PI-doping Ta2O5複合薄膜介電層之合成與物理性質之分析研究及有機薄膜電晶體元件製作

Abstract

本論文研究以溶膠-凝膠法製備聚亞醯胺-五氧化二鉭複合薄膜並探討其物理特性。由熱分析中發現當聚亞醯胺薄膜中之五氧化二鉭添加量增加時，其薄膜熱性質會變差。經由MIM結構量測薄膜之I-V與C-V特性，發現薄膜之電性與熱處理時氧分壓有關。在固定之Ta2O5含量下，在空氣氣氛下熱處理之薄膜具有最低之漏電流密度，而在純氧氣下熱處理薄膜之介電常數最高。在不同熱處理溫度下，薄膜在400℃熱處理具有最高之漏電流密度，在300℃最低。薄膜之介電常數隨五氧化二鉭添加量而增加，與熱處理溫度無明顯關係。X光光電子光譜儀（XPS）可鑑定聚亞醯胺薄膜之亞醯胺化程度，並發現熱處理氣氛影響亞醯胺化程度。故可得知薄膜之漏電流與亞醯胺化程度有關。

以聚亞醯胺-五氧化二鉭複合薄膜作為有機薄膜電晶體之閘極絕緣層，並探討不同五氧化二鉭添加量對電晶體之載子遷移率（field-effect mobility, μFE）、臨限電壓（threshold voltage, Vth）以及開關比（on/off ratio）之影響，發現電晶體之載子遷移率隨薄膜介電常數升高而增加。

The preparation and physical properties of Ta2O5 doped polyimide films utilized sol-gel processes were investigated in this study. The thermal properties of Ta2O5 doped polyimide films degraded as the content of Ta2O5 increased. The I-V and C-V measurements of the films were realized by MIM (metal-insulator-metal) structure. It was found that the electrical properties of the films significantly depended on the partial pressure of oxygen during thermal treatment. With a fixed Ta2O5 content, the films exhibited a minimum leakage current density under the air, and the maximum dielectric constant was obtained under the pure oxygen atmosphere. At different temperatures of thermal treatment, the highest and lowest leakage current densities were obtained at 400℃ and 300℃, respectively. The dielectric constants of the films increased with the content of Ta2O5 and were independent on the temperature of thermal treatment. The degrees of imidization of the films were demonstrated by X-ray photoelectron spectroscopy (XPS). It could be seen that the degrees of imidization of the films depended on the atmosphere of thermal treatment. Therefore, the leakage current densities might be affected by the degrees of imidization of the films. The Ta2O5 doped polyimide films were used as the gate insulators of the organic thin film transistors. The effects of Ta2O5 contents on the field-effect mobility, threshold voltage and on/off current ratio of the transistors were also discussed. It was found that the mobility of the transistors increased with the dielectric constant of the films.