The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Tantalum-Based Diffusion Barriers for Copper Metallization

Tomi Laurila

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Electrical and Communications Engineering, Helsinki University of Technology for public examination and debate in Auditorium S5 at Helsinki University of Technology (Espoo, Finland) on the 14th of December, 2001, at 12 noon.

Overview in PDF format (ISBN 951-22-5767-X)   [409 KB]
Errata (in PDF)
Dissertation is also available in print (ISBN 951-22-5766-1)

Abstract

Interfacial reactions between Cu and Si with different Ta-based diffusion barriers are investigated by means of the combined thermodynamic-kinetic and microstructural analysis. The reaction mechanisms and the related microstructures in the Si/Ta/Cu, Si/TaC/Cu and Si/Ta2N/Cu metallization systems are studied experimentally and theoretically by utilizing the ternary Si-Ta-Cu, Si-Ta-C, Si-Ta-N, Ta-C-Cu, and Ta-N-Cu phase diagrams as well as the activity diagrams calculated at different temperatures. The effects of oxygen on the reactions in the Si/Ta/Cu and Si/TaC/Cu metallization systems are investigated by employing also the evaluated Ta-O and Ta-C-O phase diagrams. The experimental investigations are carried out with the help of sheet resistance measurements, x-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), scanning electron microscopy (SEM), secondary ion mass spectroscopy (SIMS) and transmission electron microscopy (TEM). It is shown that by using the combined thermodynamic-kinetic approach a better understanding about the reactions taking place in the Si/Cu diffusion couples with different Ta-based diffusion barriers can be achieved. The diffusion barrier solutions using Ta are good candidates for practical applications.

This thesis consists of an overview and of the following 5 publications:

  1. T. Laurila, K. Zeng, J. Molarius, I. Suni, and J.K. Kivilahti, Chemical Stability of Tantalum Diffusion Barrier Between Cu and Si, Thin Solid Films, 373, (2000), pp. 64-67. © 2000 Elsevier Science. By permission.
  2. T. Laurila, K. Zeng, J. Molarius, I. Suni, and J.K. Kivilahti, Failure Mechanism of Ta Diffusion Barrier Between Cu and Si, Journal of Applied Physics, 88, (2000), pp. 3377-3384. © 2000 American Institute of Physics. By permission.
  3. T. Laurila, K. Zeng, J. Molarius, I. Suni, and J.K. Kivilahti, Effect of Oxygen on the Reactions in the Si/Ta/Cu Metallization System, Journal of Materials Research, 16, (2001), pp. 2939-2946. © 2001 Materials Research Society. By permission.
  4. T. Laurila, K. Zeng, J. Molarius, T. Riekkinen, I. Suni, and J.K. Kivilahti, Tantalum Carbide and Nitride Diffusion Barriers for Cu Metallisation, Microelectronics Engineering, 60, (2001), pp. 71-80. © 2001 Elsevier Science. By permission.
  5. T. Laurila, K. Zeng, J. Molarius, I. Suni, and J.K. Kivilahti, Stability of TaC Diffusion Barrier Between Si and Cu, HUT Internal Report, HUT-EPT-7, ISBN 951-22-5777-7, (2001). This report is composed of two manuscripts: "TaC as a Diffusion Barrier Between Si and Cu" (submitted to Journal of Applied Physics) and "Amorphous Layer Formation at the TaC/Cu Interface in the Si/TaC/Cu Metallization System" (submitted to Applied Physics Letters). © 2001 by authors & American Institute of Physics.

Keywords: diffusion barriers, phase diagrams, thermodynamics, microelectronics, tantalum

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© 2001 Helsinki University of Technology

Last update 2011-05-26