Vapor etching of ion tracks in fused silica

Abstract

We have used vapor etching of ion tracks to create high aspect ratio (i.e., length much greater than diameter), isolated cylindrical holes through ∼600-nm-thick films of thermally fused silica on silicon. Samples were exposed to the vapor from water-based liquids with various HF and HF+HCl concentrations. Independent control of the temperatures of the vapor and the samples provided the means to vary separately the etching rates for the tracks and the track-free material. The very rapid etching of the small latent track zone can be explained by preferential capillary condensation. Holes with diameters of ∼24 to ∼80 nm have been documented with length/diameter ratios of up to 22. Although we have restricted this study to thin-film silica, we have evidence that such holes are also formed in bulk fused silica.

Versatile ultrathin nanoporous silicon nitride membranes

“…The ITE technique allows for fabrication of thin membranes not only in SiN but also in other inorganic materials, for example, SiO 2 (43). Tuning the etching conditions is expected to result in other pore geometries (e.g., cylindrical, cigar-shaped, etc.).…”

Nanoporous SiO2/Si thin layers produced by ion track etching: Dependence on the ion energy and criterion for etchability

“…For higher energy losses, the half cone angle stabilizes around 18°-20°, typical for tracks of high-energy heavy ions in SiO 2 . 18 The constancy of the cone angles and the low level of size dispersion of the pores ͑Fig. 4͒ suggest that a continuous trail of critical damage along the ion track is only reached for S e Ͼ 4 keV/ nm.…”

“…17 Ion track etching is most commonly investigated using beams of heavy ions at high velocities ͑ϳ1 MeV/ u or larger͒, 1-3 available only at a few large irradiation facilities around the world. Recently, the prospects of ion track etching with low energy beams ͑0.1 MeV/u or lower͒, available at standard medium-energy ion implanters, 5,6,[17][18][19] have also been investigated. This energy regime is suitable for the application of ion tracks in the nanostructuring of thin films and particularly in systems like SiO 2 / Si and other thin layers useful for microelectronic devices.…”

Nanopattern transfer to SiO2 by ion track lithography and highly selective HF vapor etching

“…22 Also, the noncontinuity requires a need for high fluencies to produce a continuous volume of overlapping defects. 6 The wet etching result of an etching selectivity of 1.9 between the irradiated volume and the unirradiated bulk in the TEM samples is very similar to those of wet etched continuous ion tracks, 16,23,24 implying a continuous volume of overlapping defects. Also, the columnar sidewall of Fig.…”

“…14,15 In addition, it has been used to selectively etch individual latent tracks in fused silica. 16 In contrast to that work, we use the technique to thermally oxidized thin film amorphous SiO 2 and, moreover, etched irradiated volumes of overlapping noncontinuous latent tracks.…”