Coherent light generators – Particular active media – Gas
Patent
1998-05-20
2000-01-11
Scott, Jr., Leon
Coherent light generators
Particular active media
Gas
372 57, 372100, 372 99, H01S 322
Patent
active
060143983
ABSTRACT:
The present invention provides a very narrow band pulse excimer laser capable of producing pulses at a rate in the range of about 500 to 2000 Hz with enhanced energy dose control and reproducibility. Very small quantities of a stablizing additive consisting of oxygen or a heavy noble gas (xenon or radon for KrF lasers, or krypton, xenon or radon for ArF lasers), are added to the gas mixture. Tests performed show substantial improvements in energy stability with the addition of about 30 ppm of xenon to a KrF laser. Tests show improved performance for the ArF lasers with the addition of about 6-10 ppm of Xe or 40 ppm of Kr. In a preferred embodiment very narrow bandwidth is achieved on a KrF laser by reducing fluorine partial pressure to less than 0.10 percent and by increasing the reflectance of the output coupler to greater than 25 percent. In a preferred embodiment, prior art fused silica beam expansion prisms used in the prior art line-narrowing module were replaced with calcium fluoride prisms.
REFERENCES:
patent: 5835529 (1998-11-01), Das et al.
patent: 5856991 (1999-01-01), Ersjhov
Das Palash P.
Ershov Alexander I.
Hofmann Thomas
Ishihara Toshihiko
Cymer Inc.
Jr. Leon Scott
Ross, Esq. John R.
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