Imaging Optical System for Producing Control Information Regarding Lateral Movement of An Image Plane or An Object Plane
AssigneeNikon Corporation
InventorDaniel Gene Smith
Life of this patent
Estimating the term…
Abstract
A new and useful concept is provided by which control information for an imaging optical system such as a lithographic imaging optical system can be generated. A system and method are disclosed that are designed to detect changes in the lateral position of an image plane or object plane in an imaging optical system, particularly a lithographic imaging optical system.
Claims17
Apparatus for detecting changes in the lateral position of an image plane or object plane in an imaging optical system, comprising
- (a) a primary imaging optical system configured to direct an image along a primary imaging path from an object plane to an image plane,
- (b) a measurement diffraction grating integrally connected with one of the image plane or the object plane and configured to move with the one of the image plane or object plane in directions lateral to the primary imaging path;
- (c) a reference beam and a measurement beam that originate outside the primary imaging path;
- (d) the measurement beam directed at the measurement diffraction grating on the one of image plane or the object plane to produce a diffracted measurement beam, while the path of the reference beam is such that the reference beam is unaffected by changes in the lateral position of the one of the image plane or the object plane;
- and
- (e) a detection system that directs at least a component of the reference beam and a component of the diffracted measurement at a detector configured interferometrically to detect phase changes between the reference beam component and the diffracted measurement beam component, to produce an output related to changes in the lateral position of the one of the image plane or the object plane.
A method for detecting changes in the lateral position of one of an imaging plane or an object plane in an imaging optical system, comprising
- (a) directing an image along a primary imaging path from an object plane to an image plane,
- (b) providing a measurement diffraction grating integrally connected with one of the image plane or the object plane in a manner such that the reference diffraction grating moves with the one of the image plane or object plane in directions lateral to the primary imaging path;
- (c) providing a reference beam and a measurement beam that originate outside the primary imaging path;
- (d) directing the measurement beam at a measurement diffraction grating on the one of the image plane or the object plane to produce a diffracted measurement beam;
- and
- (e) detecting phase changes between the reference beam and the diffracted measurement beam interferometrically, to producing an output related to changes in the lateral position of the one of the image plane and the object plane.
Dependencies are inferred from the claim text.