Patent ID: 7016795

Claim:
An article comprising a machine-readable medium storing instructions operable to cause one or more machines to perform operations comprising: commencing a polishing step during which a conductive film on a substrate is polished by a semiconductor processing apparatus that includes an eddy current sensor; receiving a first portion of a signal, the first portion being generated by the eddy current sensor during the polishing step when the eddy current sensor is on-wafer, the first portion including a change in values represented by the signal; receiving a second portion of the signal, the second portion being generated by the eddy current sensor during the polishing step when the eddy current sensor is off-wafer; during the polishing step, comparing the second portion of the signal to a reference signal and determining, based on a result of the comparing, a value for a drift correction parameter; and adjusting the first portion of the signal based on the drift correction parameter.