The Phase Formation Sequence in Titanium-Silicon Thin Films
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The reliable use of TiSi 2 in integrated circuit metallizations will depend in part on an intimate knowledge of the effects of processing variables - such as annealing time, temperature, and ambient - on the phase formation sequence. For this reason, transmission electron microscopy has been used to investigate the formation of TiSi 2 thin films on silicon substrates [1]. For films formed either by reacting titanium with a silicon substrate or by sintering a codeposited (Ti + 2 Si) mixture, we find that a high resistivity (-60 t.L~cm), metastable phase -
TiSi 2 (C49 or ZrSi 2 structure)
-
forms prior to the desired low resistivity
(- 15 VDkcm), equilibrium phase - TiSi 2 (C54 structure). In titanium-silicon diffusion couples, a thin layer of TiSi is also present on top of the metastable TiSi2 . For processing temperatures above 550°C, the available data suggest that the metastable TiSi 2 forms first and acts as a template for subsequent nucleation of the TiSi phase. In codeposited (Ti + 2 Si) films, TiSi2 (C49 structure) is the only intermediate phase. The temperature at which the C49 structure transforms to the C54 structure increases significantly as the film impurity content increases. Differences in earlier reports of TiSi 2 formation [2-5] appear to be resolved if x-ray diffraction peaks attributed to Ti5 Si 3 and TiSi were actually from the metastable TiSi 2 .
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R. Beyers and R.Sinclair, J. Appl. Phys. 57, 5240 (1985) © 1985 American Institute of Physics.
2.
H. Kato and Y. Nakamura, Thin Solid Films 34, 135 (1976).
3. 4.
S.P. Murarka and D.B. Fraser, J. Appl. Phys. 51, 342 (1980). M. Ostling, C.S. Peterson, C. Chatfield, N. Norstrom, F. Runovc, R. Buchta, and P. Wiklund, Thin Solid Films 110, 281 (1983).
5.
T.P. Chow, W. Katz, and R. Goehnet, in VLSI Science and Technology/1984, edited by K.E. Bean and G.A. Rozgonyi (The Electrochemical Society, Princeton, NJ, 1984), p. 4 65.
Mat. Res. Soc. Symp. Proc. Vol. 54. , 1986 Materials Research Society
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