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Interdiffusion and Phase Formation During Thermal Annealing of Ti/Mo Bilayers on Si Substrates

Published online by Cambridge University Press:  15 February 2011

A. Mouroux ,
S.-L. Zhang ,
W. Kaplan ,
S. Nygren ,
M. Östling  and
C. S. Petersson
A. Mouroux
Affiliation:
Royal Institute of Technology, Department of Electronics, S-164 40 Kista, Sweden
S.-L. Zhang
Affiliation:
Royal Institute of Technology, Department of Electronics, S-164 40 Kista, Sweden
W. Kaplan
Affiliation:
Industrial Microelectronics Center, S-164 21 Kista Sweden
S. Nygren
Affiliation:
Ericsson Components AB, S-164 81 Kista, Sweden
M. Östling
Affiliation:
Royal Institute of Technology, Department of Electronics, S-164 40 Kista, Sweden
C. S. Petersson
Affiliation:
Royal Institute of Technology, Department of Electronics, S-164 40 Kista, Sweden
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Abstract

The formation of TiSi2 from deposited Ti layers on Si and the subsequent transformation of TiSi 2 from the C49 to the C54 phase have long been of concern, particular for the silicide formation on heavily doped, narrow polycrystalline Si lines. In this work, phase formation during rapid thermal annealing of Ti/Mo bilayers sequentially deposited on blanket Si wafers and on narrow polycrystalline Si lines (0.6 μm width) is studied. The Mo layer is always 0.5 nm thick, and the Ti either 45 nm or 60 nm. It is shown that the initial physical separation of Ti from Si by the interposed Mo layer leads to complete prevention of the formation of the C49 phase. Instead, a Mo-bearing silicide phase of hexagonal structure forms first, and the C54 phase nucleates and then grows on top of it via Si diffusion through the growing silicide layers. The significance of this finding is that the usual sequence for the formation of TiSi2,. e. the C49 phase forms as a result of the Ti-Si interaction and the C54 phase forms as the product of phase transformation, is altered by the interposition of a thin refractory metal layer, here Mo. The difficulties involved in nucleation and growth of the C54 phase are then overcome, yet by a different approach than the usually employed ones which rely on ion implantation to enhance the formation of the C49 phase and the subsequent transformation to the C54 phase.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 427: Symposium K – Advanced Metallization for Future ULSI , 1996 , 511
Copyright
Copyright © Materials Research Society 1996

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