Patent ID: 7078894
Filing Date: 2006-07-18
Classification: B24B,G01B,G01D,G01R

Abstract:
1. An apparatus for polishing a first film and a second film formed on a substrate, said apparatus comprising an eddy current sensor for measuring the thickness of the first and second films, said eddy current sensor comprising: a sensor coil for detecting an impedance of an equivalent circuit which includes said sensor coil and the substrate; a signal source for supplying said sensor coil with first AC signals having first frequencies for measuring a thickness of the first film and second AC signals having second frequencies for measuring a thickness of the second film; a phase shifter circuit for generating an in-phase component and a quadrature component from a signal detected by said sensor coil; a cosine synchronous detector for extracting a resistance component from a signal generated by said phase shifter; a sine synchronous detector for extracting a reactance component from a signal generated by said phase shifter; and a signal detector circuit for detecting a thickness of at least one of the first film and the second film by measuring changes of the resistance component extracted by said cosine synchronous detector and the reactance component extracted by said sine synchronous detector.