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1155-C10-03

Atomic Layer Deposition of Metal Oxide Films on GaAs (100) surfaces Theodosia Gougousi,1 John W. Lacis,1 Justin C. Hackley,1 and J. Derek Demaree2 1 Department of Physics, University of Maryland Baltimore County (UMBC), Baltimore, MD 21250 U.S.A. 2 Weapons & Materials Research Directorate, Army Research Laboratory, Aberdeen Proving Ground, MD 21005-5069 U.S.A. ABSTRACT Atomic Layer Deposition is used to deposit HfO2 and TiO2 films on GaAs (100) native oxides and etched surfaces. For the deposition of HfO2 films two different but similar ALD chemistries are used: i) tetrakis dimethyl amido hafnium (TDMAHf) and H2O at 275°C and ii) tetrakis ethylmethyl amido hafnium (TEMAHf) and H2O at 250°C. TiO2 films are deposited from tetrakis dimethyl amido titanium (TDMATi) and H2O at 200°C. Rutherford Back Scattering shows linear film growth for all processes. The film/substrate interface is examined using x-ray photoelectron spectroscopy and confirms the presence of an “interfacial cleaning” mechanism. INTRODUCTION The deposition of high dielectric constant (high-k) films on Si surfaces has been studied extensively as a means to extend the lifetime of Si-based microelectronics. One of the major issues in the integration of high-k materials with Si is the inadvertent formation of SiO2 interfacial layers even for oxides that are predicted to be thermodynamically stable on Si surfaces.[1-2] High mobility substrates such as GaAs and InGaAs have better electrical properties than Si but their use in the semiconductor industry has been hindered by the poor electrical quality of their native oxides.[3] However, high-k dielectrics can be deposited on any semiconductor surface and there are several recent reports of good quality devices using high-ks on GaAs surfaces.[4] Most interestingly, there are several reports of an interface etching reaction taking placing during the ALD of HfO2 and Al2O3 on native oxide covered GaAs surfaces that results in a very thin interfacial layer between the high-k film and the GaAs substrate.[ 5-12]The common thread of all these observations is the use of metal organic precursors as the metal source. In this article we examine the evolution of the high-k/GaAs interface for three ALD processes that use metal organic precursors of the amide family. EXPERIMENT Film depositions were performed in a hot-wall reactor described elsewhere.[13] HfO2 films were deposited using two different metal organic amide precursors. i) tetrakis dimethyl amido hafnium (TDMAHf) and H2O at 275°C and ii) tetrakis ethylmethyl amido hafnium (TEMAHf) and H2O at 250°C. For the deposition of TiO2 films tetrakis dimethyl amido titanium (TDMATi) and H2O were used at 200°C. Three different starting surfaces are examined. Surfaces termed “native oxide” were prepared by cleaning pieces of GaAs (100) wafers in acetone, methanol, rinsing in deionized (DI) water and blown dry in a N2 stream. This preparation has been shown to preserve the surface native oxides.[11] Surfaces with very little oxide coverage can be prepared by: 5 mi