High resolution spin-on electron beam lithography resist with exceptional dry etching resistance

Presently, no resist material has suitable properties to satisfy simultaneously all requirements on lateral resolution and plasma etching resistance for pattern transfer of high aspect ratio nano-structures. Herein, a recent innovative alumina spin-on material for use as both positive and negative high resolution resist for electron beam lithography (EBL) is presented. This system turns into an almost completely inorganic alumina system when exposed to the electron beam, showing exceptional selectivity (100:1), compared to even the most robust polymeric resist, when used as mask for dry etching of silicon in fluorinated plasmas, obviating the need for a hardmask layer deposition. A full characterization of the resist selective removal under different processing conditions, such as electrons acceleration voltage and post-exposure bake temperature and time, is presented. Owing to the high selectivity and high resolution, silicon nano-structures of size down to 11 nm and high aspect ratio (up to 20) have been obtained for the first time in a one-step process.