Abstract
Interface of TiN electrode with γ-Al2O3 layers was studied using near edge X-ray absorption fine structure, conventional X-ray photoelectron spectroscopy and photoelectron spectroscopy with high energies. Despite the atomic-layer deposited Al2O3 being converted into thermodynamically-stable polycrystalline cubic γ-phase by high-temperature (1000 or 1100 °C) anneal, our results reveal formation of a thin TiNxOy (≈1-nm thick) interlayer at the interface between γ-Al2O3 film and TiN electrode due to oxygen scavenging from γ-Al2O3 film. Formation of the TiO2 was not observed at this interface. As environmental effect, a strong oxidation resulting in formation of a TiO2(1.4 nm)/TiNxOy(0.9 nm) overlayers on the top of the TiN electrode is traced. Development of O-deficiency of γ-Al2O3 is observed and related to the polarization anisotropy due to the preferential orientation of spin states involved in the X-ray absorption in the plane parallel to the surface. Investigation of the TiN electrode reveals the predominantly “stretched” octahedra in its structure with the preferential orientation relative the interface with γ-Al2O3. This anisotropy can be correlated with ≈200 meV electron barrier height increase at the O-deficient TiN/γ-Al2O3 interface as compared to the TiN/γ-Al2O3 barrier formed under abundant oxidant supply condition as revealed by internal photoemission of electrons from TiN into the oxide.
Highlights
Interface of TiN electrode with γ-Al2O3 layers was studied using near edge X-ray absorption fine structure, conventional X-ray photoelectron spectroscopy and photoelectron spectroscopy with high energies
It is traditionally related to the inelastic mean free path (IMFP, λi)[26], which is defined as the average distance that an electron with a given kinetic energy travels between successive inelastic collisions
The main bonus of HAXPES consists in a large value of λi providing in depth analysis of nanosystems, which was realized in the current studies
Summary
Interface of TiN electrode with γ-Al2O3 layers was studied using near edge X-ray absorption fine structure, conventional X-ray photoelectron spectroscopy and photoelectron spectroscopy with high energies. Despite the atomic-layer deposited Al2O3 being converted into thermodynamicallystable polycrystalline cubic γ-phase by high-temperature (1000 or 1100 °C) anneal, our results reveal formation of a thin TiNxOy (≈1-nm thick) interlayer at the interface between γ-Al2O3 film and TiN electrode due to oxygen scavenging from γ-Al2O3 film. The EWF variations have been associated with formation of dipoles in metal-insulator-semiconductor (MIS) structures, including dipoles at the high-κ oxide/SiO2 interface[1], charged oxygen vacancies in the high-κ oxide[2] as well as dipoles induced by post-metallization anneal[3,4,5]. In the case high-κ oxide insulators used in modern ICc such as HfO2, generation of oxygen imbalance at the interface by introducing metal scavenging layer is shown to result in nearly 1 eV metal/oxide barrier variations[6, 7]. The metal/SiO2 barrier energies and have proposed an alternative model of the polarization layer, which invokes penetration of the field into the metal
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