JP5408639B2 - Working fluid composition for hydrous slicing - Google Patents

Description

  The present invention relates to a hydrous slicing working fluid composition used when a silicon wafer is produced by cutting a silicon ingot or the like with a wire saw or a band saw. In particular, the present invention relates to a composition useful for cutting an ingot with a multi-wire saw capable of cutting a plurality of ingots at once.

  In the process of producing a silicon wafer used for a solar cell or the like, a wire saw or band saw cutting device is used for cutting a silicon single crystal or a polycrystalline ingot. In a wire saw cutting device, a silicon ingot is pressed against a thin wire running at high speed, and a slurry obtained by mixing abrasive grains such as SiC with a processing liquid is supplied, and cutting is performed with abrasive grains placed on the wire.

  Although this slurry can be used in a circulating manner, as the number of uses increases, a large amount of silicon cutting powder generated when cutting an ingot is accumulated in the slurry. And this silicon cutting powder raises the viscosity of a slurry, and causes deterioration of the cutting performance of a wire saw and the processing precision of a wafer. For this reason, a part of the slurry is usually discarded and replaced with a new slurry every time the silicon ingot is cut. The disposal cost of this waste slurry and the purchase cost of a new slurry increase the running cost of wire saw cutting.

  The cut silicon wafer is subjected to a cleaning process to remove silicon chips, wire iron powder, and attached slurry, and is supplied to the next process.

  There are two types of processing fluids, water-based and oil-based. Currently, oil-based water-insoluble types that are advantageous in terms of slicing performance and running cost are generally used.

  However, the water-insoluble processing fluid is mainly composed of mineral oil and is a flammable dangerous substance. For this reason, there are restrictions on the amount of storage under the Fire Service Act.

Because of such problems, a machining fluid containing mineral oil and water has been proposed. For example, Patent Document 1 discloses a composition of a dispersion medium containing 1 to 20% by weight of water and containing inorganic or organic bentonite.
Japanese Patent Application Laid-Open No. 11-100500

However, in the case of a working fluid containing water using conventional bentonite as a dispersion medium, there are the following problems.
(A) Since the viscosity of the slurry is high from the beginning and the rise after processing is large, the cleaning performance of the wafer after slicing processing is poor.
(B) Further, the slicing workability is poor, and therefore, the silicon wafer may be cracked or chipped, resulting in poor yield.
(C) When the slurry is circulated and used, it becomes unusable due to an increase in viscosity, so the amount of waste slurry is large, resulting in environmental degradation and high costs.
(D) In addition, when left for a long period of time, the working fluid sometimes separated.

  The slurry viscosity has various factors and changes depending on this factor. Generally, the above problem is likely to occur when the viscosity exceeds 5000 mPa · s (6 rpm) at 30 ° C., and 1000 mPa at 30 ° C. at the actual machine level. -It is preferable to suppress within s (6 rpm).

  The present invention solves the above-mentioned problems, and the object of the present invention is to reduce the slurry slurry amount by suppressing the increase in viscosity even after processing, and the flash point cannot be measured. An object of the present invention is to provide a hydrous slicing processing liquid composition.

As a result of extensive research, the present inventors have found that the hydrous slicing processing liquid composition for hard and brittle materials of the present invention is (1) a base oil composed of at least one of mineral oil, fats and oils, and (2) alkenyl succinate. Acid polyalkylene polyimide and bisalkenyl succinic acid polyalkylene polyimide at least one kind of polymer agent and (3) the total amount of the composition (a) nonionic surfactant 5 to 20% by weight, and (b A) anionic surfactant 5 to 20% by weight, and (4) a composition containing 3 to 20% by weight of water based on the total amount of the composition is processed for hydrous slicing for hard and brittle materials It has been found that the liquid composition is extremely useful as a processing liquid for slicing.

  Since the processing fluid for hydrous slicing of the present invention contains a predetermined amount of moisture, the flash point cannot be measured. Under the Fire Service Act, water with a flash point of 100 ° C or higher is measured by a Cleveland open-type flash point measuring device. In this case, the aqueous solution has no flash point. For this reason, the hydrous slicing processing liquid of the present invention is regarded as equivalent to the above aqueous solution and is a non-hazardous material.

In addition, since the specific polymer dispersant is contained, the viscosity is low immediately after the abrasive grains are put into the processing liquid to form a slurry, and the rise can be suppressed even after slicing processing such as silicon ingot. Therefore, even if it is used for a long period of time, the amount of slurry discarded is small and the basic unit can be reduced.
Furthermore, since the water retention effect due to the action of the activator is high, evaporation of moisture can be suppressed.
Since the viscosity increase of the slurry is small, silicon slicing can be efficiently performed by using the processing liquid of the present invention as a slurry in a multi-wire saw cutting apparatus.

  In addition, the slicing processability of the silicon ingot is improved and the cleaning property is excellent. Furthermore, even if left for a long period of time, the processing liquid does not separate and stability is maintained.

(1) Base oil consists of at least 1 type of mineral oil, fats and oils, and synthetic ester.

The mineral oil is preferably a refined mineral oil and may be paraffinic or naphthenic. Specific examples include spindle oil, machine oil, refrigerator oil, turbine oil, and the like. In the present invention, it is particularly preferable to use a combination of refined mineral oils having a viscosity of 2-30 mm ² / s (40 ° C.).

As long as the fat and synthetic ester are synthetic esters of fatty acids obtained from animal and vegetable oils and fats and animals and vegetable oils and fats, conventionally known ones can be widely used. For example, palm oil, pig oil, castor oil, rapeseed oil, soybean oil, cottonseed oil, Babasu oil, Palm oil, olive oil, sunflower oil, low melting point palm oil, fish oil such as sardine oil, pentaerythritol beef oil fatty acid ester, palm oil fatty acid ester of 2-ethylhexyl alcohol, beef oil fatty acid methyl ester, trimethylolpropane oleate, Examples include synthetic esters such as sorbitan monooleate.
(2) As the polymer agent , an alkenyl succinic acid polyalkylene polyimide having an average molecular weight of 1000 to 50000 (NC-147 manufactured by Infinium Japan), a bisalkenyl succinic acid polyalkylene polyimide (NC-105 manufactured by Infinium Japan), or the like is used. be able to. Among them, alkenyl succinic acid polyalkylene polyimide is particularly preferable.

A preferred use amount of the polymer agent is 0.05 to 10.0% by weight.

The polymer agent has an effect of suppressing an increase in slurry viscosity due to an agglomeration effect due to the adsorption of the polymer to the iron powder of abrasive grains, silicon chips or wire chips. Furthermore, there is an effect that the abrasive grains are uniformly dispersed in the working fluid.

(3) Nonionic and anionic surfactants Examples of anionic surfactants include sulfonates such as sodium alkylbenzene sulfonates having an alkyl group having 8 to 18 carbon atoms, alkyl sulfate sodium salts, sodium laurate, etc. Carboxylate, sodium diethylhexylsulfosuccinate and the like.

  A preferred amount of the anionic surfactant is 5 to 20% by weight.

As the nonionic surfactant, there is a polyoxyalkylene alkyl ether represented by R ₁ —O— (EO) _n R ₂ , and several types are combined for adjusting the HLB. Here, R ₁ represents an alkyl having 4 to 18 carbon atoms, and R ₂ represents an alkyl group having 1 to 18 carbon atoms or hydrogen. N is an integer of 2-20. Other examples include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and polyoxyethylene alkyl naphthyl ether.

  The preferred amount of nonionic surfactant used is 5 to 20% by weight.

  By combining the nonionic and anionic surfactants, water can be dissolved in the base oil transparently and water retention is provided.

If alcohol is further added, the water holding power can be further increased. That is, alcohol has an action of suppressing the evaporation of moisture, and the amount used is 5% by weight or less. The alcohol may have a flash point of 100 ° C. or higher, and preferably 120 ° C. or higher. For example, higher alcohols such as oleyl alcohol and isostearyl alcohol can be used.
(4) Moisture 3-20% by weight
If the water content is less than 3% by weight, there is a risk of ignition. On the other hand, if it exceeds 20% by weight, it becomes difficult to transparently solubilize water in the base oil, and the viscosity of the working fluid increases. For this reason, since the rise of the viscosity of a slurry becomes remarkable, the use with a wire saw or a band saw cutting device becomes difficult.

  The water may be any of purified water, tap water, ion exchange water, pure water and the like.

In addition, a known rust preventive additive or extreme pressure additive may be appropriately added to the composition of the present invention.
The preferable usage-amount of the antirust additive in this case is 0.01 to 1% weight.

  Preferred examples of the rust preventive additive include alkylbenzene Na sulfonate, alkylbenzene Ca sulfonate, dinonylnaphthalene Na sulfonate, dinonylnaphthalene Ca sulfonate, alkenyl succinate, polyhydric alcohol ester and the like.

Further, as extreme pressure additives, sulfur compounds (sulfurized fatty acids such as sulfurized oleic acid, sulfurized fatty acid esters, sulfurized palm oil, sulfurized terpene, dibenzyl disulfide, amine salts of alkylthiopropionic acids having 8 to 24 carbon atoms or alkalis) Metal salt, amine salt or alkali metal salt of alkylthioglycolic acid having 8 to 24 carbon atoms, phosphorus compound (tricresyl phosphate, tributyl phosphate, tricresyl phosphite, n-butyl di-n-octyl phosphinate, di -N-butyl dihexyl phosphonate, di-n-butyl phenyl phosphonate, dibutyl phosphoramidate, amine dibutyl phosphate, etc.).
A preferable amount of the extreme pressure additive is 0.01 to 1% by weight.
The kinematic viscosity of the machining fluid prepared by adjusting the above components is suitably 10 mm ² / s to 30 mm ² / s (40 ° C.). .
Examples of the slicing workpiece using the composition of the present invention include hard and brittle materials such as glass, ceramic and quartz in addition to silicon.

  Using the components shown below in the ratios shown in Table 1, compositions of Experimental Examples 1 to 11 (present invention) and Comparative Examples 1 and 2 were prepared.

Water: tap water
Polymer agent : alkenyl succinic acid polyalkylene polyimide (manufactured by Infinium Japan, NC · 147)
Base oil: Mineral oil A Kinematic viscosity 22mm ² / s (40 ° C)
Mineral oil B Kinematic viscosity 2.1mm ² / s (40 ° C)
Activator: Nonionic A polyoxyethylene 2-ethylhexyl ether HLB 11.5
Nonionic B polyoxyethylene 2-ethylhexyl ether HLB 14.6
Anionic sodium sulfonate (Sulhol 465 manufactured by Matsumura Oil Research Institute)
Molecular weight 465
Alcohol oleyl alcohol rust preventive agent: calcium alkylbenzene sulfonate extreme pressure agent: methyl sulfide oleate However, the numerical values in the table indicate the weight% when the whole oil agent is taken as 100%.
Various properties of each composition thus obtained were measured.

In the present invention, the lower the moisture content, the lower the viscosity. When the water content is 20%, the water content is preferably 3 to 15% because the viscosity is high from the beginning.
From Table 1, as compared with Comparative Example 1, all of the experimental examples have lower viscosity than the initial slurry, and the increase in viscosity is suppressed even after the addition of carbon graphite.

<Increase in viscosity with actual machine>
The process of cutting a silicon ingot with a length of 155mm x 155mm and a length of 30-40cm with a wire saw cutting device (manufactured by NIPEI TOYAMA) is performed for 8-10 hours. The viscosity of the slurry before processing and the viscosity after processing are measured with a B-type rotary viscometer. Measured and compared. The results are shown in [Table 3].
Viscosity unit: mPa · s, temperature 30 ° C

In the actual machine, the same result as the viscosity increase test by adding carbon graphite was obtained.
<Flash point measurement test>
About the said Experimental Examples 1-6 and the comparative example 2, the result measured with the Cleveland open-type flash point measuring apparatus is shown in [Table 4].

The flash point was measured for Comparative Example 2 with a moisture content of 2%.

<Detergency test>
For Experimental Example 1, Experimental Example 3, Experimental Example 7-9, and Comparative Example 1, 100 g of abrasive grains (GC # 1000) and 10 g of carbon graphite were added to 100 ml of each oil agent and stirred to reproduce the liquid slurry used in actual equipment. Then, it is uniformly applied to the surface of the silicon wafer, and then immersed in water to measure the degreasing rate.
Conditions: liquid temperature 20 ° C., immersion time 2 minutes, application area 125 × 110 mm, application amount 1.5 g
Degreasing rate Experimental example 1: 94.3%
Experimental example 3: 98.2%
Experimental Example 7: 54.1%
Experimental Example 8: 46.3%
Experimental Example 9: 36.1%
Experimental Example 10: 90.7%
Experimental Example 11: 95.7%
Comparative Example 1: 67.2%

Claims (1)

A working fluid composition for slicing hard and brittle materials using a slurry,
(1) a base oil comprising at least one of mineral oil, fat and oil, and synthetic ester,
(2) at least one polymer agent selected from alkenyl succinic acid polyalkylene polyimide and bisalkenyl succinic acid polyalkylene polyimide,
(3) with respect to the total composition weight, (a) 5-20 wt% nonionic surfactant, and (b) anionic surfactants 5-20% by weight,及 Beauty <br/> (4 ) 3-20% by weight of water based on the total amount of the composition
A processing fluid composition for hydrous slicing for hard and brittle materials, comprising: