Patent ID: 7672000
Filing Date: 2010-03-02
Classification: G03F

Abstract:
1. A method of detecting positions of first and second marks, the first and second marks being associated with a substrate, and exposing the substrate to a pattern, the method comprising steps of: sensing an image including the first and second marks, an image of the first mark and an image of the second mark having respective periodic patterns, of which periods are different from each other, and being formed in respective regions separate from each other; performing an orthogonal transform of a signal of the sensed image to obtain spatial frequency components corresponding to the first and second marks, to produce a transformed signal; calculating positions of the first and second marks, based on phases of respective spatial frequency components corresponding to the first and second marks in the transformed signal; and positioning the substrate, based on the calculated positions, to expose the positioned substrate to the pattern, wherein the calculating step calculates a coarse position of the substrate based on a phase of a spatial frequency component corresponding to one of the first and second marks, and calculates a fine position of the substrate based on the calculated coarse position and a phase of a spatial frequency component corresponding to the other of the first and second marks.