Interface States of Ion-Implanted MOS Structures

Abstract

Investigations were carried out on Si-SiO₂ interface states induced by the implantation of various ion species such as He, B, N, O, Ne, Al, Si and P. Energy distribution of the induced interface state density was determined from the quasi-static capacitance-voltage curve of the implanted MOS structures.
Density of charged interface states was found to be proportional to the number of displaced atoms produced in silicon, and was independent of the ion species implanted. Besides the continuously distributed interface states in the energy band of substrate silicon, a discrete energy level was observed around 0.4 eV from the conduction band edge, independent of the ion species implanted. Annealing extinguished these continuously distributed and discrete states in the 200-400°C range with an activation energy of 0.3-0.4 eV.
Some kind of vacancy complexes in silicon substrate are conjectured as the origin of these interface states.