Analysis and Experiment of Removal Performance with Various Concentric Grooves on Pads in Chemical Mechanical Polishing

摘要

An analytical model for chemical-mechanical polishing (CMP) is developed. A Reynolds equation that considers both smoothing hydrodynamic pressure and the pattern effect at the polishing pads is used to solve the distribution of the hydrodynamic field. A wear model for solving the removed thickness of silicon oxide films is introduced. The negative hydrodynamic pressure field expands its region with increasing width and decreasing depth of grooves. The flow rate of the effective slurry thus increased, and the removal rate increased with increasing number of effective wear particles. The solid contact pressure is greatly higher than the hydrodynamic pressure. The experimental results confirmed the analytical results. The removal rate is dominated by the effective numbers of particles, which is affected by the hydrodynamic pressure variation in addition to the wear depth controlled by the solid contact pressure. The removed thickness of silicon oxide films increased with decreasing width and depth of grooves. The optimal concentric pad for silicon oxide polishing had a width of 1 mm, a depth of 1.2 mm, and a pitch of 4 mm, for a removal rate of 3250 A/min and a non-uniformity of under 5%.