Demonstration of Highly Robust 5 nm Hf0.5Zr0.5O₂ Ultra-Thin Ferroelectric Capacitor by Improving Interface Quality
Yan-Kui Liang, Jui-Sheng Wu, Chih-Yu Teng, Hua-Lun Ko, Quang Ho Luc, Chun-Jung Su, Edward Yi Chang, Chun-Hsiung Lin
Abstract
In this letter, 5 nm-thick HZO ultra-thin ferroelectric capacitors with excellent remanent polarization (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> ) and reliability are presented. The TiN/HZO/TiN metal-ferroelectric-metal (MFM) capacitor stack was deposited consecutively in the same atomic layer deposition (ALD) system without breaking the vacuum (i.e. “in-situ” like) to improve the interface quality between TiN electrodes and HZO ferroelectric layer. The samples show high P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> of 20.5 μC/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (i.e. 2P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> = 41 μC/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) under driving voltage of 3 V with low coercive voltage of approximately 0.6 V. The robustness of the MFM capacitor was presented by the outstanding endurance characteristics for keeping 2P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> value higher than 20 μC/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> after 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> cycles at a high electric field of 5 MV/cm without breakdown, though the P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> values gradually degrade with cycles at low field (i.e. 2.4 MV/cm). The highly robust endurance characteristics of the 5nm-thick HZO MFM capacitor indicate the good interface quality achieved in this study.