CO 2 laser-produced Sn plasma as the solution for high-volume manufacturing EUV lithography

Abstract

We are developing a laser produced plasma light source for high volume manufacturing (HVM) EUV lithography. The light source is based on a short pulse, high power, high repetition rate CO₂ master oscillator power amplifier (MOPA) laser system and a Tin droplet target. A maximum conversion efficiency of 4.5% was measured for a CO₂ laser driven Sn plasma having a narrow spectrum at 13.5 nm. In addition, low debris generation was observed. The CO₂ MOPA laser system is based on commercial high power cw CO₂ lasers. We have achieved an average laser power of 7 kW at 100 kHz by a single laser beam with good beam quality. In a first step, a 50-W light source is under development. Based on a 10-kW CO₂ laser, this light source is scalable to more than 100 W EUV in-band power.