Low-temperature facile solution-processed gate dielectric for combustion derived oxide thin film transistors

Abstract

In this work, acetylacetone assisted solution-processed In–Ga–Zn–O (IGZO) thin film transistors (TFTs) using Al₂O₃ as gate dielectrics were investigated. Normally, fully covered Al₂O₃ thin films are difficult to achieve by spin coating with conventional solvent, such as 2-methoxyethanol, due to the poor wettability of highly doped silicon. Here, a conventional aluminum nitrate solution with an additive was designed to spin coat robust continuous Al₂O₃ thin films, resulting from improved solution hydrophilic with a contact angle of 17°. For active layer fabrication, we utilized the previous reported combustion process to lower treatment temperature, which could be confined in the range from 220 °C to 300 °C, without losing the device performance. Results show that all the devices performed well. Especially, after 240 °C annealing of both Al₂O₃ (in thickness of around 45 nm) and IGZO thin films (in thickness of around 30 nm), we have obtained the following device parameters, namely a Al₂O₃ dielectric breakdown electric field at 7.8 MV cm⁻¹, a current density of around 1 × 10⁻⁶ A cm⁻² in the voltage range of −3 V to 3 V, a areal capacitance of 291 nF cm⁻² at 100 Hz, a carrier mobility of 0.74 cm² V⁻¹ s⁻¹, a threshold voltage of −0.4 V, a current on–off ratio of 6 × 10³, a subthreshold swing of 375 mV per decade. Fabrication of combustion-processed active layers and our facile solution processed high-k dielectrics provides a feasible approach for low cost oxide flexible TFTs applications.