Title :
Charge trapping in ultrathin hafnium silicate/metal gate stacks
Author :
Srinivasan, P. ; Chowdhury, N.A. ; Misra, D.
Author_Institution :
Dept. of Electr. & Comput. Eng., New Jersey Inst. of Technol., Newark, NJ, USA
Abstract :
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.
Keywords :
MOCVD; MOSFET; curve fitting; electron traps; hafnium compounds; high-k dielectric thin films; silicon compounds; titanium compounds; 2 nm; MOSFET; TiN-HfSiO-Si; TiN-HfSiO-SiO; charge pumping measurements; charge trapping; constant current stress; constant voltage stress; electron trapping; interface trap generation; metal organic chemical vapor deposition; power law; substrate injection; threshold voltage shift; turn-around effect; Carbon capture and storage; Charge pumps; Curve fitting; Electron traps; Hafnium; MOCVD; MOSFET circuits; Stress; Substrates; Threshold voltage; Charge pumping; charge trapping; hafnium silicate; high-; metal gate; substrate injection;
Journal_Title :
Electron Device Letters, IEEE
DOI :
10.1109/LED.2005.859677