Characteristics of the Si-SiO2 interface states in thin (70–230 Å) oxide structures

Important characteristics of the Si-SiO2 interface states, such as the interface state density distributions and the electron and the hole capture cross section versus energy profiles, were investigated in unannealed metal/silicon dioxide/silicon (MOS) structures with the gate oxide thickness in the range of 70–230 Å, using the optical MOS admittance technique. The experimentally obtained interface state density distribution, in case of p-Si/SiO2/Al structures, exhibited two peaked profiles, one near the valence-band edge Ev and the other near the conduction-band edge Ec, overlying a concave background. The state density at the peak was observed to undergo a maximum, preceded by a minimum, as the gate oxide thickness tox was increased. The peak energy versus tox and the capture cross section versus tox profiles also indicated strong features.