Three-dimension fluid dynamics simulations have been done to understand the slurry flow field created during chemical mechanical polishing (CMP) process. Empirical investigation of the flow between wafer and pad is not easy because the thickness of slurry flow in this region is as small as 10~50㎛. The slurry shearing stress on the wafer surface is usually considered to be closely related to the polishing rate. A simplified numerical model of slurry flow is constructed to obtain a velocity field in the region between wafer and pad and to determine shear stress on the wafer. In this case, the slurry is modeled as Newtonian fluid without particles and both the wafer and pad are modeled as rigid, flat and smooth walls. The simulation show that the uniformity of circumferentially averaged shear stress on the wafer surface increases with decreasing wafer rotation speed, increasing pad rotation speed, increasing distance between the centers of wafer and pad, and increasing gap between wafer and pad. The simulation results were used to represent the maximum shear stress and the uniformity of circumferentially averaged shear stress by numerical expression of process conditions.
