利用田口法最佳化鐵酸鉍摻雜鈮之MFIS電容器
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2014
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Abstract
本研究主要是在探討MFIS(金屬/鐵電/絕緣體/半導體)結構之電容器。鐵電材料為鈣鈦礦結構所產生的極化特性及極化殘留特性，而適合當作記憶體材料。近幾年來鐵酸鉍為引起關注的鐵電材料，它具有高居禮溫度(約850-860 ℃)及高尼爾溫度(約370-397 ℃)、高的極化效應的優點，但鐵酸鉍缺點為具有很大的漏電流，為了降低漏電流，利用鐵酸鉍薄膜摻雜鈮的方式來解決。
本研究的目標為利用田口法尋找在製造MFIS電容器(鋁/鐵酸鉍摻雜鈮/氧化鉿/p型矽基板)中之最佳製程參數組合。探討製程參數對於漏電流及記憶窗寬之影響。以訊雜比公式，計算電特性量測(I-V與C-V曲線)所得到的數據。此分析結果在漏電流與記憶窗寬都得到一樣的趨勢。我們得到的最佳參數組合退火溫度為700 ℃、摻雜鈮的直流濺鍍瓦數為5 W、氬氧比為15。物理特性量(XRD)分析結果，退火溫度在700 ℃時，可看鈮離子有取代鐵離子，此表示摻雜鈮會減少氧空缺。雖然摻雜鈮的濃度越多越能取代鐵離子，但鈮離子過多也會導致漏電流的增加與記憶窗寬的縮小。
This study is to investigate MFIS (Metal/Ferroelectric/Insulator/Semiconductor) structure capacitors. Ferroelectric materials have a Perovskite structure. It generated ferroelectric polarization and remnant polarization. Those properties are suitable for nonvolatile memory materials. BiFeO3 is one of the Ferroelectric materials that have been attracted to attention recently. Although BiFeO3 possesses many merits such as high Curie temperature (about 850-860 ℃), high Neel temperature (about 370-397 ℃) and large remnant polarization, it possesses demerit of large leakage current. In order to improve this problem, we resolved it in a way of Nb-doped BiFeO3 thin film. The purpose of this study is to find the optimum combination of factors in the manufacture of MFIS capacitors (Al/BiFeO3+Nb/HfO2/p-Si substrate) using Taguchi Method, and then discuss the effects of process conditions on leakage current and memory window. Based on the electrical property measurements (I-V and C-V), SNR (S/N ratio) was calculated. As a Result, the leakage current and the memory window indicated same trends. We obtained the optimal recipe which was 700℃ for RTA temperature, 5 W for DC power of Nb sputtering and 15 for Argon-to-Oxygen ratio. According to physical characterization (XRD) analysis results, Nb ions replaced iron ions at annealing temperature at 700 ℃, which this means that oxygen vacancies were reduced by Nb-doping. Although the more Nb-doping, the more Nb ions replace Fe ions, but excessive Nb-doping induces the increase of the leakage current and reduces the memory widow.
This study is to investigate MFIS (Metal/Ferroelectric/Insulator/Semiconductor) structure capacitors. Ferroelectric materials have a Perovskite structure. It generated ferroelectric polarization and remnant polarization. Those properties are suitable for nonvolatile memory materials. BiFeO3 is one of the Ferroelectric materials that have been attracted to attention recently. Although BiFeO3 possesses many merits such as high Curie temperature (about 850-860 ℃), high Neel temperature (about 370-397 ℃) and large remnant polarization, it possesses demerit of large leakage current. In order to improve this problem, we resolved it in a way of Nb-doped BiFeO3 thin film. The purpose of this study is to find the optimum combination of factors in the manufacture of MFIS capacitors (Al/BiFeO3+Nb/HfO2/p-Si substrate) using Taguchi Method, and then discuss the effects of process conditions on leakage current and memory window. Based on the electrical property measurements (I-V and C-V), SNR (S/N ratio) was calculated. As a Result, the leakage current and the memory window indicated same trends. We obtained the optimal recipe which was 700℃ for RTA temperature, 5 W for DC power of Nb sputtering and 15 for Argon-to-Oxygen ratio. According to physical characterization (XRD) analysis results, Nb ions replaced iron ions at annealing temperature at 700 ℃, which this means that oxygen vacancies were reduced by Nb-doping. Although the more Nb-doping, the more Nb ions replace Fe ions, but excessive Nb-doping induces the increase of the leakage current and reduces the memory widow.
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田口法, 鐵酸鉍, MFIS電容器, 記憶窗寬, Taguchi method, BiFeO3, MFIS capacitors, memory window