Exploring the foot-width limit of T-shaped gates using bilayer resist system RE650/UV5

Background: Fast advancing of microwave/terahertz communication constantly demands ultrashort T-shaped gates by innovative nanofabrication techniques. The emerging RE650 resist provides a promising alternative to existing resists owing to its outstanding performance in electron-beam (e-beam) lithography. Aim: To report the exploration of the minimum foot-width achievable by e-beam lithography on RE650/UV5 bilayer resists through both numerical simulation and experimental tests. Approach: Using Monte Carlo method, the spatial charge distributions by e-beam exposure in resists were calculated, followed by modeling the developing process using LAB software to obtain the lithography profiles in resists. By this way, the foot-width was compared for the RE650 thickness varying from 50 to 80 nm with various UV5 thickness fixed. Results: As narrow as 15-nm foot-width has been achieved, but 30-nm foot-width can be routinely replicated in a stable exposure latitude, indicating that the developed process for ultra short T-shaped gates is reliable. Conclusions: The bilayer of RE650/UV5 is capable of replicating 15-30-nm T-shape gates as the minimum width by e-beam lithography, which should give us high prospect for mass production of THz devices. (C) 2021 Society of Photo-Optical Instrumentation Engineers (SPIE)