Impact of polarization relaxation on ferroelectric memory performance

The authors have performed high-speed single-shot pulse measurements of ferroelectric capacitors that reveal a relaxation of the remanent polarization. This relaxation occurs within a few microseconds and may be attributed to the switching of domains with low effective coercive fields. The relaxation also manifests itself as a nonzero logic 0 signal in nonvolatile ferroelectric memories. A test sequence that determines the contribution of these volatile domains for any specified peak applied field is described. Using this sequence, the worst-case signal, i.e. the nonvolatile polarization of the ferroelectric film, for a nonvolatile ferroelectric memory is determined. Endurance characteristics at high switching fields exhibit a total collapse of this component. However, alternative technologies demonstrate the potential for very high endurance (>10¹¹ read/write cycles).