Si_(1_x)Ge_x metal-oxide-semiconductor capacitors with HfTaO_x gate dielectrics

摘要

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 ℃ (for 5 min) along with the incorporation of Ta. HfTaO_x films (with 18% Ta) remain amorphous up to about 500 ℃ anneal. Electrical characterization of post deposition annealed (in oxygen at 600 ℃) samples showed; capacitance equivalent thickness of-4.3-5.7 nm, hysteresis of 0.5-0.8V, and interface state density=1.2-3.8x10~(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.