A Methodology to Reduce the Wafer to Wafer Thickness Variation in Chemical Mechanical Planarization (CMP)

The requirement to consistently achieve the specific target mean film thickness within a tight tolerance (± 80nm) in the IC fabrication process flow is a great challenge. In general, except process time, all other process parameters such as applied pressure, both carrier and platen velocity, slurry flow rate and pad conditioning duration are kept constant in a typical process recipe so as to reduce the source of variations. This paper describes a methodology that can be implemented with or without the end point detection system to predict the optimal process time for CMP based on the hypothesis of contact mechanics. It captures the variation of incoming wafer thickness, material removal rate and erratic behavior of the process. It cal also serve as a comprehensive framework for better recipe development. Experimental work shows that this approach demonstrates promising results in reducing the target mean film thickness variation and works well with different layers and devices.