Copper deposition of HF etched silicon surfaces : morphological and kinetic studies

The kinetics and morphologies of Cu deposition on HF-treated silicon surfaces were investigated by atomic force microscopy (AFM), inductively coupled plasma mass spectroscopy (ICP/MS), and graphite furnace atomic absorption spectroscopy (GFAAS). The early stage ( < 60 s) of Cu deposition, as characterized by AFM, was found to be dominated by the nucleation of nanometer-sized Cu nuclei on HF-treated silicon surfaces. After 60 s of Cu deposition, the total grain number of Cu deposits was leveled to a constant plateau. However, a significant grain size increase of deposition Cu nuclei was noticed. We employed an AFM volume-integration technique in conjunction with the ICP/MS and GFAAS measurements to demonstrate that the Cu deposition rate was limited by the diffusion of Cu exp 2+ ions across the stationary solution layer toward the silicon surface.