3D-Millimeter Wave Integrated Circuit (3D-mmWIC): A Gold-Free 3D-Integration Platform for Scaled RF GaN-on-Si Dielets with Intel 16 Si CMOS

This paper presents a gold-free 3D millimeter wave integrated circuit (3D-mmWIC). Highly scaled GaN-on-Si front-end-of-line (FEOL) RF dielets are integrated with Intel 16 Si CMOS using Cu-Cu thermocompression bonding (TCB), solder-free 3D heterogeneous integration (3DHI). To demonstrate this process, two different 3D-mmWIC amplifiers targeting the 5G NR FR2 band are fabricated utilizing multiple dielets. The first amplifier implements a conjugate matching of the dielets, achieving a maximum small-signal gain of 4.8 dB and a 3 dB bandwidth of $26-30 \mathrm{GHz}$. The second amplifier implements additional cross-neutralization capacitance to achieve a maximum small-signal gain of 6.2 dB and a 3 dB bandwidth of $26-32 \mathrm{GHz}$. Both 3D-mmWICs are extremely compact with a total chip area of $0.49 \mathrm{~mm}^{2}$.