Analytical Modelling of Material Removal in Copper Chemical Mechanical Polishing Incorporating the Scratch Hardness of the Passivated Layer on Copper Thin Film Wafer

Abstract

Chemical mechanical polishing (CMP) is the most crucial process for semiconductor fabrication and the scale of its application is broadening year by year. And understanding the varied mechanical interaction at pad-wafer contact as well as chemical alteration of the wafer surface is essential to comprehend the mechanism of material removal in the CMP process. In this study, an analytical material removal model is established as a function of polishing pad properties and scratch hardness of copper thin film wafer in CMP slurry environment. The model incorporates both, the mechanical material wear of chemically altered surface and, the chemical dissolution of copper based on corrosion theory. The contact between the polishing pad, wafer and abrasive is analysed and, in addition, the effect of the polishing pad and wafer properties on material removal is simulated. The model predicted MRR is compared to the copper CMP experiment MRR. This study establishes a strong correlation between the experimentally measured polishing pad and wafer properties and the material removal within the nanoscale contact model assumptions. The model provides a theoretical and experimental framework for optimizing the CMP process parameters, which can be employed to develop a simulator to analyze the advanced node copper CMP process