High-Performance Metal–Insulator-Metal Capacitor Using Stacked $\hbox {TiO}_{2}/\hbox {Y}_{2}\hbox {O}_{3}$ as Insulator

Metal-insulator-metal (MIM) capacitors with single TiO₂ and a TiO₂/Y₂O₃ stack as an insulator are explored in this letter. It is found that, at the process temperature higher than 400°C, TiO₂ MIM capacitors demonstrate a high capacitance density at the price of an unacceptably high leakage current and voltage coefficient of capacitance (VCC). On the other hand, with the process temperature of 500°C, TiO₂/Y₂O₃ MIM capacitors display desirable characteristics in terms of a large capacitance density of 32.2 fF/μm², a low VCC of 3490 ppm/ V², small frequency dispersion, and a low leakage current of 4.5 × 10^-9 A/cm² at -1 V. The Y₂O₃ film not only provides a high dielectric-electrode band offset but also possesses high thermal stability against crystallization; both are important to suppress leakage current. In addition, the Y₂O₃ film prevents a TiO₂ film from crystallization at 500°C due to the increased entropy caused by incorporated Y atoms, and the amorphous TiO₂ film offers a high κ value to achieve a large capacitance density without sacrificing leakage current and VCC.