Deposition of spinel IGZO thin films with increased indium contents on textured GZO templates

Abstract

Spinel indium gallium zinc oxide (IGZO) has been identified as an interesting alternative to amorphous IGZO (a-IGZO) due to its higher resilience to the formation of oxygen deficiencies. Currently, it is not understood whether the indium content in spinel IGZO can increase beyond the atomic concentration ratio (mole ratio) of In/(In + Ga + Zn) = 33%. In this study, we explored the deposition and structural stability of spinel IGZO films with increased indium contents. Polycrystalline spinel GZO thin films were used as a template for the growth of polycrystalline spinel IGZO by physical vapor deposition, without active heating of the substrate and without the addition of oxygen in the sputtering gas mixture. Using co-sputtering, we were able to deposit spinel IGZO thin films with different compositions. The use of sputtering with pulsed DC enhanced crystallization into the spinel phase, allowing the deposition of films with In/(In + Ga + Zn) concentration ratios up to 44%. Our results suggest that the indium rich spinel IGZO phase is structurally unstable to decomposition to In2O3 and metallic indium crystallites, during forming gas annealing at 350 °C in a H2/N2 ambient for 1 h. The insights of this work contribute to the development of spinel IGZO thin films with improved properties for various thin-film transistor applications.