Abstract: Methods are provided for calibrating a tool using an eddy current probe and calibration wafers that each have a measurable predetermined property and a measurement of the measurable predetermined property of a first calibration wafer is different than a measurement of the measurable predetermined property of a second calibration wafer. The methods include determining a first set of impedance measurements of the calibration wafers while each is disposed in the tool and the tool has a tool parameter that is at a first condition, collecting a second set of impedance measurements of the calibration wafers while each is disposed in the tool and the tool parameter is at a second condition, establishing a reference point, based upon a first and a second data point from the first set of impedance measurements and a first and a second data point from the second set of impedance measurements.

Abstract: Methods and apparatus are provided for calibrating a chemical mechanical polishing (“CMP”) tool having a polishing station with a platen, an eddy current probe disposed within the platen, a polishing pad coupled to the platen, and a metal element disposed within the polishing station and configured to be selectively moved proximate the polishing pad. The method includes the steps of determining a thickness measurement of the polishing pad and adjusting at least one tool parameter based, in part, upon the determined thickness measurement of the polishing pad.