Effects of non-amorphizing hydrogen ion implantation on anisotropy in micro cutting of silicon

Modification of semiconductors by ion implantation is a promising technology for improving their machinability. As well as ion implantation that induce amorphization, non-amorphizing ion implantation is also reported to improve the machinability of silicon. However, the anisotropy in micro cutting of crystalline silicon modified by non-amorphizing ion implantation is not clear. In this study, hydrogen is implanted in (001) silicon wafer with implantation energies and doses up to 175 KeV and 3 × 1016cm-2, respectively. Transmission electron microscopy, numerical simulations and X-ray diffraction are carried out to confirm that point defects and strain are introduced by the implantation, and that crystalline damage is below the amorphization level. Plunge cutting experiments in two crystal directions are performed to study the effects of limited crystal damage induced by ion implantation on the anisotropy in micro cutting of silicon. The plunge cutting experiments show that the anisotropic behaviour is significantly changed. The critical undeformed chip thickness (CUCT) in the direction with lower CUCT before implantation exceeds that in the other direction after implantation. The ductile-regime cutting force is significantly reduced in one direction, while nearly un-affected in the other direction. The results are discussed from the perspective of the effects of ion implantation on the interaction between restricted slip systems. In addition, it is found that the scenarios of brittle-ductile cutting mode transition are significantly different in the <110> and <100> directions for both implanted and bare silicon, and the mechanisms are discussed from the perspective of the anisotropic cleavage systems.