Sol-gel derived low temperature HfO2-GPTMS hybrid gate dielectric for a-IGZO thin-film transistors (TFTs)

In this study, we prepared inorganic-organic HfO2-GPTMS hybrid films by a simple sol-gel method at low temperature for high-k dielectric gate applications. The hybrid films were deposited by spin coating process, followed by annealing at 150 °C. The hybrid dielectric material was characterized by Spectroscopic ellipsometry (SE), AFM, FESEM, FTIR, TGA, and XPS techniques. The resulting hybrid films exhibit homogeneous and smooth surface with high optical transparency. Their dielectric properties were analysed by measuring leakage current and capacitance versus voltage of metal-insulator-metal (MIM) capacitor structures. From this analysis, the leakage current density at − 5 V, capacitance and dielectric constant at 1 MHz measured on the hybrid films were 10−7 A/cm2, 51.3 nF/cm2 and of 11.4 respectively. Finally, to investigate the electrical performance of the hybrid thin films as a dielectric gate in thin film transistors (TFTs), bottom-gate TFTs were fabricated by depositing the HfO2-GPTMS dielectric gate layer on ITO-coated glass substrate and subsequently a sputtered a-IGZO thin film as the channel layer. The electrical response of the resulting TFTs demonstrated good saturation mobility of 4.74 cm2 V−1 s−1, very low threshold voltage of 0.3 V and Ion/Ioff current ratio of 104, with low operating voltage under 8 V.