Characterization of Different SOI-MOS Technologies at Cryogenic Temperatures

The operation of SOI nMOS and pMOS transistors working in both inversion mode and buried channel/accumulation mode is investigated at liquid helium temperature, and compared to conventional inversion mode bulk MOS transistors. The pronounced hysteresis and kink behaviour seen in bulk MOS inversion mode transistors is strongly reduced in SOI MOS inversion mode transistors, and fully eliminated in SOI MOS buried channel/accumulation mode transistors. A general charge based model for both bulk and SOI MOS transistors is presented and discussed. It is concluded that SOI offers some substantial advantages over bulk for operation at cryogenic temperatures.