Optimal model predictive control of overlay implemented in a ASIC fab

Abstract

A method and model-predictive controller that takes raw overlay registration data from a metrology tool, such as the KLA-5200 metrology tool, and estimates process disturbances. Once these disturbances are estimated, the controller regulates them to zero, resulting in precise control of overlay. The controller includes a state estimator which is configured to estimate the following system states: wafer x-translation, wafer y-translation, wafer scale in x, wafer scale in y, wafer rotation, wafer non-orthogonality, reticle magnification, asymmetric magnification, reticle rotation, asymmetric reticle rotation. The controller includes a regulator which is configured to regulate the system states to desired targets.

Dependencies are inferred from the claim text.