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Variation Reduction in Plasma Etching via Run-toRun Process Control and Endpoint Detection

Variation in a plasma etch process is shown to be reduced through design of processing equipment for effective control. A dual coil transformer coupled plasma etcher was integrated with multiple sensor systems. Full Wafer Interferometry and optical emission spectroscopy were used for process monitoring. This information is integrated to a run-to-run model based process controller which suggests recipe modifications to reduce variation in the product. Two separate control experiments demonstrate that design of equipment for control can improve processing performance. A new method to detect endpoint in plasma etch processes is also presented. A multivariate statistical technique that utilizes continuous broadband optical emission spectra from the plasma is employed. This technique is found to be sensitive to slight changes in the plasma emission which we believe signify endpoint. A method to make the technique both sensitive and robust is also discussed. Herbert H. Sawin Title: Professor, Chemical Engineering and EECS Thesis Supervisor: Duane S. Boning Title: Associate Professor, EECS