Filtering during in-situ monitoring of polishing

Abstract

A method of controlling polishing includes polishing a substrate, monitoring the substrate by an in-situ monitoring system during polishing, filtering a signal from the monitoring system to produce a filtered signal, and determining at least one of a polishing endpoint or an adjustment to a polishing rate based on the filtered signal. The filtering includes modeling a plurality of periodic disturbances at a plurality of different frequencies using a plurality of disturbance states; modeling an underlying signal using a factory state; and applying a linear prediction filter to the factory state and the plurality of disturbance states to produce a filtered signal representative of the underlying signal.

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