Innovative Glass-Encapsulation for Double-Side-Processed BAW Filters

This paper demonstrates a high-performance double-side-processed bulk acoustic wave (DBAW) filter designed for Wi-Fi operation, featuring a novel glass cap. We propose a new BAW structure and packaging method, and compare the performance of filters with glass caps to those using conventional high-resistivity and low-resistivity silicon caps. Notably, the glass-capped filter exhibits performance nearly identical to the high-resistivity silicon counterpart, achieving an insertion loss of 1.67 dB and comparable suppression. While the low-resistivity silicon filter shows slightly higher insertion loss, and suffers significantly from reduced suppression in Band 41 due to the feedthrough effect. These results highlight the excellent potential of glass as a cap material for high-performance BAW filters, offering a promising pathway towards low-cost RF devices and systems.