Soluble oxide gate dielectrics prepared using the self-combustion reaction for high-performance thin-film transistors

Abstract

We report the fabrication of high-performance metal oxide thin-film transistors (TFTs) with AlO_x gate dielectrics using combustion chemistry in a solution process to provide energy to convert oxide precursors into oxides at low temperatures. Our self-combustion system utilizing two Al precursors as a fuel and an oxidizer is systematically compared with conventional combustive Al precursors with urea in terms of combustion efficiency and dielectric properties. AlO_x gate dielectric layers are spin-coated from a solution of combustive AlO_x precursors in 2-methoxyethanol and annealed at 250 °C. In this process, organic compounds can be introduced to improve the resulting layer morphology. The thermal behaviors of the self-combustive AlO_x precursors are investigated and compared with those of noncombustive AlO_x precursors and combustive urea–AlO_x precursors to evaluate the generation of exothermic heat at a relatively low annealing temperature. The AlO_x dielectrics prepared from self-combustive precursors have uniform and smooth surfaces, low leakage current densities, and high dielectric constants above 8.7. They also exhibit excellent insulating properties and no breakdown at high electric fields. Furthermore, the ZnO TFTs prepared to confirm the operation of the AlO_x gate dielectrics show a good mobility of 24.7 cm² V⁻¹ s⁻¹ and an on/off ratio of 10⁵. It is believed that the AlO_x dielectrics prepared using the self-combustion reaction at a low temperature can form a good interface facilitating the growth of desirable ZnO crystal structures, which leads to a considerable improvement in ZnO TFT performance.