The article of record as published may be found at http://dx.doi.org/10.1117/1.2743657We present a systematic robustness analysis for several
feedback controllers used in photolithographic critical dimension CD
control in semiconductor manufacturing. Our study includes several controllers
based on either the exponentially weighted moving average
EWMA estimation or Kalman filters. The robustness is characterized by
two features, namely the controller’s stability margin in the presence of
model mismatch and the controller’s sensitivity to unknown noise. Simulations
on the closed-loop control system are shown for the performance
comparison. Both the analysis and the simulations prove that the
multiple-dimensional feedback controller developed in this paper using
the average of previous inputs and outputs outperforms the other controllers
in the group
