N-channel MOS FET degradation by source/drain implantation

Degraded N-channel MOSFETs have humps in their Id-Vd characteristics which are usually attributed to arsenic dopants in the channel. The arsenic dopants in the channel are due to ion channeling through the poly-silicon gate electrodes during As implantation of the source/drain regions and from direct arsenic implant into the FET channel regions. Study of this problem has led us to the discovery of a new mechanism. As implant and channeling are not the only causes of the hump. Phosphorous atoms in the gate electrode diffuse into the channel region through thin gate oxides which are damaged by channeled arsenic ions during source/drain implant. The model is verified by thermal wave experiments.