A new hot-carrier degradation mechanism in high voltage nLEDMOS transistors

The anomalous hot-carrier degradation phenomenon is observed in a high voltage n-type lateral extended drain MOS (nLEDMOS) for different stress conditions. From the analysis of the electrical data and two-dimensional device simulations, a new hot-carrier degradation in a nLDMOS is presented. The electron and hole injection mechanism depends strongly on the stress conditions: at low Vgs, the degradation mechanism affecting hot carrier effect was due to both hot-hole injection in the field oxide and hot-electron injection in the gate oxide, and at high Vgs the electron injection becomes dominant. With the stress time increasing the hot carrier injection will reach saturation and the interface trap formation in the channel region takes over. A straightforward physical explanation of the observed effects is provided.