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    Self-Assembly of Chip-Size Components with Cavity Structures: High-Precision Alignment and Direct Bonding without Thermal Compression for Hetero Integration

    Year: 2011

    Journal: Micromachines 2011, 2(1), 49-68, 20111221

    Authors: Takafumi Fukushima 1, *, Takayuki Konno 2 , Eiji Iwata 2 , Risato Kobayashi 3 , Toshiya Kojima 3 , Mariappan Murugesan 1 , Ji-Chel Bea 1 , Kang-Wook Lee 1 , Tetsu Tanaka 2,4 and Mitsumasa Koyanagi 1

    Organizations: 1 New Industry Creation Hatchery Center (NICHe), Tohoku University, 6-6-10 Aza-Aoba, Aramaki, Aoba-ku, Sendai, Miyagi, 980-8579, Japan, 2 Department of Bioengineering and Robotics, Graduate School of Engineering, Tohoku University, Sendai, Japan, 3 Micro/Nano-Machinning Research and Education Center (MNC), Graduate School of Engineering, Tohoku University, Sendai, Japan, 4 Department of Biomedical Engineering, Graduate School of Biomedical Engineering, Tohoku University, Sendai, Japan

    New surface mounting and packaging technologies, using self-assembly with chips having cavity structures, were investigated for three-dimensional (3D) and hetero integration of complementary metal-oxide semiconductors (CMOS) and microelectromechanical systems (MEMS). By the surface tension of small droplets of 0.5 wt% hydrogen fluoride (HF) aqueous solution, the cavity chips, with a side length of 3 mm, were precisely aligned to hydrophilic bonding regions on the surface of plateaus formed on Si substrates. The plateaus have micro-channels to readily evaporate and fully remove the liquid from the cavities. The average alignment accuracy of the chips with a 1 mm square cavity was found to be 0.4 mm. The alignment accuracy depends, not only on the area of the bonding regions on the substrates and the length of chip periphery without the widths of channels in the plateaus, but also the area wetted by the liquid on the bonding regions. The precisely aligned chips were then directly bonded to the substrates at room temperature without thermal compression, resulting in a high shear bonding strength of more than 10 MPa.