A Novel Technique to Measure Interface Trap Density in an MIS Capacitor Using Time-Varying Magnetic Fields

We report a technique to probe a metal-insulator-semiconductor (MIS) capacitor's interface using time-varying magnetic fields. A semiconductor's Fermi level is magnetic field dependent, unlike that of a gate metal; this gives rise to a magnetic electromotive force (EMF) across an MIS capacitor when it is subjected to an externally applied magnetic field. This magnetic EMF can access terminals in the MIS electrical equivalent circuit that are otherwise inaccessible to a standard ac electrical voltage source. Thus, one can get a fresh pair of equations, describing the MIS interface, from an impedance measurement using periodically varying magnetic fields. When combined with the commonly used pair that is obtained from a standard electrical impedance measurement, this adds a new dimension to the possibility of extracting the interface trap parameters directly from impedance measurements. Using this technique, one should be able to extract the interface trap parameters at any given frequency, with high accuracy and precision; subsequently, deriving the interface trap model and interface physics from the data should also be possible for a given MIS capacitor. Otherwise, the opposite is usually done; i.e., first an interface model is assumed and then the lumped interface parameters are obtained from impedance data using curve fitting or assumptions. This latter method is comparatively inefficient for most MIS interfaces and yields imprecise values for the interface parameters.