Nanoscale patterns made by using a 13.5-nm Schwarzschild objective and a laser produced plasma source

Abstract

Lithium fluoride (LiF) crystal is a very promising candidate as nanometer resolution EUV and soft X-ray detector. Compared with other EUV and soft X-ray detectors, charge coupled device and photographic films, LiF crystal has high resolution, large field of view and wide dynamic range. In this paper, using LiF crystal as EUV detector and a Schwarzschild objective (SO) working at 13.5nm as projection optics, mesh images with 4.2 μm, 1.2 μm and 800 nm line width and pinhole patterns with ~1.5μm diameter are acquired in projection imaging mode and direct writing mode, respectively. Fluorescence intensity profiles of images show that the resolution of mesh image is 900 nm, and the one of pinhole image is 800 nm. In the experiments, a spherical condense mirror based on normal incidence type is used to eliminate the damage and contamination on the masks (mesh and pinhole) caused by the laser plasma, and the energy density is not decreased compared with that the masks are close to the plasma. The development of the SO, the alignment of the objective and the imaging experiments are also reported.