Control of flatness for chemical mechanical planarization

To measure and control the topography of wafer surfaces at nanometer scale is essential for semiconductor manufacturing. Flatness control of chemical mechanical planarization requires compact metrology to be integrated in-line in CMP tools. Furthermore, the metrology has to be able to determine flatness on patterned wafers with high resolution. Wave front sensing based on methods according to Makyoh and Shack Hartmann enabled instantaneous, non-destructive flatness inspection of patterned wafer surfaces as, e.g., surfaces from shallow trench isolation or interconnect processes. Besides the unique capability of measuring patterned wafers, the methods are applicable to control bare silicon wafer processing as well. The achieved resolution for measuring flatness was found to be better than 100nm at 1 to 2mm lateral resolution.