EFFECTS OF HF SOLUTION IN THE ELECTROLESS DEPOSITION PROCESS ON SILICON SURFACES

We have investigated the influence of HF concentration on the initial stages of electroless deposition for various metals (Al, Au, Cu, Sn, and Pd) onto silicon using atomic force microscopy. As the HF concentration in the plating solution increased, the rate of metal deposition correspondingly increased for Au, Cu, and Pd. In the case of Au and Cu, uniformly sized nuclei comprised the first deposited layer. However for Al and Sn, deposition occurred only at sporadic sites on the surface and was independent of HF concentration. For all of the metal ion studied, deposition initiated preferentially at flaws on the surface. The electroless process indicates a direct displacement mechanism which results in the simultaneous dissolution of Si as the metal ion is reduced at the surface. For all the metal ions deposited in this manner, metal adhesion to the Si surface was poor.