Flow simulation for chemical mechanical planarization

In this paper we present a three-dimensional fluid dynamics simulation for chemical mechanical planarization (CMP) processes. The slurry shearing stress on the wafer surface is usually considered to be closely related to the polishing rate. To our knowledge, this is the first work that addresses the wafer-scale removal rate and nonuniformity based on flow simulation. The simulation results for the trends of wafer-scale-averaged slurry shearing stress and nonuniformity agree with those of existing removal rates and nonuniformity data. The present simulation can be used to analyze or predict the characteristics of removal rate and nonuniformity in the CMP processes that use a hard pad. The present predictions show that the nonuniformity value decreases with increasing wafer diameter for a fixed set of pad and wafer rotation speeds. This may explain why the recent CMP work for 12-inch wafer operated at a high pad rotation speed.