Leakage-current mechanism of a tantalum-pentoxide capacitor on rugged Si with a CVD-TiN plate electrode for high-density DRAMs

The leakage current behaviour of a high-k tantalum-pentoxide capacitor on a rugged poly-Si bottom electrode with CVD-TiN as a plate electrode was studied to determine the leakage current mechanisms. Both the rugged poly-Si electrode and the CVD-TiN electrode significantly affected the leakage current, particularly under negative voltages. These effects and the leakage current mechanisms are discussed, taking the dielectric/electrode interface and the electrodes´ surface morphology into account. We found that tantalum pentoxide with a SiO/sub 2/-equivalent thickness of 1.5 nm enables a sufficiently low leakage current, even with this electrode system, for use in 256-Mbit DRAMs.