GOALI: "Run-to-Run Feedback Control of Semiconductor Manufacturing Processes"

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9510625 Krogh The objective of this project is to develop methods for using in- line measurements from semiconductor manufacturing processes to adjust process operating points from run to run to compensate for sources of systematic drift in the process variables. Semiconductor manufacturing processes are typically monitored using statistical process control (SPC) techniques, and adjustments are made in operating setpoints only when out-of- control conditions are detected. This approach cannot effectively compensate for systematic parameter variations such as drifts in the process operating environment, material properties, or equipment conditions. Consequently, methods for adjusting the process operating point from run to run are needed to improve the quality and yield of semiconductor manufacturing processes when it is too costly or physically impossible to eliminate systematic variations. This project will combine techniques developed for system identification, parameter estimation, and feedback control, with methods for statistical and physical modeling to perform effective run-to-run control for key processes in a commercial photovoltaic cell manufacturing facility. Parameterized models will be developed to characterized the input-output relations for each process, and so-called gray-box parameter estimation, Kalman filtering, and constrained optimization will be applied to update the process setpoints for each process run based on post-process measurements from previous runs. A primary emphasis of this work will be to develop methods for incorporating process knowledge from physical models and empirical data into the on-line computations to more effectively compensate for the process variations. The key trade-off to be explored is the complexity of the models versus the efficiency and effectiveness of the on- line parameter estimation and control computations. In addition to these immediate technical objectives, this one- year project sponsored under the NSF GOALI program will enable the principal investigator, who is currently working in the area of semiconductor process control, to gain valuable experience working with industrial scientists and engineers in a commercial semiconductor manufacturing facility. The research will be conducted at - and supported in part by - EBARA Solar, Inc. Models will be obtained using process data from EBARA, and the run-to-run feedback control techniques will be implemented on actual production equipment to evaluate their effectiveness. This experience will contribute significantly to the definition of future theoretical and applied research directions in model- based control of complex manufacturing processes. ***