Degradation due to hot-carrier injection and the recovery due to annealing in air have been investigated in long channel nMOSFETs, where the passivation of the dangling bonds at the Si/SiO2 interface in the post metal anneal step is done with hydrogen or deuterium. The devices with deuterium passivation exhibit less degradation than the devices with hydrogen due to the well-known isotope effect. However, the recovery of hot-carrier induced degradation by thermal annealing in air is found to be independent of the isotope. An Arrhenius activation energy (Ea) of around 0.18 eV for threshold voltage (VT) recovery for both types of devices was calculated, indicating that the recovery mechanism may be the same.
- hot carrier degradation
- Isotope effect