Operational aspects of chemical mechanical polishing - Polish pad profile optimization

Despite recent advances in chemical mechanical polishing (CMP), some manufacturing concerns associated with successful implementation of CMP remain to be overcome, e.g.. degradation in the removal rate, nonuniformity of material removal, etc. In this work, the characteristics of the relative velocity for pad conditioning are explored and a generalized Preston equation, taking the pad topology into account. is formulated. From experimental data, important characteristics for the pad wear Juring conditioning are identified. That is the actual conditioning time, the characteristic time, plays a determinant role in the pad wear. provided with the wear rate (WR) equation, optimization on operating variables reveals that, as a result of the sweeping, it is difficult, if not impossible, to maintain a uniform pad profile. However, the setting of operating variables and design modification can be used to alleviate possible nonuniformity on the pad profile. That implies we have to make the ratio of disk-radius-to-pad-radius as small as possible (to eliminate the edge effect). Next the importance of setting of the number of zones and corresponding relative time (retention time at each zone) is emphasized. A procedure for setting these operating parameters is also given. (C) 2000 The Electrochemical Society. S0013-4651(00)02-029-9. All rights reserved.