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Thermal oxidation mechanism and stress evolution in Ta thin films

Published online by Cambridge University Press:  31 January 2011

Yusung Jin ,
Jae Yong Song ,
Soo-Hwan Jeong ,
Jeong Won Kim ,
Tae Geol Lee ,
Ju Hwang Kim  and
Junhee Hahn
Yusung Jin
Affiliation:
Department of Chemical Engineering, Kyungpook National University, Daegu 702-701, South Korea
Jae Yong Song*
Affiliation:
Division of Industrial Metrology, Korea Research Institute of Standards and Science, Daejeon 305-340, South Korea; and School of Science, University of Science and Technology, Daejeon 305-333, South Korea
Soo-Hwan Jeong*
Affiliation:
Department of Chemical Engineering, Kyungpook National University, Daegu 702-701, South Korea
Jeong Won Kim
Affiliation:
Division of Industrial Metrology, Korea Research Institute of Standards and Science, Daejeon 305-340, South Korea
Tae Geol Lee
Affiliation:
Division of Convergence Technology, Korea Research Institute of Standards and Science, Daejeon 305-340, South Korea
Junhee Hahn
Affiliation:
Division of Industrial Metrology, Korea Research Institute of Standards and Science, Daejeon 305-340, South Korea
*
a)Address all correspondence to this author. e-mail: jysong@kriss.re.kr
b)Address all correspondence to this author. e-mail: shjeong@knu.ac.kr
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Abstract

Oxidation-induced stress evolutions in Ta thin films were investigated using ex situ microstructure analyses and in situ wafer curvature measurements. It was revealed that Ta thin films are oxidized to a crystalline TaO2 layer, which is subsequently oxidized to an amorphous tantalum pentoxide (a-Ta2O5) layer. Initial layered oxidation from Ta to TaO2 phases abruptly induces high compressive stress up to about 3.5 GPa with fast diffusion of oxygen through the Ta layer. Subsequently, it is followed by stress relaxation with the oxidation time, which is related to the slow oxidation from TaO2 to Ta2O5 phases. The initial compressive stress originates from the molar volume expansion during the layered formation of TaO2 from the Ta layer, while the relaxation of the compressive stresses is ascribed to the amorphous character of the a-Ta2O5 layer. According to Kissinger's analysis of the stress evolution during an isochronic heating process, the oxygen diffusion process through the a-Ta2O5 layer is the rate-controlling stage in the layered oxidation process of forming a a-Ta2O5/TaO2/Ta multilayer and has an activation energy of about 190.8 kJ/mol.

Keywords

Thermal stressesTaOxidation
Type
Articles
Information
Journal of Materials Research , Volume 25 , Issue 6 , June 2010 , pp. 1080 - 1086
Copyright
Copyright © Materials Research Society 2010

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