Yttrium Doped Hf₀.₅Zr₀.₅O₂ Based Ferroelectric Capacitor Exhibiting Fatigue Free (>10₁₂ Cycles), Long Retention, and Imprint Immune Performance at 4 K

This work demonstrates the first electrical characterization of yttrium-doped Hf<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub>Zr<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>-based ferroelectric capacitors (Y-HZO caps) at cryogenic temperatures down to 4 K, highlighting their superior endurance and reliability. Owing to a decrease in oxygen vacancy (O-vacancy) distribution and less domain pinning (due to reduced trapping) at cryogenic temperatures, the fast pulse characterization reveals 2Pr ~ 20 μC/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of Y-HZO caps at 4 K, showing >33% improvement compared to results at 300 K. Notably, the Y-HZO caps show fatigue-free endurance up to 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> cycles at 4 K, while undoped Hf<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub>Zr<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ferroelectric capacitors (HZO caps) exhibit slight fatigue. Both capacitors (caps) show imprint immunity and long retention (>10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> s). A key observation is that while HZO caps do not require wake-up at 4 K, Y-HZO caps show an anti-ferroelectric behavior, implying wake-up operation cannot be performed in Y-HZO caps at 4 K. The Y-HZO caps must be woken up at 300 K before further electrical analysis at 4 K. These findings point towards the reduced mobility of charged defects and O-vacancies significantly suppressing the domain de-pinning process at 4 K, which plays an essential part in the wake-up and fatigue of these ferroelectric capacitors. The time-dependent dielectric breakdown (TDDB) analysis also points towards improved reliability of both the caps at 4 K. These improved characteristics and reliability of Y-HZO caps make them an attractive choice for cryogenic memory applications like quantum and neuromorphic computing.