A practical standard procedure for contamination measurements on wafer surfaces: experimental verification

The SEMI E14-90 Standard defines a method for calibrating surface contamination measurement tools based on polystyrene latex spheres and sampling statistics, background noise measurement, data analysis, and decision criteria. It is pointed out that the standard will be practical only if two different measurement tools, calibrated according to the defined procedure, give similar results on wafers with particles from process tools. The authors report a series of studies which address this issue. Measurements by two tools made by the same manufacturer but located in different factories are compared: a Tencor Surfscan 5000 at Perkin Elmer in Wilton, CT, and a Tencor Surfscan 4000 at IBM in East Fishkill, NY. Measurements by four tools made by four different manufacturers are also compared: a Tencor Surfscan 4500, an Inspex 20/20, an Esstek 8000, and a PMS SAS 5800. The studies demonstrated that it is possible to make accurate comparisons along several measurement tools, including tools at different facilities, if there is a good room environment and careful wafer handling procedures