Nucleation and growth mechanisms of copper MOCVD film on Au/Si substrates

Low pressure chemical vapor deposition of copper from copper(II) hexafluoroacetylacetonate [Cu(hfa)(2)] on different thicknesses of predeposited gold on a silicon substrate has been studied to determine the initial deposition mechanisms of nucleation and growth. The surface morphology changes of pre-deposited 30 Angstrom thick gold films were observed during heat treatment under hydrogen; fine, uniform close packed gold particle changed into agglomerated island formations on the surface leading to discontinuities covering only 20% of the overall Si surface as a result of surface diffusion. Pure metallic copper films were obtained on the agglomerated substrate. When pre-deposited 1500 Angstrom thick gold film was used as a substrate, the deposited film on the gold substrate was not a pure copper but consisted of a Cu-Au compound at the go interface as a result of strong interdiffusion from the gold and copper atomic interaction. Thermally-induced interdiffusion may thus change the film properties and the microstructure of the deposited film under the experimental conditions.