Low-Temperature Plasma-Oxidation Process for Reliable Tantalum-Oxide (TaO) Decoupling Capacitors

Low-temperature plasma-oxidation process of ultra-thin PVD-Ta is developed to fabricate MIM capacitors with high-k TaO dielectric through the current Cu-BEOL process. We found that controlling both the oxidation process and micro-structure of the initial Ta to be oxidized is a key to achieve high-quality TaO dielectrics. Laminated TiN/Ta/TiN bottom electrode with a flat surface in nano-scale contributes to high reliability. The integrated TaO-MIM capacitor in the Cu-BEOL achieves high breakdown voltage of 10 V with high capacitance of 13 fF/μm², and the TDDB lifetime at 85 °C exceeds 10 years at less than 4 V (2 MV/cm).