Ellipsometry characterization of copper complex layers for abrasive-free chemical mechanical polishing

摘要

An abrasive-free CMP process has been characterized optically using spectroscopic ellipsometry. Reliable refractive index and extinction coefficient of a copper substrate were determined using a least fitting analysis of measured data. Using a graded layer model with Cauchy dispersion functions, refractive index and extinction coefficient of the copper complex layers were precisely determined. The refractive index was found to be graded in the layers and the index of the copper complex layer close to the copper substrate increased with layer thickness. Layer thickness tended to be saturated with dipping time in a CMP solution.