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Structure of high-k thin films on Si substrate. / Si衬底上高k介电薄膜的结构研究 / Structure of high-k thin films on Silicon substrate / CUHK electronic theses & dissertations collection / Si chen di shang gao k jie dian bo mo de jie gou yan jiu / Structure of high-k thin films on Si substrate.

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.

Identiferoai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_344586
Date January 2009
ContributorsWang, Xiaofeng, Chinese University of Hong Kong Graduate School. Division of Physics.
Source SetsThe Chinese University of Hong Kong
LanguageEnglish, Chinese
Detected LanguageEnglish
TypeText, theses
Formatelectronic resource, microform, microfiche, 1 online resource (xii, 112 leaves : ill.)
RightsUse 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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