Method of detecting relative positional deviation between two objects
US5182455A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 11, 1992 |
| Grant date | Jan 26, 1993 |
| Priority date | — |
| Expiry date | May 11, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F9/7049
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A method, usable with a workpiece having a predetermined grating pattern and to be exposed to a particular pattern through a projection lens system and by use of an exposure beam of a predetermined wavelength, for detecting a positional error of the workpiece. The method includes the steps of: providing a reference plate having first and second grating marks; irradiating the first and second grating marks with a radiation beam of a wavelength different from the predetermined wavelength, so that the first grating mark produces a first diffraction beam while the second grating mark produces a second diffraction beam; superposing, through the projection lens system, the first diffraction beam and the second diffraction beam upon one another on the predetermined grating mark to form a beam spot thereat; and detecting the positional error of the workpiece, on the basis of any deviation of the predetermined grating pattern relative to the beam spot.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.