Analyzing on Nonuniformity of Material Removal in Silicon Wafer CMP Based on Abrasive Movement Trajectories

Abstract

Chemical mechanical polishing (CMP) has already become a mainstream technology in global planarization of wafer. The nonuniformity of material removal on wafer surface has a main influence on surface profile of silicon wafer in CMP process. However, the formation mechanism of nonuniformity in wafer CMP has not been fully understood and the influences of CMP process variables on nonuniformity are not fully clear. The nonuniformity of material removal on wafer surface has not been fully understood and the influences of CMP process variables on nonuniformity are not fully clear in CMP process. In this paper, firstly, the equation of particle movement trajectories on wafer surface was built by the movement relationship between the wafer and the polishing pad on a single head CMP machine with line oscillation of carrier. Then the distribution of abrasive trajectories on wafer surface was analyzed at different rotational speed. By the analysis, the relationship between the movement variables of the CMP machine and the With-In-Wafer Nonuniformity (WIWNU) of material removal on wafer surface had been derived. Last, the WIWNU tests were conducted on CP-4 machine. The analysis results are in accord with experimental results. The results will provide some theoretical guide for designing the CMP equipment, selecting the movement variables in CMP and further understanding the material removal mechanism in wafer CMP.