On-line patterned wafer thickness control of chemical-mechanical polishing

We present a gauge study of an on-line metrology system for chemical-mechan ical polishing and a 600 wafer run by run (RbR) control experiment enabled by on-line wafer measurement. The variability, reliability, and accuracy of the on-line metrology system are found to be very good. We show that a sim ple control approach provides a root-mean-squared error of less than 100 An gstrom. In contrast, using pilot wafers and sheet film equivalents to contr ol a process results in a 39% decrease in performance, and that using fewer sites may increase variability and lead to an incorrect controlled thickne ss. We outline how an 8%-80% improvement in throughput, as well as several reductions in cost of ownership, are possible using on-line metrology in co njunction with run by run control. (C) 1999 American Vacuum Society. [S0734 -2101(99)22504-3].