覆晶銲錫接點 Cu/SnAg/Ni/Cu與微凸塊接點 Cu/SnAg/Cu的電遷移研究

Abstract

近年來，電子產品的需求漸趨輕薄短小、多功能以及高效能的綜合需求下，積體電路內部接點的電遷移所造成的破壞模式，與產品的可靠度息息相關。因此，提高接點電遷移可靠度以及壽命是半導體業界中相當重要的議題之ㄧ。 本研究的第一部份為利用兩種不同凸塊高度 (15 μm以及30 μm)的Cu/SnAg/Ni/Cu覆晶接點，於不同電流密度下進行電遷移測試。觀察凸塊內部的銲錫高度對電遷移的影響，實驗條件的電流密度為1.33x104 A/cm2、1.45x104 A/cm2、1.57x104 A/cm2。當陰極端為鎳金屬墊層時，主要的破壞模式為孔洞生成 (void formation)。然而，當陽極端為銅金屬墊層時，破壞模式則為銅原子的溶解 (Cu dissolution) 為主，並於SEM側視圖觀察到大量銅墊層溶解生成介金屬化合物。第二部分為利用菊花鏈結構的Cu/8 μm SnAg/Cu銲錫微凸塊在不同溫度下之電遷移測試，其實驗的溫度為135 °C、150 °C、165 °C，並進一步探討其提早失效的原因，以利避免此現象。第三部分為Cu/8 μm SnAg/Cu 微銲錫凸塊，於260 °C加熱板上，分別在不同時間 (0、5、10、20和40 min) 迴銲，觀察內部殘餘銲錫的銀濃度變化以及Ag3Sn的析出型態。

Due to the growing demands for high performance, small form factor and multi-functions in microelectronic packaging for different types of portable electronic devices, 3D stacking is an important issue nowadays in ICs industry. The first part of this study was the electromigration test using two different bump heights (15 μm and 30 μm) of Cu/SnAg/Ni/Cu flip-chip samples. We can investigate the effect of the bump height effect of failure mode in electromigration. The current density of the experimental conditions is 1.33x104 A/cm2, 1.45x104 A/cm2 and 1.57x104 A/cm2, we can observe the failure mode is void formation, when Ni UBM at the cathode side. When the anode with Cu UBM, we also found serious copper dissolution. The second part is electromigration test of Cu/8 μm SnAg/Cu microbumps. The test temperatures were 135 °C, 150 °C and 165 °C on hot plates. We found some sample had early failure, and further explored the reasons for the failure, then we can avoid the early failure. The third part is about Cu/8 μm SnAg/Cu microbumps reflowing at different times. The microbumps were reflowed on a 260 °C hot plate for 0, 5, 10, 20, and 40 min to investigate the variation of Ag concentration in the residual SnAg solder and the morphology of Ag3Sn precipitations.