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.