Laboratory for Machine Tools and Production Technology: A Novel Assembly Method for Chip/Wafer Bumping and Mems Integration

Abstract

In this paper we report the development of an assembly method for chip/wafer bumping in flip chip packaging and for MEMS integration. In this approach, microstructures and MEMS devices are fabricated on a low cost carrier. They are then transferred onto the target chip/board. The new assembly method offers several advantages over monolithic integration of microstructures and MEMS devices. As the structures and devices are not fabricated on a target chip/wafer/board, back end processing of the latter is greatly reduced, thus the method is particularly advantageous where direct fabrication on the latter is impossible due to process incompatibility. Secondly the method allows cost effective batch fabrication of MEMS microstructures and devices. The method also offers flexibility in that the microstructures and devices can be transferred selectively. The method has been used to realise off-chip MEMS inductor devices by creating an air gap between the device and the substrate. These devices have potential applications in RF IC circuits for next generation of wireless communications. It has been shown that off-chip inductor devices offer high-Q, high frequency performance over the conventional on-chip devices by reducing the parasitic coupling to the silicon substrate [1].