单晶硅多次加工时的亚表面损伤仿真分析

Simulation and analysis of subsurface damage of monocrystalline silicon under multiple-processing

基于分子动力学(molecular dynamics,MD)仿真技术,研究了单晶硅在多次加工时的亚表面损伤。分析了已加工和未加工的单晶硅模型的亚表面损伤;对已加工和未加工的表面分别进行了纳米划痕仿真,分析了划痕加工损伤的变化。仿真结果表明:切削加工后表面的硬度和弹性有不同程度的下降,有助于单晶硅工件表面材料的去除,减少了第2次加工时的亚表面损伤层深度;第2次加工的加工深度超过残余损伤层厚度的一半时,加工后的效果最优;加工深度完全在损伤层内时,会受到亚表面损伤层的原子密集化和力学性能的双重影响,造成损伤层增大。多次加工硅片时,应充分考虑加工深度与亚表面损伤层厚度的关系。

Based on molecular dynamics （MD） simulation, the subsurface damage of the monocrystalline silicon under multiple-processing is studied. The subsurface damage of the processed and unprocessed monocrystalline silicon model has been analyzed. Then the nanoscratch simulations under different depths of the processed and original surfaces are conducted, and the change of subsurface damage during scratch processing has been discussed. The simulation results show that the hardness and elasticity of the processed surface caused by the first machining is decreased at varying degrees, which will be conducive to the material re-moval from the surface of single crystal silicon and reduce the subsurface damage of the second processing. The optimal process-ing is achieved when the depth of the second processing is more than about half of the thickness of the residual damage layer. When the processing depth is completely within the damage layer, dual effects from both the densification of atoms in the subsur-face damage layer and mechanical properties are induced, resulting in deeper subsurface damage. Studies have shown that when the silicon wafer is undergoing multiple ultra-precision machining, the relationship between the processing depth and the thickness of surface damage layer should be fully considered.