A 30-NS 256-MB DRAM WITH A MULTIDIVIDED ARRAY STRUCTURE

A 256-Mb DRAM with a multidivided array structure has been developed and fabricated with 0.25-mu m CMOS technology. It features 30-ns access time, 16-b I/O's, and a 35-mA operating current at a 60-ns cycle time. Three key circuit technologies were used in its design: a partial cell array activation scheme for reducing power-line voltage bounce and operating current, a selective pull-up data-line architecture to increase I/O width and reduce power dissipation, and a time-sharing refresh scheme to maintain the conventional refresh period without reducing operational margin. Memory cell size was 0.72 mu m(2). Use of the trench isolated cell transistor and the HSG cylindrical stacked capacitor cells helped reduce chip size to 333 mm(2).