Atomic Layer Deposition of Sb<sub>2</sub> Te<sub>3</sub> /GeTe Superlattice Film and Its Melt-Quenching-Free Phase-Transition Mechanism for Phase-Change Memory.

Yoo, Chanyoung; Jeon, Jeong Woo; Yoon, Seungjae; Cheng, Yan; Han, Gyuseung; Choi, Wonho; Park, Byongwoo; Jeon, Gwangsik et al. · Adv Mater · 2022

basic_science · Level V

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Abstract

Atomic layer deposition (ALD) of Sb<sub>2</sub> Te<sub>3</sub> /GeTe superlattice (SL) film on planar and vertical sidewall areas containing TiN metal and SiO<sub>2</sub> insulator is demonstrated. The peculiar chemical affinity of the ALD precursor to the substrate surface and the 2D nature of the Sb<sub>2</sub> Te<sub>3</sub> enable the growth of an in situ crystallized SL film with a preferred orientation. The SL film shows a reduced reset current of ≈1/7 of the randomly oriented Ge<sub>2</sub> Sb<sub>2</sub> Te<sub>5</sub> alloy. The reset switching is induced by the transition from the SL to the (111)-oriented face-centered-cubic (FCC) Ge<sub>2</sub> Sb<sub>2</sub> Te<sub>5</sub> alloy and subsequent melt-quenching-free amorphization. The in-plane compressive stress, induced by the SL-to-FCC structural transition, enhances the electromigration of Ge along the [111] direction of FCC structure, which enables such a significant improvement. Set operation switches the amorphous to the (111)-oriented FCC structure.