Vertical coaxial transitions for MM-waves 3D integration technologies

Heterogeneous integration of many technologies in a 3D chip to build a complex system is a promising concept. The purpose of this paper is to present a new approach to create interlevel transitions for millimeter wave systems, using sensors, ICs, active devices and other parts, all integrated with a System in Package (SiP) technology. One of the issues with this approach is to develop low loss vertical interconnections for millimeter waves. We suggest Au/BCB micro-coaxial technology matching with interconnections in multilevel structures using lossy material (for example Si). Simulations results of a microstrip / coaxial transition / microstrip present transmission loss lower than 0.1 dB and reflection loss better than -15 dB until 80 GHz. The technological feasibility of theses transitions has been demonstrated and structures are being manufactured.