Patent ID: 7643961

Claim:
A position detection method of detecting a position of a non-symmetrical mark, said method comprising steps of: detecting light from the mark under a first detecting condition to measure a position of the mark as first position information; detecting light from the mark under a second detecting condition to measure a position of the mark as second position information; and detecting the position of the mark by weighting the first position information by multiplying the first position information by a first coefficient to generate first weighted position information and weighting the second position information by multiplying the second position information by a second coefficient to generate second weighted position information, and adding the first weighted position information and the second weighted position information to determine the position of the mark, wherein (i) the first and second detecting conditions are determined so that a difference value between the first position information and the second position information proportionately increase with an increase in non-symmetry of the mark, and (ii) the first and second detecting conditions are different from each other in one of focus state of an image of the mark, a coherence factor of an illumination optical system for illuminating the mark, a numerical aperture of an imaging optical system for imaging the mark, and a polarization state of light for illuminating the mark.