Cryogenic Quasi-Ballistic Transport Enhanced by Strained Silicon Technologies in 14-nm Complementary Fin Field Effect Transistors Through Virtual Source Model

We present the electrical characterization of quasi-ballistic transport properties in cryogenic 14-nm complementary fin field effect transistors (FinFETs) with strained-Si technologies. In quasi-ballistic transport, drift diffusion and ballistic transport jointly determine the carrier transport in the channel of FinFETs. Electric properties of drift diffusion in cryogenic temperature were investigated based on effective hole and electron mobility through split capacitance-voltage measurement. It was found that equivalent oxide thickness (EOT) reduces as cryogenic temperature decreases. Hole mobility for pFinFETs is enhanced efficiently in cryogenic temperature due to embedded SiGe in source-drain. Scattering mechanisms of effective mobility in cryogenic temperature have been discussed as well, including phonon, surface, and remote scattering mechanisms. For ballistic transport, virtual source model (VSM) has been used to extract injection velocity and source-drain series resistance of cryogenic FinFETs. Injection velocity increases as cryogenic temperature decreases, and that of pFinFETs is much higher than that of n-ones, especially when the mask channel length shrinks, owing to strong compressive strain in the embedded SiGe source-drain. Source-drain series resistance of pFinFETs is larger than that of n-ones in cryogenic temperatures because of higher resistivity of SiGe alloy. This work provides a comprehensive understanding of quasi-ballistic transport mechanisms in cryogenic FinFETs with strained-Si technology.