Studying the effects of processes on crystalline porous low-k silica thin films

低介電係數材料在半導體工業中是極重要的需求，其中孔洞型二氧化矽具有介電常數低、熱穩定佳以及製程整合簡單的優點。本研究探討軟烤條件、水熱反應時間、離心條件以及鹼處理等因素對於製備具結晶性的孔洞二氧化矽薄膜的影響。 針對熱處理程序的研究中可以發現軟烤溫度較低所製備的薄膜將具有較多的孔洞結構，因此介電常數較低而機械強度較差。水熱製程時間越長結晶性越好但伴隨塗佈不佳的問題，因此提出以長時間離心與鹼處理程序來改善塗佈，在此部分研究結果中可建立幾個趨勢，第一是結晶性越高介電常數越低但機械強度越差；第二是界面活性劑比例越高介電常數越低但機械強度越差；第三是離心可減少薄膜的粗糙情形因而降低介電常數且使機械強度越來越高，但當離心時間過久則會使得介電常數升高；第四，加入鹼處理程序並以氨水作鹼，其改進的結果並不明顯，而以TEAOH作鹼來源的結果介電常數大幅升高且機械強度變差。 從實驗結果討論奈米沸石與界面活性劑作用的機制，奈米膠體沸石成長過程是先由二氧化矽結構包附TPAOH後再慢慢由中心開始形成結晶結構，但tween80與TPAOH均會爭取抓附Si-OH結構，所以在結晶性較差時加入界面活性劑將會使得具小孔的結構被拆散；當結晶性提升後由於結晶結構不會和界面活性劑反應，所以部分具有結晶性的小孔洞結構將不因界面活性劑的加入而被破壞。 本研究中所製備之最佳薄膜，其結果是介電常數1.83硬度1.39Gpa楊氏係數12.25Gpa。Low-dielectric-constant (low-k) material is a critical request in semiconductor industry. Porous silica possesses advantage of low dielectric constant, good thermal stability, and easily-preparation procedures. Effects of baking conditions, hydrothermal process, centrifugation, and base treatment on the properties of crystalline porous low-k silica thin film were studied in the research. Some results can be presented while studying the effect of heat treatment. The thin film prepared with lower baking temperature will possess more porous structure, thus it will have lower k value but poorer mechanical strength. While the hydrothermal process time is longer, the crystallinity is better; however the coating quality is poor. We propose long-time centrifugation process and base treatment to solve coating problem. In this part of research, we establish some trend. First, the better crystallnity would bring about lower k-value but poorer mechanical strength. Second, adding more surfactant would lead lower k-value but make mechanical strength poor. Third, centrifugation could diminish the roughness of thin film and consequently lower the k-value; however excessive centrifugation process would increase the k-value. Fourth, adding base treatment into process and using ammonium as base source, its improvement is unobvious; and altering TEAOH as base source would lead high k-value and poor mechanical strength. Base on results of experiment, we make a discussion about nanozeolite reacting with surfactant. In the beginning, silica species surround TPAOH, and then the center will crystallize slowly. However, tween80 competed with TPAOH to grab Si-OH species. As the results, adding surfactant while crystallinity is poor would induce micropore structure to be taken apart. Because crystal structure would not react with surfactant, crystalline micropore structure would not be destroyed when crystallinity advanced. The best thin film prepared in the research possesses k value =1.83, hardness =1.39GPa, and elastic modulus =12.25GPa.目錄 I要 IVbstract V目錄 VII目錄 IX一章 緒論 1-1研究背景 1-2 研究目標 5二章 文獻回顧與研究設計 6-1 低介電常數材料 6-2 孔洞型二氧化矽材料 10-3 Surfactant-templating method合成中孔洞二氧化矽低介電薄膜 11-4 Hydrothermal method合成具沸石結構之二氧化矽低介電薄膜 14-5 結合surfactant-templating與hydrothermal method 16-6 研究設計 17三章 實驗方法 18-1 實驗藥品及儀器 18-1.1 藥品 18-1.2 實驗儀器 19-2 實驗程序與合成條件 20-2.1 矽晶片的清洗程序 20-2.2 合成旋塗溶液 21-2.3 旋轉塗佈(Spin coating) 21-2.3 熱處理:軟烤與鍛燒(Baking and Calcination) 22-2.4 表面修飾 22-3 薄膜鑑定 24-3.1顯微鏡觀察 24-3.2 電性量測 24-3.2.1 介電常數量測-電容電壓系統 25-3.2.2 平帶電壓分析 26-3.2.3 半自動電性量測系統 29-3.3 機械強度量測系統 30-4 X光粉末繞射實驗 33-5氮氣吸脫附實驗 33四章 實驗結果 35-1 軟烤條件對薄膜性質的影響 35-2 拉長水熱製程提升結晶性對薄膜的影響 37-2.1 結晶性鑑定 38-2.2 電性與機械強度結果 39-2.3 孔洞體積數據 42-3 長時間離心去除大顆粒對薄膜性質的影響 44-3.1 電性與機械強度結果 45-4 加鹼程序對薄膜性質的影響 50-4.1 電性與機械強度結果 52-4.1.1 以氨水作鹼處理結果 52-4.1.2 以四乙基氫氧化胺作鹼處理結果 53五章 討論與未來展望 55-1 熱處理程序的討論與改進 55-2 結晶性與薄膜性質的關係 57-3 奈米沸石與界面活性劑的反應 65-4 漏電流的改進 69-5 製程簡化 70六章 結論 71七章 參考文獻 7