Improvement of S-factor Method for Evaluation of MOS Interface State Density

In this paper, the accuracy of the S-factor method for evaluating the energy distribution of density of interface states (Dit) at MOS interfaces is examined by device simulation. Based on the analysis, we propose an improved S-factor method including the accurate depletion layer capacitance (Cd) values as a function of gate voltage, determined by gate–substrate capacitance (Cgb) and gate–channel capacitance (Cgc), and a new term, proportion to S/s, in the analytical formulation of the relationship between Dit and the S-factor. The accuracy of Dit in this improved method is also quantitatively studied through the simulation. The above modifications for the S-factor method allow us to accurately provide the energy distribution of Dit. It has been found that the accuracy of lower half of 1010 cm−2 eV−1 order can be obtained for Dit extracted by using the improved S-factor method.