VAPORIZATION PROCESSES OF ALUMINUM BETA-DIKETONE CHELATES

Aluminum(III) trifluoro- and hexafluoroacetylacetonates, Al(C5H4F3O2)3 and Al(C5HF6O2)3, were prepared by reaction of aluminum isopropoxide with the corresponding fluorinated acetylacetone in benzene solution. The kinetics of vaporization of these fluorinated aluminum complexes and aluminum (III) acetylacetonate, Al(C5H7O2)3, was investigated by isothermal thermogravimetry at temperatures ranging from 70 to 190-degrees-C with an hydrogen or argon pressure varying between 100 and 300 Torr. The vaporization process was found to be rate-limited by the diffusion of these large complex molecules in the buffer gas (H2 or Ar). The activation energy of these processes was demonstrated to be equal to the standard enthalpy of sublimation or evaporation of metal complexes. The values of the standard enthalpy of sublimation or evaporation of aluminum(III) complexes were compared with those reported in the literature and determined by other techniques. A comparison of the volatility of these metal complexes in terms of mass of aluminum evolved in the gas phase per minute as a function of vaporization temperature is also presented in this paper and can serve as a guideline for the selection of a suitable precursor in chemical vapor deposition of aluminum-containing films.