標題: A new failure mechanism of electromigration by surface diffusion of Sn on Ni and Cu metallization in microbumps
作者: Chang, Yuan-Wei
Hu, Chia-chia
Peng, Hsin-Ying
Liang, Yu-Chun
Chen, Chih
Chang, Tao-chih
Zhan, Chau-Jie
Juang, Jing-Ye
材料科學與工程學系
Department of Materials Science and Engineering
公開日期: 12-Apr-2018
摘要: Microbumps in three-dimensional integrated circuit now becomes essential technology to reach higher packaging density. However, the small volume of microbumps dramatically changes the characteristics from the flip-chip (FC) solder joints. For a 20 mu m diameter microbump, the cross-section area and the volume are only 1/25 and 1/125 of a 100 mu m diameter FC joint. The small area significantly enlarges the current density although the current crowding effect was reduced at the same time. The small volume of solder can be fully transformed into the intermetallic compounds (IMCs) very easily, and the IMCs are usually stronger under electromigration (EM). These result in the thoroughly change of the EM failure mechanism in microbumps. In this study, microbumps with two different diameter and flip-chip joints were EM tested. A new failure mechanism was found obviously in microbumps, which is the surface diffusion of Sn. Under EM testing, Sn atoms tend to migrate along the surface to the circumference of Ni and Cu metallization to form Ni3Sn4 and Cu3Sn IMCs respectively. When the Sn diffuses away, necking or serious void formation occurs in the solder, which weakens the electrical and mechanical properties of the microbumps. Theoretic calculation indicates that this failure mode will become even significantly for the microbumps with smaller dimensions than the 18 mu m microbumps.
URI: http://dx.doi.org/10.1038/s41598-018-23809-1
http://hdl.handle.net/11536/144831
ISSN: 2045-2322
DOI: 10.1038/s41598-018-23809-1
期刊: SCIENTIFIC REPORTS
Volume: 8
Appears in Collections:Articles