Generation and characterization of spatially distributed laser produced plasma extreme ultraviolet source

Two and three dot laser produced plasma extreme ultraviolet sources have been generated using a Fourier diffractive optical element (DOE). The DOE featured a >90% diffraction efficiency and a power handling capability of >100 MW. The plasmas were formed on a planar bulk tin target by pulses from a Nd:YAG laser delivering up to 360 mJ per pulse in a time of 15 ns (full-width half-maximum intensity) at the fundamental wavelength of 1064 nm. After passing through the DOE, the laser beam was focused onto the target by a pair of lens. The resulting spot radius was estimated to be 8.2±0.2 μm 1/e ² on the target. The extreme ultraviolet radiation emitted by the plasma was imaged using a 122 μm imaging slit in conjunction with the 38 μm slit of the spectrometer. The one dimensional image of the laser produced plasma extreme ultraviolet source, together with its spectrum, was recorded by an absolutely calibrated Jenoptic 0.25 m EUV spectrograph. The spectrograph was located at an observation angle of 45 degrees with respect to the target. The vacuum chamber and spectrograph were both maintained at a base pressure of 10^-6 Torr. The recorded 1D spatial distribution and EUV spectra demonstrate the feasibility of EUV patterning by the novel optical method. The characteristics and potential applications of this method are investigated in this paper.