Advanced Packaging Dielectric for 5G

The packaging requirements for high frequency applications and heterogeneous integration have brought well established dielectric materials to their limits. While there is a demand for increased technical performance, mainly low dielectric constant and low dielectric loss, trade-offs in processing conditions and yield are hardly acceptable.

In order to address the technical challenges, Merck KGaA has developed a novel type of dielectric material, looking beyond existing classic polymers like polyimide or polybenzoxazole.

The framework of the development was established around the key requirements from the industry, both on the process and material itself. With 5G applications in mind, low dielectric constant and loss are required. From the process side, compatibility with existing photolithography, low film shrinkage during curing processes and in general reduction of the stress, seen e.g. as warpage, are considered critical.

Our materials demonstrated dielectrics properties which fit very well into 5G devices, with Dk ~ 2.5 and Df <0.005 for the frequency up to 75Ghz. In combination with low water uptake, that ensures compatibility with designed for 5G technology.

When approaching the processing aspects, we looked at broad picture of what can cause the issues, beyond purely numerical specification: Our materials are designed to be primarily curable with UV light at room temperature, with shrinkage during curing <5%, as that process ensures low build-up stress. Photosensitivity also enabled compatibility with photolithography, showing L/S feature below 5µm and still fully reworkable with standard, non-NMP, organic solvents.

Warpage issue has been addressed not only by UV cure at room temperature but also by distinctive behavior of CTE across the temperature range, where CTE values are similar at temperatures below and above Tg. That special feature, in combination with Young Modulus <2GPa and elongation >20% enables significant stress reduction during processing and subsequent use of the packaged device.

Our new materials offer a combination of advanced performance and processing advantages leading to increased throughput and yield. Thus, offering a competitive advantage for tomorrow’s packaging designs.