Title: High temperature MCP process suitable for extremely hard high functional SiC wafers

Authors: Nobuo Yasunaga, Yukiharu Yamamoto

Addresses: Department of Precision Mechanics, School of Engineering, Tokai University, 1117 Kitakaname, Hiratsuka-shi, Kanagawa, 259–1292, Japan. ' Tube Systems, Ltd., 2–2909–6 Higashi-Sayamagaoka, Tokorozawa-shi, Saitama 359–1106, Japan

Abstract: The need for SiC single crystals as the next generation, high-power electronic and optoelectronic devices is increasing. Mechanochemical Polishing (MCP) is suitable for the final, damage-free surface finishing process for such extremely hard and high functional materials. Cr₂O₃ is already known as one of the useful MCP abrasives for finishing SiC crystals. However, there is some hesitation on the actual use of Cr₂O₃ abrasive in the production field because of the formation of Cr⁶⁺ as a highly toxic substance. In this paper, the possibility of α-Fe₂O₃ powder as an environmentally safe MCP abrasive is investigated. Polycrystalline SiC wafers are MCPed on a newly developed, high temperature polishing machine. Results obtained are the following. First, α-Fe₂O₃ abrasive produces the highest polishing efficiency at a polishing temperature of about 230°C, which is more efficient than that obtained by Cr₂O₃ abrasive polishing at any experimental temperature between RT (room temperature) and 330°C. Second, the polishing efficiency of the Cr₂O₃ abrasive decreases at temperatures higher than 230°C. This is because of the excessive adhesion of the abrasive grains to the wafer surface. Third, no mechanical scratches are detected, suggesting that there is no subsurface damage. Fourth, unevenness per each crystal grain resulting in large surface roughness Ra over several tens nm is observed, which is peculiar to MCP of polycrystalline anisotropic materials.

Keywords: polycrystalline SiC wafers; single crystal SiC wafers; mechanochemical polishing; MCP; α-Fe₂O₃ abrasive; high temperature polishing; environmentally safe abrasives; surface roughness.

DOI: 10.1504/IJMTM.2006.009994

International Journal of Manufacturing Technology and Management, 2006 Vol.9 No.1/2, pp.172 - 182

Published online: 06 Jun 2006 *

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