Die-to-Wafer Hybrid Bonding Impact at MM-Wave Frequencies

This paper presents a study of the influence of direct hybrid bonding interconnections on a grounded coplanar waveguide in a 3D integration technology at mm-wave frequencies up to 120 GHz. The considered transmission line is implemented in B55X (Bi)CMOS technology from STMicroelectronics with five metal layers. The investigation explores the impact of the top die hybrid bonding interconnection for 3D integration, the presence of hybrid bonding metallization pads, and variations in their location. The performance metrics, specifically attenuation loss and relative permittivity, were evaluated, revealing that the HB interconnection results in very low loss and minimal impact. When assessing the hybrid bonding and metallization dummies without the top die, only slight effects were observed. However, when both the hybrid bonding metallization and top die are considered, slightly higher losses and an increase in permittivity due to the top die were noted. Finally, a study illustrating the impact of the spatial positioning of hybrid bonding metallization above the grounded coplanar waveguide validates the robustness of the design with 3D hybrid bonding metallization pads.