DEVELOPMENT AND OPTIMIZATION OF HIGH BRIGHTNESS NANO-APERTURE ION SOURCE FOR PROTON BEAM WRITING APPLICATIONS

Abstract

Proton beam writing (PBW) is a direct-write lithographic technique employing focused protons, for fabricating three-dimensional nano-structures. Currently, the performance of PBW is limited by low brightness ~20 A/(m2srV) of the radio frequency ion source. Nano-aperture ion source (NAIS) is a potential candidate for a sub-10 nm proton beam writing (PBW) system. Simulation was conducted and predicted that a brightness of > 106 A/(m2srV) can be delivered by NAIS. Prototype and modified sources were designed and successively micro-fabricated. The reduced brightness was obtained to be ~104 A/(m2srV) for an Ar+ beam. For further improving the performance of NAIS, the new NAIS design to avoid bulge of ionization chamber was evaluated and simulated. Equipping with the NAIS, a low energy proton microscope was proposed and examined. A compact PBW system was designed and examined, with the ability to achieve sub-10 nm resolution with comparable writing speed to electron beam lithography.