Silicon nitride films deposited by atmospheric pressure microwave PECVD

In standard production technology of crystalline silicon solar cells the deposition of an antireflective and passivating silicon nitride (SiN) layer is carried out by plasma enhanced chemical vapor deposition under vacuum. The combination of an atmospheric pressure deposition process with a similar etching technology in an advanced in-line process sequence could provide significant potential for cost saving. Deposition of silicon nitride by atmospheric pressure microwave PECVD was studied on silicon solar wafers. The plasma source, based on the concept of a cylindrical resonator with annular slots, operates at a frequency of 2.45 GHz with a working with of 156 mm. SiNx:H films were deposited on mono- and multi-crystalline 6'' Si wafers by using the metal-organic precursor tetramethylsilane (Si(CH3)4, TMS) or silane (SiH4) and ammonia as precursors. The layers were characterized by FTIR spectroscopy, spectro-ellipsometry, and microwave-induced photo conductance decay.