Disk-Shaped Stacked Capacitor Cell for 256 Mb Dynamic Random-Access Memory

A new cell structure using the disk-shaped stacked capacitor is proposed for 256 Mb dynamic random-access memory (DRAM). This capacitor structure is formed on the sidewall of a cylindrical storage node by means of a self-alignment method. The lithographic process of the disk-shaped storage node is the same as that of the cylindrical one. The distance between adjacent storage node patterns of 0.1 µ m can be realized beyond the limits set by lithographic resolution. It is estimated that the capacitance of 25 fF/cell can be obtained in the 0.4 µ m storage node height in a 0.72 µ m2 cell area. The disk-shaped stacked capacitor, to which ON dielectric film (t eq=4 or 5 nm) is applied, is investigated with regard to electrical characteristics.