Soft-pad grinding of 300 mm wire-sawn silicon wafers: finite element analysis with designed experiments

Silicon wafers are the primary semiconductor substrates used to fabricate Integrated Circuits (ICs). Recently, the industry is making a transition from 200 to 300 mm wafers. To attain very flat 300 mm silicon wafers, grinding has been used to flatten the wire-sawn wafers. However, it is challenging for grinding to remove the waviness induced in wire sawing. To enhance the waviness removal ability of grinding process, several approaches have been explored including soft-pad grinding. This paper presents a study on soft-pad grinding of 300 mm wire-sawn silicon wafers through Finite Element Analysis (FEA) with designed experiments. A 25 (five factors, two levels) full factorial design is employed to reveal the main effects as well as the interaction effects of five factors (elastic modulus, Poisson's ratio and thickness of the soft pad; waviness wavelength and waviness height of silicon wafers) on the effectiveness of waviness removal. FEA simulation results are compared with relevant experimental results. Implications of this study to manufacturing are also discussed.