B. Bent, R. Nuzzo, L. Dubois
Mar 1, 1989
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Journal
Journal of the American Chemical Society
Abstract
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. The authors 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. The authors find that TIBA decomposes on both of these aluminum surfaces above /approximately/ 470 K by /beta/-hydride elimination reactions to deposit aluminum and evolve hydrogen and isobutylene. This surface /beta/-hydride elimination reaction is the rate-determining step. The authors 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 they present evidence that a surface /beta/-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, they are ablemore » to predict the rate of steady-state aluminum deposition for TIBA pressures between 10/sup /minus/6/ and 1 Torr.« less