Recent results on the development of extreme ultraviolet sources for lithography and metrology at 6.x nm

Abstract

Recent increases in reflectance at 6.x nm of La/B4C multilayer mirrors has led to the adoption of this wavelength for the development of future sources for lithography. The emission from laser produced plasmas of Gd and Tb emit strongly in this wavelength region. The transitions responsible and the optimum plasma conditions for optimum emission have been identified both theoretically and experimentally.