Patent ID: 8467896

Claim:
A computer-implemented method, comprising: polishing a substrate having a plurality of zones, a polishing rate of each zone being independently controllable by an independently variable polishing parameter; storing a target value; measuring a sequence of values from each zone during polishing with an in-situ monitoring system; for each zone, fitting a first linear function to the sequence of values; for a reference zone from the plurality of zones, determining a projected time at which the reference zone will reach the target value based on the first linear function for the reference zone; and for at least one adjustable zone, calculating an adjustment for the polishing parameter for the adjustable zone to adjust the polishing rate of the adjustable zone such that the adjustable zone has closer to the target value at the projected time than without such adjustment, the calculation including calculating the adjustment based on a feedback error calculated for a previous substrate; after adjustment of the polishing parameter, for each zone, during polishing measuring with the in-situ monitoring system a second sequence of values obtained after the adjustment of the polishing parameter; for the at least one adjustable zone of each substrate, fitting a second linear function to the second sequence of values; and calculating the feedback error for a subsequent substrate for the at least one adjustable zone based on the second linear function and a desired slope.