A buried-plate trench cell for a 64-Mb DRAM

A technology for fabricating a 64-Mb DRAM is described. The basic cell concept is an evolution from IBM's SPT cell and a modified SPT cell. Ground-rule shrinkage and additional features permit the realization of a cell size of 1.5 mu m/sup 2/. The chip incorporates N-array transfer gates isolated from the P-substrate by an intervening buried N-layer which forms the buried plate for the trench capacitor. The N-array devices, isolated P-well, and low-resistance wordline conductors provide a dense cell with superior soft-error-rate (SER) protection. Density improvement is achieved by the use of fully borderless contacts and ground-rule shrinkage. The interconnects use a Damascene metallization scheme that repeatedly applies chemical-mechanical polishes for dielectrics and metals.<
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