AVS 55th International Symposium & Exhibition
    Thin Film Monday Sessions
       Session TF-MoA

Paper TF-MoA5
Surface Preparation and Interface Cleaning during HfO2 ALD on GaAs

Monday, October 20, 2008, 3:20 pm, Room 302

Session: ALD: Functionalization and Surface Chemistry
Presenter: T. Gougousi, UMBC
Authors: T. Gougousi, UMBC
J.C. Hackley, UMBC
J.D. Demaree, Army Research Laboratory
Correspondent: Click to Email

The atomic layer deposition of HfO2 thin films is studied on GaAs(100) surfaces. The films are grown using tetrakis(dimethyl)amino hafnium (TDMAH) and H2O precursors at a deposition temperature of 275°C. Several GaAs starting surfaces are investigated, including native oxide and both HF and NH4OH-treated substrates. Wet chemical etching in either HF or NH4OH solutions are shown to remove most of the Ga and As native oxides. Spectroscopic ellipsometry (SE) confirms linear growth rates of ~1.0 Å/cycle for all surfaces. Rutherford backscattering spectrometry (RBS) shows that steady-state growth of 2.6×1014 Hf/cm2/cycle is reached after 10 ALD cycles for the HF-etched GaAs surface while much smoother growth is observed for the native oxide surface (~2.9×1014 Hf/cm2/cycle). The interface of HfO2 films deposited on GaAs surfaces is probed by X-ray photoelectron spectroscopy. Both the HF and NH4OH treatments passivate the surface and prevent the oxidation of the interface during the deposition of coalesced HfO2 films (> 15 ALD cycles). Deposition of HfO2 films on the native oxide GaAs surfaces show gradual consumption of the native oxides during the process, indicating the presence of an “interfacial cleaning” mechanism comparable to that observed for other metal oxide ALD processes on GaAs and InGaAs substrates.1,2,3,4 The As-oxide and most of the Ga-oxide is removed after 20 ALD cycles. The presence of As oxides is not detected for films as thick as ~100Å (100 cycles) deposited on native oxide substrates.

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