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 SiO 2 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 TiO 2 and titanium oxynitride phases both at the bottom interface of the TiN film and at its surface due to oxygen scavenging from the SiO 2 and oxidation in air, respectively. Insertion of alumina layer as thin as the size of nanometers prevents the TiO 2 growth at the bottom TiN/SiO 2 interface but leads to the formation of an aluminosilicate layer. The thickness of this silicate layer is practically independent on the thickness of Al 2 O 3 . Presumably, the observed formation of SiO x ( x < 2) at the Al 2 O 3 /SiO 2 interface is a result of oxygen scavenging from silicon oxide by oxygen vacancies in alumina that formed because of Al 2 O 3 and TiN interaction. The present study demonstrates that the oxidation of TiN to a TiO 2 phase at the TiN/SiO 2 interface can effectively be inhibited by an insertion of a nanometer-thin Al 2 O 3 layer.