Development of Oscillation-Speed-Control-Type Sequential Grinding and Polishing Machine (2nd Report)

Abstract

An oscillation-speed-control-type sequential grinding and polishing machine has been developed to achieve a site flatness better than 90nm per 25-mm square except for 2mm adjacent to the edge of a 12-inch silicon wafer. The machine allows a wafer to be polished after grinding without removal from the machine. This paper describes the creation of a grinding profile, a solution to the problem of flatness degradation, and the optimum polishing conditions to obtain good flatness. The moving path of the grinding wheel is accurately transferred to the ground wafer surface except its center portion, where the profile becomes concave due to high cutting path density of the grinding wheel. Good flatness was achieved with a simple inclination adjustment method that involves hanging a weight from the grinding head or using a very low infeed rate to decrease the grinding force. The ground wafer was polished at the optimum oscillation speed and a super-high flatness of less than 0.1µm over the entire surface was achieved. In addition, this result was roughly consistent with the simulation result.