Highly sensitive resist material for deep X-ray lithography

The present paper describes the first chemically amplified negative-tone resist for deep X-ray lithography (DXRL). The choice of the resist material for this new resist has been oriented on the experience of the photo, electron beam and X-ray lithography (XRL) for microelectronic applications. In this work a negative tone resist containing a novolak, a crosslinker and an acid generator was developed by variing the different components. It was found that only few components, which proved to be good in thin films, were suitable for DXRL. The new resist fulfills all technological requirements and shows an increased sensitivity by a factor 15 as compared to the standard resist material, poly(methyl methacrylate). This tremendous increase in sensitivity leads to a huge cost reduction of the DXRL process. Furthermore, an excellent adhesion of this new resist to metallic substrates has been achieved which allows to fabricate free standing columns with an aspect ratio of 80.