Creating nanohole arrays with the helium ion microscope

Abstract

Helium Ion Microscopy has been established as a powerful imaging technique offering unique contrast and high resolution surface information. More recently, the helium ion beam has been used for nanostructuring applications similar to a gallium focused ion beam. A key difference between helium and gallium induced sputtering is the less intense damage cascade which lends this technique to precise and controlled milling of different materials enabling applications. The helium ion beam has been used for drilling 5nm holes in a 100nm gold foil (20:1 aspect ratio) while the gallium beam sputtered holes of a similar aspect ratio seem to be limited to a 50nm hole size. This paper explores the drilling of nanopores in gold films and other materials and offers an explanation for the observed differences in results between helium and gallium ions.

Understanding the interaction between energetic ions and freestanding graphene towards practical 2D perforation

“…19 These secondary events occur in the vicinity of the incident ion spot called an interaction diameter of which reported values are around 20-30 nm. 47,48 For ion exposure of graphene in HIM we achieved even smaller feature sizes. Here again we could overcome the previously reported interaction diameter limit of 5 nm 47 and repeatedly patterned pore arrays into freestanding double layer graphene with mean diameter of 3.4 nm at 25-nm-wide spacing using 30-keV He + ions at 4.4×10 5 per pore (Figure 4b).…”

“…47,48 For ion exposure of graphene in HIM we achieved even smaller feature sizes. Here again we could overcome the previously reported interaction diameter limit of 5 nm 47 and repeatedly patterned pore arrays into freestanding double layer graphene with mean diameter of 3.4 nm at 25-nm-wide spacing using 30-keV He + ions at 4.4×10 5 per pore (Figure 4b). The effect of total ion dose on the pore size can be observed by exposing a freestanding monolayer graphene with 3.9×10 5 to 6.2×10 5 He + ions (Figure 4d).…”

Focused helium and neon ion beam induced etching for advanced extreme ultraviolet lithography mask repair

“…23,24 The enhanced resolution of the new gas field ion source (GFIS) microscope [25][26][27] compared to liquid gallium ion sources and the fact that the species are inert gases makes it an intriguing option to study for mask repair. Focused helium or neon ions [27][28][29] seem a logical choice for mask-repair applications because their low atomic mass will dissipate less of the ion energy through nuclear loss-most of it being lost to electronic interactions. 30 Recently, helium and neon focused ion beams have been shown to be capable of highresolution additive deposition and subtractive etching 31,32 that is superior to the gallium focused ion beam and in some cases with enhanced nanostructures, such as higher purity platinum nanowires, relative to electron beam induced deposition.…”

Review on Fabrication of Graphene Nanoholes

“…Helium and gallium ion milling methods of different materials are discussed in Ref. [32], and it was found that helium can drill small holes. The milling process was modeled using Stopping and Range of Ions in Matter (SRIM) software.…”