Negative Tone Imaging (NTI) with KrF: Extension of 248nm IIP Lithography to under sub-20nm Logic Device

One of the most prospective alternative lithography ways prior to EUV implementation is the reverse imaging by means of a negative tone development (NTD) process with solvent-based developer. Contact and trench patterns can be printed in CAR (Chemically amplified resist) using a bright field mask through NTD development, and can give much better image contrast (NILS) than PTD process. Not only for contact or trench masks, but also pattering of IIP (Ion Implantation) layers whose mask opening ratio is less than 20% may get the benefit of NTD process, not only in the point of aerial imaging, but also in achievement of vertical resist profile, especially for post gate layers which have complex sub_topologies and nitride substrate. In this paper, we present applications for the NTD technique to IIP (Ion Implantation) layer lithography patterning, via KrF exposure, comparing the performance to that of the PTD process. Especially, to extend 248nm IIP litho to sub-20nm logic device, optimization of negative tone imaging (NTI) with KrF exposure is the main focus in this paper. With the special resin system designed for KrF NTD process, even sub 100nm half-pitch trench pattern can be defined with enough process margin and vertical resist profiles can be also obtained on the nitride substrate with KrF exposure.