Effect of Fast Components in Threshold-Voltage Shift on Bias Temperature Instability in High- $k$ MOSFETs

The effect of fast components in the threshold-voltage shift (??V_th) induced by electrical stress on the lifetime of bias temperature instability (BTI) is investigated in metal-oxide-semiconductor field-effect transistors with high-k gate dielectrics using dc and pulsed measurements. The empirical results confirm that the initial fast ??V_th (??V_th,fast,ini.) does not contribute to long-term device degradation under operating voltage conditions. Therefore, ??V_th is corrected by eliminating the initial ??V_th,fast,ini. With this adjustment, the effect of measurement time (t_m) on the corrected ??V_th (??V_th,corr.) is negligible. However, compared with the lifetime estimates made using ??V_th,corr., the dc measurements still tend toward overestimation under low voltage stress because of the ??V_th,fast,str. component induced by stress (not the initial ??V_th,fast,ini.)In conclusion, it may be stated that the ??V_th,fast,str. component could play a critical role in BTI tests conducted under operating voltage conditions.