Thermal Stability of TiO₂ Channel FE-VNAND: From Fabrication to High-Temperature Operation

In this work, we investigated the thermal stability of TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> channel ferroelectric vertical NAND (FE-VNAND) devices during fabrication and high-temperature operation. Excellent thermally stable properties are demonstrated as follows: (1) Under various annealing temperature (550°C-650°C) and times, the fabricated FE-VNAND exhibit stable device properties with threshold voltage (Vth) variations less than 180mV and an on-off ratio over 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup>; (2) At high operation temperature up to 475K, the devices maintained excellent performance and reliability, with a 1.7V memory window (MW) and endurance over 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> cycles. The observed excellent thermal stability could be attributed to the crystalline nature of TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and its compatibility with HfO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>-based FE layers. (Keywords: NAND, TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>, Thermal stability)