Plasma x-ray source for lithography generated by a ≊30 J, 30 ns KrF laser

Abstract

A plasma x-ray source for lithography is generated by focusing ≊30 J, 30 ns KrF laser pulses onto Cu targets at irradiances up to 2×1014 W/cm2. Energy conversion efficiency from 249 nm laser light to x rays at 1.0 keV≤hν≤1.4 keV is measured as a function of target irradiance and the maximum efficiency is ≊2.5%. The full width half-maximum duration of the plasma x-ray pulse is ≊5 ns which corresponds to a peak power x-ray conversion efficiency ≊7.5%.