Positioning method and projection exposure apparatus using the method
US6091481A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Aug 22, 1997 |
| Grant date | Jul 18, 2000 |
| Priority date | — |
| Expiry date | Aug 22, 2017 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F9/7049
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A positioning method for placing an object at a required position includes the steps of illuminating a grating mark formed on the object with a light beam from a light source, forming a mark coherent image corresponding to the grating mark on the surface of an image pickup means by using .+-.n-order light (n=1, 2, 3, . . . ) of reflected and diffracted light from the grating mark and superimposing a reference coherent image of a reference mark, having different periodicity from and no interfering connection with the mark coherent image, onto the image pickup means, and selecting a spatial frequency component of a beat signal inherent in a composite video signal formed by superimposition and detecting the position of the grating mark on the basis of the phase of the spatial frequency component.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.