Conformal Formation of (GeTe2)(1鈥?i>x)(Sb2Te3)x Layers by Atomic Layer Deposition for Nanoscale Phase Change Memories

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• 作者：Taeyong Eom ; Seol Choi ; Byung Joon Choi ; Min Hwan Lee ; Taehong Gwon ; Sang Ho Rha ; Woongkyu Lee ; Moo-Sung Kim ; Manchao Xiao ; Iain Buchanan ; Deok-Yong Cho ; Cheol Seong Hwang
• 刊名：Chemistry of Materials
• 出版年：2012
• 出版时间：June 12, 2012
• 年：2012
• 卷：24
• 期：11
• 页码：2099-2110
• 全文大小：566K
• 年卷期：v.24,no.11(June 12, 2012)
• ISSN：1520-5002

文摘

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鈥揝b鈥揟e). 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鈥搊rganic precursors were used to deposit various layers with compositions lying on the GeTe₂鈥揝b₂Te₃ tie lines at a substrate temperature as low as 70 掳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.

Keywords:

GeSbTe pseudobinary solid-solution; atomic layer deposition; phase change random access memory; reaction mechanism