Microwave PECVD for large area coating

Microwave Plasma Enhanced Chemical Vapour Deposition (PECVD) of thin films is the method of choice when highest deposition rates and/or high fragmentation of precursor material is desirable. However, large area applications have always suffered from poor film thickness uniformity and unacceptable variations of thin film properties. Coaxial plasma line sources in various arrangements have proven their ability to generally overcome all former technological limitations inherent in many other types of microwave plasma sources, which prevented microwave PECVD from becoming a mainstream technology in the field of large area coatings. In this article, the advantages and the potential of the coaxial plasma line sources and suitable vacuum processes are described. Improvements of the coaxial plasma lines are introduced which are indispensable for large area plasma applications and which have been investigated in several laboratory and production prototype vacuum process systems. A variety of thin films have been deposited, ranging from organic and ceramic silicon dioxide to nanocrystalline diamond and microcrystalline silicon for photovoltaic applications.