HOT-CARRIER DEGRADATION IN MOSFETS - A CHARGE PUMPING STUDY

The charge pumping technique is used to determine the increase of interface state density due to hot carrier stressing in n-channel MOSFETS. It is seen thal the interface trap created by hot hole injection is different from that due to hot electron injection. Hot hole induced interface traps are mostly acceptor type with energy distribution in the upper half of the silicon bandgap. In the case of hot electron injection, the interface traps have an energy distribution throughout the silicon bandgap, similar to that of the unstressed device. For the same increase of interface state density, the shift of threshold voltage is lower for hot hole injection than for hot electron injection. However, the maximum transconductance degradation for hot hole injection is higher than that for hot electron injection. The variation of charge pumping current with gate offset voltage has been used to identify the type of interface traps created by hot carrier injection.