Study of lateral nonuniformities and interface states in MIS structures

Methods for distinguishing between lateral nonuniformities and interface states in MIS structures and for characterizing lateral nonuniformities when these are determined to be present were studied. A simple, approximate method is presented for determining the distribution of flat-band voltages in a nonuniform MIS capacitor, which uses only the measured quasi-static high-frequency C-V curves of the structure. A more exact method based on use of the Fast Fourier Transform technique is also proposed. Methods are proposed for distinguishing between interface states and lateral nonuniformities which are based respectively on the frequency dependence of interface-state capacitance and on the temperature dependence of both minority-carrier generation and emission from interface states. Experimental results are presented to show the feasibility of these methods.