Q-band InP/CMOS receiver and transmitter beamformer channels fabricated by 3D heterogeneous integration

Q-Band receiver and transmitter beamformer channels using 250 nm InP HBTs and 130 nm Si CMOS have been fabricated in a three-dimensional wafer-stacking platform. Room-temperature face-to-face wafer bonding is accomplished using a hybrid bonding technique (Direct Bond Interconnect®) of 2.5 micron wide, 5 micron pitch copper inlaid in silicon dioxide to form electrically active vertical interconnects. 3-bit amplitude and 4-bit phase modulation receive and transmit channels are characterized. At 40 GHz, the receiver and transmitter chains have more than 25 dB gain, with 6 dB variable gain tuning, and less than 5° RMS phase error. The transmitter saturated output power is 20.3 dBm. To the authors' knowledge, this is the first demonstration of wafer-scale three-dimensional integration of Si and InP MMICs towards RF beamforming applications.