A Comprehensive Material Removal Model for CMP

摘要

A scratch intersection based material removal mechanism for CMP is proposed. The observed deformation pattern by SEM and the trends of the measured force profiles reveal that, for an isolated scratch, the material is mainly plowed with no net material removal. However, it is observed that material is detached close to the intersection zone of two scratches. It is speculated that the deformation mechanism changes from ploughing to shearing mode as the indenter approaches an existing scratch under small indentation depth for ductile metals. The proposed mechanistic MRR model yields Preston constant similar to those observed experimentally for CMP processes. This model also reveals that the nature of slurry - pad interaction mechanism, and its associated force partitioning mechanism, is important for determining the variation of MRR with particle size and concentration. It is observed that under relatively soft pads, small particles and low particle concentration, the pad undergoes local deformation yielding an increasing MRR with increasing particle size and concentration. At the other extreme, the pad segment between pores deforms globally, resembling a beam, and a decreasing trend in MRR is observed with increasing particle size and concentration. The predicted MRR values and trends are compared to existing experimental observations.