The Si-SiO2Interface - Electrical Properties as Determined by the Metal-Insulator-Silicon Conductance Technique

Measurements of the equivalent parallel conductance of metal-insulator-semiconductor (MIS) capacitors are shown to give more detailed and accurate information about interface states than capacitance measurements. Experimental techniques and methods of analysis are described. From the results of the conductance technique, a realistic characterization of the Si–SiO 2 interface is developed. Salient features are: A continuum of states is found across the band gap of the silicon. Capture cross sections for holes and electrons are independent of energy over large portions of the band gap. The surface potential is subject to statistical fluctuations arising from various sources. The dominant contribution in the samples measured arises from a random distribution of surface charge. The fluctuating surface potential causes a dispersion of interface state time constants in the depletion region. In the weak inversion region the dispersion is eliminated by interaction between interface states and the minority carrier band. A single time constant results. From the experimentally established facts, equivalent circuits accurately describing the measurements are constructed.