Study of the Surface Reactions in ALD Hafnium Aluminates

Hafnium aluminates have been investigated as high-k dielectrics for implementation in sub-45 nm nonvolatile memory technologies. The growth behavior and quality of these dielectrics strongly depend on the applied deposition technique. We examine the surface reactions that occur during the atomic layer deposition (ALD) of hafnium aluminates from HfCl(4), Al(CH(3))(3), and H(2)O. When grown in the ALD sequence (HfCl(4)/H(2)O)(a)[Al(CH(3))(3)/H(2)O](b), HfCl(4) chemisorption is enhanced while that of Al(CH(3))(3) is inhibited compared to the reaction during ALD of the respective binary oxides. Density functional theory simulations suggest that this observation is related to the more efficient hydrolysis of the Al-C bond compared to Hf-Cl. However, earlier works on ALD of HfCl(4)/H(2)O suggest that the low growth per cycle of this process is not caused by a limited hydrolysis of the Hf-Cl bond but by dehydroxylation of the generated Hf-OH surface sites into less reactive Hf-O-Hf surface sites. Hence, we propose that the enhanced HfCl(4) and inhibited Al(CH(3))(3) chemisorption during ALD of hafnium aluminates results from a difference in dehydroxylation behavior between both binary oxides. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3246802] All rights reserved.