Abstract
Mass production of ULSI devices requires a 12-inch silicon wafer to have a site flatness better than 0.1 μm/30mm. In addition, film thickness, which varies across the wafer, must be polished to within ±5% uniformity. In order to meet these requirements, the machining process has been replaced from batch to single-wafer and from one side to both sides. This paper shows that all ordinary oscillation methods in abrasive machining can be converted to a linear oscillation method where a tool oscillates on the center line of a workpiece. For linear oscillation polishing with a viscoelastic and wear polisher, equations for surface generation were obtained by using the clearance between a workpiece and a tool. A polishing simulation program was newly developed on the basis of these equations. The calculation procedures for stock removal and optimum oscillation speed, and polishing conditions for high flatness are shown. It is also clarified that it is possible to polish within ±1% uniformity with the optimum oscillation speed control.
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