692342 event 1788533357 1788533413 <![CDATA[Ph.D. Dissertation Defense - Sharadindu Gopal Kirtania]]> Title:  High-Performance, Reliable, and Radiation-Resilient Ferroelectric Field-Effect Transistors for Monolithic 3D Memory

Committee:

Dr. Suman Datta, ECE, Chair, Advisor

Dr. Shimeng Yu

Dr. Asif Khan

Dr. Vijaykrishnan Narayanan, ECE

Dr. Kai Ni, Notre Dame

]]> The increasing demand for high-density, low-latency, and energy-efficient embedded memory has motivated the development of back-end-of-line (BEOL)-compatible nonvolatile memory for M3D integration. This dissertation investigates amorphous oxide semiconductor channel ferroelectric field-effect transistors (FEFETs) as a scalable embedded memory technology and addresses their performance, reliability, retention, radiation resilience, and array-level integration. Interlayer-free W-doped indium oxide FEFETs are demonstrated with sub 1-V write operation, 20-ns switching, write and read endurance exceeding (10^12) cycles, and retention beyond 7 days at 85 °C. Physics-based analysis is used to understand ferroelectric polarization switching, channel percolation, depolarization-field-driven retention degradation, charge screening, and bias-induced reliability mechanisms. Device operation under cryogenic conditions is also investigated, demonstrating improved cycling stability and retention through suppression of thermally activated degradation processes. Radiation studies evaluate the impact of energetic particle exposure on ferroelectric and transistor characteristics, with neutron irradiation showing robust memory operation up to (10^15) n/cm(^2) and gamma radiation upto 10 MRad. These studies establish the potential of BEOL FEFETs for reliable operation in harsh environments. Finally, BEOL-compatible 1T-1FeFET memory is extended to monolithic 3D integration through two-tier demonstrations, compact modeling, and parasitic-aware array analysis. Array-level studies further examine erase disturb, capacitive coupling, and sneak-current limitations and identify design strategies for scalable operation. These results establish BEOL-compatible FEFETs as a promising platform for high-density, reliable, radiation-resilient, and energy-efficient M3D embedded memory.

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