Aluminum oxide (Al 2 O 3 ) grown by atomic layer deposition ͑ALD͒ is currently under investigation for use as a high-gate dielectric alternative to SiO 2 . Cluster calculations employing hybrid density functional theory have been carried out to examine the chemical reaction pathways between the ALD precursors, trimethylaluminum ͑TMA͒ and H 2 O, with the H/Si͑100͒-2ϫ1 surface. Results obtained using Si 9 H 14 and Si 15 H 20 , dimer and double dimer clusters to represent the surface active site

more »

... e in good agreement, providing a consistent view of reaction energetics on the H/Si͑100͒-2ϫ1 surface. The adsorption energies for TMA and H 2 O on the surface are calculated to be 0.02 and 0.15 eV, respectively. For the reaction between H 2 O and the H/Si͑100͒-2ϫ1 surface, hydroxylation of the surface accompanied by loss of H 2 was found to be the preferred pathway having an activation energy and overall reaction enthalpy of 1.60 eV and Ϫ0.75 eV, both of which are у0.70 eV lower than the corresponding values for the possible H/D exchange reaction. TMA exposure of the H/Si͑100͒-2ϫ1 surface favors the deposition of -Al͑CH 3 ) 2 with loss of CH 4 , having a barrier height of 1.30 eV and reaction enthalpy of Ϫ0.31 eV, which are 0.10 and 0.40 eV lower than the surface methylation pathway (H/CH 3 exchange͒ and 2.64 and 0.45 eV lower in energy than the H 2 loss reaction, that results in the deposition of -CH 2 -Al͑CH 3 ) 2 to the surface. Therefore, the dominant reactions identified in this work are those with direct implication in the Al 2 O 3 ALD growth mechanism, leading to the formation of Si-O and Si-Al species on the H/Si͑100͒-2ϫ1 surface.