Optical endpoint detection for the chemical mechanical polishing process

Abstract

This thesis covers the design and implementation of a mechanism for detecting the endpoint for the Chemical Mechanical Polishing process of copper wafers. The proposed mechanism will detect the reflectance difference found in semiconductor materials to trigger the stop of the polishing process. This will prevent over polishing of the wafer while ensuring the optimal removal of excess materials. The mechanism is intended to run in-situ, while the polishing occurs. This is accomplished by embedding the reflectance sensor in the polishing platen to allow a clear view of the wafer surface. The reflectance from the surface of the wafer is a function of the material properties, surface structure, angle of incident light, and polarization of light. The experimental results revealed detectable change in the reflectance of the wafer surface, which may be used to determine the endpoint of polishing.