Characteristics of short-channel MOSFETs in the breakdown regime

When a short-channel MOSFET is driven into the avalanche-induced breakdown region, the drain current increases rapidly and shows a snapback characteristic. Both the substrate current and the current collected by a nearby reverse-biased pn junction also increase with increasing drain current in this region of operation. All of these effects are associated with minority-carrier injection from the source junction into the substrate. A model for the drain I-V characteristics in the snapback region is proposed. Also presented is a related model incorporating conductivity modulation that predicts linear relationships between the substrate and the remote-junction collection currents and the drain current in this region of operation. Experimental results agree well with the models.