Smoothly polished single-crystal silicon plates were cut by wire electrical discharge machining (WEDM) in water and in oil in order to investigate the effect of WEDM on the polished surfaces. For cutting in water, polished surfaces near cut sections have chips and cracks, and are extremely rough; the rough regions are upheaved. Examinations suggest that the upheaved region is silicon dioxide and results from oxidization of the surfaces by WEDM. Moreover, the polished surfaces far from the cut section are somewhat rough. For cutting in oil, polished surfaces near a cut section are smooth and almost flat although they have chips and cracks. These findings indicate the WEDM in oil is better than that in water for cutting polished single-crystal silicon to obtain high-quality surfaces.
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