Interference lithography by a soft x-ray laser beam: Nanopatterning on photoresists

We have studied the feasibility of high-resolution laser interference lithography using a tabletop $46.9nm$⁠, $1.5ns$ Ar laser, combined with two different optical configurations based on a Lloyd’s mirror interferometer. Using one of these schemes we have encoded periodic grating structures with a half pitch of $42nm$ and a vertical modulation of $5nm$ on a commercial PMMA photoresist. Experiments performed with larger half-pitch structures and detailed theoretical calculations demonstrate the potentiality of producing periodic structures with a half-pitch resolution down to $20nm$ and a height of up to $60nm$⁠. The results can be of considerable interest for the development of a complete high-resolution lithographic process operating with the $47nm$ laser wavelength.