Ground Plane Influence on Analog Parameters of Different UTBB nMOSFET Technologies

This paper presents an analysis of the silicon film thickness (6 nm and 14 nm), the gate dielectric material (SiO2 and High- κ material) and the Ground Plane influence on the analog parameters of Ultra Thin Body and Buried Oxide (UTBB) SOl nMOSFET devices, based on experimental and simulation results. Two channel lengths (70 nm and 1μm) have been considered and the analog performance has been analyzed as a function of the back gate bias. It is shown that at zero back gate bias , the presence of a Ground Plane improves the transconductance in the saturation region due to the strong coupling between front and back gates in devices with a long channel (1 μm), thin silicon film (6 nm) and SiO2 as gate dielectric material. However, for the intrinsic voltage gain, output conductance and Early Voltage, the devices without Ground Plane present better results due to the higher drain electrical field penetration. Short-channel transistors (70 nm) with Ground Plane show an improvement of the analog parameters also due to the high drain electrical field penetration. Similar behavior is noticed in devices with a thicker silicon film (14nm). UTBB nMOSFETs with High- κ material present less influence of a Ground Plane on the parameters analyzed. Varying the back gate bias in devices with long channel (1 μm) and SiO2 as gate dielectric material, the analog parameters present better results in devices without Ground Plane, except for the transconductance in long channel transistors with a thin silicon film, for the reason explained before (strong coupling between front and back gates). Devices with High-κ material as gate dielectric show a minor improvement of the analog performance with a Ground Plane.