Hans-Joerg Timme

Acceleration threshold switches from an additive electroplating MEMS process

An acceleration threshold sensor fabricated with an electroplating technology on top of a CMOS signal processing circuit is presented in this paper. Manufacturing of the device is achieved using a standard low-cost CMOS production line and employing a specialized back-end process for adding the mechanical sensor-elements. This production technology makes the system especially interesting for automotive applications in airbag systems or transportation shock monitoring systems. These applications demand smaller size, improved functionality, high reliability and low costs, factors that can be satisfied with this new technology. The initial additive electroplating technology (AET) has been improved by coating the basic structures with an electroplated alloy. Additionally, a specialized packaging procedure has been developed to hermetically seal the sensor-structures following their release after the sacrificial layer removal. The devices are finally SMD-packaged to allow for easy handling. Samples of the device have been tested extensively and have successfully proven its functionality.

New sensor-on-chip technology for micromechanical acceleration-threshold switches

This paper describes the development of a sensor for measuring acceleration-thresholds in the low-g range. The processing of the device is based on a new integration concept for MEMS called Additive Electroplating Technology (AET). This technology allows the integration of fixed and moveable electroplated microstructures on top of a standard ASIC by a low temperature back-end process. This permits the fabrication of the sensor on top of a CMOS signal processing circuit, where the development and the fabrication of the ASIC is absolutely independent of the following back-end process. In this context, the additive electroplating technology combines the advantages of monolithic- and hybrid-integrated sensor with respect to the reduction of interconnections, short development cycles, low tooling costs, and high design flexibility. A detailed technical concept for the fabrication of electroplated micromechanical acceleration switches is presented in this paper. It comprises the aspects of the interface technology between the ASIC and the sensor structure, the sensor fabrication and the back-end processing to capsulate the dies. The paper concludes with a characterization of the devices. The measured results are compared with the expected results of the simulation.