Deformation and material removal rate in polishing silicon wafers

The aim of the present work was to explore the deformation mechanism and to estimate the material removal rate (MRR) in polishing silicon wafers. The surface roughness was studied by atomic force microscope and subsurface damage was assessed by means of cross-section transmission electron microscopy. The subsurface atomic structure was then investigated by high resolution transmission electron microscopy at the nano-scale. It was shown that the material removal was a non-linear function of pressure and velocity in polishing. Increasing the pressure or velocity accelerated the MRR. However, the variation of the polishing input parameters introduced various mechanisms of deformation in the subsurface. The process could be improved by taking into account the surface roughness of the component and the depth of the subsurface damage. The material removal in the polishing with abrasives of 15 μm in diameter was dominated by brittle fracture. However, that with abrasives of 50 nm in diameter could be fully achieved by ductile deformation, leaving the atomic structure in the polished subsurface almost undisturbed.