kW-class picosecond thin-disc prepulse laser Perla for efficient EUV generation

Abstract

, "kW-class picosecond thin-disc prepulse laser Perla for efficient EUV generation," J. Micro/Nanolith. MEMS MOEMS 16(4), 041011 (2017), doi: 10.1117/1.JMM.16.4.041011. Abstract. The technology for extreme ultraviolet (EUV) lithography sources is maturing. Laser produced plasma (LPP) sources with usable power >100 W have been used in high-volume manufacturing (HVM) applications, and 250-W sources are expected to be introduced in HVM soon. However, a further increase of power and cleanness may benefit a powerful picosecond (ps) laser in the near-infrared and wavelength converted spectral region. The HiLASE Centre has been working in thin-disc laser technology and has demonstrated a 0.5-kW platform Perla-C based on a very compact Yb:YAG regenerative amplifier. 100-kHz ps operation has been achieved with a fundamental spatial mode and excellent long-term pointing and energy stability. It is reported on a thin-disc-based ps Yb:YAG solid-state laser technology platform Perla developed in the Czech Republic and the present performance of delivering >4 mJ, <2-ps pulses at a 100-kHz repetition rate with the potential to be upgraded to 1 kW of average power and 1-MHz pulse repetition rate. The ps laser extendibility is important for kW-class LPP sources and controlled free electron laser EUV sources in 10-kW power region. © The Authors.Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. IntroductionExtreme ultraviolet (EUV) lithography is taking off from a long technology development phase to high-volume manufacturing (HVM) in major semiconductor companies. Laser produced plasma (LPP) is the selected method for the required 13.5-nm source for its advantages of scalable output power, narrow spectrum, small source size, and cleanness. The source technology is already fairly advanced in each component level for a 250-W power supply. The next step for extension to the finer line width as a 3-nm node and beyond is based on a high NA imaging system, which requires a further increase of EUV source power to the kW level. A conceptual study based on the present LPP technology on a possible path to the realization of a kW 13.5-nm tin EUV source was reported. 1 There are several key technologies in the LPP source for high average power, and conditioning of the injected micro tin droplet into the mist target is critical for realizing higher conversion efficiency (CE) of up to 6% and full ionization for efficient exhaust in a magnetic field. It was experimentally demonstrated that the resulting mist shape is dependent on the initial laser pulses, and a picosecond (ps) laser can produce a lower density mist distribution rather than nanosecond (ns) pulses. The background physics of this phenomenon is under intensive physical and experimental study.2,3 The typical repetition rate of the droplet generation is 100 kHz, and a further increase is necessary to kW generation due to t...

Balancing the conversion efficiency and beam quality of second harmonic generation of a two-picosecond Yb:YAG thin-disk laser

“…They serve as essential tools in laser material processing, such as the fabrication of functional surfaces [2], but are also valued in the scientific community for e.g. laser-produced plasma extreme ultraviolet sources [3].…”