Improvement in readout reliability of a nondestructive readout FeRAM by asymmetrical programming

A nondestructive readout (NDRO) scheme without polarization reversal in a ferroelectric random access memory (FeRAM) has been proposed as a solution for extending the number of readout cycles. However, the readout signal in the NDRO FeRAM is relatively small compared with those in current destructive readout FeRAMs. As a result, the accuracy in NDRO operation of a selected capacitor is sensitive to deformation of the polarization-voltage (P-V) hysteresis loop, which is a manifestation of imprint phenomena. In order to provide a reliable NDRO FeRAM by minimizing the influence of imprint, here we report an asymmetrical polarization program scheme.