氧化鋯電阻式記憶體搭配電晶體之電阻轉換特性研究

Abstract

科技的日新月異，不同種類的消費性電子產品都需要大容量的記憶體，其中以非揮發性記憶體需求量為最大宗，加上快閃記憶體的微縮極限，所以非揮發性記憶體研究更是蓬勃發展。電阻式記憶體具有結構簡單，操作速度快，低耗能，高密度和非破壞性讀取的優點，極有可能成為下一世代非揮發性記憶體主流。 本論文的研究是著重於電阻式記憶體串聯搭配電晶體之電性特性，主要分為兩部份。第一部份是利用氧化鋯薄膜作為轉態層並以電晶體當限流開關來改善轉態特性，第二部份則是用鋯酸鍶薄膜作為轉態層搭配電晶體之研究。氧化鋯薄膜搭配電晶體的電阻式記憶體，能有效控制限流的大小並使操作電流降低至25uA,操作電壓在1.5V 達到低功率消耗優點。此外，在單一元件上藉由電晶體控制導電細絲的形成粗細而有多組態操作特性，非破壞性讀取量測中能在施加0.3V直流電壓下可維持10000秒而無改變，資料保存能力在常溫下到達106秒。另外也探討元件尺寸微縮的影響，氧化鋯薄膜面積越縮小(1um2)，高低組態有更明顯區隔視窗，代表有微縮的優點。最後進一步利用電性結果，探討可能的電阻轉態機制。第二部份則是利用鋯酸鍶薄膜搭配電晶體的電阻式記憶體，有超過100倍的區隔視窗。

Many types of consumer electronics products require high-capacity memory with the development of the technology, in which demanding for non-volatile memory is the largest. Flash memories face the issue of scale limit, so the research of next generation non-volatile memories is booming. The resistive switching random access memory (RRAM) have these advantages, such as high operation speed, low power consumption, high cell density, and lower scale limit and non-destructive readout, which have the opportunity to become the mainstream of next generation non-volatile memory. In this thesis, the research is focus on the electric characteristic of 1T1R device, and it divides two parts. First part, we used transistor as current limiter to improve the switching characteristic based on the ZrO2 thin films, and second part is the research of 1T1R based on the SrZrO3 thin films. In the first part, ZrO2-based 1T1R devices could efficiently control compliance current and lower the operation current to 25uA, operation voltage to 1.5V, which reach the advantage of low power consumption. In addition, 1T1R device have multistate operation in a single device due to the thickness and number of filaments which controlled by compliance current; there is no data loss at the nondestructive readout test for over 10000 seconds under 0.3V DC voltage; and retention test is 106s at room temperature. Next, size effect is also studied. As the area of ZrO2 thin films scale down (1um2), the resistance ration becomes larger. At LRS, the current is independent on the area, but at HRS, the current is decreasing following the scale down of the ZrO2 area. In the second part, 1T1R devices which are based on the e SrZrO3 thin films could have large resistance ration over 100 times.