Short-channel MOS transistors in the avalanche-multiplication regime

Short-channel MOS transistors have been analyzed in the avalanche-multiplication regime. Ionization integrals, internal body effect, and parasitic bipolar turn-on have been investigated in dependence of channel doping profile and substrate doping level. Results of a two-dimensional numerical analysis offer a better understanding of the breakdown mechanisms. For devices with shallow channel doping and high-resistivity substrate, an avalanche-current-induced barrier lowering at the source junction edge is observed. Electron injection via this locally lowered barrier triggers parasitic bipolar action. A deep channel implant improves the source barrier and lower substrate resistivity shifts the parasitic bipolar trigger voltage to higher drain voltage (1-1.5 V).