On the Zero Temperature Coefficient in Cryogenic FD-SOI MOSFETs

In this article, we propose an explanation of the origin of the zero-temperature coefficient (ZTC) in fully depleted-silicon on insulator (FD-SOI) MOSFETs capacitance curves from room to cryogenic temperature. It is demonstrated that the ZTC is a natural consequence of the Fermi-Dirac function controlling the carrier population. Moreover, based on transport analysis in linear region, it is proven that the ZTC point is preserved in the drain current transfer characteristics only if the mobility varies as the reciprocal temperature, i.e., if it is purely phonon scattering-limited. The inclusion of other defective scattering mechanisms dispels the ZTC point. Finally, the model developed is validated by some TCAD simulations down to deep cryogenic temperatures.