Thermal decomposition of triisobutylaluminum (TIBA) to deposit aluminum films shows promise as a way to form conductive contacts on silicon-based electronic devices. An important step in the steady-state deposition is the reaction of TIBA with the growing aluminum surface. We have studied this chemistry by reacting TIBA with single-crystal Al(111) and Al(100) surfaces. A combination of effusive molecular beam scattering, thermal desorption spectroscopy, Auger electron spectroscopy, low-energy electron diffraction, high-resolution electron energy loss spectroscopy, and scanning electron microscopy was used in these studies. We find that TIBA decomposes on both of these aluminum surfaces above ∼470 K by β-hydride elimination reactions to deposit aluminum and evolve hydrogen and isobutylene. This surface β-hydride elimination reaction is the rate-determining step. We find that the reaction is 2-5 times faster on Al(111) than on Al(100). In the temperature range of 470-600 K, the growing film is carbon-free, crystalline, and adopts the orientation of the single-crystal substrate. At higher temperatures, the deposited aluminum contains carbon, and we present evidence that a surface β-methyl elimination reaction is responsible, at least in part, for this contamination. Using the kinetic parameters determined from monolayer thermal deposition experiments for this reaction, we are able to predict the rate of steady-state aluminum deposition for TIBA pressures between 10-6 and 1 Torr.
ASJC Scopus subject areas
- Colloid and Surface Chemistry