We have investigated the structure and interfacial structure of two types of high-k dielectric thin films on Si using combined experimental and theoretical approaches. In the Hf-based high- k dielectrics, the crystallinity of three films, pure HfO2, Y-incorporated HfO2 and Al-incorporated HfO2, is examined by transmission electron diffraction (TED), and the local coordination symmetries of the Hf atoms in the films are revealed by the profile of electron energy-loss near-edge structure (ELNES) taken at oxygen K-edge. These ELNES spectra are then simulated using real-space multiple-scattering (RSMS) method. We find a good agreement between the experimental and the simulated result of pure HfO2. The incorporation of Y indeed stabilizes HfO 2 to a cubic structure, but it also contributes to possible lattice distortion and creation of complex defect states, causing discrepancies between the experimental and the simulated result. As a comparison, the local coordination symmetry of Hf is largely degraded upon the incorporation of Al, which not only amorphorizes HfO2, but also introduces significantly amount of O vacancies in the film. We have further investigated the interfacial structures of HfO2 and Al-incorporated HfO2 thin films on Si using spatially resolved ELNES, which a series of the oxygen K-edge spectra is acquired when a 0.3 nm electron probe scanning across the film/Si interface. We find that interfaces are not atomically sharp, and variation in the local coordination symmetry of Hf atoms lasts for a couple of monolayers for both the HfO2 and the Al-incorporated HfO2 samples. Annealing of the HfO2 film in the oxygen environment leads to the formation of a thick SiO2/SiOx stack layer in-between the original HfO2 and the Si substrate. As a comparison, the interfacial stability is significantly improved by incorporating Al into the HfO 2 film to form HfAlO, which effectively reduces/eliminates the interfacial silicon oxide formation during the oxygen annealing process. The interfacial structure of SiTiO3 (STO) dielectric and Si is significant different from that between Hf-based dielectric and Si, as the crystalline STO is epitaxially grown on the Si. Together with the high resolution high-angle annular-dark-field (HAADF) image, the spatially resolved ELNES acquired across the STO/Si interface reveal an amorphous interfacial region of 1-2 monolayer thickness, which is lack of Sr, but contains Ti, Si, and O. Based on these experimental evidences, we propose a classical molecular dynamic (MD) interface model, in which the STO is connected to Si by a distorted Ti-O layer and a complex Si-O layer. The simulated results, based on the MD interface model, generally agree with the experimental results, disclosing a gradual change of the local atomic coordination symmetry and possible defect incorporation at the interface. / Wang, Xiaofeng = Si衬底上高k介电薄膜的结构研究 / 王晓峰. / Adviser: Li Quan. / Source: Dissertation Abstracts International, Volume: 72-11, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 103-112). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Wang, Xiaofeng = Si chen di shang gao k jie dian bo mo de jie gou yan jiu / Wang Xiaofeng.
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_344586 |
| Date | January 2009 |
| Contributors | Wang, Xiaofeng, Chinese University of Hong Kong Graduate School. Division of Physics. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, theses |
| Format | electronic resource, microform, microfiche, 1 online resource (xii, 112 leaves : ill.) |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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