THIN-FILM (BA,SR)TIO3 OVER STACKED RUO2 NODES FOR GBIT DRAM CAPACITORS

The high-dielectric-constant material of (Ba,Sr)TiO3 [BST] was investi gated for application as thin films in Gbit DRAM capacitors. We develo ped a new capacitor technology involving the preparation of a thin BST film by Electron Cyclotron Resonance (ECR) plasma Chemical Vapor Depo sition (CVD) over a RuO2/Ru/TiN/TiSx storage node contacting a poly-Si plug. Temperature endurance of the RuO2/Ru/TiN/TiSix storage node at 500 degrees C was confirmed by capacitance-frequency dispersion analys is of a small-size capacitor. At this temperature, capacitor-quality B ST films were prepared with a BST deposition rate of 1.1 nm/min and a Ba:Sr:Ti film composition of 0.4:0.6:1.03. The ECR-CVD also enables un iform deposition of BST films on the electrode sidewalls. Good insulat ing BST films with a small SiO2 equivalent thickness of 0.65 nm on the electrode sidewalls were obtained. The leakage current density was 1 x 10(-6) A/cm(2) at an applied voltage of 1.0 V. A simple calculation shows that a cell capacitance of 25 fF in the 1 Gbit DRAM capacitor ar ea of 0.125 mu m(2) is achieved with a storage electrode height of 0.3 mu m.