Patent ID: 7142314

Claim:
A method of calibrating a positioning stage, comprising the steps of: (a) placing a substrate on the positioning stage, the substrate having a contrast film above a portion thereof, with at least one pattern at a predetermined location above the substrate, corresponding to a predetermined location on the positioning stage if the positioning stage has zero offset from a registration position, the substrate having a second film on at least a portion of the contrast film; (b) applying a beam to a position where the pattern on the substrate would be located if the positioning stage has zero offset; (c) measuring at least one of the group consisting of reflected, transmitted and scattered portions of the beam from the contrast film and from the second film; and (d) detecting whether the positioning stage has a non-zero offset based on the measured portion of the beam reflected, transmitted or scattered from the contrast film and the measured portion of the beam reflected, transmitted or scattered from the second film.