氧化鋅電阻式記憶體之製備與特性研究

Fabrication and Characterization of ZnO Resistive Switching Memory Devices

黃信維

指導教授 ： 林樹均 ； 闕郁倫

國立清華大學/工學院/材料科學工程學系/博士(2013年)

摘要

本論文中，內容著重在於氧化鋅電阻式記憶體的改善以及應用。所有電阻式記憶體元件皆由氧化鋅為主要材料，且皆由原子層化學氣相沉積法與磁控濺鍍系統製備。
論文一開始將針對非揮發性記憶體進行簡單的介紹，包含各式的記憶體的應用，同時也簡述了本論文將對氧化鋅這材料進行研究之動機。接著回顧電阻式記憶體之現況，此部分亦統整了一些已被發表的重要效應與電阻轉換機製，如所使用的材料、電阻式記憶體的特性以及電阻轉換機制等，在文中將作進一步地解說。而第三章說明了本論文的實驗細節、元件的製作流程、材料分析原理與相關之電性量測等，論文中之研究結果均是在藉由這一連串的步驟所得到的。
四、五兩章節將呈現本論文核心內容。第四章敘述了利用原子層化學氣相沉積法配合感應耦合電漿進行氧化鋅薄膜的改質，藉此去深入探討氧化鋅薄膜的電性、材料性質與成長機製的關係，同時利用電漿改質的方法可有效改善其表面披覆的能力與增加其在電阻式記憶體上應用之可能性。而第五章將討論利用通氧量的不同來改善氧化鋅電阻式記憶體之穩定性。結果發現在濺鍍過程中通入少量的氧氣可穩定氧化鋅電阻式記憶體，此穩定的結果是受材料中微結構的改變與缺陷的影響所致。文章第六章部分將結合第四與第五章，利用兩種製程連續沉積氧化鋅雙層結構之電阻轉換元件，其結果顯示了非線性之電阻轉換特性，此特性將有助於解決在應用於交疊排列之矩陣電路時發生的短路現象。而文章最後一部分再對本文進行總結與建議。

關鍵字

氧化鋅 ； 電阻式記憶體 ； 原子層氣相沉積 ； 氧分壓

並列摘要

In this thesis, we focus on improvement of ZnO-based resistive random access memory (RRAM) researches. ZnO was a main material prepared by the atomic-layer-deposition (ALD) and magnetic sputtering technique for RAM devices.
In the first part, inductively coupled plasma technique (ICP), namely, remote-plasma treatment was used to ionize the water molecules in order to improve the deposition of ZnO film via the atomic layer deposition processes. The relationship between resistivity and formation mechanisms have been discussed and investigated through analyses of atomic force microscopy, photonluminescence, and absorption spectra, respectively. Findings indicate that the steric hindrance of the ligands plays an important rule for the ALD-ZnO film sample with the ICP treatment while the limited number of bonding sites will be dominant for the ALD-ZnO film without the ICP treatment owing to a decrease of the reactive sites via the ligand-exchange reaction during the dissociation process. Finally, the enhanced aspect-ratio into the anodic aluminum oxide with the better improved uniform coating of ZnO layer after the ICP treatment was demonstrated, providing an important information for a promising application in electronics based on ZnO ALD films.
In the second part, a stability scheme of resistive switching devices based on ZnO films deposited by radio frequency (RF) sputtering at different oxygen pressure ratios. I-V measurements and statistical results indicate that operating stability of ZnO ReRAM devices is highly dependent of the oxygen conditions. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) of ZnO at different O2 pressure ratios were investigated to reflect influence of structure to the stable switching behaviours. In addition, PL and XPS results were measured to investigate different charge states triggered in ZnO by oxygen vacancies, which affect the stability of the switching behavior.
In the final part, we combined the concept of the first and the second research to fabricate a bi-layer structure ZnO RRAM device. A non-linear behavior was observed in a small operating condition region. The results should be the solution to solve the sneak path problem in the cross-bar array RRAM application.

參考文獻

Chapter 1

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