Material removal asymmetry in the double-sided polishing process

In the double-sided polishing process both faces of the workpiece are polished simultaneously under apparently identical conditions. However, differences are observed in the material removal rate between the two workpiece faces. More surprising is that over a series of polishing runs, the side from which more material is removed changes. A polishing process model describing material removal rate is developed. Model parameter values based on experimental data are used in the model and predicted behavior corresponding to observed process behavior was obtained. The side-to-side difference in stock removal and change in workpiece side of greater material removal rate can be attributed to three interacting factors. Initial nonuniform slurry distribution, change in material removal rate with material removed due to accumulation of polishing debris in the polishing pads and slurry flow redistribution due to pad loading combine to produce a process which changes over time.