Capture cross sections of defect states at the Si/SiO2 interface

Abstract

Modulation capacitance voltage spectroscopy is applied to study the interaction between interface defect states and the conduction band of thermally oxidized n-type silicon wafers, which were prepared using a broad spectrum of preparation conditions. The modulation frequency response of metal oxide semiconductor samples is measured in depletion and accumulation as a function of temperature and of the position of the Fermi level at the interface. The data reveal two different sets of states, the capture cross sections of which differ by as much as 1–2 orders of magnitude. We assign these states to two types of defects which originate from silicon dangling bonds with three backbonded silicon atoms (Pb center) and silicon dangling bonds where one backbond is substituted by oxygen (PL center). Both capture cross sections decrease monotonically with decreasing energetic separation from the conduction band.