Compact Metal-Ferroelectric-Insulator-Semiconductor (MFIS) Approaches Versus TCAD For The Modeling Of Ferroelectric Transistors (FeFETs): Percolation, Steep-Subthreshold and Depolarization

Ferroelectric-based transistors (FeFETs) are an important emerging technology with applications both as conventional memories and in emerging computational paradigms such as in-memory, neuromorphic and edge computing. A common modeling approach in these structures is to treat the system as a Metal-Ferroelectric-Insulator-Semiconductor (MFIS) effective circuit and use this to both qualitatively and quantitatively model device behavior. However, such approaches completely ignore three-dimensional effects. In this work TCAD is used to conduct three case studies meant to highlight common situations where a non-3D-modeling approach will lead to markedly incorrect predictions of device behavior. These three cases are: 1) channel percolation effects, 2) non-unixial ferroelectricity and 3) geometric depletion effects in SOI, Gate-All-Around (GAA) and nanowire devices. Finally, as a counter-case the observed steep-subthreshold in FeFETs has been argued to be a 3D percolation effect but here it is demonstrated that such behavior is present within an MFIS approach as well.