A Direct-Capacitance-Conversion FeRAM Characterization Platform for Enabling Non-Destructive 3-D Ferroelectric Capacitor Readout

Abstract

Ferroelectric-capacitor-based memory (FeRAM) is a promising emerging non-volatile memory technology that offers fast access and high endurance. Recent studies have demonstrated Ferroelectric-capacitor-based memory (FeRAM) has the potential to support Non-Destructive Readout (NDRO) as well as 3D stacking, enabling read operations that do not disturb or minor disturb the stored polarization state and higher density. However, variations in ferroelectric materials and layer structures lead to diverse hysteresis behaviors, resulting in different sensing requirements. In addition, the reduced capacitor size in deeply stacked 3D architectures further decreases the available charge, making accurate readout increasingly challenging. To better understand these issues, this work presents a highly scalable direct-capacitance-conversion characterization circuit that is capable of extracting the equivalent ferroelectric capacitance from a 3D FeRAM array. Leveraging a continuous-time delta-sigma modulator (CTDSM), the proposed platform can accurately quantize small ferroelectric equivalent capacitances ranging from 0 to 72fF with low noise and high resolution, and achieves a capacitance resolution of $0.045\mathrm {fF_{rms}}$ while consuming only $3\mu $ W power and occupying 0.001mm² chip area under a 22nm FDSOI technology. These results demonstrate the capability to characterize 3D FeRAM arrays with up to 64 vertically stacked ferroelectric capacitors (FeCAPs) and highlight strong scalability for large-scale FeRAM evaluation and design exploration.