Atmospheric-pressure PECVD coating and plasma chemical etching for continuous processing

Plasma processing at atmospheric pressure (APPlasmas) has attractions for both economic and technological reasons. Potential costs-saving factors are associated with online-processing capability and increase throughput due to high deposition rates. Capital cost savings for both equipment and line space (foot print), and relative ease of integration, are further benefits in comparison to low-pressure-technology approaches. Three types of APPlasmas are considered for coating: microwave chemical vapor deposition (CVD), dc ArcJet-CVD based on a linearly extended plasma source, and dielectric barrier glow discharge plasma CVD. Spectroscopic plasma characterization has shown that high fluxes of activated species are available in the plasma downstream region and can be used for deep fragmentation of even stable molecules. After precursor injection, a range of atomic and molecular intermediates, precursor fragments, and reaction products were identified leading to a conclusion that a complete conversion of the element-organic precursors into an inorganic materials take place. Alternatively, the dc ArcJet source is used for plasma chemical etching. All AP-plasma-enhanced chemical vapor deposition (PECVD), reactors are designed for continuous air-to-air processing on flat or slightly shaped substrates and allow deposition of nonoxide films. Reactor design is supported by fluid-dynamic modeling. Typical thin-film growth rates for PECVD are in the range of 5-100 nm/s (static) and up to 2 nm*m/s (dynamic). The rates for plasma chemical etching are typically ten times higher. Plasma activation substantially widens the range of potential applications, e.g., coating on steel, lightweight metals, preshaped glass, and plastics. Developments are underway to explore the use of the coating technologies in areas such as scratch-resistant coatings on metals, barrier layers, self-clean coatings, biocidal functional surfaces, and antireflective coatings. The coating materials range explored, so far, includes: silica, titania, carbon, silicon nitride/carbide, and metal oxides.