Abstract :
Under appropriate bias conditions, electrons flowing through an n-channel IGFET can gain sufficient energy to be injected into the gate insulator. A fraction of the injected electrons are trapped near the channel´s drain end, and a shift in device current-voltage characteristics occurs. The shift is more pronounced if the FET is operated in the reverse mode - with source and drain interchanged. Trapped electrons also modify the bell-shaped substrate current curve. The charge trapped depends on stress time and voltages, vertical and horizontal device dimensions, and insulator trapping efficiency. Data is presented illustrating threshold voltage shift dependence on stress voltage, channel length, junction depth and substrate doping. Short-term stress data is extrapolated to predict long-term shifts. Hot electron trapping represents a design limitation for n-channel IGFETs.
