Ultraviolet surface plasmons on aluminium and a non-contact technique for characterizing short-pitch gratings

In this work we present grating-coupled surface plasmon characterization of aluminium in the ultraviolet. Light of wavelength 325 nm from a helium-cadmium laser was used to excite surface plasmon-polaritons both at a buried aluminium-silica interface and on oxidized aluminium. By fitting the angle-dependent reflectivity data to model grating theory, the optical permittivity of uncontaminated aluminium at 325 nm is deduced. These results are compared with those extrapolated from prism-coupled surface plasmon excitation in the visible. The further characterization of the oxidized aluminium allows optical non-contact profilometry to be performed on short-pitch gratings that are opaque or are comprised of materials with ill-defined optical properties. This profile characterization is demonstrated for a short-pitch grating manufactured in photoresist.