Simulation of field emission from volcano-gated tips for scanning probe lithography

Abstract

Throughput and resolution in serial lithographic methods are naturally two competing goals - improving one leads to a deterioration of the other. This is also valid for field emission based scanning probe lithography FE-SPL), wherein low-energetic electrons (<100eV) are applied for direct exposure of ultra-thin resist films (<20nm). In this work a novel variable beam spot size concept for FE-SPL based on volcano-gated nanoprobes is shown. Here, a ring electrode surrounding the FE-SPL nanotip is working as an electrostatic lens. As a result the Fowler-Nordheim field emitted electron beam becomes focusable and defocusable in order to enhance the resolution or the throughput capability, respectively. In this paper the basic concept is demonstrated and proven by simulation of the electric field, the electron trajectories and the electron current density distribution on the sample surface. Based on simulations, the underlying physical effects are revealed and pathways for optimization of the volcano-type gated probe design and lithographic operation parameters are given.