Auto focus system, auto focus method, and exposure apparatus using the same
US7460210B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Nov 9, 2005 |
| Grant date | Dec 2, 2008 |
| Priority date | — |
| Expiry date | Mar 26, 2026 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F9/7088
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An auto focus system includes a stage on which a substrate is mounted, light sources that irradiate the substrate with a plurality of focus beams directed towards the substrate at different angles, sensors that detect the focus beams reflected from the substrate, and a controller that determines the relative location of a surface of the substrate according to the locations at which the focus beams are detected by the sensors and positions the substrate accordingly. To this end, the controller performs calculations that are free from the influence of variations in the refractive index of the medium through which the focus beams propagate to the surface of the substrate. Therefore, the autofocus process is carried out with a high degree of precision.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.