探討鎳/氧化鎳/二氧化鉿核殼奈米線製備之電阻式記憶體電阻轉換特性

Abstract

現今的新型非揮發記憶體之中，電阻式記憶體是最具潛力發展的技術。因為電阻式記憶體具有許多的優勢，例如:元件製程簡單，擁有簡單的金屬-絕緣層-金屬的三明治結構、元件操作速度快、高儲存密度、低操作電壓和低耗能等優點，但其可靠度和耐久性還沒有辦法達到太高，因此如何去建立一個穩定性高且能提升其可靠度的電阻式記憶體元件，並去釐清其完整的電阻轉態機制，成為重要的課題。 本研究利用原子層化學氣相沉積系統在鎳/氧化鎳核殼結構的奈米線外面鍍覆一層金屬氧化物，包括氧化鋁和二氧化鉿，之後再有系統的去觀察其元件在各方面的特性，包含基本的電性量測、表面的形貌改變以及元件轉態時內部元素的分布…等。在電性量測方面，觀察到有二氧化鉿的電阻式記憶體元件中，其轉態次數可高達200次以上，性質對於一維奈米結構而言是非常優異的。此外，我們也利用聚焦離子束去製作穿透式電子顯微鏡的試片來做觀察，透過高分辨穿透式電子顯微鏡、能量散佈光譜儀以及繞射圖形分析之後發現元件在轉態時，在氧化鎳轉態層會形成導電燈絲連接二氧化鉿層和中間的鎳核，而此導電燈絲的成分是由純的鉿元素所形成的。 本研究結果不僅能更加的了解電阻式記憶體元件的轉態機制而且也讓元件能夠達到更優異的特性以及更穩定的操作，相信這對於電阻式記憶體未來的發展有極大的幫助。

Resistive Random Access Memory (RRAM) is one of the most promising nonvolatile memory because it has several advantages; for example, simple MIM (metal-insulator-metal) structure, fast operation speed, high endurance, high retention, and low energy consumption. However, the reliability is not persistent and completely switching mechanism is not fully understood. In this work, we deposited different metal oxide (HfO2, Al2O3) covering the Ni/NiO nanowire by atomic-layer-deposition (ALD). The different properties, including electrical characteristics, surface morphology, and elements distribution have been systematically investigated. The electrical characteristics were excellent, and the endurance could up to 200 cycles, which is pretty good for 1-D nanostructure. Also, we used focus-ion-beam (FIB) to prepare TEM sample subsequently following TEM observation. From the TEM analysis, we made sure the position of conducting filament (CF) and confirmed the element components of CF. The diffusion of oxygen vacancies formed the conducting filament, resulting in the change of morphology. The study enriched the understanding of the mechanism and provided a new design to enhance switching properties of RRAM.