RuO₂/TiN-Based Storage Electrodes for (Ba, Sr)TiO₃ Dynamic Random Access Memory Capacitors

Abstract

Sputtered (Ba, Sr)TiO 3 (BST) thin film capacitors have been fabricated with thick RuO 2 /TiN-based storage electrodes and poly-Si contact plugs, and the electrical properties of the storage electrodes have been studied. The electrode height was higher than 450 nm and the contact size was 0.8×0.8 µ m 2 . Resistance of the storage electrodes including contact plugs can be evaluated from the dispersion observed in capacitance-frequency measurements. TiN oxidation at the RuO 2 /TiN interface and native oxide at the TiN/Si contact contribute to the electrode resistance of RuO 2 /TiN electrodes. With increasing BST deposition temperature, the thickness of oxidized TiN in RuO 2 /TiN electrodes increases and the electrode resistance increases correspondingly. A Ru layer inserted at the RuO 2 /TiN interface, a T i N / T i S i 2 / S i junction and rapid thermal annealing in N 2 ambient of the TiN layer are effective ways to reduce the resistance of RuO 2 /TiN-based electrodes.