ELECTROLESS NICKEL AND COPPER METALLIZATION: CONTACT FORMATION ON CRYSTALLINE SILICON AND BACKGROUND PLATING BEHAVIOR ON PECVD SiN_x:H LAYERS

摘要

An alternative approach to the silver thick film metallization for the front side of silicon solar cells can be implemented by electroless nickel and copper deposition. One of the most challenging problems for a wet-chemical metallization sequence using nickel and copper is the phenomenon of background plating. Hereby the metal is not only deposited on the opened emitter structure but also on the insulating PECVD silicon nitride layer which causes additional shading to the solar cell. Contact properties of the metallization like contact resistance, adhesion and line resistance must be optimized. The nickel-silicon contact can be enhanced by an additional sintering step. In this paper the requirements for an adequate nickel silicide formation are discussed and it is shown how to reduce the problem of background plating on PECVD SiN_x:H surfaces.