Plasma enhanced chemical vapor deposition using forced flow through hollow cathodes

The application of hollow cathodes to the deposition of thin films from molecular gases is discussed. Precursor gases are decomposed in glow discharges created in the hollow cathode tubes while a laminar viscous gas flow is maintained through the tube towards a substrate. Either the substrate or another structure external to the hollow cathode, such as a coaxial tube, may function as the anode. Deposition rates up to 30 μ/min are observed for a-Si:H. These high-deposition rates are attributed to the high power density in the plasma combined with the efficient transport of the radicals to the substrate. A coaxial hollow cathode arrangement allows the deposition of insulating films by a direct current process. The unusual properties of amorphous silicon and silicon nitride films deposited with these electrode structures are discussed.