Off axis alignment system for scanning photolithography
US5477057A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 17, 1994 |
| Grant date | Dec 19, 1995 |
| Priority date | — |
| Expiry date | Aug 17, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/70358
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
The invention described herein is an alignment system used in semiconductor manufacturing. It is the core component used to align a mask containing a circuit pattern to a wafer during a scanning sequence. The alignment system images an alignment reticle pattern onto a wafer which contains alignment marks. During scanning, the light from the alignment reticle image is reflected and scattered by the wafer and its alignment marks. Multiple detectors are placed at a pupil plane of the alignment system to collect the reflected and scattered light in the bright-field and dark-field regions. The resulting signals and their analysis results in determination of accurate alignment of a wafer. The alignment system does not use or "look through" the projection optics of the scanning photolithographic device. The broadband spectrum used for alignment illumination cannot be used in the projection optics designed for the deep UV wavelengths without undesirable results. The broadband spectrum illumination utilized in the alignment system results in improved detection of wafer alignment marks independent of the various process wafer structures that can be encountered.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.