Influence of polishing parameters on abrasive free chemical mechanical planarization (AFCMP) of non-polar (11-20) and semi-polar (11-22) GaN surfaces

Abstract

In this study, an Abrasive free Chemical Mechanical Planarization (AFCMP) of non-polar (11-20) and semi-polar (11-22) GaN surfaces has been demonstrated. Effect of processing parameters, such as types and concentration of oxidizers, polishing pressure, platen velocity, and pH of the slurries, on the material removal rate (MRR) and surface quality (roughness) have been studied in details. The maximum MRR has been found to be 1.14 μm/hr and 1.85 μm/hr for non-polar (11-20) and semi-polar (11-22) GaN surfaces respectively, under optimized condition of 38 kPa polishing pressure, 90 rpm (100 for non polar surface) platen velocity, 30 rpm carrier velocity, slurry pH 2 and 0.4 M Oxidizer concentration. Root mean square (RMS) surface roughness of ∼1.9 nm and ∼0.8 nm, over large scanning area of 0.70 × 0.96 mm2, has been achieved on AFCMP processed non-polar (11-20) and semi-polar (11-22) GaN surfaces, respectively, using optimized slurry chemistry and processing parameters.