Long-term reliability of naturally aged hafnium oxide ferroelectric transistors for energy-efficient embedded memory

Ferroelectric field-effect transistors (FeFETs) based on hafnium oxide remain promising for embedded non-volatile memory, yet their long-term stability under realistic storage conditions is not well understood. Here, we examine silicon-doped hafnium oxide FeFETs that have undergone more than 5 years of natural aging in both ambient and cleanroom environments, without any electrical stress. The aged devices show a reduction in the memory window from 1.2 to 0.45 V after 104 program/erase cycles, consistent with the buildup of interface and oxide traps. Even so, they retain endurance above 104 cycles at 85°C and exhibit extrapolated retention exceeding 10 years at 55°C. Temperature-dependent charge-pumping measurements point to trap-assisted mechanisms as the dominant source of degradation, while waveform engineering with slower rise and fall times suppresses trap activation and stabilizes cycling behavior. These findings show that naturally aged FeFETs can meet key embedded-memory reliability targets and offer a practical route toward long-lived, energy-efficient memory technology.