Position-dependent state estimator design applied to a wafer stage

Abstract

In lithography machines, the wafer stage is themechanical structure which moves the wafer with respect tothe lens during scanning. The overall accuracy of the machinedepends among others on the accuracy of alignment of thewafer stage with respect to the lens. Since the wafer stage isa mechanical structure with limited stiffness, excitation of nonrigidbody modes leads to deformations of the wafer stage whichdeteriorates the position measurement. This paper proposes aposition dependent state estimator to remove the effect of thedeformations from the measurement and therefore enable thesynthesis of a high bandwidth position dependent wafer stagecontroller.

Date of Award	31 Oct 2014
Original language	English
Supervisor	Hans Butler (Supervisor 1), K.W. Verkerk (Supervisor 2) & R.I. Kamidi (External coach)