A coupled finite element scheme to study the grinding force and warpage of silicon wafers during the backside grinding process

Abstract

In this study, a finite element model is developed to analyze the grinding force and warpage of silicon wafers during the backside grinding process. Due to the decreasing size of consumer electronic devices, such as smartphones, notebooks, and portable electronics, it is necessary to address the issues pertaining to grinding silicon wafers. The backside grinding process is a mature technology that is widely used for silicon wafers. However, for ultrathin silicon wafers, warpage is a critical issue. Wafer warpage is induced by the residual stress and surface damage that arises during the backside grinding process. To analyze the grinding stress on silicon wafers during the backside grinding process, a finite element model is established by setting dynamic loads, and contact conditions. An explicit dynamic model is used to simulate the relationship between the grinding wheel and the silicon wafer. A static model is incorporated with the explicit dynamic model to predict wafer warpage. The simulation results for the residual stress are in good agreement with the experimental results. The results indicate that the wheel rotational speed, wafer rotational speed, and feed rate effectively control wafer warpage. Hence, the warpage of ultrathin silicon wafers can be decreased by adjusting the manufacturing process parameters. Furthermore, the developed simulation model can also be used to analyze warpage in fan-out wafers during the backside grinding process.