28-nm FDSOI nMOSFET RF Figures of Merits and Parasitic Elements Extraction at Cryogenic Temperature Down to 77 K

Abstract

This paper presents detailed RF characterization of 28-nm FDSOI nMOSFETs at cryogenic temperatures down to 77 K. Two main RF figures of merit (FoM), i.e., current gain cutoff frequency (f T) and maximum oscillation frequency (f max), as well as elements of small-signal equivalent circuit are extracted from the measured S-parameters. Increases of f T and f max by about 85 GHz and about 30 GHz, respectively, are demonstrated at 77 K. The observed behavior of RF FoMs versus temperature is discussed in terms of small-signal equivalent circuit elements, both intrinsic and extrinsic (parasitics). This paper suggests 28-nm FDSOI as a good candidate for future cryogenic applications. INDEX TERMS FDSOI, UTBB MOSFETs, RF figures of merit (FoM), cryogenic temperature, parasitic elements.

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

“…The present paper extends our previous work [18]. It is the continuation of our previous study [17] on the RF performances of 28-nm FD-SOI transistors down to 4.2 K, the liquid-helium temperature. The paper is organized as follow.…”

“…The influence of cryogenic temperature on 28-nm bulk and FD-SOI CMOS technologies with a main focus on analog parameters and modeling has been discussed in [7] and [9]. In [16] and [17], the above studies were completed by investigating the analog and RF figures of merit (FoMs) in 28nm FD-SOI CMOS technology at temperatures down to 77 K. A strong improvement of both analog and RF FoMs was demonstrated [16], [17].…”

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

“…The impact of Coulomb scattering on the mobility is more important in shorter channels [23]. The small reduction in gm from 100 K to 77 K was already reported in [10], [12] and explained by a mobility saturating at 100 K and slightly deteriorating at 77 K due to a dominant Coulomb scattering effect.…”

“…With temperature reduction from 300 K to 77 K, the gm improvement of 30 % is larger than the gd degradation of only 12 %, resulting in an overall improvement of Av by about 15% at a fixed bias condition of Vg = Vd = 1 V. The transconductance variation with temperature is mainly related to the mobility dependence on temperature. As temperature decreases, two concurrent mechanisms dictate the mobility behavior: (i) Coulomb scattering (featuring a mobility reduction with decreasing temperature) on the defects of the source/drain and extensions regions and (ii) phonon scattering (featuring a mobility improvement with decreasing temperature) [10], [12]. The impact of Coulomb scattering on the mobility is more important in shorter channels [23].…”

“…Outstanding electrostatic and variability control, excellent performance in terms of low-power, high-speed, as well as attractive analog and RF figures of merit (FoMs) offered by this technology were demonstrated in numerous publications [1]- [8]. This technology was also largely investigated at cryogenic temperatures showing promising improvement of device performance [9]- [12]. Apart from space applications, cryogenic studies are nowadays strongly motivated by a breakthrough in silicon-based quantum bits (qubit) which requires their co-integration with the control blocks and readout electronics for the realization of quantum computers [13]- [16].…”