Reverse dark field alignment system for scanning lithographic aligner
US4697087A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 31, 1986 |
| Grant date | Sep 29, 1987 |
| Priority date | — |
| Expiry date | Jul 31, 2006 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F9/7069
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An alignment apparatus wherein a wafer having a wafer target thereon and a reticle having a reticle target therethrough are aligned to each other. An alignment image is formed on the wafer, and the wafer and reticle are scanned relative to the alignment image. The alignment image has a linear extent normal to the scanning direction which is longer than the wafer target so that a portion of the alignment image is reflected by the wafer. The portion of the alignment image reflected by the wafer is reimaged onto the reticle target. Collecting optics are provided to collect light from the alignment image that is backscattered by the wafer target as the wafer target is scanned past the alignment image. Two detectors are provided: one to detect the backscattered light, the other to detect light which passes through the reticle target. The output from each of the detectors is compared to determine any misalignment.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.