A predictive model of grinding force in silicon wafer self-rotating grinding

Abstract

Silicon wafer thinning is mostly performed by the method of self-rotating grinding. In grinding, the grinding force is a crucial factor of affecting the grinding performance, form accuracy and surface/subsurface thinning quality. To control the thinning quality of ground wafer, grinding force is the most essential factor need to be controlled. However, no theoretical model is developed to correlate grinding parameters to grinding force yet. In this article, a theoretical model is established based on the removal behavior of silicon, including cutting and sliding. For the first time, the effects of processing parameters, wafer radial distance and crystal orientation on grinding force are quantitatively described in a theoretical model. Excess grinding force causes local damage of wafer in the form of subsurface cracks, as a determinant factor on the quality of wafer. Therefore, nine sets of self-rotating grinding experiments with variable processing parameters are performed, and the depth of subsurface cracks h are measured to evaluate the damage of ground wafer. Based on the scratching theory of single abrasive grain, the relationship between h and the normal grinding force Fnt is found, which is also validated by the experimental results. Finally, an optimized two-stage process is proposed to control subsurface cracks and improve material removal rate simultaneously, according to the predictive model of grinding force.