  Self-heating (SHE) TCAD numerical simulations have been performed, for the
first time, on 30nm FDSOI MOS transistors at extremely low temperatures. The
self-heating temperature rise dTmax and the thermal resistance Rth are computed
as functions of the ambient temperature Ta and the dissipated electrical power
(Pd), considering calibrated silicon and oxide thermal conductivities. The
characteristics of the SHE temperature rise dTmax(Pd) display sub-linear
behavior at sufficiently high levels of dissipated power, in line with standard
FDSOI SHE experimental data. It has been observed that the SHE temperature rise
dTmax can significantly exceed the ambient temperature more easily at very low
temperatures. Furthermore, a detailed thermal analysis of the primary heat
flows in the FDSOI device has been conducted, leading to the development of an
analytical SHE model calibrated against TCAD simulation data. This SHE
analytical model accurately describes the dTmax(Pd) and Rth(Ta) characteristics
of an FDSOI MOS device operating at extreme low ambient temperatures. These
TCAD simulations and analytical models hold great promise for predicting the
SHE and electro-thermal performance of FDSOI MOS transistors against ambient
temperature and dissipated power.
