A low magnification focused ion beam system with 8 nm spot size

Abstract

A 50 keV Ga+ beam has been focused to a spot diameter of 8 nm (full width at half-maximum) in our two-lens microprobe system by reducing the contributions of both chromatic aberration and the virtual ion source size to the final image size. Features as small as 6 to 8 nm were distinctly visible in scanning ion images. To our knowledge, this is the smallest focused beam of ions produced to date. The limiting resolution in 30-nm thick films of poly(methylmethacrylate) exposed with this beam was approximately 8 to 10 nm. Effects such as ion scattering, atomic recoil, and statistical dose fluctuations during exposure are believed to set inherent limits to the lithographic resolution.

Focused ion beam implantation of Ga in nanocrystalline diamond: Fluence-dependent retention and sputtering

“…Focused ion beams based on liquid-metal ion sources (LMIS) are also employed widely as primary sources for scanning-ion microscopy [10,11] and secondary-ion mass spectroscopy (SIMS) [12], in particular in time-of-flight SIMS instruments [13]. Because of the very high brightness (>10 6 A/cm 2 sr) and small virtual source size (<100 nm) [14,15] of LIMS, extremely high current densities (>1 A/cm 2 ) and small spot sizes ($10 nm) can be achieved using suitable electrostatic focusing columns.…”

Nanofabrication with a helium ion microscope

“…Despite the advantages of a higher sensitivity and lower proximity effects [15,16] compared to the electron beam approach, major disadvantages of the earlier FIBL work are a lower resolution due to a larger beam diameter and (certainly for Ga + ion exposure) potential damage or contamination from the ion impact or implantation [17]. Features of 12-15 nm line width in PMMA resist [18] and 30 nm dot size in polyphenylsilsesquioxane resist [19] have been reported with Ga + FIB. Typically, the smallest probe size of Ga + ion beams is nowadays around 5 nm and direct engraving in 20 nm thin membrane material yields nanopores down to 3 nm diameter [20].…”

Objective comparison of scanning ion and scanning electron microscope images

“…SIM images are in good use during the whole milling processes, that is, drawing of the milling area, milling monitoring, and confirmation of the final milling. The SIM image resolution has been improved, and 10 nm or better resolution is achievable at present (Ishitani et al 1996, Kubena et al 1991. Since both FIB milling and SIM observation are carried out in one FIB system, SIM observation is gradually replacing SEM observation, mostly for the FIB cross-sectioned samples.…”