Small width effects on MOSFET hot-electron reliability

Abstract

Short channel MOSFETs of the same channel length show a width-dependent hot electron degradation (threshold voltage shift (VT) and/or drain conductance (gD)) degradation) Devices with small widths (2-3 µm) show a VTshift, while devices with larger widths show only an gDdegradation. A detailed study of hot electron injection and trapping in MOSFETs for extended periods of time shows that the threshold voltage is the dominant reason for the observed reduction in device current. The localized nature of hot electron emission and subsequent trapping in the oxide when the device is under electrical stress is shown. Based on this effect, a simple physical model is presented to explain the differences in the behavior of wide and narrow channel devices of similar effective channel lengths under stress. The experimental results obtained during the hot electron reliability study are presented and explained on the basis of the above model.