Dependence of interface state density on the atomic roughness at the Si — SiO 2 interface

Abstract

Quasi static Capacitance Voltage (CV) measurements have been performed on Si(111) metal-oxide-semiconductor (MOS) structures with different and well known atomic roughness. The atomic roughness was determined on an atomic scale quantitatively with spot profile analysis of low energy electron diffraction pattern (SPA-LEED). The results demonstrate a strong correlation between atomic roughness and interface state density. Even after an additional post-metallization-annealing (PMA) treatment when surface states should be minimized, the remaining interface state density is strongly correlated to the atomic roughness. A simple model which is associated with each kind of step atom, i.e. edge or kink atoms, suggests the creation of a dangling bond and therefore a surface state can explain the results. The correlation of the fixed charge Q fix to the atomic roughness can be determined in the same way. Assuming that ionized atoms which are responsible for Q fix are located preferentially at those steps or kinks which are also correlated to the dangling bonds at the interface, we confirm the general opinion that Q fix and surface states have at least one common physical origin: the atomic roughness.