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In order to establish economic coating technologies for mass-produced materials, the widely used, microwave plasma-enhanced (PE) CVD technology has been extended to atmospheric pressure operation. Microwave plasma activation substantially widens the range of potential applications compared to conventional atmospheric CVD, because it is capable of processing temperaturesensitive substrates. A cylinder-type microwave cavity was scaled-up to different working diameters. The half-meter range has already been achieved, and further scale-up potential can be demonstrated. The microwave source offers access to a spatially extended, homogeneous, stable, non-thermal plasma, even in the downstream region. A range of gases can be used for plasma excitation, and the emanating plasma is clean because there is negligible wall interaction. Fluid dynamics modeling was used as a tool for both reactor design and process optimization. In-situ process characterization was provided by spectroscopic methods (optical emission spectra (OES), Fourier-transform infrared (FTIR)) and a range of atomic and molecular intermediates, precursor fragments, and reaction products were identified. A deep precursor fragmentation occurs in the remote plasma region leading to inorganic layer materials. Silica layers were deposited on stainless steel and glass. Deposition rates were in the range 15±100 nm s ±1 (static) and 0.3±2.0 nm m s ±1 (dynamic). Layer properties were determined by spectroscopic ellipsometry and FTIR reflectance spectroscopy, elastic recoil detection analysis (ERDA), and nano-indentation. The optical properties and the network structure of the silica layers on both substrates are close to bulk silica.

A new type of DC-powered plasma source (LARGE) was developed and evaluated for continuous plasma-enhanced (PE) CVD under atmospheric pressure. The linear extended emanating plasma sheet was scaled-up to various working widths with the result that a half meter range has already been achieved. A CVD reactor was designed for continuous deposition of non-oxide materials. The reactor operates in a remote atmospheric pressure (AP) PECVD configuration with typical deposition rates of 5±50 nm s ±1 (static) and 0.1±1.0 nm m s ±1 (dynamic).The potential application range of the ArcJet-CVD technology was evaluated by screening studies with various substrates, (stainless steel, glass, silicon wafers) and coating materials (silica, carbon, silicon nitride). In-situ process characterization has been provided by both optical emission and Fourier transform infrared (FTIR) spectroscopy. A range of atomic and molecular intermediates, precursor fragments, and reaction products were identified, leading to the conclusion that a complete conversion of the element-organic precursors into an inorganic layer takes place.

The present paper is focused on coating technologies compatible with industrial requirements, particularly on atmospheric pressure plasma technologies which are compatible with scaling to wide substrate widths (≥0.5 m). The AP‐PECVD reactors are designed for continuous air‐to‐air processing, and can be used for deposition of non‐oxide films. Two thermal methods for atmospheric pressure processing are considered: microwave CVD and DC ArcJet‐CVD. Typical thin film growth rates for PECVD are in the range of 5–100 nm · s−1 (static) and up to 2 nm · m · s−1 (dynamic). The rates for plasma chemical etching are typically 10 times higher. A complimentary lower energy plasma source based on dielectric barrier glow discharge plasma CVD has also been explored. Developments are underway to explore uses for the coating technology, for example scratch resistant coatings on metals, barrier layers, self‐clean functional surfaces and antireflective coatings. Coating materials range from silica, titania, aluminium oxide, metal composite layers, carbon and silicon nitride. Layer properties are close to data known from low pressure PECVD. Plasma chemical etching has been developed for crystalline silicon photovoltaics. The surface textures strongly change with the precursors and the plasma parameters used.magnified image

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