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Title: | 原子層沈積之鋁混摻氧化鉿於電阻式記憶體之應用 Application of atomic layer deposited Al-doped hafnium oxide for RRAM |
Authors: | Pei-Chen Wu 吳佩蓁 |
Advisor: | 蔡豐羽(Feng-Yu Tsai) |
Keyword: | 電阻式記憶體,原子層沈積,混摻,氧化鉿, resistive switching,atomic layer deposition,hafnium oxide,doped, |
Publication Year : | 2013 |
Degree: | 碩士 |
Abstract: | 本篇研究應用原子層沈積(ALD)製作電阻式記憶體(RRAM)的轉換材料。電阻式記憶體一直以來的問題是電阻轉換參數不夠集中,而這是由於導電燈絲的生成過於隨機。在薄膜裡面混摻不同元素已經被發現可以用於改善這問題,而原子層沈積只要透過控制混摻層層數比例就可以完美控制垂直混摻比例,所以被選用於製作混摻元素薄膜。然而,由於傳統的原子層沈積技術是層狀堆積結構,混摻層必須整層都是混摻元素,這限制了水平混摻的控制性。因此,我們提出了一種混和混摻製程可以製作出均勻混摻的薄膜。在這個製程裡,我們在同一次原子層沈積的週期內連續通入兩種有機金屬前軀物,形成了一個混和混摻層。應用這個混合混摻的技術,我們製作了三種不同混摻狀況的薄膜,分別是1:4整層混摻、1:9整層混摻以及1:4混合混摻的鋁混摻氧化鉿薄膜,並將其製備成電阻式記憶體元件;而混合混摻的證據可以透過X射線光電子能譜(XPS)量測的元素比例發現1:4混合混摻薄膜比起1:4整層混摻薄膜,的確有比較少的鋁元素比例。首先,根據燈絲理論,我們提出了示意圖來解釋導電燈絲在三種不同混摻狀況薄膜裡的狀況。接著,我們討論這三種不同導電燈絲的狀況對電阻轉換現象的影響,進而驗證我們的燈絲示意圖。這三種元件都是雙極性轉換,不一樣的是電阻轉換參數的集中性。1:4混合混摻薄膜製作的元件因為其混摻較均勻所以表現出較集中的參數;另外,再啟動電流(Reset current)也因為在此薄膜中混摻比例比較少而被有效地減小。在1:4混合混摻元件裡,因為其垂直混摻較1:9整層混摻多,但是每層混摻比例又比1:4整層混摻少,所以生成的燈絲又細又集中,所以接下來的燈絲斷裂及再生成也都比較不隨機,導致參數特別集中。最後,我們比較了三種元件的穩定性,分別是週期間穩定性,元件間穩定性以及持久性,1:4鋁混合混摻氧化鉿薄膜製作的元件都有傑出的表現。 In this study, we used ALD to deposit the switching material of RRAM. RRAM has suffered from the randomness of conductive filaments which results in poor uniformity of resistive switching parameters. It has been proved that doping can overcome this problem, and ALD is a perfect process to control vertical doping by manipulating the doping layer ratio; however, due to the layer-by-layer nature, the conventional ALD process failed to control lateral doping. Here, we developed the mixed deposition process which pulses two organometallic precursors to the chamber consecutively in the same cycle, and thus created a mixed doping layer. By utilizing the mixed deposition process, we can conduct a homogeneously doped Al:HfO2 thin films with more uniform doping vertically but less doping laterally. Here, we deposited three kinds of RRAM devices with Al:HfO2 thin films of different doping distribution, which are 1:9 conventional doping, 1:4 conventional doping and 1:4 mixed doping, and the effect of doping distribution on resistive switching behavior is discussed. First, based on the filament model, hypothetical schematic images of filaments in three devices were sketched. In these images, CFs were the narrowest and most confined in the 1:4 mixed doped Al:HfO2 based device, whereas they were stronger in the 1:4 conventional doped Al:HfO2 based device and more random in the 1:9 conventional doped Al:HfO2 based device. The different shapes of CFs in three devices can explain the difference of resistive switching parameters. All three devices showed bipolar switching, and the uniformity of parameters is compared through the statistical distribution of switching parameters during 100 consecutive cycles. The 1:4 mixed doped Al:HfO2 based device displayed excellent uniformity of parameters due to homogeneous doping; besides, the reset current was also reduced due to less doping in this device. Finally, the stability of three devices was compared, and the 1:4 mixed doped Al:HfO2 based device showed excellent stability compared to the other two devices. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/60857 |
Fulltext Rights: | 有償授權 |
Appears in Collections: | 材料科學與工程學系 |
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