Patent ID: 8187977
Filing Date: 2012-05-29
Classification: B24B

Abstract:
1. A computer-implemented method for calibrating, the method comprising: commencing a polishing step in which a film on a substrate is polished by a chemical mechanical polisher that includes a polishing pad and an in-situ monitoring system, polishing being effected by causing the film to be in contact with the polishing pad while there is relative motion between the film and the polishing pad; during the polishing step, causing the in-situ monitoring system to monitor the film being polished through a first portion of the polishing pad; during the polishing step, generating a first electronic signal from a detector in the in-situ monitoring system, the in-situ monitoring system having a gain, the detector sensitive to a characteristic of the film being polished; during a first period in the polishing step, amplifying the first electronic signal with the gain set to a first value to generate an amplified first electronic signal; during the polishing step, evaluating whether an amplitude of the amplified first electronic signal is within a first target range; when the amplified first electronic signal is evaluated not to satisfy the one or more constraints, calculating a different second value for the gain such that amplifying the first electronic signal from the first period by the gain set to the second value would cause the amplitude of the amplified first electronic signal to be within the first target range; adjusting the gain for the in-situ monitoring system to the second value; during a second period in the polishing step subsequent to the first period, amplifying the first electronic signal by the gain set to the second value.