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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.
Date of Publication: Aug. 2011