A 3D heterogeneous integration method using LTCC wafer for RF applications

This paper describes the concept, fabrication process technologies and performance of a novel 3D heterogeneous integration method developed for RF applications. This method combines the advantages of LTCC, passive integration and MEMS technologies and is promising for the miniaturization and multifunction of future RF-modules. The basic concept is to form a large-size LTCC wiring wafer, and then to form high-Q passives or MEMS directly on the wafer surface. Other functional devices such as the ICs, SAWs are mounted above the surface-formed devices. LTCC wafer can provide dense interconnects and backside pads to provide input and output paths. All of the fabrication processes are carried out at wafer level, which leads to high productivity. A miniaturized duplexer and a MEMS tunable filter were constructed to demonstrate its feasibility and effectiveness.