Flexible metal-insulator-metal capacitor using plasma enhanced binary hafnium-zirconium-oxide as gate dielectric layer

We have used a sol-gel spin-coating process to fabricate a new metal-insulator-metal capacitor comprising 10-nm thick binary hafnium-zirconium-oxide (Hf_xZr_1-xO₂) film on a flexible polyimide (PI) substrate. The surface morphology of this Hf_xZr_1-xO₂ film was investigated using atomic force microscopy and scanning electron microscopy, which confirmed that continuous and crack-free film growth had occurred on the PI. After oxygen plasma pre-treatment and subsequent annealing at 250 °C, the film on the PI substrate exhibited a low leakage current density of 3.22 × 10^-8 A/cm² at -10 V and maximum capacitance densities of 10.36 fF/μm² at 10 kHz and 9.42 fF/μm² at 1 MHz. The as-deposited sol-gel film was oxidized when employing oxygen plasma at a relatively low temperature (∼250 °C), thereby enhancing the electrical performance.