Atomic Layer Deposition of HfO 2 Thin Films on Si and GaAs Substrates
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1073-H04-19
Atomic Layer Deposition of HfO2 Thin Films on Si and GaAs Substrates Justin C Hackley1, J. Derek Demaree2, and Theodosia Gougousi1 1 Physics, UMBC, 1000 Hilltop Circle, Baltimore, MD, 21250 2 Weapons and Materials Research Directorate, Army Research Laboratory, Aberdeen Proving Ground, MD, 21005-5069
ABSTRACT The atomic layer deposition of HfO2 thin films is studied on Si(100) and GaAs(100) surfaces. The films are grown using tetrakis(dimethyl)amino hafnium (TDMAH) and H2O precursors at a deposition temperature of 275°C. The Si surfaces used include a H-terminated surface and an OH-rich chemical oxide. GaAs substrates are subjected to two different predeposition treatments involving an HF and a NH4OH wet chemical etch that has been shown to remove most of the Ga and As native oxides. Spectroscopic ellipsometry (SE) confirms linear growth rates of 1.05±0.05 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. X-ray photoelectron spectroscopy (XPS) indicates the presence of native oxides on both GaAs starting surfaces after 10 cycles due to postdeposition surface oxidation. However, the presence of the native oxide is not detected for thicker 15 and 20 cycle samples indicating passivation of the surface and suppression of the interfacial layer formation. INTRODUCTION Atomic Layer Deposition (ALD) is currently considered an enabling technology for the deposition of high quality films in applications that require high accuracy in the film composition and thickness.1 It is based on a self-limiting, complementary surface reaction that depends on the presence of “reactive” functional groups on the surface that is to be coated.2 For example, OH- terminated Si surfaces (Si-OH) have been shown to be amenable to the growth of high quality oxides while H-terminated Si (Si-H) surfaces have been shown to be unfavorable to such growth resulting in rougher and less dense films.3 This view has been challenged recently from results that have shown efficient growth of HfO2 films on Si-H at 100°C using amide precursors and heavy water.4 Hf-based oxides have received increased attention in the past few years as potential replacements of SiO2 as gate dielectrics in Metal Oxide Semiconductor Field Effect Transistors (MOSFET).5 However, one of the major issues with the application of alternative higher kdielectrics on Si for MOSFET devices is the reduced mobility of the carriers.6 As a result, alternative channel materials such as strained Si, Ge and even III-IV semiconductors such as GaAs are currently under investigation. GaAs has electrical properties significantly superior to those of Si but its native oxides are of very poor quality rendering them unusable for high quality devices.7 High-k dielectrics have been successfully deposited on various starting surfaces using an array of techniques such as ALD, chemical vapor deposition, physical vapor deposition,
etc.8,9,10As a result, one o
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