Memory Window Enhancement in Antiferroelectric RAM by Hf Doping in ZrO₂
Patrick D. Lomenzo, Songrui Li, L. Pintilie, Marian Cosmin Istrate, Thomas Mikolajick, Uwe Schroeder
Abstract
Antiferroelectric random access memory (AFERAM) is one of the newest alternative non-volatile memory technologies to emerge in recent years. ZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -based antiferroelectric films are exceptionally well-suited for memory applications with very high cycling endurance (>10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> ) and low operating voltages (< 2 V). Lightly alloying ZrO <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> is performed to assess AFERAM device performance with back-end-of-line compatible thin film Zr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1−x</sub> Hf <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (x <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\le0.13$ </tex-math></inline-formula> ) capacitors. The transition fields associated with antiferroelectric behavior are reduced with more Hf incorporation, yielding a larger magnitude switching polarization and memory window. Cycling endurance beyond 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> cycles is conducted on thin film capacitors where wake-up in AFERAM first leads to an increase, then a decrease in the memory window at a cumulative cycle number found to be dependent on the amount of Hf-incorporation. Hf-incorporation into ZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> is demonstrated to be a feasible way to improve the memory window in ZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -based AFERAM.