Study on hybrid au-underfill resin bonding method with lock-and-key structure for 3-D integration

Masatsugu Nimura*, Jun Mizuno, Akitsu Shigetou, Katsuyuki Sakuma, Hiroshi Ogino, Tomoyuki Enomoto, Shuichi Shoji

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


This paper describes a hybrid Au-underfill resin bonding method with lock-and-key structure for 3-D integration. In 3-D large scale integration (LSI), the gap between stacked chips becomes narrower because the bump dimension and pitch are smaller than those encountered in 2-D LSI. Therefore, the filling of gaps less than 10 $\mu{\rm m}$ using capillary forces often becomes insufficient because of the surface condition. To address this challenge, we study a hybrid bonding method in which the metal-metal and resin-resin bonding are carried out simultaneously with a chip resin applied previously only around the bump. To realize hybrid bonding on the entire chip, we fabricate indent and protrusion structures, which are called lock-and-key structures. The key structure is fabricated by a process that can remove the resin on the bumps by ${\rm O}2 plasma irradiation. The lock structure is fabricated by conventional photolithography and dry etching. By means of hybrid bonding with the lock-and-key structure, we have achieved the Au bump bonding and the filling of 4-$\mu{\rm m}$ gaps between the stacked chips, concurrently. The cross-sectional transmission electron microscopy image of the bonded sample demonstrated that no significant gap exists at both the Au-Au and resin-resin interfaces. In addition, the shear strength of the sample bonded with resin is 10 times higher than that without the resin. The electrical continuity of the Au bump connections after hybrid bonding has also been determined.

Original languageEnglish
Article number6449300
Pages (from-to)558-565
Number of pages8
JournalIEEE Transactions on Components, Packaging and Manufacturing Technology
Issue number4
Publication statusPublished - 2013
Externally publishedYes


  • 3-D integration
  • Au bump
  • bonding
  • flip chip
  • micro-bump
  • underfill

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Industrial and Manufacturing Engineering
  • Electrical and Electronic Engineering


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