Multichip-to-wafer three-dimensional integration technology using chip self-assembly with excimer lamp irradiation

Takafumi Fukushima, Eiji Iwata, Yuki Ohara, Mariappan Murugesan, Jichoel Bea, Kangwook Lee, Tetsu Tanaka, Mitsumasa Koyanagi

Research output: Contribution to journalArticlepeer-review

45 Citations (Scopus)


Self-assembly of multichips with metal microbump electrodes is demonstrated by using water surface tension to increase the stacking throughput/yield and chip alignment accuracy of conventional chip-to-wafer 3-D integration. Three-dimensional microbump interconnects are formed by self-assembly with thermal compression at 200 °C. Chips with In-Au microbumps with pitches of 10 and 20 μm are tightly bonded to Si wafers after the flip-chip self-assembly process, resulting in high alignment accuracies of 0.8 and 0.2 μm in the x-and y-directions, respectively. Selective hydrophilization by 172-nm excimer lamp irradiation gives a high wettability contrast between hydrophilic chip bonding areas and hydrophobic surrounding areas on the wafers. This assists high-precision multichip self-assembly. A 2500-In-Au-microbump daisy chain is formed with a yield of 100% by flip-chip self-assembly, and it exhibits ohmic contact. The resistance is sufficiently low for 3-D large-scale integration application, being comparable to that obtained by conventional mechanical chip alignment.

Original languageEnglish
Article number6298952
Pages (from-to)2956-2963
Number of pages8
JournalIEEE Transactions on Electron Devices
Issue number11
Publication statusPublished - 2012


  • 3D integration
  • Excimer light
  • flip-chip bonding
  • self-assembly
  • surface tension


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