Surface and interfacial studies of metal-organic chemical vapor deposition of coppe

The nucleation and successful growth of copper (Cu) thin films on diffusion barrier/adhesion promoter substrates during metal-organic chemical vapor deposition (MOCVD) are strongly dependent on the initial Cu precursor-substrate chemistry and surface conditions such as organic contamination and oxidation. This research focuses on the interactions of bis(1,1,1,5,5,5-hexafluoroacetylacetonato)copper(II), (Cu(hfac)$sb2$), with polycrystalline tantalum (Ta) and polycrystalline as well as epitaxial titanium nitride (TiN) substrates during Cu MOCVD, under ultra-high vacuum (UHV) conditions and low substrate temperatures (T $<$ 500 K). The results obtained from X-ray photoelectron spectroscopy (XPS), Auger Electron Spectroscopy (AES) and Temperature Programmed Desorption (TPD) measurements indicate substantial differences in the chemical reaction pathways of metallic Cu formation from Cu(hfac)$sb2$ on TiN versus Ta surfaces.;XPS results indicate that atomic hydrogen is an effective in situ precleaning agent for the removal of both organic contamination and native oxide from TiN surfaces at 450 K prior to MOCVD. Atomic hydrogen is also found to be the essential driving force for the reduction of Cu(hfac)$sb2$ and formation of metallic Cu via a disproportionation mechanism. Without atomic hydrogen exposure, TPD results indicate that Cu formation on the TiN surface is hindered by the back reaction of the intermediates. Overall, the results suggest that atomic hydrogen can be potentially used as an integrated preclean/deposition methodology to inhibit interfacial organic buildup and oxide formation during MOCVD under real industrial (non-UHV) conditions.;Cu MOCVD studies carried out on Ta showed that this substrate has a different surface chemical interaction with Cu(hfac)$sb2$ compared to TiN and other reactive substrates. A spontaneous reduction of Cu(hfac)$sb2$ to metallic Cu occurs on the Ta surface by 450 K even without exposure of the substrate to atomic hydrogen or other external reducing agents. This reduction and Cu formation on Ta occur even in the presence of substantial surface hydrocarbon and oxide contamination. Moreover, both the XPS and TPD studies indicate the stability of the Cu ad-layer on Ta at temperatures above those for grain boundary diffusion in TiN. These results suggest that Cu/Ta adhesion may prove considerable more robust than Cu/TiN adhesion.