Vertical 2T-nC FeRAM Demonstration: BEOL Read Transistor for 4F2 Memory Strings and Two-Terminal Selector Design for Polarization Disturb Mitigation

In this work, we demonstrate a vertical 2T-nC FeRAM with a back-end-of-line (BEOL) read transistor (T<inf>R</inf>) for 4 F² string and propose a selector design to mitigate polarization disturb in passive capacitor crossbar arrays. Key contributions include: 1) successful integration and operation composed of a Si MOSFET write transistor (T<inf>W</inf>), 3-layer cylindrical ferroelectric capacitors, and Si-doped In<inf>2</inf>O<inf>3</inf> BEOL T<inf>R</inf>, demonstrating the feasibility of 4 F² 2 T-nC string; 2) introducing nonlinearity into the capacitor stack to suppress ferroelectric voltage drop under inhibition biases while maintaining sufficient write voltage, reducing disturbance; 3)modeling and experimental validation of inserting a metalsemiconductor (a-Si)-metal (MSM) selector into the capacitor in mitigating the disturb, particularly achieving 9x reduction of disturb after 10⁶ cycles in the V<inf>W</inf>/ 2 scheme.