Material removal and surface evolution of single crystal silicon during ion beam polishing

The ion beam polishing techniques for silicon wafers play a key role in the fabrication of optical element. However, the dynamical ion beam polishing process at nanoscale time and space is very difficult to be recorded and observed, which most directly affects the quality of the machined surface. Here, the material removal and surface generation process during ion beam polishing are investigated using atomic simulation. In order to reveal the effects of the Ar ion dose, surface roughness, and Ar ion energy on surface integrity and subsurface damage, the surface topography, stress distribution, material removal rate, and radial distribution function are calculated and analyzed. As a result, the higher ion dose would generate the better machined surface quality, but increases the thickness of the amorphous layer. The initial surface roughness, including hill height and diameter, strongly affects the surface quality, due to the ion implantation depth to fall behind the maximum roughness value. Moreover, the average surface roughness, the material removing rate, and amorphous structure are significantly related to the Ar ion kinetic energy. This work demonstrates the potential of reasonable parameter optimization to prepare the ion beam polishing sample with high precision and few defects for optics applications.