This work presents a detailed RF characterization of 28-nm FD-SOI nMOSFETs at cryogenic temperatures down to 4.2 K. Two main RF Figures of Merit (FoMs), i.e., current-gain cutoff frequency (ft) and maximum oscillation frequency (fmax), as well as parasitic elements of the small-signal equivalent circuit, are extracted from the measured S-parameters. An improvement of up to ~130 GHz in ft and ~75 GHz in fmax is observed for the shortest device (25 nm) at low temperature. The behavior of RF FoMs versus temperature is discussed in terms of small-signal equivalent circuit elements, both intrinsic and extrinsic (parasitics). This study suggests 28-nm FD-SOI nMOSFETs as a good candidate for future cryogenic applications down to 4.2 K and clarifies the origin and limitations of the performance.

中文翻译：

---

28-nm FD-SOI CMOS RF 品质因数低至 4.2 K

这项工作展示了 28-nm FD-SOI nMOSFET 在低至 4.2 K 的低温下的详细 RF 特性。 两个主要的 RF 品质因数 (FoM)，即电流增益截止频率 (f _t ) 和最大振荡频率 (f _max ) 以及小信号等效电路的寄生元件是从测量的 S 参数中提取的。高达 ~130 GHz 的改进 ${\text{f}_{t}}$ 并且在低温下观察到最短器件 (25 nm) 的f _max约为 75 GHz 。RF FoM 随温度变化的行为是根据小信号等效电路元件，包括固有的和外部的（寄生效应）来讨论的。这项研究表明 28 纳米 FD-SOI nMOSFET 是未来低至 4.2 K 的低温应用的良好候选，并阐明了性能的起源和局限性。