Influence of slurry flow rate on material removal rate and topography of chemical mechanically planarized c-Plane (0001) GaN surface

Abstract

Chemical mechanical planarization (CMP) processing parameters greatly influence the material removal rate (MRR) and roughness of the processed wafer surface. The slurry flow rates on the polishing pad are likely to alter the polishing performance. Thus, a series of CMP experiments has been performed on c-plane (0001) GaN wafer surfaces with varying slurry flow rates to investigate their effect on the polishing rate and surface planarity for a fixed set of other CMP processing parameters. The slurry flow rate has been varied from 10–50 ml/min during the CMP experiment. An improved MRR (~228 to 687 nm/h) with decreasing surface roughness has been observed with increasing slurry flow rate from 10–40ml/min. However, at 50 ml/min, a further increase in MRR was observed (904 nm/h) with inferior surface quality. The variation in surface roughness has been studied over varying scan areas and the lowest root-mean-square (rms) surface roughness of ~1 nm, over a scan area of 5 × 5 μm2, has been achieved at 40 ml/ min slurry flow rate.