Unmasking the resolution$-$throughput tradespace of focused-ion-beam machining

TL;DR

This paper investigates the resolution and throughput trade-offs in focused-ion-beam nanofabrication using a sacrificial mask, demonstrating super-resolution effects and significant throughput improvements through experimental and theoretical analysis.

Contribution

It provides the first comprehensive study of the resolution-throughput tradespace in FIB machining, introducing a new engineering framework for mask-based super-resolution fabrication.

Findings

Achieved super-resolution factors up to 6 ± 2.

Improved volume throughput by at least 42 ± 2 times.

Applied the tradespace to increase Fresnel lens throughput by 75 times.

Abstract

Focused-ion-beam machining is a powerful process to fabricate complex nanostructures, often through a sacrificial mask that enables milling beyond the resolution limit of the ion beam. However, current understanding of this super-resolution effect is empirical in the spatial domain and nonexistent in the temporal domain. This article reports the primary study of this fundamental tradespace of resolution and throughput. Chromia functions well as a masking material due to its smooth, uniform, and amorphous structure. An efficient method of in-line metrology enables characterization of ion-beam focus by scanning electron microscopy. Fabrication and characterization of complex test-structures through chromia and into silica probe the response of the bilayer to a focused beam of gallium cations, demonstrating super-resolution factors of up to 6 $\pm$ 2 and improvements to volume throughput of at least factors of 42 $\pm$ 2, with uncertainties denoting 95 % coverage intervals. Tractable theory models the essential aspects of the super-resolution effect for various nanostructures. Application of the new tradespace increases the volume throughput of machining Fresnel lenses by a factor of 75, which we introduce as projection standards for optical microscopy. These results enable paradigm shifts of sacrificial masking from empirical to engineering design, and from prototyping to manufacturing.