Si 1 − x Ge x metal-oxide-semiconductor capacitors with HfTaO x gate dielectrics

Abstract

Interfacial reactions and electrical properties of RF sputter deposited HfTaO x high-k gate dielectric films on Si 1 − x Ge x (x = 19%) are investigated. X-ray photoelectron spectroscopic analyses indicate an interfacial layer containing GeO x, Hf silicate, SiO x (layer of Hf–Si–Ge–O) formation during deposition of HfTaO x. No evidence of Ta-silicate or Ta incorporation was found at the interface. The crystallization temperature of HfTaO x film is found to increase significantly after annealing beyond 500 °C (for 5 min) along with the incorporation of Ta. HfTaO x films (with 18% Ta) remain amorphous up to about 500 °C anneal. Electrical characterization of post deposition annealed (in oxygen at 600 °C) samples showed; capacitance equivalent thickness of ~ 4.3–5.7 nm, hysteresis of 0.5–0.8 V, and interface state density = 1.2–3.8 × 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.