Impact of Chemomechanical Polishing on the Chemical Composition and Morphology of the Silicon Surface

Abstract

ABSTRACTThe polishing technology used for manufacturing ultraflat and smooth Si surfaces on a large scale is the chemomechanical polishing (CMP) technique. This technique combines the chemical corrosive removal of silicon atoms and the mechanical transport of the agents. The removal rates strongly depend on the interaction of mechanical parameters and the chemistry involved in the polishing process like the pH of the alkaline polishing slurry used. Removal of Si during CMP is explained by a nucleophilic attack of OH− to silicon atoms catalyzing the corrosive reaction of H2O resulting in cleavage of silicon backbonds. Characterization of the surface chemistry of the silicon wafer after polishing by X-Ray Photoelectron Spectroscopy and High-Resolution Electron Energy Loss Spectroscopy reveals an oxide free, predominantly hydride covered silicon surface displaying hydrophobic properties. Morphological features like microroughness as well as localized surface irregularities on the silicon surface, also referred to as Light Point Defects, depend on different strongly interacting process parameters. Microroughness is reduced by CMP by several orders of magnitude as characterized by lightscattering techniques and Atomic Force Microscopy.