Modeling of depletion load devices made by ion implantation

An exact simulation technique for Depletion Load Devices made by Ion Implantation has been developed in the case of low drain voltages. Given the boron ion implant energy and dose, an initial doping profile is calculated from the annealing conditions and recently developed profile models. The electric field at the silicon-oxide interface and the concentration of carriers as a function of depth are calculated using a fast converging one-dimensional numerical solution to Poisson´s equation applied to the case of a non-constant doping profile. After correcting for work function differences and slow surface states, the actual drain current versus gate voltage (I-VG) for the MOS transistor are obtained. Similar calculations using the depletion approximation and an equivalent constant doping profile have been done. However, the results to be presented here show a strong dependence of the I-VGon the detailed nature of the doping profile. Excellent fit is found with the experimental data.