Optimized reactive bonding technology based on novel zirconium systems for use in microsystems technology (Join-ZiSi)

Hermetically sealed, reactive bonding of chips and sensors.
© Fraunhofer IWS
Hermetically sealed, reactive bonding of chips and sensors.


Implementing smart electronic components and systems requires the addition of logic and storage. This challenge can be monolithically integrated in a single system-on-chip (SoC) or realized as discrete components by heterogeneous system-in-package (SiP) integration. To meet the demanding specifications and requirements, more functionality must be integrated in a smaller volume. This requires new assembly and packaging materials, compatible chip-package interfaces, and heterogeneous integration of chips with different functionalities such as MEMS. Since applications must be designed to be as durable and reliable as possible, there is a particular focus on electrical capabilities and temperature limitations. Therefore, heterogeneous packaging and integration technologies have become a key issue for the performance, reliability and cost of an electronic system. Thus, new ways have to be found to realize mechanically strong, hermetically sealed, high temperature resistant and radiation resistant joints of materials with different thermal expansion coefficients not only with low stress but also reliably. If existing joining methods are more and more reaching their limits under these increased requirements, enormous progress has been made in the field of reactive joining technology in recent years.  

Aims and approach

The aim of the research project is the advancement of reactive joining technology for successful utilization in microsystems technology. The use of novel, reactive multilayer systems (RMS) based on zirconium-silicon in combination with higher-melting solders is expected to produce assemblies with outstanding properties, such as high-strength and low-stress joints with excellent electrical and thermal conductivity as well as low component stress during the joining process. In the course of the project, RMS and suitable joining interfaces will be developed and optimized based on simulation calculations, and their deposition processes and structuring options will be evaluated at the component and wafer level. Based on bonding tests with test coupons and subsequent characterization of the joints, the RMS and joining process technology will be optimized in an iterative process. Proof of the RMS joining process will be provided using functional samples at the component and wafer level. 

Innovations and perspectives

With the realization of novel zirconium-silicon RMS, a decisive contribution is provided to solving packaging and reliability issues for the integration of microsystems. Thus, on the one hand, new possibilities for joining thermomechanically incompatible materials in a complete system and, on the other hand, a significant performance improvement in the substitution of existing assembly materials are achieved through the utilization of higher-melting solders.