Thermal annealing effects on the interfacial chemistry of Ti/IGZO and TiN/IGZO structures

Oxide-semiconductor devices extensively use amorphous indium-gallium-zinc oxide (IGZO) as an active material, in which reactions at buried metal/IGZO interfaces can affect contact stability during thermal processing. Herein, we study the annealing-induced evolution of the Au/Ti/IGZO interface by cross-sectional transmission electron microscopy and energy-dispersive x-ray spectroscopy. We used positive- and negative-ion time-of-flight secondary ion mass spectrometry depth profiling and depth-resolved x-ray photoelectron spectroscopy to compare Ti/IGZO and TiN/IGZO interfaces before and after annealing. Our results show that annealing leads to significant broadening and overlap of the Ti, In, and Ga depth profiles in the Ti-IGZO stack, as well as changes in interfacial oxygen-related signals and O 1s spectral character. In contrast, the corresponding changes are substantially smaller in the TiN-containing stack. These observations support coupled elemental redistribution and interfacial reaction and highlight the importance of adhesion/contact-layer selection for the thermal stability of buried IGZO interfaces.