Role of source N+N- structure in parasitic bipolar action of lightly doped short-channel MOSFETs

Theoretical and experimental evidence of the influence of N+N- source structures, encountered in state-of-the-art short-channel NMOSTs, on the value of the breakdown sustaining voltage is presented. It appears that, by increasing the distance between the high-low diffusion junction and the N-P metallurgical junction, one decreases the emitter (source) efficiency and also the current gain of the parasitic bipolar transistor. Taking this effect into account, the same value of breakdown sustaining voltage with a lower series source and drain resistivity may be achieved. This is shown experimentally.