快閃記憶體﹙FLASH﹚是利用浮動閘(Floating gate)來儲存載子單元，然而其中的穿隧氧化層(Tunneling oxide)卻會影響FLASH的特性，如當FLASH微縮時，可能導致穿遂氧化層太薄而產生漏電，使記憶體記憶能力變差，且讀取方式為破壞性讀取，傷害元件結構，其他如耐久力和操作速度慢都是FLASH的缺點。
電阻式記憶體(RRAM)製成簡單，且擁有高速率、低耗能、結構簡單、高操作週期、並且擁有非破壞讀取及非揮發性等多項優勢，所以除了在記憶體特性上的突破與改進，在生產成本上亦有相當大的優勢，因此受到學術界及業界等眾多矚目，是目前唯一有機會與具備低成本競爭力的 NAND 型快閃記憶體對抗的記憶體。但因為電阻式記憶體的電阻轉換機制不明，且隨機形成的電流導通路徑將使得元件的電性的均勻度情形下降，而大部分的研究都是使用惰性金屬當元件某一邊的電極，但惰性金屬難以蝕刻限制了電極的位置以及電極材料的選擇，為此設計了以下實驗去改善。
本論文分為三部分去探討由二氧化鉿﹙HfO2﹚為介電層所組成的電阻式記憶體在雙極電阻轉換上的現象。
如同前面所述的問題，第一部分以濺鍍方式鍍製和CMOS製程相容的不同金屬下電極，以HfOX當作介電層材料，TiN當上電極形成電容結構的電阻式記憶體，討論哪個金屬材料適合製作電阻式記憶體，最後發現以Pd為下電極材料所製備出來的元件可以進行穩定的雙極性電阻轉換﹙Bipolar switching﹚，並且達到低操作電壓和230次電阻轉換周期的高低阻抗阻值比可以到達2個Order以上。
第二部分是以第一部分作為基礎，由於一般相信電阻轉換現象和介電層材料有極大關係故在第一部分嘗試了許多金屬當下電極，由結果可知以Pd作為下電極材料的元件展現出良好的電阻轉換特性，但是觀察元件特性可以發現元件的DC Endurance並不夠好，因而在此藉由改變不同金屬退火溫度調整元件的介電層內缺陷和離子分布，使元件的漏電流現象改變使得DC Endurance狀況改善，經由實驗可以看出元件的漏電流情形因為金屬退火改變使得元件的DC Endurance增加但是造成元件的高低阻抗阻值比變小。
第三部分則是建立在前兩部分基礎上，藉由插入不同金屬改變介電層的結構來達到提升元件特性的目的，最後實驗發現插入Ni在Pd/HfOX/TiN元件件電層內內將會提升元件的高低阻抗阻值比，但是Ni將會改變元件的活性使得元件的DC Endurance大幅下降，故藉著第二部分實驗的經驗在把元件進行金屬退火使元件達到最大限度的優化，可以再次驗證經由金屬退火後能使元件的DC Endurance提升但相對的元件的高低阻抗阻值比將會下降。

[1] M. She, “semiconductor Flash Memory Scaling”, University of California, Berkeley , Doctor of Philosophy, 2003.
[2] K. Kahng and S. Sze, “A floating gate and its application to memory devices, ” Electron Devices, IEEE Transactions on, vol. 14, no. 9, p. 629, 1967.
[3] 王之賢, 「鐵酸鉍薄膜之電阻轉換效應」, 國立清華大學材料科學工程學系，2009
[4] 鄭新川, 「Zn1-xMgxO 薄膜之單極電阻轉換」, 國立清華大學材料科學工程學所， 2008
[5] 蔡濬名, 「氧化鋅薄膜於非揮發電阻式記憶體特性之研究」, 國立清華大學材料科學工程學所， 2008
[6] 陳威亦, 「鍶鈦鋯系鈣鈦礦薄膜之電阻轉換特性研究」, 國立清華大學材料科學工程學所, 2008
[7] 張文淵, 「以LaNiO3底電極開發(Pr，Ca)MnO3非揮發性電阻記憶體特性之研究」, 國立清華大學材料科學工程學所，2006
[8] 蘇柏榮, 「二氧化鈦薄膜之電阻轉換特性研究」, 國立清華大學材料科學工程學所, 2008
[9] 蔡耀仁, 「利用高介電二氧化鉭固態電解層於電阻式轉換記憶體」, 長庚大學電子工程研究所
[10] G. Muller, et al., “Emerging non-volatile memory technologies”, Solid-State Circuits Conference, p.37-44, 2003.
[11] 陳昱丞,「二氧化鉿電阻式隨機存取記憶體元件之雙極切換特性研究」, 國立清華大學工程與系統科學系, 2010
[12] W. W. Zhuang, et al., “Novell Colossal Magnetoresistive Thin Film Nonvolatile Resistance Random”, International Electron Devices 2002 Meeting, Technical Digest, p. 193-196, 2002.
[13] M.Y. Chan, et al., “Resistive switching effects of HfO2 high-k dielectric ”, Microelectronic Engineering, Vol.85, Issue 12, p. 2420-2424, 2008
[14] A. Beck et al., “Reproducible switching effect in thin oxide films for memory applications” Appl. Phys. Lett.,Vol.77, pp139, 2000
[15] I. Kim, et al., “Low temperature solution-processed graphene oxide/Pr0.7Ca0.3MnO3 based resistive-memory device”, Appl. Phys Lett., Vol.99, 2011
[16] W. Zhu, et al., “Conduction mechanisms at low- and high-resistance states in aluminum/anodic aluminum oxide/aluminum thin film structure”, J. Appl. Phys., p.112-117, 2012
[17] A. Sawa, “Resistive switching in transition metal oxides”Materials Todays, Vol.11, p.28-36, 2008
[18] C. Y. Lin, et al., “Modified resistive switching behavior of ZrO2 memory films based on the interface layer formed by using Ti top electrode”, J.Appl. Phys, pp.102, 2007
[19] I. G. Baek, et al., “Highly Scalable Non-volatile Resistive Memory using Simple Binary Oxide Driven by Asymmetric Unipolar Voltage Pulses”, Electron Devices Meeting, 2004. IEDM Technical Digest. IEEE International, p13-15, 2004
[20] H. Y. Lee, et al., “Low-Power Switching of Nonvolatile Resistive Memory Using Hafnium Oxide”Japanese Journal of Applied Physics, Vol. 46, No. 4B, p. 2175–2179, 2007
[21] C. Rohde, et al., “Identification of a determining parameter for resistive switching of TiO2 thin films”, Appl. Phys. Lett., Vol. 86, Issue 26, p.262907-262910, 2005.
[22] R. Waser, et al., “ Nanoionics-based resistive switching memories ”, Nature Materials 6, p. 833 - 840, 2007
[23] K. Kinoshita, et al., “Bias polarity dependent data retention of resistive random access memory consisting of binary transition metal oxide” Appl. Phys. Lett. Vol. 89, p.89-92, 2006
[24] U. Russo, et al., “Self-Accelerated Thermal Dissolution Model for Reset Programming in Unipolar Resistive-Switching Memory (RRAM) Devices” Electron Devices, IEEE Transactions on Vol.56 , Issue:2, p.193-200, 2009
[25] U. Russo, et al., “Filament Conduction and Reset Mechanism in NiO-Based Resistive-Switching Memory (RRAM) Devices”, Electron Devices, IEEE Transactions on, Vol. 56, Issue: 2, p.186-192, 2009
[26] K. Szot, et al., “Switching the electrical resistance of individual dislocations in single-crystalline SrTiO3”, Nature Materials, Vol.5, p.312-320, 2006
[27] K. Tsubouchi, et al., “High-Throughput Characterization of Metal Electrode Performance for Electric-Field-Induced Resistance Switching in Metal/Pr0.7Ca0.3MnO3/Metal Structures”, Advanced Materials, vol.19, p.1711-1713, 2007.
[28] A. Baikalov, et al., “Field-driven hysteretic and reversible resistive switch at the Ag–Pr0.7Ca0.3MnO3 interface ”, Appl . Phys. Lett., vol.83, p. 957-960, 2003.
[29] S. Tsui, et al., “Field-induced resistive switching in metal-oxide interfaces” , Appl. Phys. Lett., vol.85, p. 317-320, 2004
[30] X. Chen, et al., “Direct resistance profile for an electrical pulse induced resistance change device”, Appl. Phys. Lett., vol.87, p.233506-233509, 2005
[31] A. Sawa, et al., “Hysteretic current–voltage characteristics and resistance switching at a rectifying Ti∕Pr0.7Ca0.3MnO3 interface”, Appl. Phys. Lett., vol.85, p. 4073, 2004
[32] T. Fujii, et al., “Hysteretic current–voltage characteristics and resistance switching at an epitaxial oxide Schottky junction SrRuO3∕SrTi0.99Nb0.01O3” Appl. Phys. Lett., vol.86, p.012107-012110, 2005
[33] R. Fors, et al., “Giant resistance switching in metal-insulator-manganite junctions: Evidence for Mott transition”, Physical Review B, vol.71, p.1-10, 2005.
[34] M. J. Rozenberg, et al “Strong electron correlation effects in nonvolatile electronic memory devices”, Appl. Phys. Lett., vol.88, 2006
[35] T. Hori, “Gate dielectrics and MOS ULSIs: principles, technologies, and applications” Springer, Berlin, p.8-45, 1997
[36] S. M. Sze, K. Ng Kwok “Physics of Semiconductor Devices”,3rd edition, Wiley-Interscience, p227-228, 2007
[37] Y. H. Do, et al., “Al electrode dependent transition to bipolar resistive switching characteristics in pure TiO2 films”, Journal of Applied Physics, Vol.104, Issue:11, p.114512-114514, 2008
[38] S. Seo, et al., “Reproducible resistance switching in polycrystalline NiO films”, Appl. Phys. Lett., Vol.85, 2004
[39] C. Y. Lin, et al., “Bistable Resistive Switching in Al2O3 Memory Thin Films”, Journal of The Electrochemical Society, Vol.154, p.189-192, 2007
[40] C. Y. Lin, et al., “Effect of Top Electrode Material on Resistive Switching Properties of ZrO2 Film Memory Devices”, Electron Device Letters, IEEE, Vol.28, Issue:5, p.366- 368, 2007
[41] H. Y. Lee, et al., “Low Power and High Speed Bipolar Switching with A Thin Reactive Ti Buffer Layer in Robust HfO2 Based RRAM”, Electron Devices Meeting, 2008. IEDM 2008. IEEE International, p.1-4, 2008
[42] C. C. Lin, et al., “Effect of Top Electrode Materials on the Nonvolatile Resistive Switching Characteristics of CCTO Films”, Magnetics, IEEE Transactions on, Vol47, Issue:3, p.633-636, 2011
[43] V. Jousseaume. et al., “Comparative study of non-polar switching behaviors of NiO- and HfO2-based oxide resistive-RAMs”, Memory Workshop (IMW), 2010 IEEE International, p16-19, 2010
[44] Y. B. Kim. et al., “Bi-layered RRAM with unlimited endurance and extremely uniform switching”, VLSI Technology (VLSIT), 2011 Symposium on, p.52-53, 2011
[45] K. Seo. et al., “Chemical states and electrical properties of a high-k metal oxide/silicon interface with oxygen-gettering titanium-metal-overlayer” Appl. Phys. Lett. Vol.89, p.142912-142915, 2006
[46] C. Cagli. et al., “Experimental and Theoretical Study of Electrode Effects in HfO2 based RRAM” Electron Devices Meeting (IEDM), 2011 IEEE International, p. 28.7.1 - 28.7.4, 2011
[47] Y. Y. Chen. et al., “Endurance/Retention Trade-off on HfO2 /Metal Cap 1T1R Bipolar RRAM”, Electron Devices, IEEE Transactions on, Vol.60, 2013
[48] X. P. Wang. et al., “Effect of Anodic Interface Layers on the Unipolar Switching of HfO2-based Resistive RAM ” , VLSI Technology Systems and Applications (VLSI-TSA), 2010 International Symposium on, p.140-141, 2010
[49] J. Lee. et al., “Diode-less nano-scale ZrOx/HfOx RRAM device with excellent switching uniformity and reliability for high-density cross-point memory applications”, Electron Devices Meeting (IEDM), 2010 IEEE International, p.19.5.1-19.5.4, 2010
[50] S. Yu. et al., “Improved Uniformity of Resistive Switching Behaviors in HfO2 Thin Films with Embedded Al Layers”, Electrochem. Solid-State Lett., vol.13, issue 2, p.H36-H38, 2010
[51] H. Zhang, et al., “Gd-doping effect on performance of HfO2 based resistive switching memory devices using implantation approach”, Applied Physics Letters, vol.98, p. 042105-042108, 2011.
[52] Y. Y. Chen. et al., “Insights into Ni-filament formation in unipolar-switching Ni/HfO2/TiN resistive random access memory device”, Appl. Phys. Lett., Vol100, p.113513-p113517, 2012
[53] L. Goux. et al., “Roles and Effects of TiN and Pt Electrodes in Resistive-Switching HfO2 Systems”, Electrochemical and Solid-State Letters, Vol.14, p.H244-H246, 2011
[54] E. H. et al., “Making a noble metal of Pd”, Europhys. Lett.,Vol.71, p.276-282, 2005
[55] A.Padovani, “Understanding the Role of the Ti Metal Electrode on the Forming of HfO2-Based RRAMs”, Memory Workshop (IMW), 2012 4th IEEE International, 2012
[56] Z. Fang, et al., “Temperature Instability of Resistive Switching on HfOx -Based RRAM Devices”, Electron Device Letters, IEEE, Vo.31,Issue:5, p.476 - 478, 2010
[57] 洪晧智, 「應用較高介電層及電漿處理界面層以改善金氧半元件電特性」, 國立清華大學材料科學工程學系, 2012
[58] Z. Fang. et al., “HfOx/TiOx/HfOx/TiOx Multilayer-Based
Forming-Free RRAM Devices With Excellent Uniformity”, IEEE ELECTRON DEVICE LETTERS, VOL.32, NO.4, 2011
[59] 李依璇, 「氧化鋁/氧化鉿多接層結構對改善電阻轉換特性之研究」, 國立清華大學材料科學與工程學系, 2011
[60] H. S.P. Wong, et al., “Metal–Oxide RRAM”, Proceedings of the IEEE, Vol.100, Issue:6, p.1951-1970, 2012
[61] 蔡侃學, 「雙極性氧化鉿電阻式記憶體之電極材料與轉態探討」, 國立清華大學電子工程研究所, 2010
[62] V. Sriraman. et al., “HfO2 -Based RRAM Devices With Varying Contact
Sizes and Their Electrical Behavior”, IEEE ELECTRON DEVICE LETTERS, Vol.33, NO.7, 2012