Ideal MOS Curves for Silicon

Ideal curves of MOS capacity and surface potential are computed for silicon with oxide thickness and doping as a parameter. High-frequency and low-frequency capacity curves are presented for the doping ranges between 1 X 10li and 1 X 10" cm~3 and SiO2 thickness between 100 and 12000 A. Additional curves give flatband capacitance, minimum capacitance and voltage of the minimum capacitance in the same ranges* Measurement of MOS (Metal-Oxide-Semiconductor) capacity vs voltage is a convenient and widely used technique for evaluation of the properties of semiconductor-insulator interfaces.1,2'3 Most MOS-type measurements require comparison of the experimentally measured curve with the ideal curve. This is usually time consuming because the ideal curve is represented by rather complicated functions and has to be calculated for each value of silicon doping and oxide thickness separately. The purpose of this work is to facilitate such evaluations by providing a collection of curves embracing all the practically important ranges. Three sets of curves are furnished. (i) Plots of differential capacity vs voltage with thickness as a parameter and P-doping density N A varying from plot to plot. The capacity is normalized with respect to the oxide capacity Cox . The dashed lines are the high-frequency branch of the curves. (ii) A plot of surface potential f/s corresponding to each of the preceding curves vs applied voltage V. For definition of the surface potential see below. (Hi) A set of curves giving a survey of pertinent results of this calculation.