覆晶(Flip-Chip)技術由於具有封裝密度、功能、及成本之優勢，漸成為微電子構裝技術之主流。在覆晶結構中銲球與球下金屬層(Under Ball Metallurgy，簡稱UBM)之可靠度(Reliability)問題則居此技術之關鍵地位。本實驗擬針對無鉛銲料中最主要之錫成分與銅膜之界面反應做一系統性探討。主要研究主題為錫/銅金屬薄膜界面反應對薄膜電阻之影響與介金屬化合物成長動力機制探討。
本實驗藉由濺鍍方式將銅膜沉積在氧化矽基板上，再用熱蒸鍍法於銅薄膜上鍍上錫膜，利用四點探針法於氮氣氣氛下以固定升溫速率由室溫升溫至220oC來觀測薄膜電阻變化，並以掃描式電子顯微鏡(SEM)，X光結晶繞射法(XRD)及歐杰電子能譜分析儀(AES)分析薄膜介面微結構與介金屬生成相，探討介金屬化合物之生成動力機制。研究結果指出錫-銅介金屬層(IMC)生成活化能約為0.97±0.07eV。銅膜與錫膜的相對厚度亦會對介金屬相的生成順序造成影響，在等速率升溫退火過程所生成的介金屬化合物種類會因膜厚比例不同而有所差異。而且較薄的錫/銅薄膜反應偶由於具較大之電阻變化因而對於薄膜反應生介金屬成相的偵測有較高的靈敏度。

Flip-Chip technology is becoming a mainstream process due to the advantages of packaging density, functionality and cost. The reliability of solder ball and Under Ball Metallurgy(UBM) remains the critical issue for flip-chip structures. A systematic study of interfacial reaction between Sn, a major constituent of lead free solder, and Cu metallization was conducted. We investigated the interfacial reaction of Sn/Cu bimetallic thin film and the kinetics of Cu-Sn intermetallic compounds (IMC) formation by measuring the resistance change of the Cu/Sn bilayer thin films.
Sn/Cu bilayer thin films were prepared by consecutive deposition of Cu film and Sn film onto oxidized Si substrates by sputtering and evaporation methods. Resistances of the Cu-Sn bimetallic thin film specimens were measured using an in-situ 4-point probe method when the specimens were heated from room temperature to 220□C at a fixed ramp rate in nitrogen ambient. The various Cu-Sn compounds were identified by X-ray diffraction (XRD), and the morphology of the Cu-Sn compounds was examined by scanning electron microscopy (SEM). The concertration depth profile of the Sn/Cu bimetallic samples were measured by Auger electron spectroscopy (AES). The activation energy of formation of Cu6Sn5 compounds was found to be 0.97±0.07 eV according to the in-situ resistivity measurement. The thickness of the Sn/Cu bilayer thin films was found to affect the sequence of IMC formation. Besides, the thinner reaction couples showed a better resolution for detecting interfacial reaction due to large change in thin film resistance.

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