29 April 2004 Model-based fault detection and metrology error rejection in registration APC system
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After we implemented the run-to-run feedback control system for lithographic stepper registration, we found that the metrology error introduced wrong control signals which drove the process away from normal operation. This paper presents methods of model-based fault detection and metrology error rejection. We use the fault detection method to monitor the health of run-to-run system and apply the error rejection method to proactively correct control signal to ensure the desired targets. Comparing to the old run-to-run system used in litho process that only provides warning limits and hard limits with fixed thresholds on individual physical variables, the proposed fault detection method is more sensitive to detect drift, shift and out-of-control points. It could have detected a real problem much quicker if this method was used. The error rejection method is very powerful to handle metrology errors as well as shift and drift by using the estimated output instead of the measured output. The experiments on the real data and simulation data validate the usefulness of the method.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Ziqiang John Mao and Issi Geier "Model-based fault detection and metrology error rejection in registration APC system", Proc. SPIE 5378, Data Analysis and Modeling for Process Control, (29 April 2004); doi: 10.1117/12.536810; https://doi.org/10.1117/12.536810

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