Study on the Manufacturing Process of Multilayer Silicon-based Filters Based on Au-Sn Soldering

Waveguide filters with dielectric cavities have the advantages of high quality factor, easy integration and miniaturization, and silicon is the commonly chosen dielectric material for waveguide filters due to its excellent micro-machining performance and low loss functional characteristics. In the process of filter preparation, layer-to-layer interconnection is often achieved by wafer bonding or Au-Au bonding, but these two methods require extremely high substrate roughness. The use of soldering for interlayer interconnection has become a popular research direction because it requires less surface condition of the substrate. In this study, a waveguide structure filter integrated by 9-layer silicon wafers was designed. Based on MEMS-related technologies such as photolithography, deep silicon etching and surface metallization, a single-layer filter substrate was obtained, and then Au-Sn solder was prepositioned on the substrate using a co-deposition plating method, and reliable interconnection between the 9-layer substrates was achieved by reflow soldering. In this study, a stable fabrication process for multilayer silicon-based waveguide structure filters based on the Au-Sn soldering method was obtained.