Unveiling Cryogenic Performance (4 to 300 K) Towards Ultra-Thin Ferroelectric HZO: Novel Kinetic Barrier Engineering and Underlying Mechanism
Dong Zhang, Yang Feng, Zijie Zheng, Chen Sun, Qiwen Kong, Gan Liu, Zuopu Zhou, Gengchiau Liang, Kai Ni, Jixuan Wu, Jiezhi Chen, Xiao Gong
Abstract
We perform comprehensive and in-depth investigation into the cryogenic characteristics of ferroelectric (FE) HZO thin films with varying thicknesses (3/5/7/10 nm) across a broad temperature range (4~300 K), assisted by the first-principles calculations as well as extensive material and electrical characterizations. We discover: (1) 3 and 5 nm HZO films exhibit distinct temperature dependence in remnant polarization <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(P_{\mathrm{r}})$</tex> and coercive field <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(E_{\mathrm{c}})$</tex> as compared with 7 and 10 nm ones owning to different phase transition mechanisms. (2) The concentration and location of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{V}_{\mathrm{o}}{}^{2+}$</tex> emerge as pivotal factors influencing the trap-assisted-tunneling process, and thereby the temperature-dependent behaviors of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$P_{r}$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$E_{\mathrm{c}}$</tex>. (3) <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{V}_{\mathrm{o}}{}^{2+}$</tex> possesses a lower migration energy barrier as compared with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{V}_{\mathrm{o}}$</tex>, and oxygen vacancy concentration can be engineered through <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{O}_{3}$</tex> pulse duration during ALD deposition of HZO. Building upon these insights, we propose and experimentally demonstrated, for the first time, an innovative cryogenic barrier engineering approach for <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$P_{r}$</tex> enhancement, particularly valuable for ultra-thin HZO films.