Effect of off-State Stress and Drain Relaxation Voltage on Degradation of a Nanoscale nMOSFET at High Temperature

This paper investigates the degradation mechanism of a nanoscale n-channel metal-oxide-semiconductor field-effect transistor (nMOSFET) that is subjected to off-state stress at high temperature and the impact of stress-induced defects on threshold voltage
V
_th
during drain relaxation. Experimental results indicate that acceptor-like interface traps
N
_it
, positive oxide charges
Q
_ox
, and neutral electron traps were generated by the off-state stress. Although the
N
_it
generated by the off-state stress caused an increase in
V
_th
, it did not influence
V
_th
during drain relaxation at a positive gate voltage. Drain relaxation filled the neutral electron traps and neutralized positive
Q
_ox
's, which increased
V
_th
and decreased the off-current significantly. This new observation suggests that the off -state stress-induced defects in a nanoscaled nMOSFET should be seriously taken in evaluating the reliability of inverter circuits.