High Repetition Rate Krf Laser Plasma X-Ray Source for Microlithography

As part of a development programme for a high-intensity laser-plasma X-ray source, experiments have been carried out using a high repetition rate excimer laser (up to 100 Hz; 249 nm, 300 mJ). Remedies are given to problems inherent to operating this type of source at high repetition rates. The combined remedies eliminate the target debris problem. X-ray mask structures down to 0.5-mu-m have been imaged. After implementation of tested upgrades, this source will enable exposures within ten seconds per stepfield.