title: The interfaces of lanthanum oxide-based subnanometer EOT gate dielectrics.
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.
authors.affiliation: Department of Electronic Engineering and Information Sciences, Zhejiang University, Hangzhou, China ; Department of Electronic Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong.
authors.forename: Hei
authors.initials: H
authors.lastname: Wong
authors.affiliation: Department of Electronic Engineering and Information Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Department of Electronic Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong.
authors.forename: Jieqiong
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Electronic Engineering and Information Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Jin
authors.affiliation: Frontier Research Center, Tokyo Institute of Technology, Yokohama 226-8502, Japan.
authors.forename: Kuniyuki
authors.initials: K
authors.lastname: Kakushima
authors.affiliation: Frontier Research Center, Tokyo Institute of Technology, Yokohama 226-8502, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Iwai
keywords: High-k; Lanthanum oxide; Metal gate/high-k interface; Si/high-k interface