Hostname: page-component-5d59c44645-klj7v Total loading time: 0 Render date: 2024-02-28T03:44:37.058Z Has data issue: false hasContentIssue false

Dopant Condensation beyond Solubility Limit in the Vicinity of Silicon/Silicide Interface Based on First-Principles Calculations

Published online by Cambridge University Press:  01 February 2011

Takashi Yamauchi
Affiliation:
ytakashi.yamauchi@toshiba.co.jp, Toshiba Research & Development Center, Advanced LSI Technology Laboratory, 1,Komukai-Toshiba-cho, Saiwai-ku, Kawasaki, 212-8582, Japan, +81-44-549-2192, +81-44-520-1257
Yoshifumi Nishi
Affiliation:
yoshifumi.nishi@toshiba.co.jp, Corporate Research & Development Center,Toshiba Corporation, Advanced LSI Technology Laboratory, 1,Komukai-Toshiba-cho, Saiwai-ku, Kawasaki, 212-8582, Japan
Atsuhiro Kinoshita
Affiliation:
atsuhiro.kinoshita@toshiba.co.jp, Corporate Research & Development Center,Toshiba Corporation, Advanced LSI Technology Laboratory, 1,Komukai-Toshiba-cho, Saiwai-ku, Kawasaki, 212-8582, Japan
Yoshinori Tsuchiya
Affiliation:
yoshinori3.tsuchiya@toshiba.co.jp, Corporate Research & Development Center,Toshiba Corporation, Advanced LSI Technology Laboratory, 1,Komukai-Toshiba-cho, Saiwai-ku, Kawasaki, 212-8582, Japan
Junji Koga
Affiliation:
junji.koga@toshiba.co.jp, Corporate Research & Development Center,Toshiba Corporation, Advanced LSI Technology Laboratory, 1,Komukai-Toshiba-cho, Saiwai-ku, Kawasaki, 212-8582, Japan
Koichi Kato
Affiliation:
koichi3.kato@toshiba.co.jp, Corporate Research & Development Center,Toshiba Corporation, Advanced LSI Technology Laboratory, 1,Komukai-Toshiba-cho, Saiwai-ku, Kawasaki, 212-8582, Japan
Get access

Abstract

In the trend of scaling down metal-oxide-semiconductor field effect transistors (MOSFETs), reduction of contact resistance at the silicide/silicon (Si) interface will be essential for higher performance. Nickel silicide (NiSi) is considered as a substi-tute for a present electrode material in MOSFETs, cobalt silicide (CoSi2), because silicidation temperature can be reduced as compared with the case of the conventional CoSi2. Hence, we have focused on the NiSi/Si Schottky interface. An ordinary method to increase the dopant concentration at the interface is ion implantation before silicidation process. The dopant atoms are consequently condensed around the interface by snowplow effect, leading to the effective lowering of the Schottky bar-rier height (SBH) because of the band bending enhancement of the Si layer. However, this band bending technique does not reduce the SBH in further scaled MOSFETs. In this context, we studied another possibility of SBH modulation technique, based on the first-principles calculations. Throughout our calculations, we found that a large atomic-scale dipole between impurity and silicide atoms is generated across the interface. Impurity atoms are expected to be condensed because of a large energy gain at the interfaces, leading to the dramatic reduction of the SBH. Based on these results, we proposed a novel di-pole comforting Schottky (DCS) junction. We have also found that the thickness of the Si layer interfacing with the NiSi layer can be 1nm or less. In the present work, we applied this idea to the actual process through experimental techniques. The calculated results suggest that B implantation after silicidation leads to larger B concentration at the interface than that before silicidation, and thereby larger SBH modulation due to interface dipoles can be produced. Then, the NiSi/Si Schottky diodes were formed by ion implantation after silicidation process for dopants (As, B). We evaluated the interface dipoles contribution to the measured SBH reduction. As a result, the dopant atoms were found to be condensed beyond solubility limits on the interface Si side and we confirmed the generated interface dipoles actually reduces the SBT. Furthermore, we explored the other possibility of another type of impurity atoms applicable to the DCS junction. Among some other impurity atoms (Al, In, Mg), the calculated SBH modulation due to dipoles generated around these impurity atoms were found to be further enhanced in some cases. Based on these understandings, we propose a principle for choosing dopants towards ulti-mate lowering of the contact resistance in ultimately scaled MOSFETs.

Type
Research Article
Copyright
Copyright © Materials Research Society 2008

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

1. Kim, S.-D. and Woo, J.C.S., Ext.Abst.of International Workshop on Junction Technology, 1 (2002).Google Scholar
2. Ottaviani, G., J.Vac.Sci.Technol. 16, No.5, 1112 (1979).Google Scholar
3. Gambino, J.P. and Colgan, E.G., Mater. Chem. Phys. 52, No.2, 99(1998).Google Scholar
4. Murarka, S.P., Silicides for VLSI (Academic Press, London, 1983).Google Scholar
5. Thornton, R.L., Elec.Lett. 17, 485(1981).Google Scholar
6. Ohdomari, I., Tu, K.N., Suguro, K., Akiyama, M., Kimura, I., Yoneda, K., Appl. Phys. Lett., 38, no.12, 1015(1981).Google Scholar
7. Ohdomari, I., Hori, M., Maeda, T., Ogura, A., Kawarada, H., Hamamoto, T., Sano, K., Tu, K.N., Wittmer, M., Kimura, I., Yoneda, K., J. Appl. Phys. 54, no.8: 4679(1983).Google Scholar
8. Kinoshita, A., Tsuchiya, T., Yagishita, A., Uchida, K. and Koga, J., Ext.Abst.of Solid State Devices and Materials, A-5-1(2004).Google Scholar
9. Yamauchi, T., Kinoshita, A., Tsuchiya, Y., Koga, J. and Kato, K., IEDM Tech.Dig., 2006, pp.385.Google Scholar
10. Vanderbilt, D., Phys.Rev.B 41, No.11, 7892(1990).Google Scholar
11. Tsuchiaki, M., Ohuchi, K. and Nishiyama, A., Jpn.J.Appl.Phys. 44, No.4A, 1673(2005).Google Scholar
12. Pearson, W.B., Handbook of Lattice Spacing and Structures of Metals and Alloys (Pergamon, New York, 1958).Google Scholar
13. Boulet, R.M., Dunsworth, A.E., Jan, J-P and Skriver, H.L., J.Phys.F. 10, 2197(1980).Google Scholar
14. Yamauchi, T. and Mizushima, K., Phys.Rev.B 61, No.12, 8242(2000).Google Scholar
15. Tersoff, J., Phys.Rev.Lett. 52, No.6, 465(1984).Google Scholar
16. Freeouf, J.L., Solid State Commun. 33, 1059, 1980.Google Scholar
17. Bucher, E., Schulz, S., Lux-Steiner, M.Ch. and Munz, P., Appl.Phys.A 40, 71 (1986).Google Scholar
18. Vick, G.L. and Whittle, K.M., J.Eelectrochem.Soc. 116, 1142 (1969).Google Scholar
19. Sze, S.M., Semiconductor Devices physics and technology (John Wiley /& Sons Inc., New York, 1985).Google Scholar
20. Walle, Chris G. Van de, Laks, D.B., Neumark, G.F. and Pantelides, S.T., Phys.Rev.B 47, No.15, 9425(1993).Google Scholar
21. Kawasaki, T., Katayama-Yoshida, H., Physica B 302, 163(2001).Google Scholar
22. Yamauchi, T., Kinoshita, A., Tsuchiya, Y., Koga, J. and Kato, K., IEDM Tech.Dig., 2007, pp.963.Google Scholar