Precision positioning stage with nanometer order accuracy over long travel is demanded especially for a semiconductor lithography, an ultraprecision machine tool and an ultraprecision metrology in recent year. This precision stage performance requirement is consider not easy to be fulfilled simply by improving existing stage design which depends on mechanical accuracy, so implemented in this paper a new design and control of ultraprecision stage based upon the concept of dual servo, the whole mechanism of the stage is composed of two sub-stages; one is a global stage configured with three d.c. linear motors and the order is a micro stage with piezoelectric microactuators for fine motion control. A dual servo is basically constituted in an integrated form two distinct servos with mutually compensating characteristics; the global servo for long travel whereas the micro servo for nanometer order positioning resolution and fast response. The both servos are synchronously controlled with feedback position signals supplied from plain mirror type laser interferometers. Main emphasis of this paper is given to develop an appropriate control model of the dual servo stage with aims to achieve an overall positioning reproducibility of 10 nm in aligning wafers of 200 mm diameter.
