Standardized ferroelectric capacitor test methodology for nonvolatile semiconductor memory applications

Abstract The use of integrated ferroelectric capacitors as nonvolatile memory elements in semiconductor memory designs imposes additional electrical performance requirements on the capacitor which are not normally characterized in ferroelectric materials research. This paper will describe those requirements and present a suggested set of testing procedures we have developed for their standardized measurement. The most significant property for memory design is not the oft quoted traditional Sawyer-Tower continuous remanent polarization, but rather pulsed remanent polarization which can be broken down into transient remanent polarization or depolarization, which decays within one second, and retained polarization, thereafter. Retained polarization is almost always less than continuous remanent polarization. Instead of the traditional coercive voltage, we propose the concept of threshold voltage, defined as that voltage required for 1 μC/cm2 differential pulsed long term remanent polarization of capacitors polarized in opposite states. The accurate measurement of pulsed polarization depends on the testing methodology employed. We have developed a rigorous testing procedure to produce consistent measurements in volving pulse widths, pulse risetimes, pulse delays, capacitor sizes, voltage levels, repetition rates, and other details which are presented and discussed.