Conformal Formation of (GeTe₂)_(1–x)(Sb₂Te₃)_x Layers by Atomic Layer Deposition for Nanoscale Phase Change Memories

Abstract

Phase change random access memory appears to be the strongest candidate for next-generation high density nonvolatile memory. The fabrication of ultrahigh density phase change memory (≫1 Gb) depends heavily on the thin film growth technique for the phase changing chalcogenide material, most typically containing Ge, Sb and Te (Ge–Sb–Te). Atomic layer deposition (ALD) at low temperatures is the most preferred growth method for depositing such complex materials over surfaces possessing extreme topology. In this study, [(CH3)3Si]2Te and stable alkoxy-Ge (Ge(OCH3)4) and alkoxy-Sb (Sb(OC2H5)3) metal–organic precursors were used to deposit various layers with compositions lying on the GeTe2–Sb2Te3 tie lines at a substrate temperature as low as 70 °C using a thermal ALD process. The adsorption of Ge precursor was proven to be a physisorption type while other precursors showed a chemisorption behavior. However, the adsorption of Ge precursor was still self-regulated, and the facile ALD of the pseudobinary solid solutions with composition (GeTe2)(1‑x)(Sb2Te3) x were achieved. This chemistry-specific ALD process was quite robust against process variations, allowing highly conformal, smooth, and reproducible film growth over a contact hole structure with an extreme geometry. The detailed ALD behavior of binary compounds and incorporation behaviors of the binary compounds in pseudobinary solid solutions were studied in detail. This new composition material showed reliable phase change and accompanying resistance switching behavior, which were slightly better than the standard Ge2Sb2Te5 material in the nanoscale. The local chemical environment was similar to that of conventional Ge2Sb2Te5 materials.

Nanometric holograms based on a topological insulator material

“…28). The injection/purge times for the precursors of Sb(OC 2 H 5 ) 3 and 3[(CH 3 ) 3 Si] 2 Te were 0.75 s/9 s and 0.1 s/9 s, respectively.…”

Vapor-solid growth of Te-rich SbTe nanowires on a template of nano-size trenches

“…Besides, it has been reported that a trench structure cell of high aspect ratio has a heat confinement effect to reduce thermal energy loss and cross talk between adjacent cells in the phase transition process [8,9]. Deposition has also moved from conventional physical vapor deposition (PVD), such as sputtering and evaporation, to chemical vapor deposition (CVD) and atomic layer deposition (ALD) [10,11]. However, deposition inside the trench cell without any voids is difficult even by CVD, and, up to now, ALD is the only viable solution for fine step coverage and surface roughness control.…”

Nanoscale arrays of antimony telluride single crystals by selective chemical vapor deposition

“…Choi et al reported the selective growth of stoichiometric GeSbTe on the TiN plug material in a contact hole formed in a SiO 2 dielectric layer by using multiple precursors23. Eom et al demonstrated the selective deposition of (GeTe 2 ) (1−x) (Sb 2 Te 3 ) x into 120 nm diameter pores by atomic layer deposition24. Position-controlled synthesis of single-crystal chalcogenides nanoplate arrays on mica substrates has also been reported using van der Waals epitaxy2526.…”