Three-dimensional InP-DHBT on SiGe-BiCMOS integration by means of Benzocyclobutene based wafer bonding for MM-wave circuits

• Fabrication scheme for heterogenous Si-to-InP circuits on wafer level is described.
• Wafer-to-wafer alignment accuracy better than 4–8 μm after bonding obtained.
• Interconnects with excellent performance up to 220 GHz demonstrated.
• Palladium barrier necessary when combining Al-based technology with gold based one.

In order to benefit from the material properties of both InP-HBT and SiGe-BiCMOS technologies we have employed three-dimensional (3D) Benzocyclobutene (BCB)-based wafer bonding integration scheme. A monolithic wafer fabrication process based on transfer-substrate technology was developed, enabling the realization of complex hetero-integrated high-frequency circuits. Miniaturized vertical interconnects (vias) with low insertion loss and excellent broadband properties enable seamless transition between the InP and BiCMOS sub-circuits.

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