KR20120056196A - Environment-friendly water-soluble cutting fluid for wafer, and composition containing the same cutting fluid - Google Patents

Abstract

PURPOSE: A water soluble cutting oil for cutting wafers, and a water soluble cutting liquid composition containing the same are provided to improve a work environment by providing safety to humans. CONSTITUTION: A water soluble cutting oil is shown in chemical formula 1. In the chemical formula 1, R1 and R2 are independently hydrogen or alkyl with 1-24 carbons. A water soluble cutting liquid composition contains 30-100wt% of the water soluble cutting oil. The water soluble cutting liquid composition additionally contains a water soluble polymer, glycerol, alkylene glycol, an alkylene oxide byproduct, or water.

Description

Environment-friendly water-soluble cutting fluid for wafer cutting and composition containing the same cutting fluid

The present invention relates to a water-soluble cutting oil for cutting a wafer, and a water-soluble wafer cutting liquid composition containing such cutting oil.

Deformation of materials by reducing frictional heat generated when cutting silicon ingots using wire saws during the manufacturing process of semiconductor or solar cell wafers, or by providing lubricity and dispersion stability of abrasives. Cutting fluids are used to minimize the need and to allow precise machining.

Such cutting fluids can be classified as useful and water soluble. Since the oil-soluble cutting liquid contains a mineral oil or a higher hydrocarbon compound, a separate washing step for cleaning the mineral oil or higher hydrocarbon compound remaining in the workpiece is required after cutting with the oil-soluble cutting liquid. Organic solvents used in such cleaning processes, for example, chlorine-based organic solvents are toxic to the human body, have a high flammability and poor working environment, and has a problem of causing environmental pollution when discharged.

On the other hand, water-soluble cutting fluids have a lower cutting efficiency than oil-soluble cutting fluids, but they are less widely used than oil-soluble cutting fluids due to their low environmental pollution burden and ease of work such as water washing during cutting process. The trend is increasing. As shown in Korean Patent Registration Nos. 10-0520714 and 10-0975877, commercially available water-soluble cutting fluids include diethylene glycol, propylene glycol and polyethylene glycol as main components. The alkylene glycol-based compound is included as the cutting oil, and the water-soluble cutting fluid has the advantage that it can be cleaned only by water and ultrasonic waves.

However, since the alkylene glycol-based compound mainly uses ethylene oxide or propylene oxide starting from petroleum, price volatility due to oil price is large, and thus the alkylene glycol-based compound is emerging as a large variable in a cutting environment in which alkylene glycol-based compounds are used in large quantities. It is true. In addition, when the diethylene glycol or propylene glycol alone is used, problems such as dispersibility in the cutting fluid may be reduced or a hard cake may be generated. When the polyethylene glycol is used alone, dispersion may be performed. It is relatively good and produces less hard cakes, but it is more expensive than diethylene glycol or propylene glycol.

On the other hand, in the cutting process using a wire saw or the like, the slurry containing the cutting oil or the cutting liquid and the abrasive (silicon carbide, aluminum oxide, silicon dioxide, etc.) must be continuously supplied to the cutting site. It must have adequate flow and maintain a consistent dispersion of abrasives. This is because when the flowability of the slurry is poor, the cut slurry and fine particles (fine particles) are sandwiched between the cut wafers without being discharged, which may cause a problem in removing the cattle after the cutting is completed. In addition, if the dispersibility of the abrasive contained in the slurry is low, the abrasive is settled to form a hard-cake (hard-cake) in the slurry supply tank and the supply line is difficult to redistribute the cutting process at a low abrasive concentration Supplied to. As a result, the working time may be increased, the surface roughness of the workpiece may be increased, and the slurry supply line may be clogged due to the formed hard cake. In order to prevent such a phenomenon, the dispersion stability of the slurry should be good, and for this purpose, the slurry containing the cutting oil or the cutting liquid should have an appropriate viscosity. When the viscosity is excessively high, it is difficult to efficiently supply the slurry, and when the viscosity is too low, it is difficult to stably maintain the dispersion of relatively heavy abrasives, and the slurry may flow down from the saw.

The viscosity of the cutting fluid or slurry is different for each machine in which a wire saw is used, because a large change in the viscosity of the cutting fluid or the slurry may cause a load on the supply system or difficult to supply properly. Typically, high viscosity polyethylene glycol is mainly used for wire saws using high viscosity slurry, and low viscosity diethylene glycol or propylene glycol is mainly used for wire saws using low viscosity slurry. Therefore, it is difficult to use high viscosity polyethylene glycol and low viscosity diethylene glycol or propylene glycol.

The technical problem to be achieved by the present invention is to minimize the deformation of the material by reducing the frictional heat generated in the cutting process of semiconductor or solar cell wafer using a wire saw, or provide properties such as lubricity, dispersion stability of abrasives, etc. The present invention provides an environmentally friendly water-soluble cutting oil and water-soluble wafer cutting fluid composition containing the same, which enables a precise and precise processing, and is excellent in cleanability and does not need to be cleaned using an organic solvent to improve the working environment. .

In order to solve the above technical problem, the present invention provides a cutting oil represented by the formula (1) for wafer cutting.

[Formula 1]

R ₁ and R ₂ in Formula 1 are each independently hydrogen or alkyl having 1 to 24 carbon atoms.

When R ₁ and R ₂ of Formula 1 are alkyl having an appropriate carbon number, they may be connected to each other to form cycloalkyl, and a compound in which such cycloalkyl is formed is also included in the scope of Formula 1 of the present invention.

In particular, very surprisingly, in the case of glycerol dimethyl ketalde, in which R ₁ and R ₂ in Formula 1 are both methyl groups, excellent dispersibility of abrasives and excellent cutting performances can be exhibited, as compared to conventional alkylene glycol-based compounds. When used in combination with an existing alkylene glycol compound, it exhibits excellent dispersibility and excellent cutting performance.

The inventors of the present invention have recently tried to use glycerol, which is mass-produced with the activation of the biodiesel industry, and its treatment problems are raised, and when using the compound of formula 1 obtained by condensation reaction of the glycerol with a ketone compound as cutting oil The present invention was completed by confirming that the dispersibility of the abrasive is very excellent compared to the conventional alkylene glycol-based compound.

Therefore, when the cutting oil according to the present invention is used in a semiconductor or solar cell wafer cutting process using a wire saw, etc., the dispersion stability and redispersibility of the abrasive are better than those of the conventional cutting oil, and thus the abrasive concentration is increased. Is supplied to the cutting process in a high state to shorten the cutting process time and reduce the surface roughness of the workpiece. In addition, since the slurry formed by mixing the cutting oil and the abrasive may have an appropriate viscosity and flowability, a phenomenon in which the slurry supply line is clogged or a phenomenon in which wire sawing is difficult to be removed after completion of the cutting process may be significantly reduced.

In addition, since the cutting oil for wafer cutting of the present invention has a high affinity with water and is easily dissolved in water, it does not need to be cleaned using an organic solvent or the like, which is safe for the human body and is environmentally friendly. This allows not only the cleaning to be completed in a short time, but also no cutting oil, abrasive or cutting fines remain after the drying process after cleaning.

At the same time, since the cutting oil for wafer cutting of the present invention has an inorganic or low foaming characteristic, in the process of forming a slurry by mixing with an abrasive, no bubbles are generated or fewer bubbles can be supplied to supply a uniform slurry, thereby improving cutting performance. It also has the advantage of providing.

Accordingly, the present invention provides a water-soluble wafer cutting fluid composition comprising the cutting oil according to the present invention, which can be used to cut a wafer using such a composition. That is, the present invention also provides a wafer cutting method characterized by using the cutting oil of the present invention.

Cutting oil represented by the formula (1) is contained in 1 to 100% by weight based on the total weight of the water-soluble wafer cutting fluid composition, preferably 30 to 100% by weight relative to the total weight of the water-soluble wafer cutting fluid composition. If the content is less than 1% by weight, it may be difficult to expect excellent dispersion stability or redispersibility of the abrasive.

In addition, a water-soluble polymer, glycerol, alkylene glycol, alkylene oxide adducts for the purpose of adjusting the viscosity of the water-soluble wafer cutting liquid composition of the present invention, improving the dispersion stability of the abrasive, improving the surface tension, improve the cleaning property or flow of the slurry, etc. It may further comprise one or more selected from the group consisting of a surfactant and water. For example, water, such as pure water, ultrapure water, industrial water, etc. may be included to improve the phase stability or cooling performance of the water-soluble wafer cutting liquid composition, and may preferably be included in an amount of 0.1 to 50% by weight.

As the water-soluble polymer, a polyvinyl alcohol, a polyvinylpyrrolidone having a molecular weight of 10,000 or more, preferably a molecular weight of 10,000 or more and 2,000,000 or less, or a mixture thereof may be used. The alkylene glycol is preferably ethylene glycol, diethylene glycol, Triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, hexylene glycol, polyethylene glycol, polypropylene glycol, polyethylene glycol-polypropylene glycol copolymer, 1,3-propanediol, 1,4-butanediol, 1, 6-hexanediol and the like can be used.

As the alkylene oxide adduct, a copolymer obtained by adding an alkylene oxide to at least one selected from the group consisting of fatty acids, fatty alcohols and fatty amines can be used. Preferably, the fatty acid has an alkyl group of 4 to 20 carbon atoms, the fatty alcohol has an alkyl group of 4 to 20 carbon atoms, the fatty amine has an alkyl group of 4 to 20 carbon atoms, preferably, as the alkylene oxide, Ethylene oxide (EO), propylene oxide (PO) or EO / PO copolymers containing them (e.g., (EO) n (PO) m (EO) n or (PO) n (EO) m (PO) n ) May be used alone or in combination of one or more thereof.

In addition, as the surfactant, a surfactant or the like used in a conventional cutting fluid composition may be used without limitation within the scope of not impairing the object of the present invention, for example, sulfate ester salts of fatty alcohols, alkylbenzene sulfonates Etc. may be used, but the present invention is not limited thereto.

The water-soluble cutting oil of the present invention and the water-soluble wafer cutting liquid composition comprising the same are not only environmentally friendly and safe for human body, but also have excellent abrasive dispersion and redispersibility and excellent cleaning and cutting performance.

Hereinafter, examples and the like will be described in detail to help understand the present invention. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the following embodiments. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

<Examples 1-3> Water-soluble wafer cutting liquid

The water soluble wafer cutting fluid of the present invention was prepared by mixing the components shown in Table 1 below.

ingredient Example 1 Example 2 Example 3 Glycerol Dimethyl Ketal 75 50 Glycerol Monomethyl Ketal 55 Glycerol 20 30 25 Diethylene glycol 10 20 Surfactants 5 5 5

* Surfactant: polyoxyalkylene alkylether

<Comparative Examples 1 to 3>: Commercially available water-soluble wafer cutting liquid

As shown in Table 2 below, commercially available water-soluble wafer cutting fluid was used as a comparative example.

Comparative Example 1 Comparative Example 2 Comparative Example 3 Water Soluble Wafer Cutting Fluid PEG300 DEG PG

* PEG300: polyethylene glycol (molecular weight: 300)

* DEG: diethylene glycol

* PG: Propylene Glycol

(a) Evaluation of physical properties of cutting fluid

The viscosity of the water-soluble wafer cutting liquid of Examples 1 to 3 and Comparative Examples 1 to 3 was a Brookfield DV-II + viscometer, the temperature 25 ℃, 100rpm, Spindle No. It measured on condition of 61. The thermal conductivity was measured using DECAGON's KD2-Pro using the transient hot wire method, and the temperature sensor was measured at various places in the sample at 25 ° C under the assumption that there is no convection effect.

(b) dispersion stability assessment

The slurry was prepared by mixing the water-soluble wafer cutting liquid and the abrasive (GC # 1500) of Examples 1 to 3 and Comparative Examples 1 to 3 in the same weight and then stirring at 500 rpm for 1 hour using a blade mixer. The slurry was transferred to a 100 ml measuring cylinder and left at room temperature for 6 hours to observe the dispersibility of the abrasive, and is shown in Table 3 below.

Evaluation criteria are as follows.

Good: The height of the settling layer (the height at which the abrasive is settled) is 90% or more of the whole and is in a uniform slurry state.

Normal: Sedimentation layer height is 70% or more and 90% or less.

Poor: The height of the settling layer is 70% or less of the total and the abrasive forms a hard-cake.

(c) redispersibility assessment

The slurry of (a) is left at room temperature for 24 hours to settle the abrasive. After shaking the measuring cylinder in which the abrasive is settled up and down 25 times to confirm the redispersibility of the particles are shown in Table 3 below.

Evaluation criteria are as follows.

Good: The abrasive is completely redispersed, almost identical to the original slurry.

Normal: Some of the abrasive has been redispersed but some remain as sedimentation layers.

Poor: The abrasive will form a hard cake and will not return to the original slurry.

(d) detergency evaluation

The silicon wafer is cut into 100 mm long and 100 mm long, and the slurry of (a) is evenly applied to the wafer surface and then fixed for 24 hours. Thereafter, the wafer was immersed in water at room temperature, and then ultrasonically cleaned for 1 minute. The results are shown in Table 3 below.

Evaluation criteria are as follows.

Good: The slurry was completely removed.

Normal: The slurry is removed but the abrasive is stuck.

Poor: Most of the slurry remains.

(e) Cutting performance evaluation

After mixing the water-soluble wafer cutting liquid and the abrasive of the Examples 1 to 3 and Comparative Examples 1 to 3 with the same weight, the cutting test was performed under the following conditions. TTV (Total Thickness Variation) and Warp (warpage) of the cut wafers were measured and shown in Table 3 below. The smaller the TTV and Warp values, the better the machining precision.

Cutting device: multiwire saw

Wire diameter: 0.1mm

Abrasive: Silicon Carbide GC # 1500

Silicon ingots: Monocrystalline silicon ingots with diameter 200 mm and length 250 mm

Cutting speed: 0.35mm / min

Wire speed: 600m / min

Item Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Cutting fluid
Properties Viscosity (cps) 40 24 45 70 32 52 Thermal Conductivity (W / mK) 0.206 0.207 0.202 0.207 0.204 0.206 Slurry
Properties Dispersion stability Good Good usually Good usually usually Redispersibility Good usually Good Good Bad Bad Detergency usually Good Good usually Good Good Cutting
Performance TTV (㎛) 13.8 13.1 12.9 14.9 14.6 14.2 Warp (μm) 9.1 9.2 9.0 10.0 9.7 9.6

As shown in Table 3, the water-soluble wafer cutting fluid of the present invention showed the same or superior performance overall compared to the comparative example, in particular, in terms of cutting performance is superior to Comparative Examples 1 to 3, in terms of redispersibility It confirmed that it is excellent compared with the comparative examples 2 and 3.

Claims (8)

Cutting oil represented by Chemical Formula 1 for wafer cutting.
[Formula 1]

R ₁ and R ₂ in Formula 1 are independently hydrogen or alkyl having 1 to 24 carbon atoms. The cutting oil according to claim 1, wherein R ₁ and R ₂ are both methyl. A water-soluble wafer cutting fluid composition comprising the cutting oil of claim 1. The water-soluble wafer cutting fluid composition of claim 3, wherein the cutting oil is 30 to 100% by weight based on the total weight of the water-soluble wafer cutting fluid composition. The water-soluble wafer cutting liquid composition according to claim 3, wherein the water-soluble wafer cutting liquid composition further comprises at least one selected from the group consisting of a water-soluble polymer, glycerol, alkylene glycol, an alkylene oxide adduct, and water. 6. The water-soluble wafer cutting liquid composition according to claim 5, wherein the water-soluble polymer is polyvinyl alcohol, polyvinylpyrrolidone or a mixture thereof having a molecular weight of 10,000 or more and 2,000,000 or less. The method of claim 5, wherein the alkylene oxide adduct is at least one member selected from the group consisting of fatty acids, fatty alcohols and fatty amines consisting of ethylene oxide (EO), propylene oxide (PO) and EO / PO block copolymers A water-soluble wafer cutting liquid composition, characterized in that the copolymer to which at least one alkylene oxide selected from the group is added. The cutting oil of Claim 1 or 2 using the cutting oil.