Characterization of optical depth for laser produced plasma extreme ultraviolet source

• Published in: Vacuum Vol. 231; p. 113805
• Main Authors: Wang, Tianze, Hu, Zhenlin, He, Liang, Lin, Nan, Leng, Yuxin, Chen, Weibiao
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2025
• Subjects: Conversion efficiency; Extreme ultraviolet lithography; Laser-produced plasmas; Optical depth; Solid-state laser; Extreme ultraviolet lithography; Laser-produced plasmas; Conversion efficiency; Optical depth; Solid-state laser
• ISSN: 0042-207X
• DOI: 10.1016/j.vacuum.2024.113805

This study investigates the emission mechanism of laser-produced plasma extreme ultraviolet source (LPP-EUV). In the experiment, the EUV radiation is generated by a 1064 nm laser interacting with slab Sn target. The EUV emission is characterized by EUV energy monitors and an EUV spectrometer. The dependency of CE on laser intensity and plasma relative optical depth is explored by a plasma emission-absorption layer model. The dependency is confirmed by an optical interferometry measurement of plasma electron density for the first time. Our work provides a method for characterizing and optimizing the optical depth of laser driven EUV source. •Demonstration of dependency of EUV emission on relative optical depth by angular EUV characterization combined with optical interferometry.•An EUV radiation transportation model containing optical depth as a parameter is proposed.•Angular relative optical depth by laser interferometry verified the EUV radiation transportation model.