<title>Use of magnetorheological finishing (MRF) to relieve residual stress and subsurface damage on lapped semiconductor silicon wafers</title>

Abstract

Magnetorheological finishing (MRF) is a novel process demonstrated to be effective for fine figure control and polishing of a variety of optical glasses and crystals. This paper discusses the use of MRF to stress relieve the surfaces of single crystal silicon wafers, of the type used in the semiconductor industry to fabricate integrated circuits. One hundred-mm diameter silicon wafers with a <111&gt; crystallographic orientation were loose abrasive lapped with three different sizes of alumina abrasive to introduce compressive surface stress. The stress generated in the wafer surface was characterized by interferometrically monitoring the bending of the wafer due to the Twyman effect. The thickness of the subsurface damage (SSD) layer was characterized using a dimpling method with a fixture developed at COM. Subsequent polishing by MRF was found to be effective in removing the subsurface damage and associated residual stress generated in the wafer surface during loose abrasive lapping.