Detection of Stress-Induced Interface Trap Generation on High- $k$ Gated nMOSFETs in Real Time by Stress-and-Sense Charge Pumping Technique

A stress-and-sense charge pumping (SSCP) technique is proposed in this paper to measure the stress-induced interface trap (ΔN
_it
) in real-time evolution without stress interruption. Results show that the ΔN
_it
measured by this SSCP technique is much higher than that measured by the conventional method. This difference is resulted from the recovery induced by stress interruption during the sensing measurements. The ΔN
_it
measured by SSCP method after interruption is approximately equal to that by the conventional one. The amount of recoverable ΔN
_it
is almost constant and independent of permanent damage. The stress-induced threshold voltage shift (ΔV
_th
) and ΔN
_it
under various stress frequencies and duty cycles are also measured. The ΔV
_th
seems to depend only on the total stress time of stress pulse. The ΔN
_it
measured by SSCP with different frequencies and duty cycles is similar. The ΔN
_it
also depends on the total stress time of stress pulse, but not the off time during the nonstress half cycle. In addition, it is found that the recovery induced by nonstress half cycle of ac stress is almost negligible as compared with that induced by stress interruption. Moreover, a two-stage phenomenon is observed on ΔN
_it
evolution. Results in this paper indicate that the stressing indeed induces trap generation in the first stage.