A Model for Design Optimization of Electrochemical Mechanical Polishing Polish Pad

The polishing pad plays a vital role in achieving the desired removal rate and level of surface planarity during the electrochemical mechanical planarization (ECMP) process. Material removal rate (MRR) and within wafer non-uniformity (WIWNU) are two important factors in determining the polishing performance. In this work, a theoretical model for predicting the radial distribution of tribasic ammonium citrate (TAC) concentration on the wafer is proposed. The experimentally measured MRR was found as a function of the TAC concentration in the slurry. Hence, the model could not only predict the removal rate at a given point on the wafer surface, but also reflect the WIWNU. Model predictions are in good agreement with the experimental data. The proposed model are used to perform an analysis of the effect of pad designs on the MRR and WIWNU of the wafer.