Lamp stablity diagnostic system
US5818575A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 30, 1997 |
| Grant date | Oct 6, 1998 |
| Priority date | — |
| Expiry date | Apr 30, 2017 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F7/70016
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
Two detectors are effectively positioned at a predetermined lateral position in a rectangular illumination field at a wafer plane. The ratio of the signals from the two detectors is calculated. This ratio is indicative of the quality of the illumination field and any lamp instability which may effect the illumination field, and therefore image quality. In a photolithographic device, a short arc mercury xenon lamp provides illumination for projecting the image of a reticle onto a photosensitive resist covered substrate or wafer. The desired illumination intensity profile is sensitive to lamp instability. This instability may alter the desired illumination intensity profile which may adversely effect image quality, and therefore the resulting product. The ratio of the signals received from predetermined locations laterally along the illumination intensity profile improves the detection of unstable lamps. The detectors are positioned at locations of relatively steep slope in the illumination intensity profile thereby increases sensitivity.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.