Comparison of interface-state generation by 25-keV electron beam irradiation in p-type and n-type MOS capacitors

Abstract

The interface state induced by 25‐keV electron beam irradiation in MOS capacitors having p‐ and n‐type substrates with several different doping concentrations have been studied. For radiation dosage on or above the order of 1×10⁻⁵ C/cm², all of the radiation‐induced interface‐state distributions tend to have a similar shape which is asymmetrical about the midgap, independent of the type and concentration of the silicon dopants, and independent of the initial interface‐state distributions. The states in the upper half of the silicon band gap are acceptor type which peak around 0.2 eV from the midgap, whereas the states in the lower half of the band gap are donor type with a lower density. For radiation dosage below 1×10⁻⁷ C/cm² the postradiation interface states are proportional to their initial values. An explanation based on the broken bond model is presented to account for the observations.