Sub-5-Å La<sub>2</sub>O<sub>3</sub> In Situ Dipole Technique for Large V<sub>FB</sub> Modulation With EOT Reduction and Improved Interface for HKMG Technology
Yanzhao Wei, Jiaxin Yao, Qingzhu Zhang, Guanqiao Sang, Yunjiao Bao, Jianfeng Gao, Junfeng Li, Jun Luo, Huaxiang Yin
Abstract
In this article, an in situ La-dipole technique with atomic-scale atomic layer deposition (ALD) La2O3 in laminated high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> dielectric stacks is presented, where the large flat-band voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V} _{{\text {FB}}}$ </tex-math></inline-formula> ) modulation range is observed. Meanwhile, the lower equivalent oxide thickness (EOT) and improvements in other electrical properties are obtained. With the in situ 4.6 Å La2O3 under HfO2, a 710 mV <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V} _{{\text {FB}}}$ </tex-math></inline-formula> negative modulation range and a 0.15-nm EOT reduction are obtained. As for the gate leakage, more than two orders of magnitude decreasing under the same overdrive bias-voltage is achieved, and the same decreasing level of the voltage hysteresis under dual-sweeping is demonstrated for both obviously suppressed trap/detrap electron density ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${N} _{{\text {ot}}}$ </tex-math></inline-formula> ) and interface trap density ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${D} _{{\text {it}}}$ </tex-math></inline-formula> ) by in situ La-dipole technique. Meanwhile, since the interdiffusion of La atoms and Si atoms was observed by high-resolution transmission electron microscope (HRTEM) image and energy dispersive X-ray (EDX) analysis, an interpretative model with LaSiOx formation by the element interdiffusion between laminated layer is proposed for explaining of electrical characteristics improvement by in situ La-dipole technique. The results exhibit a promising approach for multiple threshold voltage (multi- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V} _{{\text {t}}}$ </tex-math></inline-formula> ) formation and further performance boosting in future nanosheet gate-all-around field effect transistors (NS GAA-FETs).