Improvement in Long-Term and High-Temperature Retention Stability of Ferroelectric Field-Effect Memory Transistors With Metal–Ferroelectric–Metal–Insulator–Semiconductor Gate-Stacks Using Al-Doped HfO<sub>2</sub> Thin Films
So-Jung Yoon, Dae-Hong Min, Seung Eon Moon, Kun Sik Park, Jong Il Won, Sung‐Min Yoon
Abstract
Nonvolatile memory characteristics of the ferroelectric field-effect transistors (FeFETs) were investigated by introducing the metal–ferroelectric–metal–insulator–semiconductor (MFMIS) gate-stacks, employing Al-doped HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (Al:HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) ferroelectric thin films. The obtained memory window (MW) of the MFMIS FETs increased from 1.0 to 2.8 V by increasing the areal ratios of the metal–insulator–semiconductor (MIS) to the metal–ferroelectric–metal (MFM) (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</sub> /S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</sub> ) from 8 to 32. The device with an S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</sub> /S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</sub> ratio of 16 exhibited a 3-order-of-magnitude on/off memory margin even with a program pulse duration of 500 ns. The long-term data retention was also verified by improving the tolerance against the depolarization field by introducing the MFMIS gate-stacks, which can use fully saturated polarization. The temperature-dependent memory performance and operational reliabilities of the MFMIS-FETs were also investigated at high temperatures to exploit fully the thermal stability of the Al:HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . The obtained MWs were not markedly degraded for a retention time of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> s from room temperature (RT) to 80 °C.