A novel subsurface damage model in diamond wire sawing of silicon wafers

Abstract

The subsurface damages (SSDs) generated during fixed abrasive diamond wire sawing (DWS) of silicon wafers can reduce the fracture strength and increase the breakage probability of these wafers. It is crucial to accurately evaluate these SSDs. A theoretical model of SSD depth is developed for the fixed abrasive DWS of silicon wafers considering the size effects of material properties, micro-geometries of abrasive grits, and inclination/interaction effects of subsurface cracks. A series of silicon wafers are processed, and the silicon material properties, diamond wire parameters, and surface/subsurface morphologies of silicon wafers are measured. The model is experimentally validated and then used to study the effects of processing parameters on inclination/interaction effects, cutting behaviors, and SSDs. The results show that the model has a relative error of less than 5.0% after revealing that the inclination/interaction parameters, cutting behavior parameters, and SSD depth almost follow a normal distribution, with a maximum distribution probability ranging from 30% to 50%. The average inclination angle is approximately 30°, the average cutting depth is in the range of one to two hundred micrometers, the average load is a few millinewtons, and the SSD depth is in the range of a few micrometers. With an increasing density of abrasive grit, a decreasing feed rate, or an increasing wire speed, the interaction effect becomes more pronounced, while the inclination angle, cutting depth, load, active grit ratio, and SSD depth decrease. When the protrusion height increases, or the half sharpness angle or tip radius of abrasive grit decreases, there is an increase in the cutting depth, load, active grit ratio, or SSD depth. The inclination angle decreases as the protrusion height, half sharpness angle, or tip radius increases. This research helps to understand the cutting mechanism and evaluate the SSDs during the DWS of silicon wafers.