A Novel Compact Thru-silicon-via On-chip Passive MMW Bandpass Filter for 77GHz Applications

This paper presents a novel on-chip passive bandpass filter for millimeter-wave (MMW) applications that utilizes a pair of electrically-coupled thru-silicon vias (TSV). The presented TSV bandpass filter can be used in MMW applications such as radar, medical imaging, and communication. The TSV bandpass filter uses two TSVs to extend two electrically-coupled conductors into the silicon substrate in the z-direction instead of horizontally in the x-y plane. There is a metal layer on the bottom side of the silicon substrate that shorts the ends of the two TSVs to ground. Using TSVs in the bandpass filter design reduces the silicon area required to implement the filter compared to the silicon area required for the equivalent conventional filter in the above-silicon metal-dielectric interconnect stack. The operating performance of the bandpass filter is controlled at the design stage by choosing the separation distance between the TSVs. In this work, the two TSVs were 145 μm in height (z-direction) and 3μm × 50 μm in the x-y plane. The long edges of the TSVs (50μm long edges) faced each other to maximize capacitance coupling between the TSV pair. The TSVs were separated by a distance of 5μm. Full-wave electromagnetic simulations of a TSV filter designed in an IBM SiGe technology that included TSVs show a minimum pass-band insertion loss of −3.9 dB at 77 GHz with a usable pass band from 75–85GHz is possible. The simulated operating range of the TSV bandpass filter design presented in this paper show that it is well suited for automotive radar applications.