Novel stacked capacitor technology for 1-Gbit DRAMs with (Ba,Sr)TiO3 thin films.

Novel stacked cell capacitors with (Ba,Sr)TiO₃ (BST) films were prepared as dielectrics for Gbit-scale DRAMs. The BST films were deposited by the liquid source chemical vapor deposition (CVD) method, and Ru was used as an electrode material for storage nodes and cell plates. For BST films on Ru electrodes, a two-step film deposition process by repetition of low-temperature deposition and subsequent-high temperature annealing was shown to result in smooth surface morphology and conformal step coverage; in addition, no residues were formed on the mask side walls during Ru etching in oxygen-containing plasmas. The surfaces of the Ru electrodes were not oxidized during the BST deposition and annealing process, and these results indicate that Ru is a most possible material for capacitor electrodes. The electrical properties obtained for the 25-nm-thick BST films on Ru electrodes are: leak current density 2 × 10^-8 A/cm², silicon dioxide equivalent thickness 0.5 nm. Using these techniques, minute stacked capacitors were fabricated with storage nodes 0.24 μm wide, 0.60 μm deep, and 0.2 μm high (spaced 0.14 mm apart), and their applicability for 1-Gbit DRAM memory cells was examined. © 1997 Scripta Technica, Inc., Electron Comm Jpn Pt 2, 80(5): 70–78, 1997 [ABSTRACT FROM AUTHOR]