Charge trapping in ultrathin hafnium silicate/metal gate stacks

P. Srinivasan, N. A. Chowdhury, D. Misra

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Charge trapping characteristics of MOCVD HfSixOy (20% SiO2) gate stack of n-MOSFETs during substrate injection have been investigated. Positive constant voltage stress (CVS) and constant current stress (CCS) were applied at the gate of TiN-HfSixOy-SiO2/p-Si n-MOSFETs having EOT of 2 nm. Significant electron trapping is observed from the positive shift of threshold voltage (ΔVt) after stress. Curve fitting of the threshold voltage shift data confirms power law dependence for Hf-silicate gate stacks. Charge pumping measurements for both cases showed significant electron trapping at bulk Hf-silicate while interface trap generation was comparatively insignificant. A turn-around effect is noticed for ΔVt as the stress current and voltage increases under CCS and CVS. Dependence of spatial distribution of charge trapping at shallow traps on stress level in the Hf-silicate film and redistribution of trapped charges during and after removal of stress is possibly responsible for the turn-around effect.

Original languageEnglish (US)
Pages (from-to)913-915
Number of pages3
JournalIEEE Electron Device Letters
Issue number12
StatePublished - Dec 2005

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering


  • Charge pumping
  • Charge trapping
  • Hafnium silicate
  • High-k
  • Metal gate
  • Substrate injection


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