Influence of surface additives iodine and indium on the initial growth in copper chemical vapor deposition

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The influence of surface additives, iodine and indium, on copper chemical vapor deposition (CVD) in its initial growth period is studied. The Cu CVD has been carried out on TaN/SiO2 and Cu(sputtered)/TaN/SiO2 substrates using Cu–hexafluoroacetylacetonate–vinyltrimethylsilane (Cu(hfac)(vtms)) precursor. Addition of iodine enhances the horizontal growth and reduces the vertical growth of Cu nuclei on the TaN surface. Addition of indium increases the number density of copper nuclei significantly on TaN. Both effects accelerate the initial growth rate and shorten the initial period. The X-ray photoelectron spectra confirm that iodine floats out to the growing copper surface, but indium does not. Since iodine is floating on the copper surface, it is a surfactant and its influences persist throughout the deposition. On the other hand, the influences of extranucleation sites provided by indium cease at the end of initial growth. Hence, Cu CVD on the In-added TaN surface develops a continuous film quickly, but its growth afterwards is similar to that without indium. On the Cu(sputtered)/TaN/SiO2 substrate, the surface is featured with faceted and protruded Cu grains in the initial growth. The iodine adsorption on sputtered copper worsens the initial morphology and leads to a porous and less conductive film. After 1-h deposition at 145°C, the sheet resistivity of Cu film on iodine-adsorbed TaN/SiO2 substrate is 1.8 ± 0.1μΩ-cm.