Surface characterization driven CMP optimization for gallium nitride

Abstract

Gallium nitride is a hard and chemically inert material demoting high material removal rates in the chemical mechanical planarization (CMP) applications. This paper focuses on the optimization of the process conditions to enhance material removal rates while controlling surface defectivity for GaN CMP. Two different crystallographic orientations of the GaN are characterized and compared to a commercial 2” GaN wafer to optimize the CMP performance on the basis of the wafer crystallographic nature, surface charge and topography. Slurry pH, the type of polishing pad and applied conditioning were evaluated to increase material removal rates of GaN while minimizing defect formation and enhancing the selectivity against silica.