Conformity of Silica-like Thin Films Deposited by Atmospheric Pressure Townsend Discharge and Transport Mechanisms

Abstract

In this paper, homogeneous and dense silicon-based coatings have been deposited from hexamethyldisiloxane (HMDSO: Si 2 O(CH 3 ) 6 ) on patterned silicium in a Townsend dielectric barrier discharge operating at atmospheric pressure. A brief description of the physical mechanisms ruling the step coverage is first described, followed by a description of the atmospheric pressure plasma process used. The step coverage is discussed with regard to the aspect ratio of the patterned wafers. Coatings deposited in and after the discharge region have also been characterized to understand the influence of plasma activation. In order to understand the experimental results, numerical simulations have been performed using a simplified reactive transport model. These results provide information and first general insight on the physical mechanisms ruling the conformity of silicon-based films deposited with this technique.Index Terms-Atmospheric pressure Townsend discharge (APTD), dielectric barrier discharge (DBD), glow discharges, plasma-enhanced chemical vapor deposition (PECVD), reactive transport modeling, silicon oxide, step coverage.

Hydrogenated Silicon Nitride SiNx:H Deposited by Dielectric Barrier Discharge for Photovoltaics

“…The higher is the pyramid the larger is the difference, which can be related to the high reactivity of SiH 4 radicals. In agreement with the literature, for pyramids smaller than 10 μm this effect is negligible …”

“…In agreement with the literature, for pyramids smaller than 10 mm this effect is negligible. [40] This is confirmed by optical microscope observations made on textured mc-Si wafers. As the chemical texturization is an anisotropic reaction which attacks distinctly different silicon crystallographic orientations, [31] the different grains of mc-Si samples show different morphological characteristics, namely different pyramid heights and shapes.…”

“…One possible way to improve coating conformity would be to increase substrate temperature, but a larger thermal cost has to be avoided for industrial applications. Another alternative is to reduce the reactivity of the radicals, for example using liquid precursors. Work is under progress to optimize this point.…”

Nebulization of Nanocolloidal Suspensions for the Growth of Nanocomposite Coatings in Dielectric Barrier Discharges

“…It can also be seen in Figure c that the thickness of the layer deposited on the top of the particle (350 nm) is larger than the one on the side (205 nm). This non‐conformity is often observed using atmospheric‐pressure PE‐CVD processes, and has been already studied in the case of SiO 2 coating deposited by Atmospheric Pressure Townsend Discharge . It has been attributed to the very low diffusion of radicals in the gas‐phase at atmospheric pressure.…”

Analysis of transport phenomena during plasma deposition of hydrophobic coatings on porous cellulosic substrates in plane‐to‐plane dielectric barrier discharges at atmospheric pressure

“…In fact, as the HMDSO is fragmented and its radicals are deposited, the concentration of the precursor in the plasma along the flow direction is expected to decrease. [23,51,52] However, such a trend was not observed on flat silicon wafers. Over the range of experimental conditions examined, the thickness of the plasma-deposited coatings estimated from spectroscopic ellipsometry was 195 ± 5 nm, with a fairly constant value between the entrance and the exit.…”