Observation of HfO₂ thin films by deep UV spectroscopic ellipsometry

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• 作者：F. Ferrieu ; K. Dabertr ; S. Lhostis ; V. Ivanova ; E. Martinez ; C. Licitra ; G. Roll
• 关键词：UPS/XPS ; X-ray diffraction ; Dielectric properties ; relaxation ; electric modulus ; Ellipsometry ; Optical properties
• 刊名：Journal of Non-Crystalline Solids
• 出版年：2007
• 期刊代码：50_00223093
• 类别：ms
• 出版时间：1 April 2007
• 卷：353
• 期：5-7
• 页码：658-662
• 文件大小：350 K

摘要

Deep UV spectroscopic ellipsometry (SE) is used for structure change observations in thin hafnia (HfO₂) layers deposited by p-MOCVD on silicon substrate. The absorption edge E_g and most of the critical point transitions in HfO₂ are above 6 eV, which makes the extension to Deep UV SE (5–9 eV) very suitable. The phase mixture changes as function of thickness and deposition process temperature, deduced from SE correspond well to XRD and Angle Resolved (AR)-XPS spectroscopy observations. From the absorption spectra at 4.5 eV, defects such as oxygen vacancies are detected, whereas from XPS spectra the estimation of the O/Hf ratio follows the same trend. Deep UV SE reveals differences in the dielectric function with orthorhombic/monoclinic phase mixtures essentially with peaks at 7.5 and 8.5 eV. Quantum confinement originated from the grain size of the films and the excitonic origin of the 6 eV feature are discussed.