Study on mechanism and characteristics of laser repair of surface damage after ultra-precision grinding of monocrystalline silicon

Abstract

The surface damage caused by ultra-precision grinding of monocrystalline silicon will affect the material performance and limit its application. In order to weaken or eliminate the surface defects and damages of monocrystalline silicon, laser repair research was carried out on the surface of monocrystalline silicon after ultra-precision grinding. The principle of laser repair of surface damage was described, and the relationship between laser damage threshold and laser power, ablation pore size and waist radius were clarified through theoretical model. A laser perforation experiment system based on grating scanning method was designed, and laser ablation pore sizes with different parameter combinations were obtained. Through analysis and calculation, it was determined that the damage threshold of monocrystalline silicon laser is 0.1188 ∼ 0.2419 J/cm². The theoretical model of laser damage threshold and the experimental results of laser perforation showed that the energy density of laser repair should be below the laser damage threshold. The experiment results of laser repair showed that the higher the laser power is, the better the surface repair effect is. Surface laser repair result was relatively good at 20mW laser power. And the laser power over 40mW will also have a negative effect on the repair effect. The nanoindentation experiment of monocrystalline silicon material was carried out, and the results showed that the laser repaired monocrystalline silicon surface had higher ultimate fracture strength and plastic deformation than the original grinding surface. The results of Raman spectrum analysis showed that laser repair can transform the amorphous structure into single crystal structure in the ultra-precision grinding monocrystalline silicon material. The laser repair method of surface damage implemented in this study provides guidance and reference for the suppression and removal of surface damage of monocrystalline silicon and other hard-brittle materials.