Multibit Ferroelectric FET Based on Nonidentical Double HfZrO₂ for High-Density Nonvolatile Memory

Abstract

A double-HZO (HfZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) FeFET (ferroelectric FET) with nonidentical ferroelectric thicknesses is experimentally demonstrated with as low as |V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P/E</sub> | = 5 V, 2-bit endurance > 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> cycles and retention > 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> s. Inserting an insulator to separate the ferroelectric layers and avoid the monoclinic formation of a thick Fe-HZO (ferroelectric-HZO) is a useful method to enhance the MW (memory window) for MLC (multilevel cell) applications. Double-HZO has a lower ER (error rate) and shows a 600X improvement compared to single-HZO. The stacked HZO FeFET has potential as an MLC for high-density NVM (nonvolatile memory) applications.