Threshold voltage Vt extracted by gm-maximum extrapolation method under early stage hot carrier stress is proven to be an inappropriate method once electrons are trapped in a nitride spacer. The trapping of electrons in a nitride spacer increases the series drain resistance, reducing the transconductance gm and the corresponding gate-to-source voltage Vgs at which peak gm occurs. It ultimately decreases the threshold voltage Vt extracted by the gm-maximum extrapolation method. A novel algorithm is derived to determine the relationship between the measured data and the true threshold voltage of such a device under hot carrier stress by considering the effect of series resistance in gm-maximum extrapolation method.
Relation:
IEEE Transactions on Electron Devices Volume 49, Issue 8, August 2002, Pages 1488-1490
