Effects of carrier film physical properties on W CMP

The roughness, displacement under load, and thickness of 28 carrier films have been measured and their effects on polishing non-uniformity (NU) and removal rate (RR) on wafer surfaces during W CMP have been evaluated. All three properties significantly affect polishing results. In addition, the displacement of films under load depends on the initial thickness of the films, so that these two parameters are not independent. Prior stress-based CMP modeling and simulation efforts indicate that the uniformity of the stress transferred to the back of wafers by carrier films plays an important role in polishing NU. The displacement and carrier film roughness influence the ability of the carrier film to transfer stress to the wafer, and we interpret the observed NU based on potential stress transfer mechanisms. Our experimental and response surface analysis suggests that films that displace slightly during polishing do not show significant changes in NU or RR with increasing roughness, although increasing the film displacement may decrease NU and increase RR. On the other hand, films which displace greatly show little change in NU or RR with increasing displacement, while increasing roughness may reduce NU and increase RR.