Disproportionation of dimethylalane on aluminum surfaces. Part I. Experimental studies

An experimental study of the growth chemistry of dimethylaluminum hydride (DMAH) has been performed to elucidate the reaction pathways underlying the growth of aluminum by chemical vapor deposition. Results find that DMAH grows clean aluminum films through a surface disproportionation mechanism, which produces trimethylaluminum (TMA) and hydrogen as byproducts. Effusive beam scattering and temperature programmed desorption experiments provide evidence that the growth mechanism proceeds through the adsorption and decomposition of DMAH into Al(CH ₃) ₂, Al(CH ₃), and CH ₃ surface species. TMA is produced via recombination reactions involving freely diffusing surface methyl groups as primary intermediates. At high temperatures (>560-600 K), these methyl groups undergo dehydrogenation reactions which lead to irreversible carbon contamination. This latter reaction pathway is proposed to be accompanied by methyl radical ejection reactions.