A Paradigm Shift in the Development of Chemical Mechanical Polishing (CMP): Cost-Effective CMP Planarization in Next Generation Substrate/Package Design and Manufacturing

Abstract

This paper discusses an on-going research effort to investigate planarization strategies capable of meeting next generation high density package performance and cost requirements. The approach entails the development of an ultra-high removal rate (∼15 μm/min) copper CMP process used in the fabrication of package substrate inter-connects. Initial slurry recycling feasibility has also been investigated as part of the strategy to further reduce operating costs. A recent key thrust in advanced packaging interconnects necessitates the use of damascene-like processing techniques to fabricate build-up substrate layers having high-aspect ratio conductor traces. Inherent thickness variations resulting from the feature forming and copper electroplating processes require subsequent planarization to preserve design requirements for critical trace and ground plane uniformities. The removal rates that have been achieved are nearly one order of magnitude greater than any known ‘high removal rate’ copper slurries commercially available today. Slurry re-use feasibility evaluations were performed using a series of tests designed to characterize the slurry solubility limits. Preliminary data collection indicates promising results for recirculation/recycling of copper slurries without compromise of removal rate stability. CMP process modeling using CAD simulation tools have been shown to be successful in validating the slurry recirculation model with the experimental polish data collected.