Fabrication of ultra-short T gates by a two-step electron beam lithography process

Abstract

This paper proposes a two-step electron beam lithography process, i.e., exposing feet and heads in two separate steps for ultra-short T gates, using a PMMA/UNIII resist stack separated by a thin lift off resist (LOR) layer. Results from both experiments and Monte Carlo simulations show that the two-step lithography process has advantages over the traditional one-step process of being able to pattern shorter feet with a much thicker top layer. The optimum thickness of the LOR for patterning T shape profiles in the PMMA/UVIII resist stack has been found to be about 20 nm.