氧化鋯電阻式記憶體之單極性電阻切換特性研究及其應用

Abstract

在本篇論文中，主要探討了利用氮化鉭電極搭配氧化鋯之電阻式記憶體結構，其在單極性電阻轉換之機制與特性。 實驗分為兩部分，第一部分著重在1D1R結構的實現與其電性探討。其中二極體部分是由p型的氧化鈷與n型的氧化鋅薄膜所組成之氧化物二極體，其整流比可達到80000倍且經7000次之高電流流經亦能維持高整流之特性。至於電阻式記憶體的部分則是氧化鋯與氧化鉿薄膜所形成雙層氧化物搭配氮化鉭電極，可呈現單極性電阻轉換的特性；兩部分組合而成之1D1R結構可直流操作3000次以上，且超過3000次後才開始有所衰退。 第二部分則是希望透過此結構搭配鎳上電極，改善前一部分的電阻式記憶體。此元件有著單極性電阻切換之特性，並透過後金屬退火的方式改善其原來之特性；且透過這樣的方式，可有效降低操作電壓(寫入/抹除,0.7/1.5伏特)以及操作電流(數毫安培)，且可更進一步地大幅改善其直流持久性(17000次)。不僅如此，此結構也能有效改善前一部分的電阻式記憶體部分，而能進一步使用在後續之1D1R結構，來避免錯誤讀取的問題在crossbar結構中出現。

In this thesis, the unipolar resistive switching mechanism and characteristics are investigated in the structure of ZrO2-based resistive random access memory (RRAM) with TaN electrode. There are two parts in the thesis. The first part we focus on the implementation and electrical properties of one diode one resistor (1D1R) structure. In the 1D1R structure, the oxide diode is composed of p-type CoO and n-type ZnO film. The rectifying ratio of the oxide diode can reach 8×104 and after 7000 cycles with high current passing, it can still remain the high rectifying ratio. On the other hand, the RRAM is consisted of ZrO2 and HfO2 bilayer structure with TaN electrode, and demonstrates the unipolar switching behavior. Finally, the DC endurance didn’t show any degradation until over 3000 cycles in the 1D1R structure. The second part is that we hope by using Ni as the top electrode in Ni/ZrO2/TaN structure, the device would improve the RRAM characteristics in first part. It shows the unipolar resistive switching characteristics. Furthermore, we can improve the electrical properties by post metal annealing. With the annealing process, both the operation voltage (Vreset/Vset, 0.7/1.5V) and current can be decreased effectively. It also enhanced the DC endurance up to 17000 cycles. Moreover, the structure in this part can actually improve the RRAM in the first part, and it could be used in further 1D1R structure to prevent mis-reading problem in cross-bar structure.