Atomic layer deposition of Al2O3 thin films using dimethylaluminum isopropoxide and water

Abstract

Dimethylaluminum isopropoxide (DMAI), (CH3)2AlOCH(CH3)2, a precursor originally developed for the metalorganic chemical vapor deposition of alumina, was adopted as a new precursor for growing aluminum oxide thin films on HF-treated Si(001) substrates by atomic layer deposition (ALD). This precursor is stable for a prolonged period of storage time under inert atmosphere (such as in nitrogen or argon) and does not react vigorously in air, and therefore is easy to handle and safe, without causing hazards. The self-limiting ALD process by alternate surface reactions of DMAI and H2O was confirmed by thicknesses of the grown aluminum oxide films measured as functions of the DMAI pulse time and the number of DMAI-H2O cycles. A maximum growth rate of ∼1.06 Å/cycle was achieved in the substrate temperature range ∼120–150 °C. Growth of stoichiometric Al2O3 thin films without appreciable carbon incorporation was verified by Rutherford backscattering spectrometry. Atomic force microscopy images showed atomically flat and uniform surfaces. In particular, a cross-sectional high-resolution transmission electron microscopy image of an Al2O3 film shows that there is no distinguishable interfacial oxide layer between the Al2O3 film and the Si substrate. These results prove the validity of DMAI as a new ALD source for aluminum oxide.