Optical alignment system for use in photolithography and having reduced reflectance errors
US4855792A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 13, 1988 |
| Grant date | Aug 8, 1989 |
| Priority date | — |
| Expiry date | May 13, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F9/7069
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A direct reticle reference alignment system for use in photolithography for use with substrates having optical transmissivity. The system includes a movable stage (14), a transmissive substrate (11) held by the stage and bearing at least one plate mark (15) upon its upper surface, an optical system having a light source (1) for illuminating and projecting a reticle alignment image (4) upon the substrate (11) for alignment with the plate mark (15), a sensor (17) mounted in the stage (14) below the substrate (11) and the plate mark (15) to receive light from the projected alignment image (4), the sensor (17) producing an electrical signal related to the degree of alignment, and a stage control actuated by the signal to position the stage (14) and, so, align the substrate (11) with the reticle (4). The sensor (17) includes a light channel (19), such as a fiber optic rod, positioned to receive images from the lower surface (13) of said substrate ( 11) and carry them to the photocell. The detector may include a quadcell and a corresponding light channel for each cell in the quadcell.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.