Fabrication of ZnO Thin-Film Transistors by Chemical Vapor Deposition Method using Zinc Acetate Solution

Zinc oxide (ZnO) thin-film transistors (TFTs) were fabricated by thermal chemical vapor deposition (CVD) using aqueous solutions of zinc acetate (ZnAc₂) dihydrate as a source. The precursor was supplied to the substrate by the nitrogen bubbling method through a plate with numerous orifices in the ZnAc₂ solution. The ZnO thin films were grown on silicon substrates in the growth temperature (T_G) range from 280 to 700 °C. The growth rate of ZnO thin films were linearly proportional to the growth temperature, which suggested that the growth rate is limited by the decomposition of ZnAc₂. Depletion-mode TFTs with the ZnO film grown at T_G = 350 °C was found to exhibit a relatively low saturation mobility (µ_sat). However, µ_sat increased from 1 to 14 cm²·V^-1·s^-1 and the operational mode was changed from the depletion mode to the enhancement mode by annealing treatment at 200 °C for 2 h under N₂ ambient.