The interfaces of lanthanum oxide-based subnanometer EOT gate dielectrics

Hei Wong*, Jian Zhou, Jieqiong Zhang, Hao Jin, Kuniyuki Kakushima, Hiroshi Iwai

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

When pushing the gate dielectric thickness of metal-oxide-semiconductor (MOS) devices down to the subnanometer scale, the most challenging issue is the interface. The interfacial transition layers between the high-k dielectric/Si and between the high-k dielectric/gate metal become the critical constraints for the smallest achievable film thickness. This work presents a detailed study on the interface bonding structures of the tungsten/lanthanum oxide/silicon (W/La2O3/Si) MOS structure. We found that both W/La2O3 and La2O3/Si are thermally unstable. Thermal annealing can lead to W oxidation and the forming of a complex oxide layer at the W/La2O3 interface. For the La2O3/Si interface, thermal annealing leads to a thick low-k silicate layer. These interface layers do not only cause significant device performance degradation, but also impose a limit on the thinnest equivalent oxide thickness (EOT) to be achievable which may be well above the requirements of our future technology nodes.

Original languageEnglish
Article number472
JournalNanoscale Research Letters
Volume9
Issue number1
DOIs
StatePublished - 2014

Keywords

  • High-k
  • Lanthanum oxide
  • Metal gate/high-k interface
  • Si/high-k interface

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