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 0.1 mu m 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 10(-4) cm(2) has been obtained. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3391538] All rights reserved.