Gas-assisted focused electron beam and ion beam processing and fabrication

TLDR

Electron and ion beams, routinely focused to nanometer scales, enable direct nanofabrication by adding or removing material through precursor gases, sputtering, or implantation, and are applied in mask repair, circuit restructuring, and sample sectioning, yet the atomic‑level mechanisms of precursor activation remain poorly understood and process resolutions often exceed beam diameters. The study reviews the state of the art in direct ion and electron beam fabrication, discusses research and demonstration structures, and highlights unsolved problems, contrasting this direct approach with indirect lithography. The authors conduct a comprehensive review of direct ion and electron beam fabrication techniques, assessing current understanding and identifying remaining challenges.

Abstract

Beams of electrons and ions are now fairly routinely focused to dimensions in the nanometer range. Since the beams can be used to locally alter material at the point where they are incident on a surface, they represent direct nanofabrication tools. The authors will focus here on direct fabrication rather than lithography, which is indirect in that it uses the intermediary of resist. In the case of both ions and electrons, material addition or removal can be achieved using precursor gases. In addition ions can also alter material by sputtering (milling), by damage, or by implantation. Many material removal and deposition processes employing precursor gases have been developed for numerous practical applications, such as mask repair, circuit restructuring and repair, and sample sectioning. The authors will also discuss structures that are made for research purposes or for demonstration of the processing capabilities. In many cases the minimum dimensions at which these processes can be realized are considerably larger than the beam diameters. The atomic level mechanisms responsible for the precursor gas activation have not been studied in detail in many cases. The authors will review the state of the art and level of understanding of direct ion and electron beam fabrication and point out some of the unsolved problems.