Channel hot carrier induced volatile oxide traps responsible for random telegraph signals in submicron pMOSFETs

Abstract

The effect of channel hot carrier stress has been investigated in pMOSFETs with respect to channel hole trapping by the gate oxide traps and the resultant Random Telegraph Signals (RTS) observed at the output. Process- and stress- induced oxide traps have been identified through RTS measurements. These traps are believed to be E′ centers, acting as hole-attractive or repulsive centers, causing RTS through correlated carrier number and mobility fluctuations. Generation of E′ centers as well as activation of the passivated oxide defects as a result of stress are thought to be the reasons behind observing the stress-induced RTS. Two of the observed defects: one process-induced and one stress-induced trap have disappeared and reappeared randomly with stress. We report the reaction of the defects with hydrogen to be responsible for the volatile nature of the traps. Hydrogen is either bound to the Si/SiO2 interface or trapped at the oxide defects. Applying the stress releases these hydrogen species, which then drift towards the gate through the oxide layer and react with the oxide defects to passivate them. Reaction with another hydrogen de-passivates the defect releasing H2. This is the first article that reports hydrogen to deactivate and reactivate oxide traps responsible for RTS.