Ultra-Miniaturized Integrated Cavities on High-Resistivity Silicon Thin-Film MCM-D Technology

Millimeter-wave commercial communication systems are getting a lot of attention in the recent years, and therefore there is a need of implementing miniaturized high-quality passive components at these frequencies. In this paper, we demonstrate the integration of ultra-miniaturized cavities on the thin-film multi-chip module technology (MCM-D) by using through-substrate vias on 100 mum thick high-resistivity silicon (HRSi) wafers. Having HRSi as filling material, the proposed cavities are 3.4 times smaller than air filled cavities. Being integrated cavities, no assembly step is needed, which is an advantage as compared to air filled cavities where wafer stacking is required. The influence of leakage through the via fences is studied in detail showing that having a via diameter of 100 mum, and a pitch of 220 mum, one via row is enough to eliminate radiation at 29 GHz, but at 60 GHz 2 via rows are necessary. Additionally, this study shows that the probe feeding mechanism used in this work is very effective and does not lead to any leakage. Second-order filters using integrated cavities are demonstrated at 29 GHz and 60 GHz yielding low losses and a highly accurate center frequency prediction the first time that the filters were manufactured. Being able to implement small and high-quality components, the proposed technology is a viable platform for the implementation of commercial millimeter-wave components.