Dielectric Properties Investigation of Metal–Insulator–Metal (MIM) Capacitors

This study presents the construction and dielectric properties investigation of atomic-layer-deposition Al₂O₃/TiO₂/HfO₂ dielectric-film-based metal-insulator-metal (MIM) capacitors. The influence of the dielectric layer material and thickness on the performance of MIM capacitors are also systematically investigated. The morphology and surface roughness of dielectric films for different materials and thicknesses are analyzed via atomic force microscopy (AFM). Among them, the 25 nm Al₂O₃-based dielectric capacitor exhibits superior comprehensive electrical performance, including a high capacitance density of 7.89 fF·µm^-2, desirable breakdown voltage and leakage current of about 12 V and 1.4 × 10^-10 A·cm^-2, and quadratic voltage coefficient of 303.6 ppm·V^-2. Simultaneously, the fabricated capacitor indicates desirable stability in terms of frequency and bias voltage (at 1 MHz), with the corresponding slight capacitance density variation of about 0.52 fF·µm^-2 and 0.25 fF·µm^-2. Furthermore, the mechanism of the variation in capacitance density and leakage current might be attributed to the Poole-Frenkel emission and charge-trapping effect of the high-k materials. All these results indicate potential applications in integrated passive devices.