Reduction of Slurry Flow Rate in Oscillation Polishing Using a Small Tool

Abstract

CMP is the standard planarization method for silicon wafers. For environment reasons, semiconductor manufacturers have to reduce the consumption of materials, such as slurry. The oscillation-speed-control-type polishing machine uses a small tool and supplies slurry from a pad center, so the slurry spreads to the polishing area easily. This report shows the polishing characteristics under low slurry flow rate conditions. In non-oscillation polishing, it is difficult to reduce the slurry flow rate to less than 200 ml/min since a shortage of slurry results in a damaged area on a wafer. In uniform oscillation speed polishing, no damaged area was found to occur even with a slurry flow rate of only 5 ml/min. In addition the experimental results corresponded with the simulated ones. It was demonstrated that in oscillation speed control polishing, the minimum oscillation speed and slurry flow rates were different for different pad materials. In experiments, a flatness of better than 0.2 μm over the entire surface was achieved using both an IC1000 pad with a slurry flow rate of 20 ml/min and a SUBA800 pad with a flow rate of 40 ml/min.