Influences of annealing in reducing and oxidizing ambients on flatband voltage properties of HfO2 gate stack structures

K. Ohmori, P. Ahmet, M. Yoshitake, T. Chikyow, K. Shiraishi, K. Yamabe, H. Watanabe, Y. Akasaka, Y. Nara, K. S. Chang, M. L. Green, K. Yamada

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

We have applied a combinatorial technique to fabricate work function (WF) tuned Pt-W alloy films and used the films as metal electrodes for HfO2 SiO2 Si capacitors. As the ratio, RPt, of Pt to W changes from 0 to 1, the WF value varies continuously from 4.7 to 5.5 eV. This tunability enables us to systematically investigate the effect of WF variation on electrical properties. After a forming gas annealing process, the values of flatband voltage (Vfb) from capacitance-voltage properties are almost constant, regardless of the WF variation, because of oxygen vacancy formation that results in Fermi level pinning. On additional oxidizing gas annealing (OGA), the effect of WF value on Vfb becomes dominant. However, the difference in Vfb between W and Pt is 0.34 V, which is much smaller than the observed WF difference of 0.8 eV. We attribute this phenomenon to the lowering of the effective WF due to an electric dipole, induced by oxygen vacancy formation at the metal/ HfO2 interface. Moreover, a decrease in Vfb in W-rich regions was observed following the OGA, suggesting the formation of a W-O bond at the interface. These results clearly indicate that the control of bonding states at the metal/ HfO2 interfaces on an atomic scale is essential for the realization of a combination of metal and high- k dielectric films in future complementary metal-oxide-semiconductor devices.

Original languageEnglish
Article number084118
JournalJournal of Applied Physics
Volume101
Issue number8
DOIs
Publication statusPublished - 2007 May 9

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

Fingerprint Dive into the research topics of 'Influences of annealing in reducing and oxidizing ambients on flatband voltage properties of HfO<sub>2</sub> gate stack structures'. Together they form a unique fingerprint.

  • Cite this

    Ohmori, K., Ahmet, P., Yoshitake, M., Chikyow, T., Shiraishi, K., Yamabe, K., Watanabe, H., Akasaka, Y., Nara, Y., Chang, K. S., Green, M. L., & Yamada, K. (2007). Influences of annealing in reducing and oxidizing ambients on flatband voltage properties of HfO2 gate stack structures. Journal of Applied Physics, 101(8), [084118]. https://doi.org/10.1063/1.2721384