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研究生:陽靖宇
研究生(外文):Ching-Yu Yang
論文名稱:銅薄膜高溫凝聚行為之研究
論文名稱(外文):Investigation of copper agglomeration at elevated temperature
指導教授:陳貞夙陳貞夙引用關係
指導教授(外文):J. S. Chen
學位類別:碩士
校院名稱:國立成功大學
系所名稱:材料科學及工程學系碩博士班
學門:工程學門
學類:材料工程學類
論文種類:學術論文
畢業學年度:90
語文別:中文
論文頁數:84
中文關鍵詞:銅薄膜凝聚行為
外文關鍵詞:agglomerationcopper interconnectTaN diffusion barrier
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中文摘要
本實驗主要研究方向在探討銅金屬薄膜經高溫退火後凝聚的行為,並進一步改善凝聚現象的發生。在本實驗中,利用改變不同銅薄膜的厚度(50nm或200nm)、是否在Cu/TaN間添加10nm Ta中介層及不同的基材材料(Si或SiO2/Si)等參數,經不同溫度(400℃-900℃)30分鐘真空退火後,以四點探針(four point probe)量測片電阻值的變化,以θ-2θ X光繞射(θ-2θ X-ray diffraction)分析相的變化,利用掃瞄式電子顯微鏡(SEM)觀察試片表面形態,利用歐傑電子分析儀(AES)及拉塞福背向散射分析(RBS)做試片縱深成份分析,以X光射線光電子能譜儀(XPS)來分析薄膜表面的化學鍵結,並利用穿透性電子顯微鏡(TEM)觀察銅薄膜晶粒大小。
從實驗的結果可以知道,當銅薄膜厚度為200nm時,不論銅薄膜是直接沉積在TaN上,或是在Cu/TaN間加了一層Ta中介層,都不會有凝聚現象的發生。而銅凝聚的現象只發生在銅薄膜較薄(50nm),且直接鍍製於TaN之上時;若在Cu/TaN間添加了一層10nm的Ta中介層,銅薄膜凝聚的現象明顯的改善。由RBS及XPS的分析結果中可以知道,在Cu/TaN間添加一層Ta中介層,經高溫退火之後(700℃), Ta會擴散至銅薄膜的表面,形成一層cap-layer,阻礙銅的凝聚。比較未添加Ta中介層及在Cu/TaN間添加Ta中介層的SEM照片後也可以發現,添加一層Ta中介層可以明顯減緩銅晶粒的成長,進一步降低銅凝聚的情形。然而,從實驗中的結果也可以發現,在添加Ta中介層後會因為TaN中的N遭到稀釋,因此降低TaN高溫阻障效果。另外,實驗的結果也顯示出,銅薄膜凝聚與否與基材材料並沒有一直接的關係。但是,從實驗中的結果也可以發現,利用SiO2/Si為基材可以明顯阻止Cu-Si間的反應。
從本實驗的結果可以知道,增加銅薄膜的厚度以及在Cu/TaN間添加一層Ta中介層,可以明顯的阻止銅薄膜在TaN擴散阻障層上的凝聚行為。基材材料對銅凝聚的現象雖然沒有直接的關連性,然而,以SiO2/Si為基材可以明顯的阻止以Si為基材時,銅與矽之間的反應。
Abstract
In this work, the agglomeration behavior of copper thin film after high temperature annealing is investigated. Copper film thickness (50nm or 200nm), with or without a 10nm Ta interlayer between Cu and TaN, and different substrate materials (Si or SiO2/Si) were used as the experimental factors. After samples were annealed at various temperatures (400℃-900℃) in vacuum for 30 min, material characteristics were analyzed. The change of sheet resistance was measured by four-point probe. θ-2θ X-ray diffraction was used for phase identification, and scanning electron microscopy (SEM) was employed to investigate the surface morphology. Compositional depth profiles were measured by Auger electron spectroscopy (AES) and Rutherford backscattering spectrometry (RBS). X-ray photoelectron spectroscopy (XPS) was used to examine chemical bonding states, and transmission electron microscopy was employed to investigate copper grain size.
Experimental results reveal that either with or without a Ta interlayer between Cu and TaN, no copper agglomeration was observed when the copper has a thickness of 200nm. Copper agglomeration was only observed when copper has a thickness of 50nm. It was also observed that copper agglomeration was significantly improved while a Ta interlayer was added between Cu and TaN. When a Ta interlayer was added between Cu and TaN, RBS and XPS reveal that after high temperature annealing (700℃), Ta will diffuse to the copper surface and forming a cap-layer. The cap-layer might prevent copper agglomeration. By comparing the SEM photographs of samples with or without a Ta interlayer, it is observed that the grain growth of copper was slow down when a Ta interlayer was induced. The slow grain growth may result in the prevention of copper agglomeration. However, the interposed Ta layer would also dilute the overall nitrogen concentration in the barrier layer, and consequently brought the failure of the barrier. From the results of this experiment, the connection between copper agglomeration and substrate material was not obviously. Besides, the reaction between Cu and Si could be prevented when the SiO2/Si substrate was used.
From the results of this experiment, copper agglomeration on TaN diffusion barrier could be prevented significantly by increasing copper thickness and adding a Ta interlayer between Cu and TaN. The relationship between copper agglomeration and substrate material was not obvious. However, using SiO2/Si as substrate material could prevent reaction between Cu and Si.
目錄
第一章 前言與研究目的 1
1-1前言 1
1-2 研究目的 4
第二章 理論基礎 7
2-1 電阻-電容延遲(RC delay) 7
2-2 TaN擴散阻障層 9
2-3 銅金屬導線 11
2-4 薄膜凝聚現象探討 11
2-5 文獻中對薄膜凝聚現象的探討 18
第三章 實驗方法與步驟 19
3-1 實驗材料 19
3-2 實驗設備 20
3-2.1 濺鍍系統 20
3-3.2退火系統 20
3-3 實驗流程 23
3-4 鍍膜分析 28
3-4.1 片電阻值及厚度量測 28
3-4.2 結晶繞射分析 30
3-4.3 SEM表面觀察 32
3-4.4 AES成份、縱深分析 32
3-4.5 XPS化學態分析 34
3-4.6 拉賽福背向散射(RBS)分析 34
第四章 實驗結果與討論 36
4-1 銅/阻障層於矽晶片上之行為 36
4-1.1 片電阻量測 36
4-1.2 XRD及SEM分析 38
4-2 銅/阻障層於覆有二氧化矽之矽晶片上之行為 51
4-2.1 片電阻量測 51
4-2.2 XRD及SEM分析 53
4-3 實驗參數對界面反應及銅凝聚的影響 65
4-3.1 添加Ta中介層 65
4-3.2 銅薄膜厚度 68
4-3.3 Si基材與SiO2/Si基材的差異 69
第五章 結論 77
參考文獻 79
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