Electrical and Structural Characterization of Electroless Nickel–Phosphorus Contacts for Silicon Solar Cell Metallization

Abstract

Electroless nickel plating is a very promising process for metallization of silicon solar cells. It can be used to form a seed layer for an electrolytic deposition of copper or silver because it ensures the required adherence, a low contact resistance, and prevent copper from diffusing into the silicon. The nickel plating technique developed in this work consists of a selective electroless nickel–phosphorus (NiP) deposition without the activation step from an alkaline bath containing sodium hypophosphite as a reducing agent and ammonia for pH control. Experimental results of the deposit properties are presented. Thin NiP layers of about on silicon were annealed under different conditions. Rutherford backscattering spectrometry, glancing incidence X-ray diffraction, and scanning electron microscopy were used to obtain information on silicide formation vs temperature. These results were correlated with contact resistivity measurements by the transmission line model. A typical contact resistivity of has been obtained.