Self-Heating in FDSOI UTBB MOSFETs at Cryogenic Temperatures and its Effect on Analog Figures of Merit

Abstract

This work studies the self-heating (SH) effect in ultra-thin body ultra-thin buried oxide (UTBB) FDSOI MOSFETs at cryogenic temperatures down to 77 K. S-parameter measurements in a wide frequency range, with the so-called RF technique, are employed to assess SH parameters and related variation of analog figures of merit (FoMs) at different temperatures. Contrary to the expectations, the effect of self-heating on analog FoMs is slightly weaker at cryogenic temperatures with respect to roomtemperature case. The extracted thermal resistance and channel temperature rise at 300 K and 77 K in short-channel devices are of the same order of magnitude. The observed increase in SH characteristic frequency with temperature reduction emphasizes the advantage of the RF technique for the fair analysis of SH-related features in advanced technologies at cryogenic temperatures.

28-nm FD-SOI CMOS RF Figures of Merit Down to 4.2 K

“…Therefore, the curves showing small-signal parameters varying with temperature are referenced to the ambient temperature. Their study referenced to the channel temperature of the device would require a systematic study of self-heating effect [22] and is out of scope of this paper. Nevertheless, an estimation of the channel temperature for different devices is provided in Table 1, along with the dissipated power (Pdc), at an ambient temperature of 4.2 K. These estimations are computed based on the thermal resistance extracted at an ambient temperature of 77 K from [22].…”

“…Their study referenced to the channel temperature of the device would require a systematic study of self-heating effect [22] and is out of scope of this paper. Nevertheless, an estimation of the channel temperature for different devices is provided in Table 1, along with the dissipated power (Pdc), at an ambient temperature of 4.2 K. These estimations are computed based on the thermal resistance extracted at an ambient temperature of 77 K from [22]. The thermal resistivity of doped silicon and dielectrics are known to increase with temperature reduction below 77 K [23], [24].…”

Characterization of 22 nm FDSOI nMOSFETs With Different Backplane Doping at Cryogenic Temperature

“…From the Fig. 7, at low frequency, due to the influence of dynamic self heating effect, g ds shows an increasing trend, but at about a few GHz, the dynamic self heating effect is suppressed [28], [29]. In the frequency range from 10 9 Hz to 10 10 Hz, the g ds -frequency curves are relatively flat, so the g ds values of all the devices are extracted at 5 GHz in this paper.…”

Extensive Electrical Characterization Methodology of Advanced MOSFETs Towards Analog and RF Applications

“…2, 3) stays valid in a wide frequency range. Moreover, SH-induced degradation of analog FoM is slightly attenuated at cryogenic temperatures [65]. Thermal time constant is further reduced with temperature lowering and thus wide-frequency technique (we often cite it as "RF technique", because it requires measurements up to GHz range) for SH features extraction becomes even more relevant.…”

“…Normalized output conductance(a) and intrinsic gain (b) as a function of frequency in FDSOI MOSFETs at different temperatures[65].…”