Atmospheric pressure pecvd coating and plasma chemical etching for continuous processing

Summary form only given. In recent years there has been increasing interest in APPlasma surface processing, however the potential of the technology to coat or etch surfaces offers further significant future potential. Plasma processing at atmospheric pressure (APPlasmas) has attractions for both economic and technological reasons. Potential cost saving factors are linked to on-line processing capability, which substantially reduce substrate handling cost, 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. Considering coating technologies compatible with industrial requirements three key challenging aspects will be treated: (i) availability of scalable wide area plasma sources having sufficient "robustness" for long-term continuous operation, (ii) APPlasma reactors being applicable for continuous air-to-air processing, and (iii) coating/etching processes being characterized by both high dynamic rates being compatible with the throughput requirements of the whole production line and high surface performance being compatible to specifications of homogeneity, structure, etc. At Fraunhofer IWS, currently two methods for atmospheric pressure processing are under development, microwave CVD and DC arcjet-CVD based on a linearly extended plasma source. All kinds of AP-PECVD reactors are designed for continuous air-to-air processing on flat or slightly shaped substrates. They comprise purged curtains for control of deposition atmosphere which allows deposition of non-oxide films. The reactors operate in a remote plasma mode being imperative for long term stability of the coater head. Supported by extensive fluid dynamic modeling a gas flow system has been designed which effectively balance out the three main factors being on influence on process performance: (i) throughput/high deposition rate, (ii) avoid/control powder formation, and (iii) avoid stray deposition or etch attack on reactor walls/plasma source. Typical rates for PECVD are in the range of 5-100 nm/s (static) and up to 2 nm*m/s (dynamic). The rates for plasmachemical etching are typically 2-3 times higher. Developments are underway to explore the use the innovative coating technology for e.g. scratch resistant coatings on metals, barrier layers, self-clean functional surfaces and, for antireflective coatings. Coating materials range comprise: silica, titanium, carbon and silicon nitride. Layer characterization, still underway; demonstrates that both composition/structure and optical/mechanical properties are close to data being well known from low pressure PECVD