電遷移對不同銀成份之晶片接點的可靠度影響評估

在電子元件上，常見的銲墊質材為銅或鎳。與銲墊相接處的銲料，多屬高Sn銲料。常用的高Sn銲料主要係以Sn-Ag、Sn-Zn、Sn-Cu爲基體，再添加其它適量金屬元素組成三元合金或多元合金。其中以Sn-Ag-Cu銲料與銅(或鎳)金屬銲墊所組成之銲點，最常被工業界所使用。近年來，在印刷電路板或晶片承載基板上，銲點尺寸明顯隨著封裝而越變越小。這也促使銲點之電遷移(electromigration)現象開始受到重視。電遷移會導致下列幾項銲點失效現象：(I) 過高電流密度會使得銲點溫度急速上升，最後可能導致local melting。(II) 金屬銲墊/銲料不斷的被電遷移，導致銲墊快速消耗與銲料變形。(III) 大量的原子由陰極端被電遷移至陽極端，造成陽極端產生凸起物(hillock)或鬚晶(whisker)，並在陰極端(cathode)留下valley 或孔洞(void)。在情況嚴重時，導線就會因此短路或斷路，而造成元件的失效。本研究將探討Sn-Ag-Cu銲料對電遷移的抵抗性。因此，本研究使用Cu/Sn/Cu、Cu/Sn-Ag-Cu/Cu line-bump覆晶銲點，其中銲點組成為pure Sn、Sn1Ag0.5Cu、Sn2Ag0.5Cu、Sn3Ag0.5Cu、Sn4Ag0.5Cu，通電觀察各種銲料與電遷移現象之關係。在本實驗中最明顯之電遷移現象為銲點變形與銲墊消耗。由本研究之實驗結果得知，銲料中添加微量Ag元素後能有效抵抗電遷移現象。

關鍵字

電遷移； Cu/Sn-Ag-Cu/Cu ； Cu/Sn/Cu ；銲點變形；銲墊消耗

並列摘要

Electromigration phenomena in Cu/Sn/Cu、Cu/Sn-Ag-Cu/Cu solder joint were investigated in this study. In this study, we observed the Sn-Ag-Cu solder can reduce electromigration damages. The joints had a typical line-to-bump geometry with the Cu/Sn-Ag-Cu/Cu configuration, and the Ag contents of the Sn-Ag-Cu were 0, 1, 2, 3, 4 wt.%, respectively. Electromigration tests were carried out at an ambient temperature (25 degree Celsius) with a fixed 9000 A/cm2 at the contact of the Cu/Sn-Ag-Cu. Research showed doping an adequate Ag to the Sn-Cu alloy significantly increased resistance to electromigration. This diminished the electromigration-induced Sn-Cu alloy deformations and Cu metallization consumption, extending the lifetime of solder joints. In this study, we observed more Ag content in the Sn-Ag-Cu solder show better reduce electromigration damages. This is because the c-axis of b–Sn perpendicular to the electron flow in high Ag–content solder joints. The b–Sn orientation can be controlled by adopting Ag to solder joints. More details about the Ag effect on the electromigration reliability of solder joints will be presented in this thesis.

並列關鍵字

metallization consumption ； electromigration ； Cu/Sn-Ag-Cu/Cu ； Ag effect ； deformations

參考文獻

[1] B. Z. Chen, C. N. Chen, and C. E. Ho, TMS Annual Meeting Repor,2011.

[3] S. W. Liang, Y. W. Chang, C. Chen, Y. C. Liu, K. H. Chen, and S. H. Lin, Journal of Electronic Materials, vol.35, p.1647, 2006.

[5] Y. S. Lai and C. L. Kao, Microelectronics Reliability, vol.46, p.1357, 2006.

[11] L. Zhang, S. Ou, J. Huang, K. N. Tu, S. Gee, and L. Nguyen, Journal of Applied Physics, vol.88, p.012106, 2006.

[12] S. W. Liang, Y. W. Chang, and C. Chen, Applied Physics Letters, vol.88, p.172108, 2006.

國際替代計量

電遷移對不同銀成份之晶片接點的可靠度影響評估

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