Abstract
ULSI devices, which consist of fine patterns of less than 0.1 μm, require a large silicon wafer having a site flatness better than 0.1 μm/30mm. We have developed an oscillation-speed-control-type sequential grinding and polishing machine, which can accurately polish a 12-inch wafer to less than 0.3 μm in flatness by measuring wafer profile on machine after highly accurate grinding. This paper describes the structure and motion accuracies of the machine, the basic polishing characteristics, and the polishing profiles at uniform oscillation speed. Pressure and stock removal increase in the periphery of a wafer when the tool overhangs from the wafer. They agreed with the theoretical results. Super-high flatness of less than 0.2 μm over the entire surface was achieved by adjusting the oscillation range at a uniform oscillation speed. This result is consistent with a simulation corrected on the basis of an experimental result that shows that stock removal saturates with the increase of relative velocity.
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