A new simulation method for CMP slurry flow is proposed that uses lubrication equations modified to account for a grooved pad. The grooves are accounted for by performing detailed Navier-Stokes simulations for small pad elements containing grooves. The simulation results give the flow through a pad element as a function of pressure gradient and pad/wafer relative velocity. The method is applied to Nikon-type CMP systems in which a small rotating pad is swept back and forth over a rotating wafer. The slurry flow simulation allows calculation of the hydrostatic lift force caused by slurry fed directly into the pad/wafer gap. A new polishing rate model is proposed that accounts for the freshness of the slurry passing over a given region of the pad.
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