前瞻新結構電阻式記憶體元件之製作( I )

Abstract

電阻式記憶體(RRAM)為目前最具發展潛力的非揮發性記憶體，其擁有極低的操作電壓、極短的寫入抹除時間及高度的元件可微縮性，極有機會取代NAND Flash及DRAM，成為下一世代的非揮發性記憶體。對於filament導通為基礎的RRAM而言，目前研究指出不穩定導通路徑的filament造成電阻切換變異，而轉換層的氧元素的散逸可能會造成耐操度、阻值差異，所以我們想以引入新結構的方式來達到抑制上述兩者的缺點，進而增進電阻式記憶體元件之阻態切換的穩定性(stability of operation)、耐操度(endurance)，元件間的均勻性(uniformity)、並藉此新結構的方式釐清其RRAM相關的物理機制。研究內容將分成兩部份：(Ⅰ)延伸電極結構、(Ⅱ)氧控制層結構，以及上述項目之物理機制研究，研究架構如(圖一)所示。 (Ⅰ)延伸電極結構 (a)擴散電極:利用具擴散能力之金屬薄膜作為電極並透過電場將金屬離子驅入到介電層中，藉此形成延伸電極結構，以改善電阻式記憶體元件特性。並比較不同擴散金屬所形成的延伸電極結構之差異。 (b)誘發金屬絲:更進一步，利用摻入金屬路徑的方式，誘發形成金屬絲延伸傳導路徑。 (c)金屬擴散層:使用利於金屬擴散的材料，以提升金屬延伸結構的形成。 (Ⅱ)氧控制層結構 (a)氧離子吸附層:將電阻轉換反應界面上引入具氧吸附能力之元素，形成氧離子吸附層，改善電阻式記憶體操作特性，以提高介電層的電阻轉換特性與穩定度。 (b)多層控制:引入多層氧控制層的概念，更進一步提升氧離子的控制力。

Resistive random-access memory (RRAM) with the advantages of simple structure, fast read/write speed, highly density, lower cost, lower power consumption, and nonvolatile, has attracted research attention in the industry, academy, and research organizations. Therefore, RRAM has a great chance to replace NAND Flash and DRAM memories, becoming next generation nonvolatile memory. Recent research has suggested that variation of the low and high resistance states in RRAM could be caused due to the instability in the formation and disruption of the filament. In addition, the endurance and stability of RRAM may be related to the dissipation of oxygen ions in the switching layer. In this project, new device structures are employed to improve RRAM performance and to clarify the physical mechanism. The project will divide to two parts: (I) extending the electrode structure and (Ⅱ) oxygen ions confined structure. The physical mechanism of RRAM materials will be also studied. (I) Extending the electrode structure (a) Diffusion electrode: By employing the diffusion metal thin film as an electrode and inducing the diffusion metal into the dielectric layer by applying bias to the electrode, the diffusion metal filament is formed and enhances the resistive switching characteristics of the dielectric layer. (b) Trigger filament: Moreover, trigger metal conduction path by doping metal. (c) Metal diffusion layer: using the material of contributive metal diffusion to improve the formation of extending the electrode structure. (Ⅱ) Oxygen ions confined structure (a) Oxygen ions absorption: Introducing oxygen-absorbable atom into the interface of resistive switching layer to confines the range of movement of oxygen ions. It can improve the stability, performance and reliability of resistive switching behavior. (b) Multi-layer control: Introducing multi-layer control concept to improve the controllability of oxygen ions.