厚膜UBM之覆晶銲錫接點電遷移及銲錫電遷移臨界長度之研究

Abstract

本計畫預計在銲錫電遷移議題上作一有系統且深入的研究，包含厚膜 UBM 之覆晶銲錫接點電遷移以及銲錫電遷移臨界長度(critical length)之研 究。本計劃的第一年中，我們將製作不同長度的錫鉛銲料合金錫膜， 求出臨界值(critical product)、飄移速度(drift velocity)、DZ*值等重要之電遷 移參數。並針對SnPb 及SnAg 銲錫的覆晶凸塊試片進行研究。首先建立厚 膜與薄膜UBM 之銲錫failure time 之資料，進而分析此他們的破壞模式。 本年度計畫首要是在探討出厚膜UBM 銲錫凸塊其電遷移行為，來和薄膜 UBM 做比較。 第二年的研究將利用第一年所建立之技術來製作出 SnCu、SnAg 與 SnAgCu 之solder stripe 進行無鉛銲錫之研究。求出臨界值(critical product)、 飄移速度(drift velocity)、DZ*值等重要之電遷移參數外。於真實solder bump 方面，將針對不同材料UBM 之厚膜UBM 銲錫接點進行研究。預計預計會 有Cu/Cu，Ni/Cu 之材料的厚膜UBM。然後再搭配Kelvin bump probes 的量 測方式來建立銲錫接點中，不同通電狀態下之微結構變化之資料。 第三年的研究重點將改變原本 Blech 試片結構中之濕潤層，用Ni 墊層來取 代原本的Cu 墊層。藉以探討當Ni 與銲錫形成Ni3Sn4 時將如何影響電遷 移之重要參數。另外，將針對不同Bump Height 之厚膜UBM 銲錫接點進 行研究，預定探討出Volume effect 在銲錫接點中所帶來的影響。同時我們 將以3D 電腦模擬來輔助研究電遷移破壞模式，研究在通電候不同階段電 與熱的重新分佈。相信在三年後能在銲錫電遷移領域有很大的貢獻。

The goal of this project is to investigate electromigration of solder joints systematically, including solder bumps with thick Ni UBM, and the critical length of electromigration of solder. In the first year, we will fabricate solder stripes with different length, and measure their important electromigration parameters, such as critical length, drift velocity, and DZ*. In addition, we will study the electromigration behavior with thick-film UBM, investigating their failure time and failure mechanism. In the second year, we will measure the electromigration parameters for Pb-free solders, including SnCu, SnAg, and SnAgCu. For real solder bumps, we will study the electromigration behavior for the solder with thick Cu UBM. By employing Kelvin bump probes, the microstructure of the solder bump during electromigration can be monitored under various stressing condition. In the third year, we will use Ni metallization to prepare solder Blech stripes. The Ni layer will reaction with solder to form Ni3Sn4 IMC, and the electromigration behavior for the interface will be investigated. In addition, solder joints with different bump height down to 20 μm will be prepared and the volume effect of EM in solder bump will be studied. In the mean time, three-dimensional simulation will be used to assist the investigation of failure mechanism of solder joints, and the redistribution of current and temperature at various stage of electromigration. We are quite confident that we will have many important contributions on the field of solder joint electromigration after three years.