CMP process involving frequency analysis-based monitoring

A method for monitoring a chemical-mechanical polishing process comprising:

• (a) receiving a real-time data signal from a chemical-mechanical polishing process, wherein the real-time data signal pertains to a frictional force, torque, or motor current,
• (b) submitting the real-time data signal to an algorithm that separates the data signal into a power spectrum of signals with different frequencies whose sum equals that of the real-time data signal,
• (c) identifying at least one signal component of the power spectrum corresponding to an aspect of the chemical-mechanical polishing process,
• (d) monitoring the at least one signal component of the power spectrum during the chemical-mechanical polishing process for a change in the amplitude or frequency of the signal component,
• (e) detecting a change in the amplitude or frequency of the at least one signal component, and
• (f) altering the chemical-mechanical polishing process in response to the detected change.