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 prepar ed as dielectrics for Gbit-scale DRAMs. The BST films were deposited b y 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 repe tition of low-temperature deposition and subsequent-high temperature a nnealing was shown to result in smooth surface morphology and conforma l 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 ann ealing 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 densi ty 2 x 10(-8) A/cm(2), silicon dioxide equivalent thickness 0.5 nm. Us ing these techniques, minute stacked capacitors were fabricated with s torage nodes 0.24 mu m wide, 0.60 mu m deep, and 0.2 mu m high (spaced 0.14 mm apart), and their applicability for 1-Gbit DRAM memory cells was examined. (C) 1997 Scripta Technica, Inc.