Abstract
Interfacial reactions and electrical properties of RF sputter deposited HfTaOx high-k gate dielectric films on Si1-xGex (x = 19%) are investigated. X-ray photoelectron spectroscopic analyses indicate an interfacial layer containing GeOx. Hf silicate, SiOx (layer of Hf-Si-Ge-O) formation during deposition of FifTaO(x). No evidence of Ta-silicate or Ta incorporation was found at the interface. The crystallization temperature of HfTaOx film is found to increase significantly after annealing beyond 500 degrees C (for 5 min) along with the incorporation of Ta. HfTaOx films (with 18% Ta) remain amorphous up to about 500 degrees C anneal. Electrical characterization of post deposition annealed (in oxygen at 600 degrees C) samples showed; capacitance equivalent thickness of similar to 4.3-5.7 nm, hysteresis of 0.5-0.8 V. and interface state density = 1.2-3.8 x 10(12) cm(-2) eV(-1). The valence and conduction band offsets were determined from X-ray photoelectron spectroscopy spectra after careful analyses of the experimental data and removal of binding energy shift induced by differential charging phenomena occurring during X-ray photoelectron spectroscopic measurements. The valence and conduction band offsets were found to be 2.45 +/- 0.05 and 2.31 +/- 0.05 eV, respectively, and a band gap of 5.8 +/- 05 eV was found for annealed samples. (C) 2011 Published by Elsevier B.V.