Influences of bath chemistry and plating variables on characteristics of electroless Ni-P films on Si wafers from alkaline citrate solutions

Abstract

Electroless nickel-phosphorus (Ni-P) films were produced on the surface of p-type monocrystalline silicon in the alkaline citrate solutions. The influences of bath chemistry and plating variables on the chemical composition, deposition rate, morphology, and thermal stability of electroless Ni-P films on silicon wafers were studied. The as-deposited Ni-P films were almost all medium- and high-P deposits. The concentrations of Ni2+ and citric ions influenced the deposition rate of the films but did not affect P content in the deposits. With increasing H2PO-2 content, the P content and deposition rate were steadily increased. The pH and plating temperature had a significant effect on the chemical composition and the deposition rate of the films. The thermal stability of the medium-P film was better than that of the high-P deposit. At the same time, the proposed mechanism of Ni-P films on monocrystalline silicon substrates in the alkaline bath solution was discussed and addressed.