Apparatus and methods for measuring thermally induced reticle distortion

摘要

An apparatus and method for measuring thermo-mechanically induced reticle distortion or other distortion in a lithography device enables detecting distortion at the nanometer level in situ. The techniques described use relatively simple optical detectors and data acquisition electronics that are capable of monitoring the distortion in real time, during operation of the lithography equipment. Time-varying anisotropic distortion of a reticle can be measured by directing slit patterns of light having different orientations to the reticle and detecting reflected, transmitted or diffracted light from the reticle. In one example, corresponding segments of successive time measurements of secondary light signals are compared as the reticle scans a substrate at a reticle stage speed of about 1 m/s to detect temporal offsets and other features that correspond to spatial distortion.

主权项

1. A method for detecting reticle pattern distortion, the method comprising:
(a) directing at least one optical beam to be incident on the reticle as the reticle undergoes a first scanning motion; (b) detecting at least one segment of a secondary light signal associated with an interaction of the at least one optical beam with the reticle during the first scanning motion; (c) directing at least one optical beam to be incident on the reticle as the reticle undergoes a second scanning motion, the second scanning motion performed at a time different than a time associated with the first scanning motion; (d) detecting at least one segment of a secondary light signal associated with an interaction of the at least one optical beam and the reticle during the second scanning motion; and (e) based on the detected segments associated with the first scanning motion of the reticle and the second scanning motion of the reticle, determining that the reticle pattern is distorted.