氧化鋅電阻式記憶體表面效應與化學腐蝕的抑制

Abstract

本文中，我們藉由摻雜氮與氟原子改善氧化鋅電阻式記憶體的操作電性，並且使得氧化鋅電阻式記憶體更能抵抗外界的影響因子，包含氧氣分子吸附以及化學腐蝕。 首先，摻雜氮可以有效使氧化鋅電阻值提升，使得原本過於導電而無法運作的原子層沉積氧化鋅薄膜可以產生良好的電阻式記憶體特性。我們更進一步將氮摻雜氧化鋅薄膜在大氣下進行退火，藉此活化摻雜於薄膜中的氮原子，能得到更加優良的記憶體特性，包含良率提升至82%，所需電流降低至5 mA，以及更高的操作穩定性。此外，由於氮原子取代氧原子並抑制氧空缺的形成，可以有效消除氧氣分子吸附在氧化鋅表面形成的能帶彎曲，避免表面效應對氧化鋅電阻式記憶體的劇烈影響。 最後，藉由摻雜氟原子，氧化鋅電阻式記憶體的電性可以有效被改善，元件操作電壓與電流值呈現較為集中的分佈趨勢。同樣地，氟原子取代氧原子並抑制氧空缺的形成，能有效消除氧氣分子對於氧化鋅電阻式記憶體的表面效應，使氧化鋅電阻式記憶體維持穩定性不受環境氣氛影響。更重要的是，摻入氧化鋅薄膜中的氟能夠扮演鈍化層的角色，避免外界的化學物質與氧化鋅產生反應並腐蝕氧化鋅，進一步使得氧化鋅薄膜能夠應用於嚴苛環境。本研究之概念與技術將有助於非揮發性記憶體的優化與發展。

In this thesis, the performance of ZnO-based resistive memory could be improved by employing nitrogen/fluorine doping. The memory devices become immune to surrounding effects, including surface effect and chemical corrosion. Metal oxide suffering from oxygen molecule chemisorption shows the environment-dependent metastability, leading to unstable resistive memory characteristics and performance degradation. For obtaining the ambient-independent characteristics, we introduced nitrogen into ZnO resistive memory, compensating the native defects and suppressing the oxygen chemisorption, giving rise to a significant improvement in switching behavior against undesired surface effects. Moreover, by thermal activation of nitrogen doping via annealing, a raised yield ratio from 50% to 82%, reduced current compliance from 15 mA to 5 mA, and more stable cycling endurance are obtained. Finally, we investigated the resistive switching characteristics of the ZnO thin films with CF4 plasma treatment. The fluorine incorporation can effectively stabilize the cycling endurance and improve the distribution of switching parameters, including set voltage (Vset), reset voltage (Vreset) and reset current. With the material analysis technique, we could obtain the chemical composition of the fluorinated ZnO devices. Moreover, the formation of Zn-F bond at the ZnO surface is able to inhibit the generation of oxygen vacancies and prevent the Zn atoms from dissolution, making a great contribution to defeat the surrounding effects. Our findings give physical insights into designing resistive memory devices.