Control of TiN oxidation upon atomic layer deposition of oxides

Abstract

The interfaces of a physical-vapor deposited (PVD)-TiN electrode with atomic-layer deposited (ALD) HfO₂ layers were studied using photoelectron spectroscopy with high kinetic energies of photoelectrons enabling nondestructive in-depth chemical profiling and phase analysis. Our results reveal the presence of only TiN_xO_y at the TiN/ALD-HfO₂ interface with no measurable traces of the TiO₂ phase. By contrast, the interface formed by ALD of HfO₂ on top of PVD TiN contains both TiO₂ and TiN_xO_y compounds and may be compared to an HfO₂/TiN interface with intentional ALD TiO₂ interlayer (IL) formation prior to HfO₂ growth. Pre-growth of ALD Al₂O₃ IL drastically reduces the TiO₂ and TiN_xO_y amounts present at the HfO₂/TiN interface, which can be ascribed to oxygen scavenging from the initially oxidized TiN surface by energetically more favorable Al–O bonds. The present study demonstrates that the amount of TiO₂ phase can be effectively controlled, i.e., increased or decreased, during the ALD process enabling engineering of vacancy-mediated processes.