On the Physical Mechanism of Negative Capacitance Effect in Ferroelectric FET

Negative capacitance FET is a promising CMOS technology booster which may break the limit of 60mV/dec in subthreshold swing (SS) without degrading performance. We investigated the physical mechanism of negative capacitance in ferroelectric FET (FeFET) by considering the dynamics of the polarization in ferroelectric gate insulator: transient negative capacitance (TNC). Polarization switching and depolarization effect are essential to cause negative capacitance effect, that is, apparent surface potential amplification in deep subthreshold region with small depletion layer capacitance. Moreover, unique features of reverse DIBL and negative differential resistance (NDR) are also reproduced by the transient negative capacitance theory. Modeling charged defect in FeFET, hysteresis-free sub-60mV/dec SS can be realized. TNC theory is regarded as a comprehensive framework to model subthreshold characteristics of FeFET.