1089
(Invited) Scavenging Kinetics of Interfacial SiO2 in HfO2/SiO2/Si Gate Stacks

Tuesday, October 13, 2015: 14:00
103-B (Phoenix Convention Center)
A. Toriumi (The University of Tokyo) and X. Li (The University of Tokyo)
SiO2-interface layer (IL) “scavenging” in high-k gate stacks needs to be understood for the interface control as well as for further EOT scaling. A simple model that the oxygen vacancy (Vo) was involved in the scavenging was proposed, but further details have not been elucidated well.

We have studied the SiO2-IL scavenging in HfO2/SiO2/Si gate stacks in UHV condition in place of metal electrode scavenging. This method has enabled us to study the diffusion and reaction in this system from the top surface without a metal gate.

In this talk, we particularly focus on the following three steps in the scavenging process.  

(1)   VO diffusion kinetics in scavenging

This has been studied by controlling as-deposited HfO2 stoichiometry by changing the deposition conditions.

(2)   Substrate effect on scavenging

Various types of substrates with a same gate stack have been used for the scavenging experiment.

(3)   Si diffusion kinetics in scavenging

Si out-diffusion from HfO2/SiO2/Si gate stacks has been investigated through the mass spectroscopy.

We present experimental results in each step. In particular, we notice that SiO2/Si interaction may be involved in this process, as well as that the scavenging causes SiO2-IL reduction. Furthermore, we propose an analytical model for the SiO2-IL scavenging. Interestingly, it looks like the Deal-Grove model for Si oxidation, but coefficients are related to each other in the scavenging.  

These results are important not only for scavenging SiO2-IL in HfO2/SiO2/Si stacks but also for establishing the oxide electronics, because understanding of both cation and anion kinetics in oxides is critical to control the hetero-interface characteristics.