Inhibition of Oxygen Scavenging by TiN at the TiN/SiO₂ Interface by Atomic-Layer-Deposited Al₂O₃ Protective Interlayer

Chemical composition of interfaces between physical-vapor-deposited TiN and SiO₂ as affected by introduction of a thin (0.5–3 nm) alumina interlayer was studied using photoelectron spectroscopy with high kinetic energies of photoelectrons (HAXPES) and a near-edge X-ray absorption fine structure (NEXAFS). Our results reveal the formation of TiO₂ and titanium oxynitride phases both at the bottom interface of the TiN film and at its surface due to oxygen scavenging from the SiO₂ and oxidation in air, respectively. Insertion of alumina layer as thin as the size of nanometers prevents the TiO₂ growth at the bottom TiN/SiO₂ interface but leads to the formation of an aluminosilicate layer. The thickness of this silicate layer is practically independent on the thickness of Al₂O₃. Presumably, the observed formation of SiOₓ (x < 2) at the Al₂O₃/SiO₂ interface is a result of oxygen scavenging from silicon oxide by oxygen vacancies in alumina that formed because of Al₂O₃ and TiN interaction. The present study demonstrates that the oxidation of TiN to a TiO₂ phase at the TiN/SiO₂ interface can effectively be inhibited by an insertion of a nanometer-thin Al₂O₃ layer.