THEORETICAL THRESHOLD VOLTAGES FOR MOS FIELD EFFECT TRANSISTORS

By employing the charge neutrality condition in the vicinity of the gate insulator in the MOS structure, theoretical curves of the threshold voltages for both n- and p-channel MOSFETs are obtained as a function of substrate doping concentration, built-in positive charge at the oxide-silicon interface, oxide thickness, and surface trapping. Curves of theoretical threshold voltages for MOSFETs employing Al2O3-SiO2 gate insulators are also obtained. The effect of gold doping of the silicon substrate upon the threshold voltages of MOSFETs is discussed. As a result, the conditions which determine whether a particular MOSFET will be a depletion type or an enhancement type are specified as a function of the construction parameters of the device. © 1968.