Dielectric properties of solution-processed ZrO₂ for thin-film transistors

We have proposed an optimized ZrO₂ dielectric layer via solution processing for use in amorphous oxide semiconductor (AOS) thin-film transistors (TFTs). The optimized conditions were 5 applied spin-coatings and an annealing temperature of 350°C. These conditions were based on capacitance-voltage (C-V) characteristic measurements. When a gate bias stress of -10 V was applied to the ZrO₂ films coated 5 times for 10 minutes, the flat-band voltage (V_FB) shifted by +1.553 V. The leakage current density was 5.18 × 10^-6 A/cm² at a gate voltage of -10 V. Furthermore, when the ZrO₂ films deposited from a 0.2 M solution of ZrO₂ were annealed at 350°C for 2 h, a small difference in the C-V hysteresis curve of 20 mV was observed. The optimized ZrO₂ film had a thickness of 139 nm, a capacitance in the accumulation region of 138.23 nF/cm² and a dielectric constant of 21.70. Based on these results, the fabricated IGZO/ZrO₂ TFT showed a saturation mobility of 0.604 cm²/Vs, which is higher than that of IGZO/SiO₂ TFTs.