A study on the microstructural and chemical evolution of In–Ga–Zn–O sol–gel films and the effects on the electrical properties

• The chemical state and microstructure of sol–gel InGaZnO films were investigated.
• InGaZnO formation occurred in a two-step process, first at 200 °C and then 250–350 °C.
• The transistors show a sharp transition in electrical behavior over 250–350 °C.

This study examines the chemical and microstructural evolution of In–Ga–Zn–O (IGZO) sol–gel films during post-annealing. Thorough material characterization discloses that the film annealed at 300 °C is in an intermixed state of metallorganics and IGZO compound, and that the film annealed at 400 °C or higher is a fully transformed IGZO layer with many pores produced by the evaporation of residual organics. Device characterization of transistors fabricated from the films reveals that the electrical characteristics also change sharply over the same temperature range (300–400 °C): the 300 °C sample exhibits a smooth transfer curve with a very low current while the samples annealed at 350 °C or higher display a clear transistor behavior, reflecting the sensitive dependence of the device performance on the chemical state of IGZO sol–gel films.