Observation of combined self-heating and hot-carrier degradation in n-type poly-Si thin-film transistors

Different degradation behaviors of n-type poly-Si thin film transistors under dynamic voltage stresses have been demonstrated. Combined self-heating (SH) and hot-carrier (HC) degradation is first observed under a certain dynamic stress, where the device degradation is dependent on the pulse rising time (t_r) but independent of the falling time (t_f). Absence of the degradation during t_f is attributed to the SH suppression of the HC mechanism. Typical HC degradation under pure V_g pulses is dependent on t_f but in dependent of t_r. While in the channel saturation mode, AC HC effect is dependent on both t_r and t_f. For the low frequency synchronized stresses, AC SH degradation behavior related to the pulse duty time is the same as DC SH.