Adaptive and Predictive Kalman Filters for Drift Correction

摘要

This research disclosure relates to drift correction by applying adaptive and predictive Kalman filters. Especially, it relates to corrections that may be applied to prevent grid drift in an exposure apparatus, as well to drift correction in a metrology apparatus. After calibrating a system, for example an exposure apparatus or a metrology apparatus, the system may start to drift from its calibrated slate. The drift may occur due to hardware imperfections, gravity, and or creep due to the manufacturing process and or system usage. Drifts may have a negative impact on the system performance. Without (counter) actions, the system may not meet the required specifications. For example, an exposure apparatus may not be able to perform according the strict specifications regarding focus and or overlay.