Patent ID: 8755927

Claim:
A polishing system, comprising: a platen to support a polishing pad; a carrier head to hold a substrate against the polishing pad, the carrier head including a plurality of independently pressurizable chambers to independently control each zone of a plurality of zones on the substrate; a motor for generating relative motion between the platen and the carrier head; an in-situ monitoring system to monitor the substrate and generate a sequence of values for each zone during polishing; and a controller configured to store a target value, for each zone, fit a first linear function to the sequence of values, for a reference zone from the plurality of zones, determine a projected time at which the reference zone will reach the target value based on the first linear function of the reference zone, for at least one adjustable zone from the plurality of zones, calculate an adjustment for a pressure in a chamber associated with the adjustable zone to adjust a 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 from measurements by the in-situ monitoring system of a previous substrate, after adjustment of the pressure, for each zone, during polishing measuring with the in-situ monitoring system a second sequence of values obtained after the adjustment of the pressure, 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 for the adjustable zone.