JP5764067B2 - Water-soluble cutting liquid for fixed abrasive wire saw, ingot cutting method using the same, recycling method thereof and wafer obtained by cutting - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a water-soluble cutting solution for a fixed abrasive wire saw used for cutting a silicon ingot using a fixed abrasive wire saw, a method for cutting an ingot using the same, a recycling method thereof, and a wafer obtained by cutting. .

  Conventionally, for cutting silicon ingots, cutting with a band saw or wire saw using loose abrasive grains has been used. When cutting with a band saw or wire saw using loose abrasive grains, the slurry adheres to the cut wafer and the cleaning load in the subsequent process is high.In addition, loose abrasive grains, sludge, and cutting liquid are removed from the cutting liquid used for silicon ingot. There are problems that separation is difficult and recyclability is poor.

  In response to these problems, fixed wire saws have been developed in which abrasive grains are fixed to the wire using electrodeposition or resin bond, simplifying the cleaning process and separating the cutting fluid and sludge from the silicon ingot cutting fluid. This has the advantage of improving recyclability. Water and water-soluble cutting liquids such as Patent Documents 1 and 2 have been proposed as cutting liquids used when cutting silicon using this fixed wire saw.

JP 2003-82334 A JP 2009-57423 A

  However, when silicon is cut using these water-soluble cutting solutions, there is a disadvantage that silicon gas reacts with water to generate hydrogen gas, and hydrogen gas due to the reaction between silicon and water generates bubbles and agglomerates silicon. Occurs, the viscosity of the cutting fluid increases, and the target cutting performance cannot be obtained. Further, there is a problem that the recyclability by the subsequent centrifugal separator is poor due to the foaming property of the hydrogen gas and the cutting liquid itself due to the reaction between silicon and water.

  Accordingly, the present invention provides a water-soluble cutting solution for a fixed abrasive wire saw that has high cutting performance and can suppress generation of hydrogen gas due to reaction between silicon and water, a method for cutting an ingot using the same, and a method for recycling the same And a wafer obtained by cutting.

Means to solve the problem

  In order to solve the above-mentioned problems, the present inventors have conducted extensive research, and as a result, (a) a polyether having a predetermined general formula, (b) a glycol and a low molecular weight glycol ether having a molecular weight of 100 to 300, By using a water-soluble cutting liquid containing at least one kind and (c) water in a predetermined ratio, cutting performance is high even when used for a fixed abrasive wire saw, and silicon and water. It has been found that the generation of hydrogen gas due to the reaction can be suppressed. That is, the present invention includes (a) a polyether represented by the formula (1), (b) at least one kind of glycol and a low molecular weight glycol ether having a molecular weight of 100 to 300, and (c) water, A water-soluble cutting solution for a fixed abrasive wire saw, wherein the ratio of a) to (b) is from 1:99 to 50:50, and the content of (c) is from 5 to 50% by weight.

  In addition, the present invention provides an ingot cutting method characterized in that a silicon ingot is cut with a fixed abrasive wire saw using the water-soluble cutting liquid for the fixed abrasive wire saw, and the ingot is cut by the ingot cutting method. After performing the above, the water-soluble cutting liquid for fixed abrasive wire saws is separated from the silicon using a centrifuge, and the water-soluble cutting liquid for fixed abrasive wire saws is cut by the above ingot cutting method. Wafer.

  As described above, according to the present invention, the cutting performance is high, and the water-soluble cutting solution for a fixed abrasive wire saw capable of suppressing the generation of hydrogen gas due to the reaction between silicon and water, and the method for cutting an ingot using the same The wafer obtained by the recycling method and cutting can be provided.

In formula (1) of the polyether (a) used in the water-soluble cutting solution for fixed abrasive wire saw according to the present invention, R ₁ is a hydrogen atom or an alkyl or alkenyl group having 1 to 8 carbon atoms, EO is An oxyethylene group and AO are oxyalkylene groups having 3 or 4 carbon atoms, and m and n each represent an added mole number of 1 to 20. The polyether represented by the formula (1) may be polymerized by random polymerization or polymerized by block polymerization. The weight average molecular weight of the polyether represented by the formula (1) is preferably 200 to 2,000. The reason why the polyether is limited to the polyalkylene glycol butyl ether represented by the formula (1) is that an ether such as methyl or ethyl cannot obtain sufficient cutting performance in a fixed abrasive wire saw. Examples of such polyalkylene glycol butyl ether include Yucanol 50MB-5 (manufactured by NOF Corporation).

  The glycol of (b) preferably has two OH groups and has a molecular weight or weight average molecular weight of 60 to 3,500. For example, monoethylene glycol, diethylene glycol, triethylene glycol, monopropylene glycol, dipropylene Examples include propylene glycol, tripropylene glycol, hexylene glycol, and polyalkylene glycols such as polyethylene glycol and polypropylene glycol. Further, the low molecular weight glycol ether (b) may have a molecular weight of 100 to 300, and examples thereof include diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, and diethylene glycol monohexyl ether.

  This (b) includes (b1) a polyalkylene glycol represented by the formula (2), and (b2) a glycol other than (b1) and at least one kind of a low molecular weight glycol ether having a molecular weight of 100 to 300, The content of b1) is preferably 0.01 to 5.0% by weight with respect to the entire water-soluble cutting solution. In formula (2), x, y, and z each represent an added mole number of 1 to 20. The weight average molecular weight of the polyether represented by the formula (2) is preferably 1,000 to 3,000. Moreover, (b1) is 0.01 to 5.0% by weight. If it is less than 0.01% by weight, foaming is not improved and recyclability is deteriorated. Because it gets worse. The content of (b1) is more preferably 0.1 to 2.0% by weight.

  The water-soluble cutting liquid for fixed abrasive wire saws according to the present invention can contain (d) a dispersant as required. The dispersant used is a polycarboxylic acid obtained by graft polymerization of a polyoxyalkylene monoalkyl ether to an allyl alcohol / maleic anhydride copolymer or a salt thereof, an allyl alcohol / maleic anhydride / styrene copolymer. Examples include graft-polymerized polycarboxylic acids of alkylene monoalkyl ethers and salts thereof, naphthalenesulfonic acid condensates and salts thereof, and those generally sold as dispersants can be used. The content of the dispersant is preferably 0.1 to 5.0% by weight. In 0.1 to 5.0 weight%, the dispersibility of the chip | tip at the time of a cutting | disconnection is favorable, and it can suppress the fall of the cutting performance and recyclability by foaming. The content of (d) a dispersant is more preferably 0.1 to 1% by weight.

  In the water-soluble cutting solution for fixed abrasive wire saw according to the present invention, when the ratio of (a) and (b) is 1:99 to 50:50, the effect of suppressing the generation of hydrogen gas due to the reaction between silicon and water Is high, generation of bubbles due to generation of hydrogen gas and aggregation of silicon are less likely to occur, and viscosity change can be reduced. Moreover, there is little influence on the resin parts used in the machine tool, and the cutting performance can be improved. A more preferable ratio of (a) to (b) is 5:95 to 30:70.

  In the water-soluble cutting solution for a fixed abrasive wire saw according to the present invention, when (c) water is 5 to 50% by weight, there is no problem of flammability at the time of cutting, and the ability to cool the heat generated at the time of cutting is high. Since the amount of moisture evaporation due to the is small, the cutting performance is improved. In addition, drying of the wafer surface during cutting can be suppressed, and the load of the subsequent cleaning process can be suppressed. A more preferable water content is 5 to 40% by weight.

  The water-soluble cutting liquid for fixed abrasive wire saws according to the present invention may contain a rust preventive, preservative, fragrance, dye or the like, if necessary.

  The water-soluble cutting liquid for a fixed abrasive wire saw according to the present invention uses a fixed abrasive wire saw as a cutting tool and a multi-wire saw as a cutting machine in the cutting of a silicon wafer that is a material for semiconductor elements and solar cells. be able to.

  After cutting the water-soluble cutting liquid for fixed abrasive wire saw according to the present invention, silicon and the water-soluble cutting liquid can be separated and recycled using a centrifuge.

  The wafer cut by the ingot cutting method according to the present invention can obtain a wafer having better surface roughness and undulation than a wafer cut using a conventional water-soluble cutting solution for fixed abrasive wire saws. It can be used as a semiconductor device or solar wafer.

  Next, although the Example of the water-soluble cutting liquid for fixed abrasive wire saws concerning this invention is described, this invention is not limited by this. First, according to the compounding amount of Table 1 thru | or Table 4, these are mixed by a conventional method, The water-soluble cutting liquid for fixed abrasive wire saws which concern on Example 1 thru | or Example 12, and Comparative Example 1 thru | or Comparative Example 10 The water-soluble cutting liquid for the fixed abrasive wire saw which concerns was obtained.

(Cutting test)
Next, using the water-soluble cutting liquid for fixed abrasive wire saw according to Example 1 to Example 12 and the water-soluble cutting liquid for fixed abrasive wire saw according to Comparative Example 1 to Comparative Example 10, a cutting test is performed, The cutting distance was measured. The cutting test was performed using a wire saw testing machine: 3032-4 (manufactured by WELL), wire: core wire 0.12 mm, diamond diameter 12-25 μm (manufactured by Asahi Diamond Co., Ltd.), wire speed: 200 m / min, processing load: 30 g, processing time: It was performed under the conditions of 30 minutes, workpiece: 20 mm × 30 mm × 30 mm, test temperature: 25 ° C. The results are shown in Tables 5 and 6. From Table 5 and Table 6, it turns out that the water-soluble cutting liquid for fixed abrasive wire saws according to the present example has good cutting performance.

(Viscosity and gas generation test)
Next, assuming an active silicon scrap mixed when cutting an ingot of single crystal silicon from a fixed abrasive wire, a water-soluble cutting liquid for a fixed abrasive wire saw according to Examples 1 to 12, In addition, 20% by weight of silicon powder (particle size of about 5 μm) is added to the water-soluble cutting liquid for fixed abrasive wire saws according to Comparative Examples 1 to 3 and Comparative Examples 5 to 9, and coarsely pulverized with a planetary ball mill. The viscosity at 25 ° C. was measured with a BL type rotational viscometer (rotor No. 1 60 rpm) (viscosity 1). Then, it was put in a polyethylene bag (thickness: 0.04 mm) that could be sealed, degassed, and after confirming the amount of silicon reactive gas after storing at 50 ° C. for 24 hours, the viscosity at 25 ° C. was measured (viscosity 2). . Coarse pulverization was performed under conditions of cup: 500 ml zirconia pot, media: φ2 mm zirconia beads, sample amount: 200 ml, media amount: 200 ml, rotation speed: 250 rpm, time: 30 minutes. The amount of reaction gas was confirmed under the conditions of polyethylene bag: Pacoal chuck bag (manufactured by Nippon Hitech Co., Ltd.), thickness: 0.04 mm, and confirmation method: visual observation (the degree of swelling of the polyethylene bag). The results are shown in Table 7 and Table 8. From Tables 7 and 8, it can be seen that the water-soluble cutting liquid for fixed abrasive wire saws according to the present invention has an infinitely small amount of reaction gas between silicon and water, and the change in viscosity is small.

(Cleaning test)
Next, assuming an active silicon scrap mixed when cutting an ingot of single crystal silicon from a fixed abrasive wire, the water-soluble cutting liquid according to Examples 1 to 12 and Comparative Example 3 and 20% by weight of silicon powder (particle size of about 5 μm) was added to the water-soluble cutting liquid according to Comparative Example 6, and the liquid coarsely pulverized by the planetary ball mill under the same conditions as the coarse pulverization described above (viscosity and gas generation test). The wafer was attached to the entire surface of a 3-inch silicon wafer, and was allowed to stand at room temperature for 24 hours while keeping the wafer vertical. Then, it wash | cleaned with running water and the washability was confirmed. The results are shown in Table 9. From Table 9, it can be seen that the water-soluble cutting liquid for fixed abrasive wire saws according to the present invention is well cleaned in the subsequent process.

(Bubbling test)
Next, assuming the foaming during cutting and the foaming during recycling, the water-soluble cutting liquid for fixed abrasive wire saw according to Examples 1 to 12 and the fixing according to Comparative Example 1, Comparative Example 2, and Comparative Example 6 A water-soluble cutting solution for abrasive wire saws was put in a stoppered type 100 and a graduated cylinder 50. After stoppering, it was shaken vigorously. The amount of foaming thereafter and the defoaming time until the liquid surface was visible were confirmed. The results are shown in Table 10. From Table 10, it can be seen that the water-soluble cutting solution according to the present invention is good with less foaming.

Claims (5)

(A) polyether represented by formula (1), (b) (b1) polyalkylene glycol represented by formula (2), glycol other than (b2) (b1), and low molecular weight of 100 to 300 Comprising at least one molecular weight glycol ether and (c) water,
The ratio of (a) and (b) is 1:99 to 50:50, the content of (c) is 5 to 50% by weight, and the content of (b1) is based on the entire water-soluble cutting solution 0.01 to 5.0 wt% der bonded abrasive wire saw for aqueous cutting liquid, wherein Rukoto.

(D) a dispersant 0.1 to 5.0 wt% more fixed abrasive wire saw for aqueous cutting liquid of claim 1 Symbol mounting, characterized in that it contains. A method for cutting an ingot comprising cutting a silicon ingot with a fixed abrasive wire saw using the water-soluble cutting solution for fixed abrasive wire saw according to claim 1 or 2 . A water-soluble cutting for a fixed-abrasive wire saw, wherein the water-soluble cutting solution for a fixed-abrasive wire saw is separated from silicon using a centrifuge after the ingot is cut by the ingot cutting method according to claim 3. Liquid recycling method. A wafer cut by the ingot cutting method according to claim 3 .