A simple method to evaluate device lifetime due to hot-carrier effect under dynamic stress

A method to evaluate hot-carrier-induced NMOSFET degradation under dynamic stress is discussed, based on an empirical relation between device lifetime and substrate current in static stress. The device lifetime τ under dynamic stress is given by
\tau = A.I_{sub,peak}^{-2.5}/R
, where
I_{sub,peak}
is the peak value of pulsive substrate current and R is its duty ratio. The device lifetime experimentally obtained in an inverter circuit is in good agreement with the calculation results obtained from the proposed method. This method is useful to estimate device lifetime in actual circuit operational conditions.