利用氮化鈦底電極改善溶膠凝膠法製備之鈦酸鉍薄膜電阻轉態特性之研究

Abstract

近年來，對於新世代非揮發性記憶體的研究當中，如:相變化記憶體(PCM)、鐵電記憶體(FeRAM)、磁阻式記憶體(MRAM)與電阻式記憶體(RRAM)…等已受到廣泛的注意。其中，由於電阻式記憶體具有結構簡單、操作速度快、低耗能、高密度及與半導體製程技術相容…等優點。因此，極有可能成為下一新世代非揮發性記憶體的主流之一。 本論文以溶膠凝膠法製備鈦酸鉍(Bi4Ti3O12)作為電阻式記憶體的轉態層薄膜，並以氮化鈦金屬(TiN)作為底電極來改善其轉態特性。結果發現氮化鈦金屬(TiN)可以降低元件操作的限流值、提升轉態次數、提升良率、使轉態區域固定在鈦酸鉍(Bi4Ti3O12)/氮化鈦(TiN)的介面層…等優點。在記憶體可靠度的測試中，如:儲存能力、非破壞性讀取、高溫量測…等，也有極佳的表現。此外，我們也將探討元件的記憶體特性，並比較及討論不同金屬電極對記憶體特性的影響，更進一步由電性分析和材料分析的結果，去探討並佐證可能的電阻式記憶體的電阻轉換特性以及傳導機制。

In recent years, the next-generation nonvolatile memory (NVM) research, such as: phase change memory (PCM), ferroelectric random access memory (FeRAM), magnetic random access memory (MRAM) and resistive random access memory (RRAM), have attracted great attention. Among them, as a result of RRAM has excellent characteristics of simple structure, high-speed operation, low-power consumption, high-density integration and compatibility to semiconductor process technology… and so on. Therefore, RRAM has been proposed to be one candidate of next-generation nonvolatile memory. In this thesis, the RRAM devices manufactured based on Sol-Gel derived Bi4Ti3O12 thin films are studied and developed. The electrical properties are improved by using TiN as bottom electrode. The results show that TiN can reduce the operation compliance current, enhance the endurance, promote the device yield and clamp the resistive switching region at BTO/TiN interface. In memory reliability test, such as: retention, voltage stress and high temperature measurement, the device shows the best performance. Furthermore, we discuss and compare the effects of various metal electrodes in three different device structures. Finally, the possible resistive switching mechanism based on electrical and physical analyses results is also discussed in this thesis.