Temporal and spatial characteristics of a 13.6 nm EUV light source

Abstract

Spatial and temporal characteristics of a table-top scale laser produced plasma formed on the surface of a tungsten target are reported. The emitted radiation was spectrally filtered to a narrow band of ca. 1 nm full width half maximum (FWHM) centred on a wavelength of 13.6 nm using a combination of Zr thin film transmission filters and a Mo-Si multilayer mirror (MLM). The temporal profile of the 13.6 nm flux was measured for different laser fluences while the spatial profile of the emission was sampled in one region using a back illuminated charge coupled device (CCD), both done with the aid of a flat MLM. The emitting plasma was imaged at 13.6 nm by replacing the flat MLM with a curved mirror which returned an extreme ultraviolet (EUV) source size of up to ca. 130 µms. The peak flux was estimated to be ca. 1014 photons nm−1 sr−1. For comparison purposes the W target was replaced by a solid Sn target which produced, on average, almost double the EUV flux at 13.6 nm, albeit with greater shot to shot jitter.