Session 11: Flexible Electronics Applications II

All-solution-processed ferroelectric capacitors for flexible non-volatile memory applications: processing conditions and short circuits
Wednesday, February 14, 2018
4:20 PM - 4:40 PM

Flexible electronics as a new trend in electronics industry has recently attracted much attention because of their potential in providing low-cost, light-weight, thin-film, large-area, and robust solutions to modern electronics. The market for flexible electronics is expected to reach as high as $13.23 billion by 2020. The need for storage components makes non-volatile memories which retain their information even if the power supply is removed, one of the key elements to implement flexible circuits. One of leading candidates for building flexible non-volatile memory is a polymer ferroelectric capacitor which is constructed by sandwiching a ferroelectric polymer thin film between electrodes. In a ferroelectric capacitor, information is stored by aligning the direction of spontaneous polarization either up (data “1”) or down (data “0”) with an external electric field. The information stored can be retrieved by sensing the displacement current (high or low) when applying a sufficient voltage bias across the ferroelectric capacitor. The fundamental issues with polymer ferroelectric capacitors are relatively high operating voltages due to the requirement of high electric field of about 100 MV/m for polarization reversal and poor fatigue behavior. Using thinner films can effectively reduce operating voltage. However, the limit is about 100 nm, and a film thinner than that suffers from severe increase in switching time and coercive field (the minimum field required for polarization reversal). In past decades, many research and engineering efforts have been exerted to address the thinning-induced increase in switching time and coercive field. On the other hand, another thinning-induced problem, “short circuits”, seems forgotten by industry and research community, and surprisingly no report can be found to specifically deal with this issue. In fact, reducing the operating voltage of ferroelectric-capacitor-based Ferroelectric Random Access Memories (FeRAM) by using thinner polymer films is mainly bottlenecked by severe short circuits in 200 nm thick films before reaching the sub-100 nm where thinning-induced increase in switching time and coercive field start taking effects. In this work, we have demonstrated our all-solution-processed 20-bits polymer FeRAMs, and for the first time specifically investigated the short circuits conditions. The relation between processing conditions and short circuits is established.