Implicit and Explicit Finite Element Simulation of Soft-Pad Grinding of Silicon Wafers

Silicon wafers are used to fabricate more than 90% of all integrated circuits. Surface grinding is the preferred technique used to flatten wire-sawn wafers. While conventional grinding is not effective in removing the waviness induced by wire-sawing process, experiments and finite element analysis indicated that soft-pad grinding is a promising method to remove waviness effectively. This paper presents the simulations of the process of the waviness removal of wire-sawn wafers by both implicit and explicit finite element methods using ANSYS and LS-DYNA respectively. Contact algorithms are important in the simulation of wafer grinding. Since the wafer thickness and pad thickness are in the range of millimeters which is thin in comparison with the wafer diameter (in the range of hundreds of millimeters), and the waviness height is usually in the range of tens of micrometers, selecting suitable penetration values in the contact algorithm is challenging. This paper is focused on the selection of contact model, element type, and other solution control parameters in both implicit and explicit methods. The study will be helpful for finding a generalized methodology in similar simulations of contact analysis.