Molecular Dynamics Study of Sapphire Polishing Considering Chemical Products

The sapphire chemical mechanical polishing (CMP) process is complicated. The silicate products such as Al2SiO5 are produced during the polishing process. This paper applies molecular dynamics (MD) to study sapphire CMP process considering chemical products. The effects of Al2SiO5 on sapphire polishing as well as the polishing depth, speed and abrasive particle's radius on the polishing of sapphire covered with Al2SiO5 were investigated by comparing polishing force, coefficient of friction (COF), temperature, removed atoms and subsurface quality. The results show that the Al2SiO5 film is beneficial to improving the removal rate and the subsurface quality of sapphire. Increasing the polishing depth can raise the material removal rate, but will aggravate the subsurface damage. The balance of chemical products and polishing depth should be controlled to keep them equivalent during sapphire polishing to minimize subsurface damage. The temperature of the workpiece will rise and the polishing force will decline with the increasing polishing speed. The removed atoms become more but the subsurface damage fluctuates. As the radius of the particle increases, the COF decreases, and the subsurface quality first rises and then declines. The best polishing quality was obtained at 150 m s-1 and 40 angstrom.