IMPROVEMENT IN NON-DESTRUCTIVE READOUT RELIABILITY OF FERAM WITH ASYMMETRICAL PROGRAMMING

ABSTRACT A nondestructive readout (NDRO) scheme without polarization reversal in a ferroelectric random access memory (FeRAM) is proposed as a solution for extending the number of readout cycles. However, the readout signal in an NDRO FeRAM is so small that the NDRO operation is sensitive to deformation of the P−V hysteresis loop, which is a manifestation of imprint phenomena. In order to minimize the imprint effect in the NDRO FeRAM, we introduced an asymmetrical polarization programming scheme. Using this scheme, we can expect an extended number of readout cycles more than 1016 regardless of the imprint phenomena in ferroelectric capacitors.