Polishing time calculation method to reduce oxide-film-CMP send-ahead works

In order to obtain higher throughput maintaining high precision in the CMP process, it is important to reduce send-ahead work and rework related to film thickness over the within-wafer distribution. This paper presents a new polishing time calculation method that ensures film thicknesses at all measurement positions satisfy the control limit, and gives a judgment on whether send-ahead work is necessary, with the margin of variation of film thicknesses from the control limits after CMP based on the within-wafer distribution of the removal rate and film thickness before CMP. The CMP-APC system applying these methods reduces the defects in film thickness after CMP, along with the amount of send-ahead work, which is half that of the former CMP-APC run-to-run control system.