Effects of carrier film physical properties on WCMP

The roughness, displacement under load, and thickness of 28 carrier films h ave been measured and their effects on polishing nonuniformity (NU) and rem oval rate (RR) on wafer surfaces during W CMP have been evaluated. All thre e properties significantly affect polishing results. In addition, the displ acement of films under load depends on the initial thickness of the films, so that these two parameters are not independent. Prior stress-based CMP mo deling and simulation efforts indicate that the uniformity of the stress tr ansferred to the back of wafers by carrier films plays an important role in polishing NU. The displacement and carrier film roughness influence the ab ility of the carrier film to transfer stress to the wafer, and we interpret the observed NU based on potential stress transfer mechanisms. Our experim ental and response surface analysis suggests that films that displace sligh tly during polishing do not show significant changes in NU or RR with incre asing roughness, although increasing the him displacement may decrease NU a nd increase RR. On the other hand, films which displace greatly show little change in NU or RR with increasing displacement, while increasing roughnes s may reduce NU and increase RR. (C) 1999 Elsevier Science S.A. All rights reserved.