Metrology measurement method and apparatus

Abstract

Disclosed is a method of measuring a target on a substrate using a metrology tool comprising an illumination source operable to emit an illumination beam for illuminating the target and a metrology sensor for collecting the scattered radiation having been scattered by the target. The method comprises calculating a target angle based on cell dimensions of a unit cell of said target in a first direction and a second direction orthogonal to said first direction; and order numbers of a selected pair of complementary diffraction orders in said first direction and second direction. At least one pair of measurement acquisitions is performed at a first target orientation and a second target orientation with respect to the illumination beam, wherein said target angle for at least one of said at least one pair of measurement acquisitions is an oblique angle.

Dependencies are inferred from the claim text.