| 摘要 |
A device to measure a phase shift of a step in a reticle is disclosed. The phase shift measuring device has a common path interferometer for receiving light from a light source and providing two point images separated from each other by an adjustable distance. A microscope having an objective focuses two point images to form two focused points along a reticle surface of the reticle. The reticle is moved between first and second positions, wherein at the first position, light beams from the two focused points enter the reticle surface, and wherein at the second position, the light beams from the two focused points enter a step surface of the step A detector receives light from the reticle for detection of the step phase shift.
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