Temperature and pH dependence of the electroless Ni–P deposition on silicon

The sensitization, activation, nucleation and growth of electroless Ni–P deposition on silicon in an acid plating bath with sodium hydrophosphite as reducing agent and sodium succinate as complexing agent were studied by transmission electron microscopy, field emission scanning electron microscopy and atomic force microscopy. The results show that a continuous polycrystalline SnCl 2 film was formed on the silicon surface in the sensitization process, and small crystalline Pd particles were dispersedly produced on SnCl 2 film in the activation process. In the initial deposition stage, the small Ni–P particles had already emerged on the silicon surface in a deposition time of less than 2 s. When Ni–P particles grew, their size increased but their number decreased, and they later developed into a columnar structure. The deposition rate of the electroless Ni–P deposit increased as the pH value and the temperature of the plating bath increased (from 1.36 to 29.66 μm/h). The activation energy of the electroless Ni–P deposition on silicon increased as the pH value of the plating bath decreased (from 68.8 to 79.4 kJ/mol).