使用ZrO2 當做緩衝層的多階電阻式記憶體之電阻轉 態特性研究

Abstract

非揮發性記憶體技術在電子產品市場中起著重要的作用。廣泛應用於手機，數碼相 機，門戶存儲設備，MP3 播放器等。由於快閃式記憶體的優良特性主導了目前的非揮 發性記憶體的領域。然而，快閃記憶體的穿隧氧化層是否能繼續為縮是目前技術的關 鍵。隨著厚度的變薄載子容易流失,這將會導致控制不易或資料讀取錯誤。目前有許多 磁阻是記憶體,相變化記憶體和電阻式記憶體。但由於電阻式有著高操作速度、簡單製 程和低功耗的特性使得其在未來是一種可以取代傳統記憶體的潛力。 電阻式記憶體具有簡單的結構金屬/絕緣體/金屬（MIM）結構並以低電阻狀態（LRS） 和高電阻狀態（HRS）的形式來儲存數據。是種可以應用於低工作電壓，高耐久性等 優點整合在陣列中。 在本論文中，研究了基於二氧會鋯的電阻式元件的I-V 開關特性，並與文獻進行比 較。從Ni/ZrO2/TaN RRAM 元件中,我們觀察到雙極開關的特性。此RRAM 元件從高 電阻到低電阻狀態（HRS 到LRS）間轉換，其功耗為5.19μW（復位功率為7.70μW， 設定功率為40.43μW），限制電流為1mA，設定電壓為3V。多級電阻狀態分別實現 了功耗為0.128mW，30.75μW 和50.19μW，分別為1 級，2 級和3 級。在25˚C， 50˚C，75˚C 和100˚C 的不同溫度下觀察其多級電阻狀態的響應。隨著溫度升高，LRS 和HRS 會增加，而功耗也因洩漏電流而增加。此外，實現了良好的耐久性和保留性。 在125 次切換週期內獲得良好的電性耐力特性，並在85℃下測量具有小的HRS / LRS 衰減104 秒的良好保留特性。與文獻相比,我們元件的均勻性和電阻記憶區間均有顯著 提高。

Non-volatile memory technology plays a significant role in the market of electronics products. It is widely used in mobile phone, digital camera, portal storage devices, MP3 players and so on. Currently, flash memories dominating the nonvolatile memories due to their key properties. However, the data is stored by injecting the charge carriers in floating gate. This will results degradation of oxide, so it encounter a serious technical challenge while scaling down of the oxide thickness. Therefore, it is essential to find the scalability, viable alternatives for this memory. Several non-volatile memories based on different concepts have aroused such as Magnetoresistive RAM (MRAM), Phase change RAM (PRAM) and Resistive RAM (RRAM). Compared with other types, RRAM shows relatively high speed, simple structure and the lowest power consumption. Therefore, RRAM are potential candidates for future conventional non-volatile memory to overcome the physical and technological limitations. The RRAM has a simple structure metal/insulator/metal (MIM) structure. These nano devices are nonvolatile, and can store data in form of both low resistance state (LRS) and high resistance state (HRS) in nanoseconds. The other incentives are its low operating voltage, high endurance and integration in crossbar arrays. In this thesis, the I-V switching characteristics of the ZrO2 based RRAM devices are investigated and compared to the performance of similar devices from the literature in order to confirm process viability. The Ni/ZrO2/TaN RRAM devices have synthesized and bipolar switching observed. This RRAM device can be set from high- to low-resistance state (HRS to LRS) with power consumption 5.19μW (reset power 7.70μW and set power 40.43μW) as compliance current is 1mA and set voltage is 3V. Multi-level resistance states have realized with power consumption of 0.128mW, 30.75μW and 50.19μW for level1, level2 and level3 respectively. Multi level resistance states have examined at different temperatures 25˚C, 50˚C, 75˚C and 100˚C. As temperature increases, the LRS and HRS increases and results into more power consumption due to leakage current. Moreover, good endurance and retention characteristic have achieved. Good electrical endurance characteristics has obtained up to 125 switching cycles, and good retention with a small HRS/LRS decay for 104 sec has measured at 85˚C. Device to device uniformity and resistance window have significantly improved as compared with the devices from the literature.