AN ANALYTIC SATURATION MODEL FOR DRAIN AND SUBSTRATE CURRENTS OF CONVENTIONAL AND LDD MOSFETS

An analytic saturation model for conventional and LDD MOSFET's is developed by using the pseudo-two-dimensional approximation (PTDA) in the channel and drain regions to obtain both the channel length modulation factor and the maximum electric field. Using the established I-V model in the linear region, the drain currents of conventional and LDD MOSFET's can be explicitly calculated. Furthermore, the substrate currents of conventional/LDD MOSFET's are calculated by using an existing simplified substrate current formula and the developed maximum electric field model. Using a two-dimensional numerical MOS device simulator, it is shown that the accuracy of the developed maximum electric field model is acceptable for calculating the substrate currents of conventional/LDD MOSFET's. Moreover, the parameters used in the developed model can be determined by the existing extraction methods and the developed optimization technique. Comparing the calculated drain and substrate currents with the experimental data measured from the test transistors with conventional/LDD MOS structures, the developed saturation model is shown to be valid for a wide range of channel lengths and bias conditions. © 1990 IEEE