鈦上電極與鉬金屬嵌入層對濺鍍法製備之氧化鋯材料於電阻轉換記憶元件之研究

Abstract

近年來，由於非揮發性記憶體的應用與發展受到矚目，加上快閃記憶體的微縮極限，關於新世代非揮發性記憶體的研究正緊鑼密鼓地展開。其中，電阻式非揮發性記憶元件具有高密度、高操作速度、低功率消耗、高耐久性、微縮能力高及非破壞性資料讀取等優點，使其成為新世代非揮發性記憶元件的熱門人選。 這篇論文中，電阻轉換特性研究是著重於鈦/氧化鋯/鉑的結構，其內容可分為兩大部份，包含本體及界面的特性。在本體的特性部份，含嵌入2奈米鉬金屬層的氧化鋯記憶元件，其轉態層總厚度為43奈米。經過800oC快速熱退火處理後，鉬原子擴散使初始電阻處於低電阻狀態，使記憶元件不需形成過程，且並不影響電阻轉換特性。此元件具有不錯的性能，耐久性測試中可轉換超過2000次，資料保存能力可達十年，非破壞性讀取量測中也能在施加0.3V直流電壓情況下維持8000秒而無資料狀態改變。另外的界面特性部份，記憶元件的復原現象顯示利用吸氧能力較強的上電極金屬材質可增進導電細絲斷裂的過程，進而改善元件轉換至高電阻狀態的能力。另外，藉由改變鈦上電極的厚度，界面層的特性也隨之變化，進而影響到轉態特性。

Recently, since nonvolatile memories acquire a lot of attention and flash memories face the issue of scale limit, the extensive studies have been carried out to explore the next generation nonvolatile memory. The resistive switching random access memories (RRAMs) having the advantages of high cell density, high operation speed, low power consumption, high endurance, lower scale limit and non-destructive readout, is one of the potential substitution for flash memories. In this thesis, the resistive switching characteristics are investigated based on the Ti/ZrO2/Pt structure, and the research focus on two parts, the bulk and the interface properties. In the part of bulk properties, the memory cells of the Ti/ZrO2/Mo/ZrO2/Pt structure are studied. The embedded Mo layer is 2 nm in thickness, and the total thickness of ZrO2/Mo/ZrO2 resistance switching layer is about 43 nm. It is found that after RTA 800oC the cells exhibit the forming-free behavior, resulting from Mo diffusion. The performances in endurance, retention and non-destructive readout tests also achieve 2000 cycles, over ten years, and no data loss for 8000 s under 0.3V DC bias stress, respectively. In the second part, the recovery phenomena reveal that the top electrodes with high oxygen gettering ability improve the filament rupture process. It is also discovered that by varying the thickness of Ti top electrode the switching characteristics can be modified.