Mapping of local argon impingement on a virtual surface: an insight for gas injection during FEBID

Abstract

During the last decades, focused electron beam induced deposition (FEBID) has become a successful approach for direct-write fabrication of nanodevices. Such a deposition technique relies on the precursor supply to the sample surface which is typically accomplished by a gas injection system using a tube-shaped injector nozzle. This precursor injection strategy implies a position-dependent concentration gradient on the surface, which affects the geometry and chemistry of the final nanodeposit. Although simulations already proposed the local distribution of nozzle-borne gas molecules impinging on the surface, this isolated step in the FEBID process has never been experimentally measured yet. This work experimentally investigates the local distribution of impinging gas molecules on the sample plane, isolating the direct impingement component from surface diffusion or precursor depletion by deposition. The experimental setup used in this work maps and quantifies the local impinging rate of argon gas over the sample plane. This setup simulates the identical conditions for a precursor molecule during FEBID. Argon gas was locally collected with a sniffer tube, which is directly connected to a residual gas analyzer for quantification. The measured distribution of impinging gas molecules showed a strong position dependence. Indeed, a 300-lm shift of the deposition area to a position further away from the impingement center spot resulted in a 50 % decrease in the precursor impinging rate on the surface area. With the same parameters, the precursor distribution was also simulated by a Monte Carlo software by Friedli and Utke and showed a good correlation between the empirical and the simulated precursor distribution. The results hereby presented underline the importance of controlling the local precursor flux conditions in order to obtain reproducible and comparable deposition results in FEBID.

Continuum models of focused electron beam induced processing

“…By default it maps the impingement distribution on planar substrates, the molecule flux along the tube, and the angular nozzle effusion distribution. The code was validated by capillary injection experiments for both flow regimes [ 31 – 32 ].…”

“…The capillary entry distribution is implemented as a cosine point source. The implementation of these angular distributions of wall and molecule collisions was shown to be correct by independent experiments [ 31 – 32 ].…”

Chlorine based focused electron beam induced etching: A novel way to pattern germanium

“…While hydrocarbon contamination in former times originated from oil diffusion pumps, the source of residual hydrocarbons in oil-free pumping systems is widely unclear [18] and can only be avoided by oxidative cleaning procedures [11], in an oxygen atmosphere [19] or in UHV systems [20]. With hydrocarbon levels being below the threshold limit of surface analysis techniques [21][22], only the solid deposits could be analyzed and composition varied around 90 at.% C and 10 at.% O [18].…”

Analysis of carbon content in direct-write plasmonic Au structures by nanomechanical scanning absorption microscopy

“…Focused electron beam induced deposition (FEBID) is such a direct-write approach that allows for a mask-free and resist-free deposition of plasmonic nanostructures. [11][12][13][14][15][16][17] In FEBID volatile precursor molecules of the desired material are injected into a scanning electron microscope through a gas injection system (GIS) and are locally deposited by the impinging electron beam.…”