Thermally robust Ta/sub 2/O/sub 5/ capacitor for the 256-Mbit DRAM

The thermal degradation of the Ta/sub 2/ O/sub 5/ capacitor during BPSG reflow has been studied. The cause of deterioration of Ta/sub 2/O/sub 5/ with the TiN top electrode was found to be the oxidation of TiN. By placing a poly-Si layer between TiN and BPSG to suppress oxidation, the low leakage current level was maintained after BPSG reflow at 850/spl deg/C. The Ta/sub 2/O/sub 5/ capacitor with the TiN/poly-Si top electrode was integrated into 256-Mbit DRAM cells and excellent leakage current characteristics were obtained.