P(VDF-TrFE) ferroelectrics: Integration in hybrid and thin-film memories

Poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE) is a promising ferroelectric polymer with potential application for both high density hybrid and printable low-cost memory. This talk will review the structural, polarization, and electrical properties of this polymer ferroelectric, identifying the key challenges and opportunities at the system level from both processing and architectural standpoints. The unique hysteresis and time-response properties permit fabrication of large crosspoint arrays which, coupled with the low processing temperatures, allow fabrication of 3D stacks to achieve dense memory chips. As with inorganic ferroelectrics, control of the polymer morphology and the polymer-metal interfaces are critical to achieve acceptable fatigue lifetime and minimize environmental degradation. The role of crystallinity, electrode materials, and electrode processing on fatigue and time-dependent polarization properties will be discussed. Transient charge traps in these films have also been characterized for the first time using a fast ramp-rate thermally stimulated current technique. In collaboration with Intel, full integration of the polymer into high density (512 Mb) hybrid memory devices was demonstrated. Several of the integration challenges associated with the formation of 3D memory stacks on conventional CMOS wafers will be presented. More recently, these polymer ferroelectric films have shown tremendous promise as one of very few potential non-volatile memory technologies for flexible and printed electronics. Crosspoint memories have been demonstrated on flexible (polymer and paper) substrates by both conventional and direct inkjet printing using either organic or nanoparticle metal conductors. A roadmap for continued development of these printed memories to track the requirements of flexible electronics will be presented.