New Insights into the Physical Origin of Negative Capacitance and Hysteresis in NCFETs

In this paper, direct experimental observation of negative capacitance (NC) in a standalone ferroelectric (FE) capacitor is reported for the first time, which proves that the physical origin of NC is the domain switching dynamics rather than the stabilized switching. Based on this origin, the “dynamic polarization (DP) matching”, different from the traditional capacitance matching, is rigorously derived and verified to be the prerequisite for sub-60mV/dec subthreshold swing $(\boldsymbol{S}\boldsymbol{S})$ in NCFET. The proposed DP matching can accurately describe and predict the features of NCFET based on our developed device model, showing that the $\boldsymbol{S}\boldsymbol{S}$ and hysteresis are highly sensitive to the input sweeping voltage and FE switching dynamics, as well as other device parameters. Moreover, an intrinsic conflict is found between hysteresis and $\boldsymbol{S}\boldsymbol{S}$ optimization. This work provides new understanding for the NCFET mechanism.