Atomic Layer Deposition of Sb2Te3/GeTe Superlattice Film and Its Melt-Quenching-Free Phase-Transition Mechanism for Phase-Change Memory

Abstract

Atomic layer deposition (ALD) of Sb2Te3/GeTe superlattice (SL) film on planar and vertical sidewall areas containing TiN metal and SiO2 insulator is demonstrated. The peculiar chemical affinity of the ALD precursor to the substrate surface and the 2D nature of the Sb2Te3 enable the growth of an in situ crystallized SL film with a preferred orientation. The SL film shows a reduced reset current of approximate to 1/7 of the randomly oriented Ge2Sb2Te5 alloy. The reset switching is induced by the transition from the SL to the (111)-oriented face-centered-cubic (FCC) Ge2Sb2Te5 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.