In-Depth Investigation of Seed Layer Engineering in Ferroelectric Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> Film: Wakeup-Free Achievement and Reliability Mechanisms
Xiaopeng Li, Jixuan Wu, Lu Tai, Xiaoyu Dou, Pengpeng Sang, Hao Xu, Xuepeng Zhan, Xiaolei Wang, Jiezhi Chen
Abstract
Seed layer engineering in ferroelectric (FE) Hf <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{0.5}}$</tex-math> </inline-formula> Zr <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{0.5}}$</tex-math> </inline-formula> O <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{2}}$</tex-math> </inline-formula> (HZO) film has been investigated systematically in this work. Among four kinds of seed layers (ZrO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{2}}$</tex-math> </inline-formula> , HfO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{2}}$</tex-math> </inline-formula> , Al <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{2}}$</tex-math> </inline-formula> O <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{3}}$</tex-math> </inline-formula> , and TiO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{2}}$</tex-math> </inline-formula> ), the HZO capacitor with TiO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{2}}$</tex-math> </inline-formula> seed layer achieves preferable performance (larger Pr, smaller Ec, and nearly wakeup-free). It is considered that the suppression of interfacial defects by seed layers could be a key for wakeup-free achievement. For further understanding, with reliability characterizations and theoretical calculations, it is found that defects (oxygen vacancy V <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_\text{O}^{{+}}$</tex-math> </inline-formula> ) generation at the TiN/HZO interface and their migration into inner film could be dominant reasons for the leakage and Pr degradation in cycling, while V <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_\text{O}^{{+}}$</tex-math> </inline-formula> at the TiO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{2}}$</tex-math> </inline-formula> /TiN interface can attribute to the imprint effect. Thereby, a novel asymmetric stress field cycling (ASFC) scheme is proposed to suppress Pr fatigue by keeping defects at one-side interface rather than migrating into the inner film.