利用金屬嵌入層提升溶膠凝膠法製備之鈦酸鉍薄膜電阻轉態特性

Abstract

近來新世代非揮發性記憶元件受到廣泛的注意，諸如相變化記憶體、磁阻式記憶體、鐵電記憶體、電阻式記憶體等。其中又以電阻式記憶元件最受囑目，由於其具有低操作電壓、結構簡單、讀寫速度快、低耗能、非破壞讀取等優點，將有助於達到高密度積體整合及低操作功率的目的，因此可以期待電阻式記憶體成為未來非揮發性記憶體的主流。 本論文選用層狀鈣鈦礦結構材料（鈦酸鉍）作為電阻式記憶體的轉態層材料，利用溶膠凝膠法製備鈦酸鉍薄膜，並且首次在薄膜中間嵌入兩奈米厚度的鉻金屬層來改善轉態特性，而此結構的轉態層厚度約為二十二奈米。本論文著重在於如何降低並穩定操作電壓，除了嵌入鉻金屬外，更利用後續高溫退火步驟來實現。結果發現退火600度下，擁有最低的操作電壓(約為-2伏特)，而且，在記憶測試中，例如：耐久度、非破壞讀取、儲存能力等都擁有極佳的表現度。本實驗更利用材料分析結果去驗證電性表現，並探討嵌入金屬層對於轉態層的影響。隨後我們也探討電壓電流關係，去探討可能的電阻式記憶體的電阻轉換特性及傳導機制。

In recent year, next-generation nonvolatile memories (NVM), such as OUM, MRAM, FRAM and RRAM, have attracted a lot of attention because of its ascendant advantages such as simple device structure, low operation voltage, low power consumption, long retention time, small cell size, high operation speed, low cost, good endurance, and non-destructive readout, which help for attaining to objects of high density integration and low power operation. In this thesis, the RRAM devices manufactured based on Sol-Gel derived Bi4Ti3O12 thin films are studied and developed. The electrical properties are enhanced by using embedded 2nm-Cr in BTO thin film. The thickness of switching oxide is about 22nanometer. The main point is accented on how to decrease and stabilize the operation voltage. Except using embedded metal, thermal treatment like post deposition annealing is used as well. Accidentally, the lowest operation voltage (-2V) appears at the condition with annealing at 600oC. Also, in memory test such as endurance, retention and voltage stress, the device shows the best performance. The material analyses are applied to verify the electrical phenomenon. In addition, the related conduction mechanism is discussed in detail.