Patent ID: 8582114
Filing Date: 2013-11-12
Classification: G03F

Abstract:
1. A method for measuring overlay utilizing pupil phase information, comprising: measuring a first phase distribution across a pupil plane of a portion of illumination reflected from a first overlay target of a semiconductor wafer, wherein the first overlay target is fabricated to have a first intentional overlay; measuring a second phase distribution across the pupil plane of a portion of illumination reflected from a second overlay target of the semiconductor wafer, wherein the second overlay target is fabricated to have a second intentional overlay, wherein the second intentional overlay is along a direction opposite to the first intentional overlay, wherein the first intentional overlay and the second intentional overlay have substantially the same magnitude; determining a first phase tilt associated with a sum of the first phase distribution and the second phase distribution; determining a second phase tilt associated with a difference between the first phase distribution and the second phase distribution; calibrating a set of phase tilt data utilizing the determined second phase tilt and the magnitude of the first and second intentional overlay; and determining a test overlay value associated with the first overlay target and the second overlay target by comparing the first phase tilt to the calibrated set of phase tilt data.