A High-Endurance Read/Write Scheme for Half-Vcc Plate Nonvolatile DRAMs with Ferroelectric Capacitors

Hiroki FUJISAWA  Takeshi SAKATA  Tomonori SEKIGUCHI  Kazuyoshi TORII  Katsutaka KIMURA  Kazuhiko KAJIGAYA  

IEICE TRANSACTIONS on Electronics   Vol.E84-C   No.6   pp.763-770
Publication Date: 2001/06/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Nonvolatile Memories)
Category: FeRAMs
DRAM,  ferroelectric memory,  high speed,  low-power,  high-endurance,  

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A small data-line-swing read/write scheme is described for half-Vcc plate nonvolatile DRAMs with ferroelectric capacitors designed to achieve high reliability for read/write operations. In this scheme, the normal read/write operation holds the data as a charge with a small data-line-swing, and the store operation provides sufficient polarization with a full data-line-swing. This scheme enables high read/write endurance, because the small data-line-swing reduces the fatigue of the ferroelectric capacitor. Two circuit technologies are used in this scheme to increase the operating margin. The first is a plate voltage control technique that solves the polarization retention problem of half-Vcc plate nonvolatile DRAM technologies. The second is a doubled data-line-capacitance recall technique that connects two data lines to a cell and enlarges the readout signal compared to normal operation, when only one data line is connected to a cell. These techniques and circuits improve the write-cycle endurance by almost three orders of magnitude, while reducing the array power consumption during read/write operations to one-third that of conventional nonvolatile DRAMs.