ENDPOINT DETECTION WITH LIGHT BEAMS OF DIFFERENT WAVELENGHTS

摘要

PURPOSE: A polishing end-point detector is provided to more accurately and reliably determines when to stop the polishing process. and to have means for in-situ determination of the thickness of a layer on a substrate during a CMP process. CONSTITUTION: A chemical mechanical polishing apparatus includes two optical systems which are used serially to determine polishing endpoints. The first optical system includes a first light source to generate a first light beam which impinges on a surface of the substrate, and a first sensor to measure light reflected from the surface of the substrate to generate a measured first interference signal. The second optical system includes a second light source to generate a second light beam which impinges on a surface of the substrate and a second sensor to measure light reflected from the surface of the substrate to generate a measured second interference signal. The second light beam has a wavelength different from the first light beam