- 學位論文
探討製程對結晶性孔洞型二氧化矽薄膜性質的影響
Studying the effects of processes on crystalline porous low-k silica thin films
摘要
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。
並列摘要
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.