Characteristics of Extreme Ultraviolet Emission from CO₂ Laser-Produced Plasma

Abstract

In the development of extreme ultraviolet (EUV) lithography source using laser-produced plasma (LPP), it is important to investigate the optimum wavelength of the driver laser to obtain the high conversion efficiency. We have proposed the EUV generation pumped by CO₂ laser-produced plasma. In this article, we show the characteristics of EUV emission from gas and solid Xe irradiated by a TEA CO₂ laser. The conversion efficiency to 13.5 nm was ∼0.2 %. This value is comparable to those of Nd: YAG LPP with Xe in early works. In order to gain insight into the difference between the CO₂ LPP and Nd:YAG LPP, we investigated the emission characteristics from Nd: YAG LPP and CO₂ LPP with solid tin under the same experimental setup. As the results, we confirmed that the conversion efficiency of CO₂ LPP is comparable to that of Nd: YAG LPP. The conversion efficiency was estimated to be 2 % in maximum.