High resolution radially symmetric nanostructures from simultaneous electron beam induced etching and deposition

Abstract

Electron beam induced etching (EBIE) and deposition (EBID) are promising fabrication techniques in which an electron beam is used to dissociate surface-adsorbed precursor molecules to achieve etching or deposition. Spatial resolution is normally limited by the electron flux distribution at the substrate surface. Here we present simultaneous EBIE and EBID (EBIED) as a method for surpassing this resolution limit by using adsorbate depletion to induce etching and deposition in adjacent regions within the electron flux profile. Our simulation results indicate the possibility of growth control of radially symmetric nanostructures at the sub-1 nm length scale on bulk substrates. The technique is well suited to the fabrication of ring-shaped nanostructures such as those employed in plasmonics, sensing devices, magneto-optics and magnetoelectronics.

Advances in gas-mediated electron beam-induced etching and related material processing techniques

“…It can limit the etch rate, and can give rise to complex dependencies of etch rate on electron flux [58]. -EBIE performed using a precursor gas mixture comprised of an etch precursor and a deposition precursor [16,54]. Mixtures are implemented by setting up a differential equation for each molecular species making up the gas, and can be used to simulate the resulting dependencies of the etch (and deposition) rate on electron flux.…”

“…Mixtures play a role in EBIE when residual contaminants such as hydrocarbons are present in the vacuum chamber and give rise to unintended EBID that competes with etching [18,29,16]. Mixtures can also be used to intentionally modify and control reaction kinetics, and hence control the morphology [54] or composition [59-61, 53, 62-66, 49, 67] of nanostructures fabricated by electron beam fabrication techniques. -The potential well and energy barrier associated with activated chemisorption [68], a type of adsorption in which a gas molecule overcomes an energy barrier and forms a chemical bond with a surface ( Fig.…”

“…The above continuum models of EBIE [16,23,54,55,58,69] and analogous (continuum and Monte Carlo) models of EBID have been used to simulate the timeevolution of the geometries (and in some cases the composition [53]) of structures fabricated by these techniques. The key limitations of existing models are that: (i) the model input parameters are often not known for precursor-substrate combinations of interest, (ii) changes in sample geometry caused by EBIE (or EBID) and their consequences for the electron flux profile, f (x, y), have not been modeled realistically over large areas and for long processing times, and (iii) all of the individual effects listed above have thus far been studied in isolation, and are yet to be consolidated into a generic, predictive model of etching and deposition.…”

Lateral resolution in focused electron beam-induced deposition: scaling laws for pulsed and static exposure

“…A transition between simultaneous etching and deposition of the contamination deposit was discussed in [20]. The continuum model, which explains this effect including two types of adsorbates species-one etching and another one forming a deposit-was developed in [21]. Simultaneous co-adsorption of two precursor gases for deposition without taking surface diffusion into account was studied in [22,23].…”

“…8 with the values derived from the numerical solution of Eq. 1B, which has been solved using pdepe MATLAB Ò solver 1 for onedimensional initial-boundary differential system and using logarithmic transformation of the spatial variable l ¼ ln " r ð Þ, which allows accounting for the adsorbates that are diffusing over long distance far from the irradiated area [21].…”