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Self-clean process and real time etch rate monitor development for sub-quarter micron device etching

Advanced sub-quarter micron ULSI plasma etching in production environment has two major requirements. Number one is the ability to accurately control the resulting micro-feature in every aspect. Number two is to produce such results in a cost effective way. In other words, the etching equipment has to run thousands of wafers without interruption such as dry or wet clean, replacement of consumable and other failures. In this paper, we present an innovative interferometer technology for real time etch rate monitoring and the self-clean process development methodology. Self-clean processes eliminate the need for a periodic dry clean to ensure the cleanliness of optical windows and particle free performance. More importantly, the mean wafer between clean (MWBC) with self-clean processes can reach more than 10000 so that the equipment up-time can achieve 95% or more.