Warp of Silicon Wafers Produced from Wire Saw Slicing: Modeling, Simulation, and Experiments

The slicing of wafers from a silicon ingot by the wiresaw process involves the cutting action of the fine slurry particles trapped between the wire and the ingot surface being cut. The heat generated from the cutting action of the slurry is partly convected away by the fast moving slurry at the point of cut. The remainder of the heat leads to differential thermal expansion of the ingot depending on the local conditions at the instant and location of cut. It is conjectured that the non-uniform heat generation and partition is responsible for the warp observed in wafers as cut by the wiresaw process. In this study, a coupled thermal and structural finite element based approach is utilized to model and simulate warp of sliced wafers. Within the constraints and assumptions of the coupled FE model, excellent comparison of simulation results with experimental warp data is observed.