Hot-Carrier-Induced Forward and Reverse Saturation Current Degradations for the n-Type Symmetric EDMOS Transistor

In this letter, hot-carrier-induced degradations of forward and reverse saturation current (I_sat) under the worst stress condition are experimentally investigated for the n-type symmetric extended drain MOS (ns-EDMOS) transistor. It shows that the degradation of the reverse I_sat is much larger than that of the forward I_sat. Further experiments demonstrate that the phenomenon mainly results from different influences of the substrate current (I_sub) degradation upon the I_sat degradation between the forward and the reverse operational conditions. At forward operational condition, the generated acceptor-like interface states will capture the electrons and enhance the Kirk effect. Subsequently, the I_sat degradation is partially neutralized by the increase of I_sub. However, for the reverse operational condition, the I_sub shift aggravates the degradation of the I_sat. Therefore, instead of forward I_sat, reverse I_sat should be selected as the critical parameter to evaluate hot-carrier lifetime of the ns-EDMOS device.