Characterization of Dressing Behaviors and Optimization Technique in Chemical Mechanical Polishing

Abstract

Chemical mechanical polishing (CMP) is the planarization technology most often used for semiconductor processes. The polishing pad needs to be dressed by a dresser to maintain the stability and the throughput of the planarization process. The uniformity of the dressing process is crucial to the in-situ CMP equipment. In this study, the dressing process is characterized by calculating the scratch number of the diamonds over a given cross section of pad and this method was experimentally verified. Effects of different dressing conditions were studied through this model. Then, a uniformity index (UI) was defined to find the optimum sweep frequency for a certain dressing condition. The sweep frequency is the factor that influences the uniformity most. The sweep frequency with small UI can ensure that the pad to be regenerated uniformly anytime. The UI can be obtained under any given dressing conditions.