Patent · US Expired

Method for purging an optical lens

US7304716B2 · kind B2 · utility

3Cited by

8References

24Claims

0Family size

Assignee

Infineon Technologies AG · DE

Inventors

Thorsten Schedel · Dresden, DE
Sebastian Schmidt · Weisendorf, DE
Gunter Hraschan · Dresden, DE

Key dates

Filing date	May 12, 2005
Grant date	Dec 4, 2007
Priority date	—
Expiry date	Dec 30, 2025

Classification

Technology area (CPC G)Physics
CPC primaryG03F7/70933
WIPO fieldOptics
WIPO sectorInstruments

Abstract

By a unit for determining fractions of a substance in a gas or gas mixture, measurements are carried out on the gas or gas mixture for purging a lens in a projection apparatus for projecting patterns onto a substrate. The results of a first measurement on the gas fed to the lens are compared with the results of a measurement of the gas removed from the lens. If, the substance is a contaminating substance that leads to a deposit on the lens under the influence of high-energy radiation from an illumination source, the difference is used to infer photochemical reactions on the surface of the lens that lead disadvantageously to the deposition. A signal is generated as a consequence of the comparison and is used to take preventive measures against a degradation of the lens. Mass spectrometers, electric or optical sensors and other known methods for substance analysis are used as measurement units.

Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.