In manufacturing semiconductor products, a silicon ingot (that is brittle in nature) needs to be cut. In such a case, a wire saw processing is generally employed in terms of cutting accuracy and productivity. Herein, a cutting method of the silicon ingot includes: a loose abrasive grain method of cutting the silicon ingot with a working fluid (machining fluid) in which grains are dispersed; and a fixed abrasive grain method of cutting the silicon ingot with a wire having grains fixed on its surface in advance.
The working fluid used for the loose grain method includes a water-soluble working fluid containing, for instance, a friction coefficient reducer, an auxiliary corrosion-resistance agent and the like. The friction-coefficient reducer contained in the working fluid is an unsaturated fatty acid. The auxiliary corrosion-resistance agent is benzotriazole (see Patent Literature 1). According to the loose grain method, a large margin is required when a thick wire is used, so that a large amount of cut particles are generated and the yield rate after cutting a silicon ingot is deteriorated. Further, since the wire is worn after being used, there naturally is a limit for reducing a diameter of the wire. Accordingly, the productivity of the loose grain method is not so good for use in manufacturing silicon wafers for solar cells and the like, of which production is expected to greatly increase in the future.
On the other hand, the working fluid used for the fixed grain method includes a water-soluble working fluid containing, for instance, glycols (see Patent Literatures 2 and 3). According to the fixed grain method, since abrasive grains are rigidly attached to a wire in advance, the diameter of the wire can be reduced and less amount of cut particles are produced, so that productivity can be enhanced.