Design and Experimentally Verification of a Vertical Coaxial Transmission Structure in High resistivity Si Interposer

This paper proposes a vertical coaxial transmission structure made of a centered Cu TSV surrounded with a cycle of TSVs as grounding shield. To verify the feasibility, a set of vertical coaxial transmission structure linked with CPW lines is designed to be able to work at 40GHz and parametric study is conducted in the meantime. By changing the diameter of the grounded TSV ring array and the space of centered RF TSVs, the results show that test structures have good high frequency transmission performance; the larger the diameter of the grounded TSV ring array, the better the transmission performance; the S21 parameter does not change significantly when the space between the two centered RF TSVs is changed. With developed TSV process, sample is fabricated and tested. The insertion loss is less than 1.2dB@40 GHz for the two vertical coaxial transmissions structures linked with CPW lines, and it can be derived that it has a less than 0.15dB@40GHz for a single coaxial transmissions structure.