Galvanic Deposition of Copper, Silver and Gold on Silicon Surfaces from Fluoride Free Aqueous Solutions

Abstract

Deposition of copper, silver and gold onto silicon surfaces is investigated in this work. Traditionally, direct deposition of Cu, Ag and Au onto silicon surfaces is carried out using fluoride based solutions. In the fluoride based solutions unavoidably present SiO2 at the surface of semiconductor is successfully removed and then deposition of metals such as Au or Ag proceeds via the galvanic displacement process. The results of the present work demonstrate that the direct deposition of Cu, Ag or Au onto silicon surface is very successful from fluoride-free alkaline solutions containing Cu(II), Ag(I) or Au(I) ions at pH higher than 12. The deposition of these metals does not require a reducing agent, i.e. process proceeds via galvanic displacement reactions. The approach can further be applied on any metal with the standard electrode potential more positive than that of silicon, as long as the alkaline complexes of the targeted metals are reasonably stable in the strong alkaline electrolytes with pH more than 12.