Effect of eco-friendly solvents in solution-based ZrOx dielectrics

Abstract

Over the past decade, solution-based dielectric oxides have been widely studied in electronic applications, enabling the use of low-cost processing technologies and device improvement. Among many high-к dielectrics, zirconium oxide (ZrOx) has been regarded as one of the most promising inorganic dielectric materials for its excellent properties. This work aims to study the effect of environmentally friendly solvents, in order to replace the conventional ones and obtain a safer working environment and optimize solution-based ZrOx. dielectrics. For this, ZrOx thin films were produced with different solvents and different process conditions by sol-gel method. Its microstructure and electronic properties as dielectrics in thin films metal-insulator-semiconductor structured capacitors for high-frequency circuits were investigated systematically. It was found that the capacitors obtained from a zirconium nitrate-based precursor solution with a concentration of 0.2 M in 2-methoxyethanol (2-ME) annealed at 300 °C showed an average dielectric constant of 8.7 ± 0.6 and a low leakage current density of (2.2 ± 2.7) × 10-8 A/cm2 at 1 MV/cm. However, 2-ME is a toxic solvent that can cause serious harm to human health as such eco-friendly solvents were tested. Ethanol-based ZrOx capacitors were successfully produced at 300 °C showing an average dielectric constant of 10.8 ± 0.2 and a leakage current density of (8.7 ± 0.4) × 10-7 A/cm2 at 1 MV/cm. Looking towards the future of electronics, metal-insulator-metal capacitors were processed on a flexible substrate at a low temperature of 150 °C combined with deep ultra-violet (DUV) irradiation, showing an average dielectric constant 11 ± 1 and a low leakage current density of (4.7 ± 4.7) × 10-7 A/cm2 at 0.5 MV/cm. Finally, the optimized ZrOx dielectric thin films were successfully applied as gate insulator in solution-processed In2O3 TFTs.