  Silicon ferroelectric field-effect transistors (FeFETs) with low-k
interfacial layer (IL) between ferroelectric gate stack and silicon channel
suffers from high write voltage, limited write endurance and large
read-after-write latency due to early IL breakdown and charge trapping and
detrapping at the interface. We demonstrate low voltage, high speed memory
operation with high write endurance using an IL-free back-end-of-line (BEOL)
compatible FeFET. We fabricate IL-free FeFETs with 28nm channel length and
126nm width under a thermal budget <400C by integrating 5nm thick Hf0.5Zr0.5O2
gate stack with amorphous Indium Tungsten Oxide (IWO) semiconductor channel. We
report 1.2V memory window and read current window of 10^5 for program and
erase, write latency of 20ns with +/-2V write pulses, read-after-write latency
<200ns, write endurance cycles exceeding 5x10^10 and 2-bit/cell programming
capability. Array-level analysis establishes IL-free BEOL FeFET as a promising
candidate for logic-compatible high-performance on-chip buffer memory and
multi-bit weight cell for compute-in-memory accelerators.
