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  • 學位論文

介電層和電極材料對ZrTiOx電阻式記憶體的影響

Impact of Dielectric and Electrode Materials on ZrTiOx-based Resistive RAM (RRAM)

指導教授 : 巫勇賢

摘要


隨著電子產品發展之迅速,所搭配的記憶體效能也被要求,因此傳統的記憶體元件已不敷使用,許多新型的記憶體結構紛紛在此時被提出來。其中電阻式記憶體(RRAM)具有結構簡單、寫入速度快、低操作電壓等優點,還利於元件尺寸的微縮,容易整合在現今的CMOS技術上,所以RRAM在未來極有發展潛力,故選用RRAM來作為我們研究的方向。 在RRAM中,我們特別選擇了可在後段製程和別的電路作整合的MIM結構RRAM,MIM RRAM可避開高溫製程,因為高溫容易惡化高介電係數材料的特性。從D. Lee et al. [1] 2005年發表的文章發現到,這篇的RRAM採用ZrOx作為介電層,使得RRAM的特性十分穩定;又參考了C. Kugeler et al. [2] 2008年的文章,這篇的RRAM採用TiO2作為介電層,由於TiO2可以自己形成氧空缺來作為傳導路徑的粒子,如此可降低RRAM的操作電壓。為了結合ZrOx和TiO2的優點,我們選用了ZrTiOx (ZTO)來作為RRAM的介電層,且使用電子槍蒸鍍系統(E-gun)來作堆疊。另外金屬電極的部分,則是使用電子槍蒸鍍系統(E-gun)及真空濺鍍系統(Sputter)。 對於RRAM我們分為兩個主題作討論:(一)介電層結晶與不結晶對RRAM的影響、(二)不同電極對RRAM的影響。實驗結果發現,主題一結晶與不結晶的討論,ZTO介電層在600 oC時會結晶,而介電層沒有結晶的RRAM電性表現都比有結晶的來的好,可得ZTO介電層的RRAM並不適合作高溫處理的結論。主題二不同電極的特性比較,發現元件受上下電極的材料影響很大,因為金屬電極會影響介電層材料中所存在的氣空缺濃度。實驗中以Ni/ZTO/TaN/SiO2/Si結構的電性最好,操作電壓可以在1 V以下,高低阻態比可達4500倍,在高溫下的可靠度也表現極佳。 目前RRAM的切換機制並沒有一個統一的說法,所以我們在研究上特別加強在機制上的討論,利用實驗結果及物性分析,驗證我們所提出的元件電阻切換機制。

並列摘要


As the progress of electrical products, the traditional memories can’t match these products anymore. Therefore, many the new generation memory device candidates are proposed, and resistive random access memory (RRAM) is one of them. The advantages of RRAM are simple structure, fast switching speed, low voltage operation, and easy for CMOS integration. In our research, we present ZrTiOx (ZTO) thin film in metal/insulator/metal (MIM) structured RRAM because ZTO contains the merits of ZrOx and TiO2. There are two experiment topics in the research: 1. The impact of dielectric on ZTO-based RRAM, 2. The impact of electrode materials on ZTO-based RRAM. As our experiment results, we found that the properties of crystalline ZTO RRAM was worse than amorphous ZTO RRAM in topic 1. To short, ZTO is not good to crystallize in RRAM process. In topic 2, we found that the concentration of oxygen vacancies in dielectric is the point of resistance switching. Furthermore, the other important thing is the cooperation between dielectric and electrode, since it will affect the concentration of oxygen vacancies in the dielectric. Finally, the structure of Ni/ZTO/TaN/SiO2/Si shows the best properties in all samples. Because of the mechanism of RRAM is not clearly presently, we especially emphasize the discussion of the mechanism of ZTO RRAM in our research.

並列關鍵字

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參考文獻


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