Improved characterization of the Si-SiO2 interface

Refined quasi-static and conductance methods, based on effectively thin composite insulating layers, low-carrier-concentration bulk semiconductors, and low-level illumination, have been applied to an improved characterization of the (100) Si-SiO2 interface. Accurate measurement of both the total density of interface states and its major components as a function of energy in the forbidden gap have been made over four decades (10-billion to 100-trillion states/eV sq cm) on a single sample. The normal U-shaped density of states is resolved into separate valence- and conduction-band-derived contributions as well as impurity-derived contributions corresponding to concentrations on the order of 20 ppm at the interface.