Non-contact edge detector
US5739913A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Aug 2, 1996 |
| Grant date | Apr 14, 1998 |
| Priority date | — |
| Expiry date | Aug 2, 2016 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB65H2553/46
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A non-contact substrate alignment system for a lithography system is disclosed that comprises three substrate edge detectors. Each edge detector comprises a projector, preferably located above the substrate, that projects a light field down onto a substrate and a stage. The light field has a predetermined shadow line that is straight and runs perpendicularly to the direction of the substrate's edge. A camera is also located above the substrate and detects the light from the light field. The height differential between the substrate and stage causes a shift in the shadow line from the perspective of the camera. A controller connected to the camera utilizes this shift to locate the edge of the substrate. The problems associated with the mechanical banking techniques are thus avoided. Moreover, the technique uses detectors and projectors that can be located entirely above the substrate; specially designed stages with incorporated detectors or projectors are not required. The technique is also very tolerant of different types of substrates with different edge characteristics.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.