Study on resistance switching characteristics in Cr2O3 thin film for resistive random access memory

氧化鉻薄膜之電阻式記憶體轉態特性研究與探討

陳世陽

指導教授 ： 葉鳳生

國立清華大學/電機資訊學院/電子工程研究所/碩士(2010年)

摘要

由於數位相機、智慧型手機和消費電子產品廣泛的使用，非揮發性記憶體的使用將在未來幾年快速成長。但由於傳統懸浮式閘極快閃記憶體在微縮上遇到了瓶頸，所以有許多新穎的非揮發性記憶體正在研發想來取代傳統記憶體，例如電阻式記憶體。電阻式記憶體之所以被廣泛的注意是因為它擁有許多出色的性能，它具有相當出色的潛力成為下一世代的非揮發性記憶體。但其電阻轉態的物理機制與原理至今尚未明朗，因此對於電阻式記憶體的發展而言，釐清其物理機制是非常重要的。
在本篇論文中我們研究氧化鉻Cr2O3薄膜的電阻式記憶體在不同電極搭配下的轉態特性，Pt/Cr2O3/Pt、Pt/Cr2O3/TiN、Pt/Ti/Cr2O3/TiN和Ti/Cr2O3/Pt等結構。從實驗結果中我們直接觀察到氧氣的移動以及其轉態機制。此外我們發現使用TiN當作氧儲存槽是比Ti來得穩定許多。接著我們分析Pt/Cr2O3/TiN結構在各種不同偏壓下的傳導機制，這對於了解電阻轉態的物理機制是非常的有幫助。此外我們討論Pt/Cr2O3/TiN結構做多元儲存應用的可能性，發現利用不同低阻態當作多元儲存是比高阻態來得適合。此外，由於Pt/Cr2O3/TiN 結構擁有出色的轉態特性，高低阻態在直流電壓操作下都能穩定的轉態、高低阻值比超過100倍且資料記憶的特性也相當穩定，所以最後我們認為Pt/Cr2O3/TiN 結構的電阻式記憶體是很有潛力成為下一世代的非揮發性記憶體的。

關鍵字

RRAM

並列摘要

Due to digital cameras, smart phones and consumer electronics products are used widely, non-volatile memory (NVM) for use in the next few years will grow substantially. With increasing challenges of scaling conventional floating gate flash memory technology, alternative non-volatile memory technologies are under investigating, such as resistance random access memory (RRAM). RRAM has attracted extensive attention due to it has a lot of prominent performances. Therefore, it has promising potential in the next-generation non-volatile memory. However, the physical origin of this switching phenomenon is not yet clearly. Therefore, elucidation of mechanism is very important in the development of RRAM.
In this thesis, we investigate the resistance switching characteristics of Cr2O3-based RRAM with different electrodes, such as Pt/Cr2O3/Pt, Pt/Cr2O3/TiN, Pt/Ti/Cr2O3/TiN and Ti/Cr2O3/Pt structures. In our results, we directly observed the oxygen migration and realized the RESET mechanism. Furthermore, we find that using TiN as oxygen reservoir is more stable than Ti. Subsequently, we discuss the conduction mechanism of Pt/Cr2O3/TiN structure under different bias region by current fitting. It is very helpful to realize the physical origin of the switching phenomenon. Moreover, we investigate the multi-level feasibility of Pt/Cr2O3/TiN structure. It is reported that using On-states as multi-level is suitable than Off-states. Furthermore, Pt/Cr2O3/TiN structure exhibits prominent resistive switching behavior. Both low resistance (ON state) and high resistance (OFF state) are stable and reproducible during a successive resistive switching by using a DC voltage sweeping. The resistance ratio of ON and OFF state is over 100 times. The retention properties of both states are also very stable. Finally, we conclude that Pt/Cr2O3/TiN has promising potential in the next-generation non-volatile memory.

參考文獻

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