應用混合薄膜及雙層結構改善單層二氧化鉿薄膜電阻轉換的均勻性; Uniformity Improvement of Resistive Switching in HfO2 Thin Films with Mixed Oxide and Bilayer Structure

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Title:	應用混合薄膜及雙層結構改善單層二氧化鉿薄膜電阻轉換的均勻性;Uniformity Improvement of Resistive Switching in HfO2 Thin Films with Mixed Oxide and Bilayer Structure
Authors:	張哲維;Jhe-wei Chang
Contributors:	化學工程與材料工程研究所
Keywords:	均勻性改善;三氧化二鋁;二氧化鉿;雙層結構;混合薄膜;電阻式記憶體;RRAM;Mixed oxide;Bilayer structure;HfO2;Al2O3;Uniformity improvement
Date:	2011-07-19
Issue Date:	2012-01-05 11:22:21 (UTC+8)
Abstract:	電阻式記憶體(RRAM)結合了快閃記憶體的非揮發性、靜態存取記憶體的快速存取、動態存取記憶體的高密度，配合低耗能、低成本、構造簡單、保存資料能力佳的優勢，使其在非揮發性記憶中受到極大的矚目。但直至今日，電阻式記憶體的高低阻態隨著施加偏壓而改變的轉換機制尚未明瞭，導致電阻式記憶體的電阻轉換均勻性仍有待改善。本實驗使用MOCVD方式沉積HfO2薄膜及不同厚度的Al2O3薄膜，利用混合以及雙層薄膜結構，濺鍍Ni金屬電極於薄膜上，開發金屬/氧化層/半導體的三明治(sandwich)結構之RRAM元件，藉此改善單層HfO2的電阻轉換均勻性缺點。以Al2O3薄膜在HfO2薄膜的上層或下層或者改變上層Al2O3薄膜厚度，去區分雙層薄膜的電阻轉換特性。當Al2O3薄膜在HfO2薄膜的下方時，只能操作Bipolar switching，而當Al2O3薄膜在HfO2薄膜的上方時，可以操作Nonpolar switching，但當Al2O3薄膜厚度達到一定厚度時，只能操作Bipolar switching。另外藉由單層薄膜的電性量測，去加以驗證其燈絲機制是以金屬Ni主導或是氧空缺主導。最後，本實驗利用此結果，建立其電阻轉換機制。 Resistance Random Access Memory (RRAM) has attracted increasing attention in recent years as the next-generation nonvolatile memory, due to its non-volatile property like Flash memory, fast access speed like SRAM, high-density storage like DRAM. Furthermore, RRAM has the advantages of low-power operation, low cost, simple structure, and good retention. However, understandings of RRAM mechanisms behind resistive-switching (RS) were still unknown. So it is hard to well control the uniformity of RS behaviors. In this study, various thickness of the Al2O3 layer and HfO2 layer by MOCVD deposition with the Ni top electrode. The improved uniformity of RS behaviors is demonstrated in the HfAlOX mixed oxide and the Al2O3/HfO2 bilayer RRAM devices. Furthermore, the RS properties of the bilayer structure with various Al2O3 thicknesses and the position of Al2O3 layer compared to the HfO2 have been investigated. Finally, we established the possible RS mechanisms in detail according to the electrical and physical analysis.
Appears in Collections:	[National Central University Department of Chemical & Materials Engineering] Electronic Thesis & Dissertation

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