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金属学报  2017, Vol. 53 Issue (5): 592-600    DOI: 10.11900/0412.1961.2016.00499
  论文 本期目录 | 过刊浏览 |
Cu/Sn-52In/Cu微焊点液-固电迁移行为研究
张志杰1,黄明亮2()
1 江苏科技大学材料科学与工程学院 镇江 212003
2 大连理工大学材料科学与工程学院 大连 116024
Liquid-Solid Electromigration Behavior of Cu/Sn-52In/Cu Micro-Interconnect
Zhijie ZHANG1,Mingliang HUANG2()
1 School of Materials Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, China
2 School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, China
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摘要: 

采用同步辐射实时成像技术对比研究了Cu/Sn-52In/Cu微焊点在120和180 ℃,2.0×104 A/cm2条件下液-固电迁移过程中In、Sn和Cu原子的扩散迁移行为及其对界面反应的影响。由于没有背应力,液-固电迁移条件下Sn-52In焊点中In原子的有效电荷数Z*为负值是其定向扩散迁移至阳极的物理本质,这与Sn-52In焊点固-固电迁移条件下背应力驱使In原子迁移至阴极的机理不同。基于液态金属焓随温度的变化关系,修正了计算液态金属Z*的理论模型,计算获得In原子在120和180 ℃下的Z*分别为-2.30和-1.14,为电迁移方向提供了判断依据。液-固电迁移过程中In和Cu原子同时由阴极扩散至阳极并参与界面反应使得界面金属间化合物(intermetallic compounds,IMC)生长表现为“极性效应”,即阳极界面IMC持续生长变厚,并且厚于阴极界面IMC,温度越高,界面IMC的“极性效应”越显著。液-固电迁移过程中阴极Cu基体的溶解与时间呈抛物线关系,温度越高,阴极Cu的溶解速率越快。

关键词 电迁移Sn-52In微焊点有效电荷数界面反应金属间化合物    
Abstract

Electromigration (EM), which describes the mass transport due to the momentum exchange between conducting electrons and diffusing metal atoms under an applied electric field, has become a serious reliability issue in high-density packaging. With the increasing demands for miniaturization, liquid-solid (L-S) EM will pose a critical challenge to the reliability of solder interconnects. In this work, The interfacial reactions and diffusion behaviors of In, Sn and Cu atoms in Cu/Sn-52In/Cu interconnects during L-S EM under a current density of 2.0×104 A/cm2 at 120 and 180 ℃ have been in situ studied by using synchrotron radiation real-time imaging technology. During L-S EM, since there was no back-stress, the In atoms directionally migrated toward the anode due to the negative effective charge number (Z*) of In, which is different from the In atoms directionally migrated toward the cathode due to the back-stress induced by the preferential migration of the Sn atoms over the In atoms toward the anode during the solid-solid (S-S) EM. Furthermore, a modified expression for calculating the effective charge number Z* of liquid metals was proposed based on the enthalpy changes of melting process. The Z* of In atoms was calculated to be -2.30 and -1.14 at 120 and 180 ℃, respectively, which was consistent with the migration behavior of In atoms. The model provides a theoretical basis for determining the direction of the EM. The polarity effect, evidenced by the IMC layer at the anode growing continuously while that at the cathode was restrained, was resulted from the directional migration of In and Cu atoms toward the anode during L-S EM, which was more significant at high temperature. The consumption of cathode Cu during L-S EM followed a parabolic relationship with the EM time, and the consumption rate was magnitude higher at high temperature. The migrations of In atoms was discussed in terms of diffusion flux.

Key wordselectromigration    Sn-52In micro-interconnect    effective charge number    interfacial reaction    intermetallic compound
收稿日期: 2016-11-10      出版日期: 2017-02-14
基金资助:国家自然科学基金项目Nos.51475072和51671046

引用本文:

张志杰,黄明亮. Cu/Sn-52In/Cu微焊点液-固电迁移行为研究[J]. 金属学报, 2017, 53(5): 592-600.
Zhijie ZHANG,Mingliang HUANG. Liquid-Solid Electromigration Behavior of Cu/Sn-52In/Cu Micro-Interconnect. Acta Metall, 2017, 53(5): 592-600.

链接本文:

http://www.ams.org.cn/CN/10.11900/0412.1961.2016.00499      或      http://www.ams.org.cn/CN/Y2017/V53/I5/592

图1  Cu/Sn-52In/Cu线性焊点示意图
图2  初始Cu/Sn-52In/Cu焊点显微组织SEM像
图3  Cu/Sn-52In/Cu焊点在120 ℃、2.0×104 A/cm2条件下液-固电迁移过程中的同步辐射照片
图4  120 ℃、2.0×104 A/cm2液-固电迁移1 h后的Cu/Sn-52In/Cu焊点显微组织SEM像
图5  Cu/Sn-52In/Cu焊点在180 ℃、2.0×104 A/cm2条件下液-固电迁移过程中的同步辐射照片
图6  180 ℃、2.0×104 A/cm2液-固电迁移1 h后的Cu/Sn-52In/Cu焊点显微组织SEM像
图7  Cu/Sn-52In/Cu焊点在120和180 ℃、2.0×104 A/cm2条件下电迁移过程中阴极Cu基体溶解动力学曲线
图8  Cu/Sn-52In/Cu焊点液-固电迁移过程In原子扩散通量示意图
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