發光二極體(LED)因其節能、省電、壽命長優點被視為未來可取代日常生活照明的元件，為達此目的，發光源之亮度成為一個急需突破的關鍵技術。LED之亮度提高伴隨而來的問題為元件散熱，熱量的累積除了造成元件溫度上升外，更會影響其發光效率。因此，本研究以使用高熱傳導係數且成本較低的Si基板取代現行的氧化鋁基板之前提，探討金屬化鍍層在Si基板上經熱循環測試後之界面反應。
本研究選用Ti/Ni/Ag/Au薄膜作為Si基板LED之金屬化鍍層，以熱循環方法模擬LED元件運作溫度，探討熱循環測試後界面反應和界面電性之變化，並進一步了解通過Ni/(Ag/Au)層界面電流值較低之原因。實驗利用真空濺鍍方式將欲濺鍍多層金屬層依序濺鍍在Si基材上，再進行332~2558次熱循環測試，熱循環條件是於-40℃持溫 15 分鐘，接著再將升溫到125℃持溫15 分鐘升降溫速率皆固定為11℃/min。熱循環測試後的試片在研磨拋光後先使用SEM觀察其表面形貌，並用多探針奈米電性量測系統量測層與層之間的電性。
Ti/Ni/(Ag/Au)與Ni/(Ag/Au)等多層膜之電性量測結果顯示，通過Ni/(Au/Ag)間之電流與Ti/Ni/(Ag/Au)、Ti/Ni層相比相對微小許多。由ESCA成分縱深分析可發現Au與Ag間有明顯擴散現象，且經熱循環測試後表面的Ag濃度達到68%。藉FIB蝕刻輔助分析，可發現由於向Ni、Au層擴散之Ag原子流量大於向Ag層內擴散Ni、Au原子，因而在Ag層內有孔洞生成，孔洞形貌依Ni/Ag、Ag/Au間擴散係數差異影響程度不同可大致分為四類：(a)位於Au/Ag界面交界處之孔洞(b)於Ag層內接近Ni層，尺寸微小的孔洞(c)於Ag層中數個小孔洞聚集(d)於Ag層中尺寸較大，約有90nm~150nm左右之拱型孔洞。孔洞的生成亦使得通過Ni/Ag界面及Ag/Au界面電流變得極微小，成為Ni/Au/Ag層影響整體金屬化鍍層電性表現不佳之原因。

Light-emitting diodes (LEDs) are becoming a promising device for lighting. However, heat dissipation becomes a technological challenge which may reduce luminance as well as product life of the device. In order to solve this difficult problem, Si substrate was among the alternatives to replace traditional sapphire substrate. Si substrate offers many advantages such as good thermal conductivity, large wafer size and lower cost of the Si fabrication process. The Ti/Ni/Ag/Au multilayers combination, intended for LED metallization was deposited on Si substrate for interfacial interaction study. The interfacial interactions and electrical characteristics of the Ti/Ni/Ag/Au multilayers was investigated under various periods of thermal cycling between -40℃ and 125℃. The electrical properties of the multilayer thin films were measured by two-probe nano-electronics measurement. The depth profile was performed by ESCA (Electron Spectroscopy for Chemical Analysis). The interfacial reaction behavior was investigated with FIB (Focused Ion beam) and SEM.
The electrical property of Ti/Ni/(Ag/Au) and Ni/(Ag/Au) multilayer show that the Ni/(Ag/Au) predominates the overall electrical performance of the multilayer combination. It is obvious that the resistance of Ni/(Ag/Au) interface is much higher than Ti/Ni interface.
The results of ESCA (Electron Spectroscopy for Chemical Analysis) depth profile analysis indicate that Ag atoms diffuse passing through the pure Au layer to the surface after thermal cycling. The atomic concentration of Ag at the surface increases up to 68% after thermal cycling of 627 cycles. The outward diffusion of Ag atoms towards Au and Ni cause voids formation in Ag layer and thus higher electrical resistance.

Four types of void morphology were observed (a) void formed between Au and Ag layer, (b) a small void formed in the Ag layer closing to the Ni layer. (c) several small size voids aggregating at the Ag layer. (d) larger arcuate void forming in Ag layer. The disparity of diffusion coefficient among Au, Ag and Ni elements give rise to large voids formation in the Ag layer. The formation of void is responsible for the poor electrical performance of the Ni/(Ag/Au).

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