Solution-processed high-k HfO2 gate dielectric processed under softening temperature of polymer substrates

Abstract

A low-temperature, solution-processed high-k HfO2 gate dielectric was demonstrated. To decompose a hafnium precursor at a temperature lower than 200 °C, an aqueous solution of HfCl4 was used because the strongly hydrated hafnium precursor was decomposed at a much lower temperature than anhydrous or partially hydrated hafnium chloride. No hazardous organic material was required in the low-temperature HfO2 coating process. Thus this precursor solution is environmentally safe and it is preferable to use this solution for gate dielectric coating on flexible substrates. The fabricated HfO2 gate dielectric shows reliable breakdown characteristics and high dielectric constant. We fabricated a thin film transistor (TFT) device with this gate dielectric and a maximum processing temperature of 150 °C for all the components of the TFT. The ZnO TFT on the HfO2 gate dielectric shows field-effect mobility of 1.17 cm2 V−1 s−1 and threshold voltage of 5.87 V. These results demonstrate the potential of our HfO2 thin film for flexible electronic device fabrication.