• An exhaust system with a scrubber or a burn box to process the outlet gasses.
• An electronic and control part that consists of a dc or rf power generator with a matching box and vacuum, pressure and temperature gauging.
The deposition of a-Si:H layer from a silane plasma can be described as a four step process [18]:
(1) The primary reactions in the gas phase, in which SiH4 molecules are decomposed by electron impact excitation, generate various neutral radicals and molecules, positive and negative ions, and electrons.
(2) The secondary reactions in plasma between molecules and ions and radicals result in the formation of reactive species and eventually in large silicon-hydrogen clusters, which are described in the literature as dust or powder particles. Neutral species diffuse to the substrate, positive ions bombard the growing film, and negative ions are trapped within the plasma.
(3) Interaction of radicals with the surface of the growing film, such as radical diffusion, chemical bonding, hydrogen sticking to the surface or abstraction from the surface.
(4) The subsurface release of hydrogen and relaxation of the silicon network.