For a variety of micro systems, the bond interface can be considered as lifetime limiting factor which directly affects the reliability of the devices. Depending on the bonding parameters, an intensive analysis of the bond interface or intermediate bond layer is required to ensure the functionality of these systems.
At Fraunhofer ENAS, the development of new bonding technologies on chip and wafer level as well as their application-oriented improvement is carried out in combination with an extensive evaluation of the bond interface. I addition to non-destructive methods for the detection of bond defects, the research is thereby focused on the analysis of the microstructure as well as the characterization of the hermeticity and mechanical strength.
The detection of bond defects like voids, particles and cracks is based on the infrared- and ultrasonic microscopy. These methods can be included in the manufacturing process and are used for an in-line monitoring of the bond quality. Thereby, the IR microscopy and SAM enable an in line optimization of the process by adjusting the bond parameters. Furthermore, the variation of the bond parameters in combination with the analysis of the microstructure by SEM, EDX and FIB enables the improvement of the bond quality by minimizing microscopic defects.
To ensure the reliability and functionality of the micro systems, the mechanical properties of the bond interface are characterized extensively. While the determination of the hermeticity is based on the helium leak test, the FTIR Spectroscopy and specially designed resonator structures, the bonding strength is analyzed shear, tensile and micro chevron tests.