Design and structure of the ferroelectric (FE) negative Capacitance FETs (NCFETs) for sub-60 mV/dec subthreshold swing

Abstract

The ferroelectric (FE) negative capacitance FETs (NCFETs) is a promising device to achieve SS of sub-60mV/dec. This paper shows the characteristics of the Subthreshold Swing (SS) respect to the TFE (ferroelectric thickness) and the gate bias (VG) in NCFETs. The relation between the external field (E) and the polarization charge per unit area (P) is considered for the analysis of the characteristics of the SS of the NCFET. By considering slope in polarization of a ferroelectric material, we show the TFE range for SS of sub 60 mV/dec. Two ways of analyzing the characteristic of SS of NCFET were compared. The way using the real value of the dE/dP was chosen to investigate the characteristic of NCFET. The characteristics of the SS are also analyzed in the various conditions (ferroelectric material, Na, Tox, temperature and the structures (3-D MOSFET, Nanowire FET, Double Gate FET)). For SS of sub-60 mV/dec, the NCFET should have high Na, low Tox and low temperature. The D/G FET is optimal structure for the NCFET among the four FET structures in the same device physical specification.