Impact of silicon nitride CESL on NLDEMOS transistor reliability

Aging of the linear drain current during OFF stress on a N-type lateral drain extended MOS is shown to be induced by the amorphous silicon nitride Contact Etch Stop Layer (CESL). A design of experiment on its PECVD conditions enables to demonstrate that the higher its Si-rich composition or at least of its interface, the higher the degradation. Supported by TCAD simulations, we propose a charge displacement model in the CESL that leads to the depletion of the extended drain region during stress explaining the on-resistance increase monitored by the linear drain current.