1. Field of the Invention
The present invention relates to a nonvolatile ferroelectric memory device including a failed cell repairing circuit and a repair method thereof, and more specifically, to a technology of effectively processing randomly distributed cell data as well as failed cell repairing circuits of a multi-bit nonvolatile ferroelectric memory device.
2. Description of the Related Art
Generally, a ferroelectric random access memory (hereinafter, referred to as ‘FeRAM’) has attracted considerable attention as the next generation memory device because it has a data processing speed as fast as a Dynamic Random Access Memory (hereinafter, referred to as ‘DRAM’) and preserves data even after the power is turned off.
The FeRAM having structures similar to the DRAM includes the capacitors made of a ferroelectric substance, so that it utilizes the characteristic of a high residual polarization of the ferroelectric substance in which data is not deleted even after an electric field is eliminated.
The technical contents on the above FeRAM are disclosed in the Korean Patent Application No. 2001-57275 by the same inventor of the present invention. Therefore, the basic structure and the operation on the FeRAM are not described herein.
Meanwhile, a conventional multi-bit nonvolatile ferroelectric memory device has a wide data distribution in its initial process. In this case, the cell data are distributed between “00” and “01”, “01” and “10”, and “10” and “11”. When the cell data are randomly distributed, it is difficult to repair a failed cell with a general repair circuit and to effectively utilize cell data.