Crystalline Orientation Effect of Single-Grain Sn-Rich Cu Pillar Bumps on Electromigration Lifetime

Yu Chen Huang, Chieh Pu Tsai, Chung Yu Chiu, Wei Chieh Huang, Mei Hsin Lo, Cheng Yi Liu, Jui Shen Chang, Chen Nan Chiu, Yao Chun Chuang

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Electromigration (EM) is the critical issue for the micro-bumps in the advanced chip stacking technology. The diffusion of solute atoms, such as Cu and Ni, driven by high current density in the Sn-based solder bumps is the underlying process for the EM reliability issue, which is highly related to the crystalline orientation of the Sn matrix. Thus, if the single-Sn-grain structure can be produced in the Sn-based solder bump, the EM lifetime can be studied and correlated to their specific crystalline orientation (c-axis). In this present work, intriguingly, we found that a single-Sn-grain structure formed in the Sn1.5Ag0.1Cu solder matrix of Cu/Ni/Sn1.5Ag0.1Cu/electroless-Ni/electroless- Pd/immersion-Au bumps. As the c-axis of the single-grain solder bumps is aligning more vertically to the currentstressing direction, the EM lifetime of solder bumps would be prolonged. In contrast, the electroless-Ni layer under the solder bump with a c-axis more parallel to the current-stressing would be consumed more and form a porous Ni3P phase (with higher resistivity), which causes early EM failure. According to the present EM results, we found that the EM lifetime of the single-grain solder bumps correlates to their specific crystalline orientation (c-axis) under current stressing with 4 104 A/cm2 at 140 ?C. Hence, we can conclude that the anisotropic property of single-grain solder matrix in diffusivity plays a key role in EM reliability and lifetime.

Original languageEnglish
Pages (from-to)5784-5787
Number of pages4
JournalIEEE Transactions on Electron Devices
Volume71
Issue number9
DOIs
StatePublished - 2024

Keywords

  • Anisotropy
  • crystalline orientation
  • diffusivity
  • electromigration (EM)

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