Novel dry-developed focused ion beam lithography scheme for nanostructure applications

Abstract

Focused ion beam (FIB) lithography has certain advantages over the rival direct-write electron beam lithography in terms of resist sensitivity, scattering and proximity effects. Combining the FIB lithography with both top surface imaging (TSI) and reactive ion etching (RIE) will further strengthen its advantages towards anisotropic processing of thicker resist layers in comparison to those used by the conventional lithography processes. Some of the inherent limitations to the FIB lithography, such as low-penetration depth and substrate damage, could also be eliminated. Our recently developed NERIME (negative resist image by dry etching) process combines these advantages due to the incorporation of focused Ga + ion beam (Ga + FIB) exposure, near UV exposure, silylation and dry development process steps. The work described in this paper follows our investigations into the NERIME process for nanostructure applications and also outlines a simplified (two-step) process, which incorporates Ga + FIB exposure and oxygen dry development. The two-step NERIME process is a negative working TSI system for DNQ/novolak based resists. In this paper, nanometer resist patterns as small as 30 nm and having a high aspect ratio of up to 15 were resolved using the NERIME and the simplified two-step NERIME processes.