Quality improvement of chemical-mechanical wafer planarization process in semiconductor manufacturing using a combined generalized linear modelling - non-linear programming approach
This paper is aimed at how to develop and utilize a specialized response surface method, combined with state-of-the-art mathematical programming techniques, for quality improvements of the chemical-mechanical planarization (CMP) process in semiconductor manufacturing. CMP is one of the fastest growing technologies that enables to polish the topography of interlayer dielectrics (ILDs) and to obtain a high degree of global planarity due to increasingly stringent requirements of photolithography between process steps. A wafer held on a carrier is rotated against a polishing pad in the presence of a silica-based alkaline slurry while applying a down-force onto it. Two major challenging works posed by CMP involve maintaining stable removal rate with polishing time and achieving acceptable within-wafer non-uniformity (WIWNU) over an entire die. In this research, to robustly characterize and therefore optimize such a still unclear and fully complex process, the response surface methodology (RSM) as an external modelling technique and non-linear programming (NLP) approaches as an optimum-seeking procedure are proposed to the bicriteria situation. An example with real CMP data is rigorously investigated, revealing that not only does the proposed method flexibly and appropriately portray CMP, but also helps locate the optimal parameter settings that attain better polishing quality.