This paper focuses on the understanding of the main mechanisms that participate in the growth process of an SiO2‐like film in an atmospheric pressure Townsend discharge in N2 with small ad‐mixtures of HMDSO and N2O. The approach consists of analyzing the influence of operating parameters on the growth rate profile through a fluid dynamics model. The suggested chemical mechanism is constituted by one volume reaction and one surface reaction. This simple model enables us to assume which phenomena control the film growth process among the following mechanisms: HMDSO dissociation by N2(A3Σ) in Si‐containing radicals, radicals transport to the surface, and surface activation process by plasma.magnified image

The aim of this paper is to improve the understanding of the mechanisms controlling the uniformity of thin films made by atmospheric pressure plasma enhanced chemical vapour deposition (AP-PECVD). To reach this goal, the influence of the gas flow-rate and injection design on the thin film thickness uniformity is studied through experiments and numerical simulation in the case of silica-like layers deposited from silane and nitrous oxide using a nitrogen Townsend dielectric barrier discharge. Results show that whatever the gas flow-rate, when the gas is injected uniformly parallel to the substrate, the obtained layer is always uniform along the substrate width, while when the gas is injected perpendicularly to the substrate, the width-uniformity of the layers decreases when the gas flow-rate increases. The layer non-uniformity is related to the penetration of gas recirculation into the discharge zone, which was confirmed by computational fluid dynamics. This link is corroborated experimentally by a clear improvement of the deposit uniformity when the discharge cell dimensions are modified in order to reduce the recirculation influence on the discharge. A plausible hypothesis for the layer uniformity dependence on the recirculation is the possible enhancement of powder formation and growth in the recirculation zone: when the particle size is large enough, electrons may attach on the powder inducing electron depletion at the origin of the discharge instabilities.

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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.