Estimation of the Lyman-α line intensity in a lithium-based discharge-produced plasma source

Abstract

Extreme ultraviolet (EUV) discharge-based lamps for EUV lithography need to generate extremely high power in the narrow spectrum band of 13.5±0.135 nm. A simplified time-dependent collisional-radiative model and radiative transfer solution were utilized to investigate the wavelength-integrated Lyman-α line light outputs in a hydrogen-like lithium ion. The study reveals in particular that a steady-state or magnetically confined lithium plasma radiates in the desired spectrum band not less than 1 kW in 2π sr even at an ion density region as low as 1017 cm−3.

Pressure Broadening of Lyman‐Lines in Dense Li2+ Plasmas

“…For a recent description of a lithium-based discharge-produced plasma source, see Ref. [9]. Besides lithium, tin is studied as a possible candidate [5,10], but its use requires more sophisticated debris control.…”

Counter-facing plasma guns for efficient extreme ultra-violet plasma light source

“…In addition, we adopted lithium as the plasma source which has a narrow and strong spectrum at 13.5 nm wavelength [2]. By using the counter-facing plasma focus system and lithium source, we aim to improve the energy conversion efficiency, spectral efficiency and repetition capability [3,4]. Figure 1 shows the operating principle of the counter-facing plasma guns.…”

Analysis of atomic and ion debris features of laser-produced Sn and Li plasmas

“…3 and 4͒ and discharge-produced plasmas ͑DPP͒. [3][4][5][6][7] LPPs have several advantages over DPPs, such as power scalability, minimal heat loads, and a larger angle of collection. 4 Much research has been conducted on generating LPPs from a number of different target materials, including Sn, 8,9 Xe, 10 and Li.…”

“…4 Much research has been conducted on generating LPPs from a number of different target materials, including Sn, 8,9 Xe, 10 and Li. 6,11 The essential requirements of a LPP source for EUVL are a high conversion efficiency ͑CE; conversion from laser energy to 13.5 nm with 2% bandwidth͒ with minimum debris generation. Among the targets analyzed, Li and Sn provided highest CE from laser energy to 13.5 nm radiation.…”