Subsurface damage and brittle fracture suppression of monocrystalline germanium in ultra-precision machining by multiple ion implantation surface modification

Abstract

Monocrystalline germanium has been widely used in semiconductor industry and optical engineering because of its excellent electrical and optical properties. However, its hard and brittle properties present difficulties in ultra-precision machining, resulting in surface cracks due to brittle mode cutting. A lot of research has been done on ultra-precision machining of single crystal materials to improve their machinability, including ion implantation surface modification. The ultra-precision manufacturing of semiconductor single crystal materials still faces great challenges. The optimization of ion implantation strategy and the cutting mechanism of samples after ion implantation are still problems that need to be solved. This study presents a novel surface modification strategy for germanium using multi-ion implantation to improve its machinability. In this study, simulation software visualizes the distribution and induced displacement of implanted ions on the subsurface of a germanium wafer. Ultra-precision diamond scratching experiments confirm the improved cutting performance of the ion-implanted germanium, demonstrating a significant increase in the ductile cutting region. The deformation mechanism of different modified layers of germanium during cutting was studied by TEM. The results showed that the subsurface damage of germanium after ion implantation was effectively suppressed. Finally, the microcrack free microlens array was successfully fabricated on the surface of ion-implanted germanium, demonstrating the improved machinability of germanium through ion implantation. This study broke through the limitation of surface modification by single ion implantation, deepened the understanding of brittle-ductile transition in ultra-precision machining of monocrystalline germanium, and provided theoretical basis and technical support for optimizing ion implantation assisted machining of single crystal materials in the future.