Fabrication of 3-D microstructures with permanent dielectric dry film

Smarter and cheaper encasing of devices is essential to bring packaging costs down. Two different types of packages are described in this paper. Both use wafer level processes which make them very cost effective. In the first approach dry film resist functions as a glue and as a spacer at the same time. Frames of dry film resist are structured on the cap wafer by lamination and photolithography. This wafer is then bonded with a wafer-to-wafer-bonder onto the device wafer. Finally the stack is diced. In the second approach, frames of photopolymer are structured on the device wafer. In the next step another layer of polymer is laminated on top of it. The second layer is then photo-structured to form the "roof" of the housing while the frame works as its "side walls". Both packages can be used for encasing of for example SAW or BAW filters. The same processes can be used with different designs to create fluidic structures e.g. nozzles in ink print head or for medical appli cation like lab-on-chip.