, it is 1,000 to 30,000. These polymers, or negatively charged repeating units in these polymers, are preferably passed through various graft bonds, such as ester, ether, or carbon-carbon bonds, through polyalkylene glycols (PAG), particularly polyethylene glycol ( One or more water-soluble polymers, such as PEG, may be grafted and are preferably grafted.

  The amount of dispersant in the cutting fluid is typically at least 0.01 wt%, more typically 0.1 wt%, based on the total weight of the fluid. The maximum amount of dispersant in the cutting fluid is mostly a matter of economic benefit and convenience, but typically does not exceed 20 wt%, more typically does not exceed 15 wt%, and even more typically Specifically, it does not exceed 10% by weight.

Defoamer Compatible with other components of the cutting fluid and pumped from the tank while the fluid is being stored, for example while being placed in the storage tank of a diamond wire saw device and during use Any compound that minimizes or eliminates foaming of the cutting fluid while applied to the surface of a wire saw or workpiece can be used in the practice of this invention. Representative antifoaming agents include organo-modified polysiloxanes and polyethers. Typical antifoaming agents include dimethylpolysiloxane, diethylpolysiloxane, dipropylpolysiloxane, methylethylpolysiloxane, dioctylpolysiloxane, dimethylpolysiloxane, methylpropylpolysiloxane, dibutylpolysiloxane and didodecylpolysiloxane. Organophosphorus compounds such as n-tri-butyl phosphate, n-tributoxyethyl phosphate or triphenyl phosphite, or mixtures thereof; and polyalkylene oxides (ethylene oxide, propylene oxide, and butylene oxide) Of the copolymer. Preferably, these water-dispersible or water-soluble antifoaming agents are as described in US Pat. No. 4,024,072 and references described therein.

  Typically, the cutting fluid of this invention includes an antifoaming agent. The amount of antifoam in the cutting fluid is typically heavier than 0 wt%, more typically at least 0.01 wt%, and even more typically less than 0. 0%, based on the total weight of the fluid. 1% by weight. The maximum amount of antifoam in the cutting fluid is largely a matter of economic effectiveness and convenience, but typically does not exceed 5% by weight and more typically does not exceed 3% by weight.

Corrosion Inhibitor Any compound that works well with other components of the cutting fluid and inhibits and removes the corrosion of the surface of the diamond wire saw device where the cutting fluid slides in the normal reservoir location. Can be used. Exemplary corrosion inhibitors include alkanolamines, boric acid esters, amine dicarboxylates, and triazoles. Typical corrosion inhibitors include phosphorus-containing chemicals such as orthophosphate, pyrophosphate, polyphosphate; hydroxycarboxylic acids such as gluconic acid and salts thereof; glucaric acid; alkanolamine; nitrite; carboxylate Silicates; phosphonates, and azole compounds such as benzotriazole, tolyltriazole, mercaptobenzothiazole, and halogenated azoles. More preferred is water dispersible or water soluble corrosion that exhibits excellent adhesion to the substrate under flow conditions, as described in US Pat. No. 6,572,789 and references therein. It is an inhibitor.

  Typically, the cutting fluid of this invention includes a corrosion inhibitor. The amount of corrosion inhibitor in the cutting fluid is typically heavier than 0 wt%, more typically at least 0.01 wt%, and even more typically less than 0. 0%, based on the total weight of the fluid. 1% by weight. The maximum amount of corrosion inhibitor in the cutting fluid is largely a matter of economic effectiveness and convenience, but typically does not exceed 2% by weight and more typically does not exceed 1% by weight.

Complexing agent Compatible with other components of the cutting fluid and collects fine dust or other particulates from the cutting waste present in the cutting fluid due to processing of the workpiece or formulation, transportation or storage of the cutting fluid Any compound that otherwise attaches to them can be used in the practice of this invention. Exemplary complexing agents include ethylenediamine N′N′-tetraacetic acid (EDTA) and its salts and derivatives; hydroxyethyliminodiacetic acid (HEIDA and its salts and derivatives; methyl-glycine-diacetic acid (MGDA) and And glutamic acid-N, N-diacetic acid (GLDA) and salts and derivatives thereof HEIDA, MGDA, and GLDA are often preferred due to biodegradability.

  Typically, the cutting fluid of this invention includes a complexing agent. The amount of complexing agent in the cutting fluid is typically heavier than 0 wt%, more typically at least 0.01 wt%, and even more typically less than 0. 0%, based on the total weight of the fluid. 1% by weight. The maximum amount of complexing agent in the cutting fluid is largely a matter of economic effectiveness and convenience, but typically does not exceed 2% by weight and more typically does not exceed 1% by weight.

Biocides Any compound that is compatible with other components of the cutting fluid and that effectively minimizes or eliminates cell growth, such as bacteria, algae, etc. in the cutting fluid. Can be used in practice. Cutting fluid is often well formulated prior to use and is often stored for long periods in storage tanks of the equipment in which the cutting fluid is used, such as a diamond wire saw. The presence of cell growth in the cutting fluid results in diminished fluid capacity and impediments in the apparatus, such as spray nozzle clogging. Exemplary biocides include triazine, oxazolidine, sodium omadin, and iodocarbamate.

  Typically, the cutting fluid of this invention includes a biocide. The amount of biocide in the cutting fluid is typically heavier than 0 wt%, more typically at least 0.01 wt%, and even more typically less than 0. 0%, based on the total weight of the fluid. 1% by weight. The maximum amount of biocide in the cutting fluid is mostly a matter of economic effectiveness and convenience, but typically does not exceed 2 wt%, more typically does not exceed 1 wt%, and even More typically it does not exceed 0.8% by weight.

Additives The cutting fluid may contain other components or polar solvents (eg, alcohols, amides, esters, ethers, ketones, glycol ethers, or sulfoxides), thickeners (eg, xanthan gum, rhamzan gum, or hydroxymethylcellulose, carboxy Alkyl cellulose), such as methylcellulose), dyes, fragrances, and the like. These other ingredients are used in known ways and in known amounts. When the additive is present in the cutting fluid, the amount is typically 0.01-20, more typically 0.05-10, and even more typically 0.1-5 weight percent ( % By weight).

Cutting Fluid Formulation The cutting fluid of the present invention is formulated using known equipment and known techniques. The various components are typically used at room temperature, eg, 23 ° C., using a conventional agitation device that provides agitation to facilitate good mixing of the components to produce a homogeneous mixture or blend. Or they are added in any order with one another at low heat, eg 30 ° C. or 40 ° C. Because the major component of a fully formulated fluid is water, typically the other components are added to water.

  In one embodiment, the cutting fluid includes at least one of an antifoaming agent, a wetting agent, a dispersing agent, a corrosion inhibitor, a complexing agent, or a biocide. In one embodiment, the cutting fluid includes at least two of antifoaming agents, wetting agents, dispersing agents, corrosion inhibitors, complexing agents, or biocides. In one embodiment, the cutting fluid includes at least three of antifoaming agents, wetting agents, dispersing agents, corrosion inhibitors, complexing agents, or biocides. In one embodiment, the cutting fluid includes at least four of antifoaming agents, wetting agents, dispersing agents, corrosion inhibitors, complexing agents, or biocides. In one embodiment, the cutting fluid includes at least five of antifoaming agents, wetting agents, dispersing agents, corrosion inhibitors, complexing agents, or biocides. In one embodiment, the cutting fluid includes all six of antifoaming agents, wetting agents, dispersing agents, corrosion inhibitors, complexing agents, or biocides.

  In one embodiment, the cutting fluid is fully formulated and packaged at the manufacturing facility, shipped with or without interim storage, and shipped to the end consumer who may or may not store further before use. .

  In one embodiment, the cutting fluid is a premix, or, for example, a water, 95, or 90, or 80, or 70, or 60, or 50 or 40 or 30 or 20 or 10 weight percent concentrate, or It is a concentrated formulation that contains all of the non-water materials, including but not most, if not all. In this embodiment, the non-water component of the formulation is agitated to form a premix or concentrate using conventional agitation equipment and techniques, with or without a small amount of water, and then packaged, Shipped to end consumer with or without intermediate storage and may or may not store further before use. Concentrates typically include, at a minimum, PAGs, wetting agents, and antifoams dissolved in a small amount of water to provide each desired concentrate when the cutting fluid is fully formulated. Contains a sufficient amount. When ready for use, the premix or concentrate is simply diluted with water to the desired concentration.

  In another embodiment, the cutting fluid is simply agitated as an in-situ formulation.

Use of cutting fluid Cutting fluid is used in a known manner. Typically, the cutting fluid is distributed on the cutting wire as the workpiece contacts the wire. Cutting wires are typically part of a cutting device known as a wire saw or wire web, and typically include thin wire rows, each installed in parallel and with a fixed width. For these thin wires (usually having a diameter of 0.1-0.2 millimeters (mm)) running parallel to each other in the same direction as cutting fluid is supplied between the workpiece and the wire, the workpiece Is pressed and sliced into a wafer by a grinding wheel grinding operation. These wire saws are more fully described in US Pat. Nos. 3,478,732, 3,525,324, 5,269,275, and 5,270,271. . Abrasive particles are firmly attached to the moving wire or wire against the diamond wire saw.

  The cutting fluid of this invention is used in other processing of hard and brittle materials such as ingots, crystals, or silicon wafers, gallium arsenide (GaAs), gallium phosphide (GaP), or sapphire. These other treatments include, without limitation, crushing, chopping and polishing. These fluids perform particularly well in applications where the abrasive particles are attached to a substrate such as a wire, ceramic, and the like.

  The following examples are illustrative of certain embodiments of the present invention. All parts and percentages are on a weight basis unless otherwise indicated.

Materials The materials used in the following examples are detailed in Table 1.

  PCA is a member of the Jiangsu New Materials Co. , Ltd., Ltd. It is sold under the trademark PCA-I. For PAG1, “x + y = 26” is a general representation of the copolymer structure. The polymer is synthesized by first building PO blocks and adding EO. EO is randomly added to both sides of the PO block. The sizes on both sides are usually fairly close, for example, each of x and y is about 13.

  PAG5 is a modified secondary alcohol ethoxylate and is sold under the trademark ECOSURF ™ LF-45 by The Dow Chemical Company.

  PAG6 is also a modified secondary alcohol ethoxylate, but is sold under the trademark ECOSURF ™ LF-30 under The Dow Chemical Company.

  PAGs 1-4 are commercially available or can be prepared using known procedures. For example, a suitable alcohol, glycol or oligomer thereof, or polyol, such as butanol, monopropylene glycol, diethylene glycol, secondary alcohol, is alkoxylated with an alkylene oxide compound. The alkoxylation process can be carried out, for example, in the presence of an acidic or alkaline catalyst or by using a metal cyanide catalyst. Alkaline catalysts may include sodium or potassium hydroxides or alcoholates including, for example, NaOH, KOH, sodium methoxide, potassium methoxide, sodium ethoxide, and potassium ethoxide. The base catalyst is typically used at a concentration of 0.02 weight percent to about 5 weight percent, preferably about 0.05 weight percent to about 1 weight percent, based on the starting material.

  Addition of alkylene oxide (eg, ethylene oxide, propylene oxide, or butylene oxide) can be performed, for example, in a high-pressure kettle under a pressure of about 10 psig to about 200 psig, preferably about 60 psig to about 100 psig. The temperature of alkoxylation may range from about 30 ° C to about 200 ° C, preferably from about 100 ° C to about 160 ° C. After completion of the oxide feed, the product is typically reacted until the residual oxygen is less than about 10 ppm. After cooling the chemical reactor to an appropriate temperature of about 20 ° C. to 130 ° C., the remaining catalyst can be neutralized with an organic acid, such as acetic acid, propion, or citric acid, while remaining unneutralized. May be. Alternatively, the product may be neutralized with an inorganic acid, such as phosphoric acid or carbon dioxide. Residual catalyst may be removed using ion exchange or adsorption media, such as diatomaceous earth.

Experimental method Wear test of four balls

  FIG. 1 represents the results of a four ball wear test. The shorter the diameter, the better the lubricity.

Conclusion Formulations with no polyglycol additive result in large wear scars. By adding PAG4 or PAG1 with a cloud point near or below the test temperature of 60 ° C., the size of the wear flaw is significantly reduced and exhibits better lubricity. PAG2 or PAG3, which has a cloud point higher than the working temperature, is used as a PAG and shows a less improved lubricity. The results show that maintaining the cloud point of the PAG near or below the working temperature provides excellent lubricity. Considering that the local temperature at the point of contact of the wire saw with the silicon ingot will be as high as 60-80 ° C., a PAG suitable in the practice of this invention should have a cloud point not exceeding 80 ° C.

Hydrogen gas generation When in contact with water under diamond wire cutting conditions, new silicon (either from a new wafer surface or from a silicon powder surface) may react with water and generate hydrogen gas. Such a surface reaction results in difficulty in cleaning the wafer surface. In this invention, the oil layer that emerges on the silicon surface can suppress the reaction between silicon and water when the temperature is higher than the cloud point of the PAG in the water-soluble cutting fluid. As specified below in Table 5, quantification in the hydrogen gas evolution of silicon powders in different formulations was performed to compare the impact of PAG on the silicon surface reaction.

  In this experiment, a new silicon surface is generated by friction between silicon powder and sea sand under vibrating conditions. The amount of hydrogen generated by this method is analyzed by GC-TCD. An Agilent 6890N gas chromatograph coupled to a temperature conduction detector is used. The TCD detection temperature is set to 180 ° C. The reference feed rate is 20 mL / min and the additional feed rate is 6 mL / min. 0.5 g Si powder, 4 g aqueous diluted coolant (coolant: water = 1: 12), and 2 g sea sand are placed in a 22 mL sealed headspace glass bottle and shaken in a G1888 autorecovery device for 20 hours with shaking. Heat at 60 ° C. Hydrogen generated in the headspace glass bottle is quantified using GC-TCD. The sea sand here is used to confirm that the Si powder has excellent dispersion in the coolant during vibration.

Results FIG. 2 shows the results of the hydrogen gas generation test.

Conclusion Compared to PAG3 with water and a cloud point higher than 60 ° C, two PAGs, namely PAG1 and PAG4 with cloud points near or below 60 ° C, show less hydrogen evolution and surface reaction It was shown to be suppressed. The results demonstrate that silicon surface reactions are suppressed by using PAGs with cloud points near or below the working temperature. Considering the local temperature at the point of contact between the wire saw and the silicon ingot, which can be as high as 80 ° C., a suitable PAG should have a cloud point not exceeding 80 ° C.

Formulation Stability PAG with cloud point near or below 30 ° C., used for the formulations in Table 7, the stability of the formulation becomes significantly unstable at normal storage temperature of 23 ° C. For example, a separate phase is seen in formulations where PAG6 with a cloud point near 30 ° C. is used as the PAG.

Actual Diamond Wire Wafer Slicing Test Aqueous cutting fluids with the formulations described in Table 8 were used in a commercial diamond wire wafer slicing machine to place a monovalent crystal silicon ingot (300 mm * 2) on a 6 ″ wafer (wafer thin wafer). A test is performed to slice to (S = 180 microns). In the formulation, PAG5, a secondary alcohol polyglycol ether material with a cloud point of 40-45 ° C. is used. In this test, the cutting fluid is diluted with water at a ratio of 1: 8.

  An overall average yield of 92.4% is achieved. There is no indication of any wafer surface cleaning problems. This test shows that the cutting fluid formulation of the present invention can slice a silicon wafer using diamond wire without hydrogen generation or major surface cleaning problems.

The invention is not limited to the embodiments and examples contained herein, but includes those portions of the embodiments and combinations of elements of different embodiments that fall within the scope of the following claims. It is specifically intended to include modifications.
Some of the embodiments of the invention related to the present invention are shown below.
[Aspect 1]
An aqueous cutting fluid comprising water and water-soluble polyalkylene glycol (PAG) having a cloud point of 30 ° C to 80 ° C.
[Aspect 2]
(A) a water-soluble PAG having a cloud point of 30 ° C to 80 ° C;
(B) water and
(C) a wetting agent,
(D) a dispersant,
(E) antifoaming agent,
(F) a corrosion inhibitor,
A cutting fluid comprising: (G) a complexing agent; and (H) at least one of a biocide.
[Aspect 3]
A method of cutting a hard and brittle material with a wire saw used in conjunction with an aqueous cutting fluid, the method comprising contacting the material with the wire saw and cutting fluid under cutting conditions. The cutting fluid is
(A) a water-soluble PAG having a cloud point of 30 ° C to 80 ° C;
(B) water
(C) a wetting agent,
(D) a dispersant,
(E) antifoaming agent,
(F) a corrosion inhibitor,
A method comprising: (G) a complexing agent; and (H) at least one of a biocide.
[Aspect 4]
(A) a water-soluble PAG having a cloud point of 30 ° C to 80 ° C;
(B) water and
(C) a wetting agent,
(D) a dispersant,
(E) antifoaming agent,
(F) a corrosion inhibitor,
A cutting fluid premix comprising: (G) a complexing agent; and (H) at least one of a biocide.
[Aspect 5]
The cutting fluid according to any one of the above aspects 1 to 4, comprising at least two of a wetting agent, a dispersing agent, an antifoaming agent, a corrosion inhibitor, a complexing agent and a biocide.
[Aspect 6]
The cutting fluid according to any one of the above aspects 1 to 4, comprising at least three of a wetting agent, a dispersing agent, an antifoaming agent, a corrosion inhibitor, a complexing agent and a biocide.
[Aspect 7]
The cutting fluid according to any one of the above aspects 1 to 4, comprising at least four of a wetting agent, a dispersing agent, an antifoaming agent, a corrosion inhibitor, a complexing agent and a biocide.
[Aspect 8]
The cutting fluid according to any one of the above aspects 1 to 4, comprising at least five of a wetting agent, a dispersing agent, an antifoaming agent, a corrosion inhibitor, a complexing agent and a biocide.
[Aspect 9]
The cutting fluid according to aspect 1, wherein the PAG is present in an amount of 0.01 to 20 weight percent based on the weight of the cutting fluid.
[Aspect 10]
The cutting fluid of embodiment 9, wherein water is present in an amount of 90 to 98 weight percent based on the weight of the cutting fluid.
[Aspect 11]
The above embodiment wherein at least one of the wetting agent, dispersing agent, antifoaming agent, corrosion inhibitor, complexing agent and biocide is present in an amount of 0.01 to 2 weight percent based on the weight of the cutting fluid. The cutting fluid according to 10.
[Aspect 12]
12. The cutting fluid of aspect 11, further comprising one or more of a polar solvent thickener, a dye, or a fragrance.
[Aspect 13]
The cutting fluid premix of aspect 4, wherein water is present in an amount not exceeding 80 weight percent, based on the weight of the premix.
[Aspect 14]
The cutting fluid premix according to any one of the above aspects 4 to 13, wherein the wetting agent and antifoaming agent are present.
[Aspect 15]
4. The method according to aspect 3, wherein the hard and brittle material is a silicon ingot or a wafer.

Claims (15)

  An aqueous cutting fluid comprising water and water-soluble polyalkylene glycol (PAG) having a cloud point of 30 ° C to 80 ° C. (A) a water-soluble PAG having a cloud point of 30 ° C to 80 ° C;
(B) water and
(C) a wetting agent,
(D) a dispersant,
(E) antifoaming agent,
(F) a corrosion inhibitor,
A cutting fluid comprising: (G) a complexing agent; and (H) at least one of a biocide. A method of cutting a hard and brittle material with a wire saw used in conjunction with an aqueous cutting fluid, the method comprising contacting the material with the wire saw and cutting fluid under cutting conditions. The cutting fluid is
(A) a water-soluble PAG having a cloud point of 30 ° C to 80 ° C;
(B) water and
(C) a wetting agent,
(D) a dispersant,
(E) antifoaming agent,
(F) a corrosion inhibitor,
A method comprising: (G) a complexing agent; and (H) at least one of a biocide. (A) a water-soluble PAG having a cloud point of 30 ° C to 80 ° C;
(B) water and
(C) a wetting agent,
(D) a dispersant,
(E) antifoaming agent,
(F) a corrosion inhibitor,
A cutting fluid premix comprising: (G) a complexing agent; and (H) at least one of a biocide.   The cutting fluid according to claim 1, comprising at least two of a wetting agent, a dispersing agent, an antifoaming agent, a corrosion inhibitor, a complexing agent and a biocide.   The cutting fluid according to any one of claims 1 to 4, comprising at least three of a wetting agent, a dispersing agent, an antifoaming agent, a corrosion inhibitor, a complexing agent, and a biocide.   The cutting fluid according to any one of claims 1 to 4, comprising at least four of a wetting agent, a dispersing agent, an antifoaming agent, a corrosion inhibitor, a complexing agent and a biocide.   The cutting fluid according to any one of claims 1 to 4, comprising at least five of a wetting agent, a dispersing agent, an antifoaming agent, a corrosion inhibitor, a complexing agent and a biocide.   The cutting fluid of claim 1, wherein the PAG is present in an amount of 0.01 to 20 weight percent based on the weight of the cutting fluid.   The cutting fluid of claim 9, wherein water is present in an amount of 90 to 98 weight percent based on the weight of the cutting fluid.   The at least one of the wetting agent, dispersing agent, antifoaming agent, corrosion inhibitor, complexing agent and biocide is present in an amount of 0.01 to 2 weight percent based on the weight of the cutting fluid. The cutting fluid according to 10.   12. The cutting fluid of claim 11, further comprising one or more of a polar solvent thickener, a dye, or a fragrance.   The cutting fluid premix of claim 4, wherein water is present in an amount not exceeding 80 weight percent, based on the weight of the premix.   The cutting fluid premix according to any of claims 4 to 13, wherein the wetting agent and antifoaming agent are present.   The method according to claim 3, wherein the hard and brittle material is a silicon ingot or a wafer.