Finite element analysis on processing stress of polysilicon cut by diamond multi-wire saw

Abstract

At present, diamond multi-wire sawing technology has been applied to the slicing of polysilicon wafers. The residual microcracks on the surface and subsurface of the silicon wafer due to material brittle removal are prone to expand and interfere under the sawing stress, which reduces the fracture strength of the silicon wafer and leads to breakage. However, the dynamic change and distribution of sawing stress is still difficult to measure by experiment. In this paper, the two ways of ductile and brittle material removal of abrasives at different azimuth angles on the saw wire surface were considered, the sawing force model of diamond wire sawing was established. Then based on the sawing force model, a finite element model of multi-wire sawing polysilicon was established. The distribution and coupling characteristics of sawing stress and the influence of process parameters and silicon wafer size characteristics on the stress value and distribution were studied. The research results show that the mechanical stress value during the sawing process is relatively small and accounts for a small proportion of the coupling stress, but it will affect the distribution of the coupling stress, and the thermal stress is dominant. The coupling stress increases with the increase of saw wire speed and feed speed. When the ratio of saw wire speed to feed speed is constant, the larger the value of saw wire speed and feed speed is, the larger the coupling stress is. The increase in the size and thickness of the silicon wafer will increase the coupling stress, while the change in the thickness of the silicon wafer has little effect on the value of the coupling stress. The research results of the paper provide a theoretical reference for understanding the changes and distribution of sawing stress, optimizing process parameters and improving the quality of sawing.