Solution-processed hafnium oxide dielectric thin films for thin-film transistors applications

Hafnium oxide (HfOx) dielectric thin films were fabricated on heavily-doped silicon (100) substrates by a solution process. The precursor solution was prepared by dissolving HfCl4 in ethanol. The annealing effects on the microstructural and electrical properties of HfOx thin films were studied. The HfOx thin film annealed at 500 °C exhibited the best insulating performance with a current density of 1×10−9 A/cm2 at an electric field of 4.5 MV/cm. In order to demonstrate the possible application of HfOx thin films in thin-film transistors (TFTs), the indium-zinc oxide (IZO) channel layer was fabricated by magnetron sputtering at room temperature. The IZO TFT based on 500 °C-annealed HfOx can be operated under an operation voltage of 5 V, with a high field-effect mobility of 36.9 cm2/V s, a threshold voltage of 1.8 V, a subthreshold swing of 0.38 V/dec, and an on/off current ratio of 109. The results demonstrate that HfOx thin film prepared by the solution process is a promising gate dielectric for high-performance oxide electronic devices.