利用熱氧化法製備氧化銅薄膜於電阻式轉態記憶體之研究

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，有關新世代非揮發性記憶體的發展呈現百家爭鳴的情形。其中，電阻式非揮發性記憶元件具有低功率消耗、高密度、高操作速度、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。 而研究氧化銅這個材料的原因之一，是因為氧化銅在標準先進半導體CMOS製程技術中有銅導線製程做為元件之間的連接，所以氧化銅和CMOS製程具有很高的相容性。其次的原因是因為NiO做為電阻式記憶體被廣為研究，而Ni和Cu在元素週期表相鄰。進而想研究CuO這個氧化物材料是否有做為新一帶電阻式記憶體的潛力。這篇論文中，著重電阻轉態特性的研究與探討，其內容可分為兩大部份，包含不同限流和不同停止電壓對轉態特性的影響。藉由這兩個不同的量測方式探討導電細絲在薄膜內轉態的情況以及介面對轉態特性的影響，進而提出轉態之模型解釋實驗觀察到的現象。另外藉由不同的限流可以控制低電阻態的電阻值；而以鈦做為上電極，電阻轉態由原本無極性變為有極性狀態使轉態次數增加，並可藉由不同的停止電壓可以控制高電阻態的電阻值，在應用方面可以做為多重位元儲存記憶體的潛力。

Recently, since nonvolatile memories acquire a lot of attention and flash memories are faced with the scale limit issue, the extensive studies have been carried out to discover the next generation nonvolatile memory. The resistive switching random access memories (RRAMs) having the strengths of low power consumption, and high-density integration, high speed, high endurance, nondestructive read as one of the next-generation nonvolatile memory candidates. One reason is that the fabrication of Cu-oxide based RRAM has great advantages of full compatibility with Cu interconnection process in state-of-art complementary metal oxide semiconductor CMOS technology, promising easy integration with current semiconductor processing technology. The other reason is the material, NiO, has been studied widely. Thus, we want to investigate the potential of the material, CuO, to become resistive switching memory. In this thesis, the resistive switching characteristics are investigated, and the research can be categorized into two parts, the current compliance influence and the stop voltage influence resistive switching characteristics. By means of these two kind measures, we investigate the filament transform in the resistive switching layer, when resistive switching occurs. We propose a model to explain the phenomenon, which was observed in experiment. The resistance of ON-state was controlled by current compliance. The polarity of resistive switching changed to bipolar switching by using Ti top electrode, and the resistance of OFF-state was controlled by stop voltage. In application, Ti/CuO/Pt device has a potential for nonvolatile multiple-valued memory device.