A Reliable Si3N4/Al2O3-HfO2 Stack MIM Capacitor for High-Voltage Analog Applications

In this paper, we propose for the first time an attractive Si₃N₄/laminated Al₂O₃-HfO₂ (LAHO) stack metal- insulator-metal (MIM) capacitor with a low-leakage characteristic, good voltage linearity, high capacitance density, and excellent time-dependent dielectric breakdown (TDDB) reliability. The capacitor demonstrates a capacitance density of 4.2 fF/μm², quadratic voltage coefficients (α) of 106 ppm/V², and 18.92-year TDDB lifetime under a stressing voltage of 6.6 V. For the extended performance, it is projected that such a capacitor can possess a maximum capacitance density of 4.13 fF/μm² with α ≤ 100 ppm/V² and TDDB lifetime of 10 years under an analog operation of 7 V. Furthermore, this paper shows that α and TDDB lifetime of the new capacitor are very sensitive to the thickness of the Si₃N₄ film. Comparison of the new MIM capacitors with the SiO₂/HfO₂ stack MIM capacitors shows that the SiO₂/HfO₂ capacitor is more suitable for low-voltage applications, whereas the new Si₃N₄/LAHO capacitor is superior for operations requiring a higher biasing condition.