Development of Low Temperature Bonding Technology for Glass and Polymer Substrates in Ambient Air for Future Three-Dimensional MEMS Packaging

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In this study, a homo/heterogeneous bonding technology for Cu, glass (including both SiO2 and quartz), and polyimide was realized at 150 oC in ambient air-like condition. In order to create a good bondability to these materials at the same time, a compatible bridging layer was created with the vapor-assisted surface activation method. In this, water vapor was introduced onto the atomically clean surfaces of materials and it helped create the adhesive aqueous compounds. The chemical structure and thickness of the bridging layers are tunable only with the number of water molecules colliding with the surface in unit area and time, which resulted in high binding energy on entire surface and good electric conduction at Cu-Cu interface at the same time. Moreover, a Cu bumpless substrate and a polyimide insulator was bonded to demonstrate high feasibility of this process.