IPD-GLAS

The IPD-GLAS partner project was initiated in collaboration with the ILT (Fraunhofer Institute for Laser Technology) and the IAF (Fraunhofer Institute for Applied Solid State Physics) and approved for the period from January 1, 2023 to December 31, 2023. The aim of the project was to develop novel processes for the precise processing of glass wafers that are suitable for high-frequency and quantum technologies. This primarily includes the optimization of processing technologies.

The IPD-GLAS project is driven by the close cooperation of several institutes, with each institute focusing on its respective strengths:

At the heart of the project is the further development of 3D glass structuring using selective laser-induced etching (SLE) technology. This enables the high-precision processing of 200 mm glass wafers, particularly those made of materials such as Schott AF32eco and quartz glass. The SLE process uses laser beams to create complex microstructures in the glass before these are refined by wet chemical etching. A central concept here is the hatching and slizing technique, developed by the ILT in the course of the project. These are laser processes in which fine line structures (hatching) and precise cuts (slizing) are introduced into the glass to create complex channel geometries. Another focus is on adapting beam parameters and improving the etching process for aluminum silicate glasses. In parallel, ISIT has further developed the process for filling glass structures with molten aluminum. This enables the production of electrical cables in glass wafers, which are particularly suitable for 5G and 6G technologies due to their flexible geometries and excellent high-frequency properties. In addition, demonstrators for IPD modules for high-frequency front-end applications were developed together with the IAF as part of the project.

To date, there are several competing technologies for the production of electrically conductive vias in wafer substrates, most of which are based on the use of solder or electroplated copper. These methods require an additional bonding layer, which makes the production process more complex and limits the possible applications. These methods are particularly problematic for high-frequency applications due to the so-called skin effect: as the frequency increases, the electrical current concentrates on the surface, which leads to undesirable losses with less conductive materials such as adhesion promoters. An alternative approach uses pin vias embedded in glass made of materials such as silicon or tungsten. However, these materials also offer poorer high-frequency properties and are less suitable for quantum technologies. This is where the IPD-GLAS project comes in with a revolutionary process: The pressure filling of glass feedthroughs with a molten aluminum. This innovative technology allows through-holes in dielectric substrates to be filled with aluminum - and with different geometries, such as hole diameter, flank angle, channel inclination and channel length.