Sensing in Ferroelectric Memories and Flip-Flops

Abstract

Ferroelectric (FE) materials, by virtue of their polarization retention in the absence of the electric field, offer a unique method to introduce non-volatility in memories and logic. The exploration of FE materials in context of their application in compute and storage has been carried out in two forms: (1) as capacitors, in which the FE material is sandwiched between two metal layers and (2) in ferroelectric transistors (FEFETs), in which, FE is integrated into the gate stack of FETs. Both the devices have been explored to design non-volatile memories and flip-flops. The commonality between the two technologies is that they use remnant polarization in the FE to define the binary logic states. However, the sensing as well as the switching of the polarization requires considerably different techniques for FE capacitors and transistors. Moreover, the requirements of the application (memory, flip-flop, etc.) also dictate the methodology for reading or writing the logic state. This chapter discusses the device–circuit aspects of FE capacitors and FEFETs in the context of non-volatile memory and logic design, with a focus on the sensing techniques. We present a comparative description of the two technologies, highlighting the pros and cons of each and how different device structures yield significantly different sensing strategy.