Energy stabilized gas discharge laser

US6714577B1 · kind B1 · utility

Assignee

• Lambda Physik AG · DE

Inventors

• Uwe Stamm · Göttingen, DE
• Igor Bragin · Göttingen, DE
• Wolfgang Zschocke · Göttingen, DE

Key dates

• Filing date: Feb 25, 2000
• Grant date: Mar 30, 2004
• Expiry date: Feb 25, 2020

Classification

• Technology area (CPC H): Electricity
• CPC primary: H01S3/2251
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

An excimer or molecular fluorine laser, such as a KrF- or ArF-laser, or a molecular fluorine (F2) laser, particularly for photolithography applications, has a gas mixture including a trace amount of a gas additive. The concentration of the gas additive in the gas mixture is optimized for improving energy stability and/or the overshoot control of the laser output beam. The concentration is further determined and adjusted at new fills and/or during laser operation based on its effect on the output pulse energy in view of constraints and/or aging on the discharge circuit and/or other components of the laser system. Attenuation control is also provided for increasing the lifetimes of components of the laser system by controlling the concentration of the gas additive over time. A specific preferred concentration of xenon is more than 100 ppm for improving the energy stability and/or overshoot control. The laser system may be equipped with an internal gas supply unit including an internal xenon gas supply, or a xenon generator for supplying xenon gas from condensed matter xenon.