Patent ID: 6190234
Filing Date: 2001-02-20
Classification: B24B

Abstract:
A chemical mechanical polishing apparatus to polish a substrate having a first surface and a second surface underlying the first surface, comprising:a first polishing station having a first optical system, the first optical system including a first light source to generate a first light beam to impinge the substrate as it is polished at the first polishing station, the first light beam having a first effective wavelength, and a first sensor to measure light from the first light beam that is reflected from the first and second surfaces to generate a first interference signal; anda second polishing station having a second optical system, the second optical system including a second light source to generate a second light beam to impinge on the substrate as it is polished at the second polishing station, the second light beam having a second effective wavelength that differs from the first effective wavelength, and a second sensor to measure light from the second light beam that is reflected from the first and second surfaces to generate a second interference signal; andat least one processor to determine a polishing endpoint at the first and second polishing stations from the first and second interference signals, respectively.