以氧化鈣摻雜氧化鋯層於單極性電阻轉態效應之研究

Abstract

隨著科技越來越進步， 各種消費性電子產品的發展快速，各種產品所需要的記憶體容量越來越大，而其中不需要電源供應仍能儲存資料的非揮發性記憶體，也漸漸受到矚目。其中，電阻式非揮發性記憶體具有高密度、高操作速度、低功率消耗、高耐久性、可微縮化、非破壞性讀取資料、能符合現在CMOS製程以及結構簡單等特性，因此有機會取代flash memory，使其成為次世代非揮發性記憶體的熱門選擇。 在這篇論文中，電阻轉換特性研究是著重在鈦/氧化鈣摻雜在氧化鋯/氧化鋯/鉑的結構。首先，研究改變上電極的影響。其次，試著討論不同濃度摻雜的影響和不同沈積時間對於摻雜層的影響。最後，為了討論單極性轉態機制，我們做了不同結構來加以討論。 首先，我們比較不同上電極的靜態轉態特性，得到最佳條件是鈦上電極。第二步，有四種不同濃度的氧化鈣摻雜在氧化鋯內，分別為：0.03at%、0.06at%、0.12at%和0.16at%。最佳條件的濃度是0.12at%，針對0.12at%討論。第三步，不同沈積時間的摻雜層有三種時間：5、10和15分鐘。而5分鐘是最合適條件。因此，我們找到最好的結構條件。並且目前靜態轉態特性可以超過300次以上；時間耐久度超過106秒；然後非破壞性讀寫特性超過50000秒。最後，為了探討電阻式記憶體轉態機制，分別做了不同的結構。一個方面，瞭解必須使用雙層結構。另一方面，結構上也探討了上層電極接觸面必需有氧缺的摻雜層。這些結果分別在後面章節會討論。而最終本篇論文不僅希望改善特性同時也尋求可能的單極性轉態機制。

Many kinds of consumer electrical commercial products are becoming more and more popular following with the development of the technology. All kinds of products need the memory, especially non-volatile memory, which can store data without power. The resistive switching random access memory (RRAM) is one of the next generational memories that have the chance to become the mainstream. It has the advantages of high cell density, high operation speed, low power consumption, high endurance, lower scale limit, non-destructive readout, and easy processing that can fit in the CMOS process, so it is one of the potential substitutions for flash memories. In this thesis, the resistive switching characteristics are investigated based on the Ti/CaO:ZrO2/ZrO2/Pt structure, and the research focus on some issues. First, the top electrodes are changed. Second, the doped concentration of CaO:ZrO2 and the deposition time of CaO:ZrO2 are changed. In the end, we will change the structure to understand the mechanism of unipolar switching.

First, we use the various top electrodes to compare the DC sweep cycles, and the suitable condition is Ti top electrode. In the second part, the concentration of the CaO:ZrO2 is changed to four concentrations:0.03at%,0.06at%,0.12at%and0.16at%. The optimal value is 0.12at%, so the following research will be focused on 0.12at%. In the third part, the deposition time of the CaO:ZrO2 is changed to three kinds:5min,10min and 15min.The proper time is 5min.Therefore,the best condition for our structure is Ti/CaO:ZrO2(0.12at% 5min)/ZrO2/Pt. The performance of the structure is good. DC sweep cycle times can over 300 times; retention test is 106s; and there is no data loss at the nondestructive readout test for over 50000 seconds. In the end, the purpose is to know the mechanism of the RRAM, so the structure is changed. First, it is necessary for double layer. Second, the top electrode is necessary to contact on the doped layer. The results will be discussed on the thesis in the following chapters. This thesis is not only improving the unpolar switching but searching for the possible mechanism for the unipolar switching.