Nikon Corporation

Ryoichi Kawaguchi

Bausan Yuan

Kazuhiro Hirano

Yi-Ping Hsin

Kazuo Masaki

Gabor D Szoboszlay

Christopher B Smith

Embodiments of the invention relate to a cable force feedforward approach that takes into account the cable force in the counter-mass trajectory computation to reduce or eliminate vibration of the lens body caused by the cable force disturbance and corrective force exerted by the trim motors. In one embodiment, a method provides cable force feedforward control for a counter-mass of a stage with a cable connected to the counter-mass and using the cable force feedforward control to control one or more trim motors to produce a trim motor output force to be applied to the counter-mass, the counter-mass moving in response to a reaction force from movement of the stage. The method comprises measuring a counter-mass position y of the counter-mass in response to forces applied to the counter-mass; measuring a cable force &#x192; exerted on the counter-mass by the cable which is connected to the counter-mass; generating a cable force function {circumflex over (&#x192;)}(y, {dot over (y)}) of the measured cable force &#x192; versus the counter-mass position y; and computing the trim motor output force u as where w is a weighting function having a value from 0 to 1 and is selected for optimization.

Minimum force output control method for counter-mass with cable

A method and apparatus minimizes the relative difference between motions of two stages driven by a single input signal, where the motions of the two stages ideally are perfectly synchronized. In practice, synchronization is imperfect due to mechanical/environmental disturbances in each stage as well as electrical differences affecting the stage controller. The two stages are serially coupled for control purposes so that a signal indicating the position of the first stage is used as an input driving signal to the second stage. The relative location error between the two stages is thereby minimized, compared to the case where the two stages are driven simultaneously but in parallel by a common input signal. Furthermore, by using the lower bandwidth stage as the driver (first) stage and the higher bandwidth stage as the follower (second) stage, the relative position error is no larger than the smaller of the absolute position errors of either stage alone. One exemplary application is improved alignment of a reticle stage and a wafer stage in a scanning exposure system for semiconductor lithography.

Dual stage following method and apparatus

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Tokyo, Japan

Ryoichi Kawaguchi