Spread-vertical-capacitor cell (SVC) for high-density dRAM's

An advanced three-dimensionally (3-D) stacked-capacitor cell, the spread-vertical-capacitor cell (SVC), was developed. SVC realized a storage capacitance (C_s) of 30 fF with a cell area of 1.8 μm², a capacitor height of 0.37 μm, and an equivalent SiO₂ film thickness of 7 nm for oxide-nitride-oxide (ONO). By extrapolating these results to 256-Mb DRAMs, a C_s of 24 fF is obtained with a cell area of 0.5 μm², a capacitor height of 0.4 μm, and an equivalent SiO₂ thickness of 5 nm, and these values satisfy the specifications for 256-Mb DRAMs. The low capacitor height of SVC makes possible a fabrication process using ArF excimer laser lithography