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Design of Amorphous Diffusion Barriers for Cu Metallization Open Access


Other title
Diffusion Barrier
Copper Metallization
Type of item
Degree grantor
University of Alberta
Author or creator
Dalili, Neda
Supervisor and department
Liu, Qi (Chemical and Materials Engineering)
Ivey, Douglas (Chemical and Materials Engineering)
Examining committee member and department
Elias, Anastasia (Chemical and Materials Engineering)
Chung, Hyun-Joong (Chemical and Materials Engineering)
Xia, Guangrui (University of British Columbia)
Cadien, Ken (Chemical and Materials Engineering)
Department of Chemical and Materials Engineering
Materials Engineering
Date accepted
Graduation date
Doctor of Philosophy
Degree level
The incorporation of Cu interconnects into the manufacturing of integrated circuits has accompanied several modifications to the fabrication process and the associated material systems. The new fabrication process involves the development of dual damascene process, while the new materials systems include development of diffusion barrier materials. The latter imposes a critical challenge as Cu is a fast diffuser in Si and the adjacent dielectric layers, and results in device deterioration and failure. Technology development has been driven mainly by continuous feature size scaling, thus the developed barrier will be required to perform satisfactorily at the continuously reduced thicknesses. The conventional barriers used for Cu interconnects are TaNx based films which require the deposition of an additional Cu seed layer prior to filling of the interconnects by electrochemical deposition. In the face of reducing feature size and barrier thickness, there has been great interest in developing diffusion barriers that are amenable to direct electrodeposition of Cu without the need for a seed layer. However, there is a need for a suitable guide for selecting material systems suitable for diffusion barrier applications. In this thesis, a systematic approach is adopted to select an amorphous, low resistivity diffusion barrier material with the possibility of direct electrodeposition of Cu. After comprehensive consideration of possible alloys, the Ta-Rh system is selected as the candidate barrier. Thermodynamic calculations are performed to select the most stable amorphous composition in the system. The predictions made based on the thermodynamic calculation are verified by detailed structural characterizations. The performance of the selected TaRhx alloy as a diffusion barrier is evaluated by metallurgical and electrical characterizations. The metallurgical characterizations are performed by in-situ and ex-situ heating experiments on Si/diffusion barrier/Cu stacks. The common issues associated with in-situ transmission electron microscopy heating of Cu metallization stacks are identified and addressed. The electrical characterizations are performed by monitoring the capacitance-voltage characteristics of metal oxide semiconductor capacitors after bias temperature stress testing. For comparison, TaNx barriers are deposited and tested as diffusion barriers using a similar methodology. The reliability of the developed barrier system is compared with the current industry solution, i.e. TaNx.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
[1] N. Dalili, Q. Liu, D.G. Ivey, Acta Mater., 61, 5365-74 (2013).N. Dalili, D.G. Ivey, J. Mat. Sci.: Mat. Electron, DOI: 10.1007/s10854-013- 1662-8.N. Dalili, P. Li, M. Kupsta, Q. Liu, D.G. Ivey, Micron, DOI:10.1016/j.micron.2013.11.002.N. Dalili, Q. Liu, D.G. Ivey, J. Mater. Sci. 48, 489-501 (2013).N. Dalili, A. He, Q. Liu, D.G. Ivey, J. Electron. Mat. 39, 1554-1561 (2010).

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