Patent ID: 7682221
Filing Date: 2010-03-23
Classification: B24B,G01B

Abstract:
1. A method of measuring conductive layer thickness during chemical mechanical polishing, the method comprising: positioning a substrate having a conductive layer disposed thereon in contact with a polishing surface of a polishing pad; creating relative motion between the substrate and the polishing pad to polish the substrate; driving an inductor with a drive signal to generate an alternating magnetic field that induces eddy currents in the conductive layer during polishing; measuring a strength of the magnetic field and a phase difference between the magnetic field and the drive signal during polishing; calculating a correction factor based on the strength of the magnetic field; calculating a thickness of the conductive layer from the phase difference and the correction factor; and polishing a test substrate with a first polishing pad having a first known thickness and with a second polishing pad having a second known thickness, and generating at least one coefficient to relate pad thickness to magnetic field strength during polishing; and calculating the thickness of the polishing pad contacting the substrate from at least the strength of the magnetic field and the coefficient.