Electrical Characterization of 3D Interconnection Structures up to Millimeter Wave Frequencies

We present high frequency electrical characterization of 3D interconnection structures. The 3D interconnections are realized using on-chip metallization and through silicon vias (TSVs). We analyze and compare two types of 3D transitions. The first transition is made of TSVs that form a 3D coplanar waveguide. The second transition is realized using a 3 x 5 array of parallel connected TSVs. We use a novel concept for the characterization of a single transition through the wafer. The concept is based on thru-reflect-line (TRL) calibration algorithm. In contrast to standard methods, our approach enables accurate determination of all four S-parameters of a single transition. It allows the generation of very accurate models of the transitions up to millimeter wave frequencies. We show measurement results up to 60 GHz of various cascade connections formed of 3D transitions and coplanar transmission lines manufactured on both sides of the wafer. We compare the results to measurements of transmission lines without vertical interconnects and to simulations. Finally, we highlight the importance and the difficulty of an accurate characterization of a single transition (front-to-back) in terms of scattering and impedance/admittance parameters.