Raymond Pinkham

A technique for modelling p-n junction depletion capacitance of multiple doping regions in integrated circuits

Abstract The continuing advancements in integrated circuit technology have placed new burdons on the circuit design engineer, who must rely extensively upon computer simulation to correctly predict circuit behavior. One challenge is to develop better modelling techniques to more accurately deal with complex p-n junction structures often used in modern VLSI designs. This paper presents an easily implemented method for deriving parameters which accurately model the behavior of MOS VLSI structures containing complex p-n junction capacitance components. The methodology is applicable to both planar and laterally diffused junctions, whether formed by direct ion implantation or by diffusion from a finite or infinite source. The theories behind the equations used and results of the application of this new technique are discussed. A flow chart for a fitter program based on the new method is presented and described. The corresponding program written for the TI-59 scientific programmable calculator is available. Final model parameters are given and are shown to produce a numerical capacitance model which is accurate to within 2%.