Pad Characterization and Experimental Analysis of Pad Wear Effect on Material Removal Uniformity in Chemical Mechanical Polishing

Abstract

In this study, we investigated the effects of pad wear on the nonuniformity of material removal in chemical mechanical polishing (CMP). In order to verify the mechanical aspect of the material removal mechanism, pad characterization was conducted. Pad conditioning plays a key role in obtaining stable material removal during polishing. However, the polishing pad is gradually worn as conditioning proceeds during CMP. The pad profile was measured using the contact profile measuring system to analyze pad wear after each polishing run. From experimental results, the within wafer nonuniformity (WIWNU) was unstable at the initial polishing run because of the first wafer effect. In addition, the WIWNU deteriorated as determined from a polishing pad worn by conditioning. Therefore, pad wear has a significant effect on the nonuniformity of material removal in CMP.