Fabrication and Characterization of 1T2C-Type Ferroelectric Memory Cell with Local Interconnections

概要

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A 1T2C-type ferroelectric memory cell, which has advantages such that the depolarization field is not generated in the ferroelectric film, and therefore the data retention time is long, was fabricated and characterized. The fabricated cell structure was planar with local interconnections between two ferroelectric capacitors on an interlayer dielectric and a polysilicon gate of a conventional n-type metal-oxide-semiconductor field effect transistor (MOSFET). This structure has an advantage over the stacked gate structure we previously fabricated, such that the process damage to the MOSFET becomes low. It was found in the "read-out" operation of the fabricated cell that the drain current on/off ratio for data "0" and "1" was as high as about l0^4 and this ratio was not degraded even if the "read-out" operation was repeated (nondestructive read-out). Furthennore, the stored data were found to be retained for one week after the "write" operation. These excellent properties are considered to be due to the newly developed device structure, in which the ferroelectric capacitors are separated from the MOSFET so that the process damage to the field effect transistor (FBI) becomes low.
社団法人応用物理学会の論文
2002-11-30