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This work presents a detailed characterization of 28 nm FDSOI CMOS process at cryogenic temperatures. Electrostatic, Analog and RF Figures of Merit (FoM) are studied. At liquid nitrogen temperatures, 30% to 200% enhancement of drain current, Id, and maximum transconductance, gm_max, values are demonstrated. Current gain cutoff frequency, fT, increase by about 85 GHz is shown. Temperature behavior of analog and RF FoMs is discussed in terms of mobility and series resistance effect. This study suggests 28 nm FDSOI as a good contender for future read-out electronics operated at cryogenic temperatures (as e.g. around qubits or in space).

This work provides a detailed study of 28 nm fully-depleted silicon-on-insulator (FD-SOI) planar ultra-thin body and BOX (UTBB) MOSFETs for high frequency applications. All parasitic elements such as the parasitic gate and source/drain series resistances, total capacitances are extracted and their effects on RF performance are analyzed and compared with previous work on similar devices. Two main RF figures of merit (FoM) such as the current gain cut-off frequency ( f T ) and the maximum oscillation frequency ( f max ) are determined. It is shown that f T of ∼280 GHz and f max of ∼250 GHz are achievable in the shortest devices. Based on the extracted parameters, the validation of the small-signal equivalent circuit used for modeling UTBB MOSFETs is investigated by comparing simulated and measured S -parameters.

In this work self-heating and its effect on analogue device parameters are compared in 28 nm technology bulk and FDSOI MOS devices. It is shown that for self-heating characterisation in advanced MOSFETs the RF extraction technique is more suitable than the pulsed I – V . It is found that the thermal resistance is ∼3.4 times higher and the temperature rise is ∼2.5 times higher in 28 nm gate length FDSOI than in bulk. However, in spite of stronger self-heating, FDSOI devices outperform bulk over a wide frequency range. Moreover, device parameters degradation with temperature is attenuated in FDSOI transistors.

This work presents an in-depth wide-frequency band assessment of 28 nm FDSOI MOSFETs for analogue and RF applications. The focus is mainly on such figures of merit (FoM) as the transconductance gm, the output conductance gd, the intrinsic gain Av and the cut-off frequencies fT and fmax. Firstly, 28 nm FDSOI MOSFETs are compared with other advanced devices and are shown to outperform them. Secondly, gm–Av analogue metric is demonstrated to be affected by operation frequency. Small-signal parameters variation is limited and dominated by self-heating effect. This is in contrast to the first generation of ultra-thin body and BOX devices without a ground plane where coupling through the substrate has a considerable effect. Thirdly, the self-heating effect is analysed and shown to be smaller than previously predicted by simulations for such devices. Fourthly, it is shown that fT of 280 GHz and fmax of 250 GHz are reachable in the shortest devices. These values are compared to those of the first generation of UTBB devices through the effect of parasitic elements.

The Drain Induced Barrier Lowering (DIBL) behavior in Ultra-Thin Body and Buried oxide (UTBB) transistors is investigated in details in the temperature range up to 150 °C, for the first time to the best of our knowledge. The analysis is based on experimental data, physical device simulation, compact model (SPICE) simulation and previously published models. Contrary to MASTAR prediction, experiments reveal DIBL increase with temperature. Physical device simulations of different thin-film fully-depleted (FD) devices outline the generality of such behavior. SPICE simulations, with UTSOI DK2.4 model, only partially adhere to experimental trends. Several analytic models available in the literature are assessed for DIBL vs. temperature prediction. Although being the closest to experiments, Fasarakis’ model overestimates DIBL(T) dependence for shortest devices and underestimates it for upsized gate lengths frequently used in ultra-low-voltage (ULV) applications. This model is improved in our work, by introducing a temperature-dependent inversion charge at threshold. The improved model shows very good agreement with experimental data, with high gain in precision for the gate lengths under test.

A complete 65 nm CMOS platform, called LP/GP Mix, has been developed employing thick oxide transistor (IO), Low Power (LP) and General Purpose (GP) devices on the same chip. Dedicated to wireless multi-media and consumer applications, this new triple gate oxide platform is low cost (+1mask only) and saves over 35% of dynamic power with the use of the low operating voltage GP. The LP/GP mix shows competitive digital performance with a ring oscillator (FO = 1) speed equal to 7 ps per stage (GP) and 6T-SRAM static power lower than 10 pA/cell (LP). Compatible with mixed-signal design requirements, transistors show high voltage gain, low mismatch factor and low flicker noise. Moreover, to address mobile phone demands, excellent RF performance has been achieved with F T = 160 GHz for LP and 280 GHz for GP nMOS transistors.