Electroless deposition of NiWB alloy on p-type Si(1 0 0) for NiSi contact metallization

Recently, we have proposed a novel method to form NiSi contacts using electroless plating of Ni-alloys (NiP, NiWP, NiWB) on p-type Si(1 0 0) modified by aminopropyltriethoxysilane (APTS) activated with Pd-citrate [A. Duhin, Y. Sverdlov, Yishay Feldman, Y. Shacham-Diamand, Microelectron. Eng. 84 (2007) 2506]. In this work we focus on NiWB thin films that were formed by this method. Alkali metal free electroless plating was developed using dimethylamine-borane (DMAB) and tungstatic acid (H₂WO₄) as a reducing agent and a source of tungsten ions, respectively. Using this method we succeeded to receive relatively high tungsten concentration (maximum value of 19-21 at%) in the electroless deposited NiWB films with good adhesion to the Si-substrate. In this paper, the advantages of using the APTS activated with Pd-citrate for NiWB alloy deposition on the Si substrate is discussed. The chemically deposited NiWB samples were annealed for 1-2 h in vacuum (<10^-6 Torr) forming the silicide layer. The annealing temperatures were 650 °C for NiWB alloys. X-ray diffraction (XRD) measurement confirmed the presence of NiSi phase after annealing. In addition the WSi₂ phase was formed. The results are reported and summarized.