Apparatus and method of measuring a property of a substrate

摘要

The present invention makes the use of measurement of a diffraction spectrum in or near an image plane in order to determine a property of an exposed substrate. In particular, the positive and negative first diffraction orders are separated or diverged, detected and their intensity measured to determine overlay (or other properties) of exposed layers on the substrate.

主权项

1. An inspection apparatus configured to determine a property of a substrate, comprising:
a radiation source configured to output a radiation beam toward an overlay target on a surface of the substrate; a collimator configured to collimate and focus the radiation beam once reflected from the overlay target, and to separate diffraction orders of a diffraction spectrum of the reflected radiation beam; a detector configured to detect at least a subset of the separated diffraction orders of the reflected radiation beam and to determine first and second properties of respective first and second portions of the subset; and a processor configured to:
determine the property of the substrate by comparing the first and second properties in a plane positioned in a range from where the radiation beam is converging toward an image plane of the collimator to where the radiation beam is diverging from the image plane;determine a position of the overlay target with respect to an optical axis of the collimator; and remove an error of relative positioning from the determination of the property of the substrate based on the determined position of the overlay target.