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Study of Ta as a Diffusion Barrier in Cu/SiO2 Structure

Published online by Cambridge University Press:  17 March 2011

J. S. Pan ,
A. T. S. Wee ,
C. H. A. Huan ,
J. W. Chai  and
J. H. Zhang
J. S. Pan
Affiliation:
Institute of Materials Research & Engineering, 3 Research Link, Singapore 117602
A. T. S. Wee
Affiliation:
Department of Physics, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260
C. H. A. Huan
Affiliation:
Department of Physics, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260
J. W. Chai
Affiliation:
Institute of Materials Research & Engineering, 3 Research Link, Singapore 117602
J. H. Zhang
Affiliation:
School of Mechanical and Production Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798
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Abstract

Tantalum (Ta) thin films of 35 nm thickness were investigated as diffusion barriers as well as adhesion-promoting layers between Cu and SiO2 using X-ray diffractometry (XRD), Scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). After annealing at 600°C for 1h in vacuum, no evidence of interdiffusion was observed. However, XPS depth profiling indicates that elemental Si appears at the Ta/SiO2 interface after annealing. In-situ XPS studies show that the Ta/SiO2 interface was stable until 500°C, but about 32% of the interfacial SiO2 was reduced to elemental Si at 600°C. Upon cooling to room temperature, some elemental Si recombined to form SiO2 again, leaving only 6.5% elemental Si. Comparative studies on the interface chemical states of Cu/SiO2 and Ta/SiO2 indicate that the stability of the Cu/Ta/SiO2/Si system may be ascribed to the strong bonding of Ta and SiO2, due to the reduction of SiO2 through Ta oxide formation.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 612: Symposium D – Materials, Technology & Reliability for Advanced Interconnects.. , 2000 , D9.18.1
Copyright
Copyright © Materials Research Society 2000

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