CROWN-SHAPED STACKED-CAPACITOR CELL FOR 1.5-V OPERATION 64-MB DRAMS

A new self-aligned stacked-capacitor cell called the CROWN cell (a crown-shaped stacked-capacitor cell), used for experimental 64-Mb DRAM's operated at 1.5 V, has been developed using 0.3-mu-m electron-beam lithography. This memory cell has an area of 1.28-mu-m2. The word-line pitch and sense-amplifier pitch of this cell are 0.8 and 1.6-mu-m, respectively. In spite of this small cell area, the CROWN cell has a large capacitor surface area of 3.7-mu-m2 because 1) it has a crown-shaped capacitor electrode, 2) its capacitor is on the data line, and 3) it has a self-aligned memory cell fabrication process and structure. The large capacitor area and a Ta2O5 film equivalent to a 2.8-nm SiO2 film ensure a large storage charge of 33 fC (storage capacitance equals 44 fF) for 1.5-V operation. A small CROWN cell array and a memory test circuit were successfully used to achieve a basic DRAM cell operation.