Review of current progress in nanometrology with the helium ion microscope

Abstract

Scanning electron microscopy has been employed as an imaging and measurement tool for more than 50 years and it continues as a primary tool in many research and manufacturing facilities across the world. A new challenger to this work is the helium ion microscope (HIM). The HIM is a new imaging and metrology technology. Essentially, substitution of the electron source with a helium ion source yields a tool visually similar in function to the scanning electron microscope, but very different in the fundamental imaging and measurement process. The imaged and measured signal originates differently than in the scanning electron microscope and that fact and its single atom source diameter may be able to push the obtainable resolution lower, provide greater depth-of-field and ultimately improve the metrology. Successful imaging and metrology with this instrument entails understanding and modeling of new ion beam/specimen interaction physics. As a new methodology, HIM is beginning to show promise and the abundance of potentially advantageous applications for nanometrology has yet to be fully exploited. This paper discusses some of the progress made at NIST in collaboration with IBM to understand the science behind this new technology.

Novel nanosample preparation with a helium ion microscope

“…The TRIM calculations are in good agreement with our experimental data and with previous studies 1,8 showing that at high enough dose, Si within ion propagation path becomes completely amorphous and small nanobubbles are formed in the amorphous region. Further implantation of He ions leads to a deformation of the amorphous surface layer and the formation of a balloon-like structure.…”

“…When compared with other ions, He ions have a particular sample interaction that generates a relatively high number of low-energy secondary electrons and a low yield of backscatter ions, which allows the remarkable imaging of a range of samples, including samples with high local specimen charging. 4,7,8 Being used for nanofabrication, HIM is reported to yield 4-nm-wide lines with a pitch of 10 nm as lithography tool. 9,10 Very narrow structures with almost no overspray can be made with the gas-induced deposition.…”

Development of the metrology and imaging of cellulose nanocrystals

“…The differences in the imaging between the SEM and the HIM are currently being explored. Some differences between the SEM and the HIM imaging are expected due to the secondary electron generation processes and subsequent images produced (see [35] in this issue). Figure 7 is a visual comparison between the three methods employed.…”

Review Article: Advanced nanoscale patterning and material synthesis with gas field helium and neon ion beams

“…1 Several reviews have extensively discussed the operation and inherent advantages of the GFIS source for generation of high resolution ion beams. [2][3][4][5] In short, a cryogenically cooled tungsten tip is sharpened by field evaporation until an atomically sharp apex is formed. When a high electrical bias is applied between the tip and an extraction electrode, a generated electric field is concentrated at the apex of the tip.…”