基於氮化鍺碲碳非砷化物選擇器的高熱穩定性、低電壓變異性及高循環耐久性 (>10¹¹) 的物理分析;The Physical Analysis of High Thermal Stability, Low Voltage Variability, and High Endurance (>10¹¹) Based on a Germanium Tellurium Carbon Nitride Non-Arsenide Selector

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Title:	基於氮化鍺碲碳非砷化物選擇器的高熱穩定性、低電壓變異性及高循環耐久性 (>10¹¹) 的物理分析;The Physical Analysis of High Thermal Stability, Low Voltage Variability, and High Endurance (>10¹¹) Based on a Germanium Tellurium Carbon Nitride Non-Arsenide Selector
Authors:	吳湧峰;Wu, Yung-Feng
Contributors:	電機工程學系
Keywords:	OTS選擇器;物理模型分析
Date:	2024-11-26
Issue Date:	2025-04-09 17:48:58 (UTC+8)
Publisher:	國立中央大學
Abstract:	時至今日數據儲存量的需求爆炸性增長，迫切需要能夠在更短時間內儲存大量數據的記憶體技術，而這是 Flash 或 DRAM 無法實現的壯舉。Intel Optane，通常被稱為三維相變記憶體，是最有前途的候選者之一。具有交叉點架構的 Optane 透過層疊記憶體和稱為歐姆臨界開關 (OTS) 的選擇器來構建。OTS 裝置使用 chalcogenide 薄膜，因此近年來引起了越來越多的關注。在本研究中，我們探索了氮摻雜的GeTeC材料，作為一種Ovonic閾值開關選擇器，並且其電性能優於商業化的GeSe基選擇器。這種選擇器具有大於10⁴的關閉到開啟電流比，能夠相容於後段製程（400°C持續30分鐘），並擁有變異性低的大電壓窗口（0.8V）。為了探索微量氮元素為何顯著改變材料特性，我們在這項計算研究中應用了Berry相位方法，對GeTe基材料施加均勻電場，觀察到能隙內的局域態轉變為非局域的導帶邊緣電子態。我們採用了嚴謹的第一性原理計算和從頭算分子動力學來分析材料內的化學鍵結（化學8-N規則）以及ICOHP分析方法，以揭示低變異性的來源，這是由於穩定的C-N和C-Ge鍵結以及C-C鏈條的形成。這些原子鍵結增強了GeTe基硫族化物材料內的四面體簇結構，抑制了原子移動性並減少了相分離，從而改善了循環間的Vth變異性。透過電場模擬計算。我們的研究深入探討了OTS材料中摻砷的影響，為先進選擇器的設計和應用鋪平了道路。;To date, the demand for data storage has seen explosive growth, creating an urgent need for memory technologies capable of storing large amounts of data in a shorter time—something that Flash or DRAM cannot achieve. Intel Optane, often referred to as 3D phase-change memory, is one of the most promising candidates. Built with a cross-point architecture, Optane uses stacked memory and a selector known as an Ovonic Threshold Switch (OTS). OTS devices utilize chalcogenide thin films, which have drawn increasing attention in recent years. In this study, we explore nitrogen-doped GeTeC material as an Ovonic threshold switch selector, which demonstrates superior electrical performance compared to commercial GeSe-based selectors. This selector has an off-to-on current ratio greater than 10⁴, compatibility with back-end processes(400°C for 30 minutes), and a low variability with a large voltage window (0.8V). To　investigate how trace nitrogen elements significantly alter material properties, we applied the Berry phase method in this computational study, imposing a uniform electric field on GeTe-based materials. We observed that localized states within the band gap transition to delocalized conduction band edge states. We employed rigorous first-principles calculations and ab initio molecular dynamics to analyze chemical bonding within the material (following the 8-N rule for chemistry) and used the ICOHP analysis method to reveal the source of low variability, attributed to the formation of stable C-N and C-Ge bonds and C-C chains. These atomic bonds enhance the tetrahedral cluster structure within GeTe-based chalcogenide materials, suppress atomic mobility, and reduce phase separation, thereby improving Vth variability across cycles. Through electric field simulation calculations, our research provides an in-depth exploration of the effects of arsenic doping in OTS materials, paving the way for the design and application of advanced selectors.
Appears in Collections:	[Graduate Institute of Electrical Engineering] Electronic Thesis & Dissertation

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