A new process developed by the Karlsruhe Institute of Technology, KIT, allows printing of quartz glass structures at nanometer scale directly onto semiconductor chip. As a feedstock, a hybrid organic-inorganic resin is used for 3D printing silicon dioxide. As the process is not sintering-based, temperatures required for the process are much lower. Nanophotonics with visible light is enabled by increased resolution. Researchers report their findings in Science.
Printing micro- and ultra-nanometer-scaled quartz structures out of pure silicon dioxide offers many new applications to optics, photonics and semiconductor technologies. Processes have so far been based on traditional sintering. Temperatures required for sintering silicon dioxide nanoparticles are above 1100°C, which is much too hot for direct deposition onto semiconducting chips. A team led by Dr. Jens Bauer from KIT’s Institute of Nanotechnology has developed a new method to produce transparent glass with a very high resolution, and also excellent mechanical properties.
Hybrid Polymer Resins as Feedstock
Bauer, who is the head of the Emmy Noether Junior Research Group at KIT “Nanoarchitected metamaterials”, and his colleagues from University of California Irvine and Edwards Lifesciences in Irvine, present the process. Science. The feedstock is a hybrid inorganic-organic polymer. This liquid resin is made up of small silicon dioxide molecules called polyhedral silsesquioxane molecules (POSS). These molecules are cage-like and have organic functional groups.
After cross-linking the material via 3D printing to form a 3D nanostructure, it is heated to 650°C in air to remove the organic components. The inorganic POSS cells coalesce at the same time to form a continuous microstructure or nanostructure of quartz glass. This temperature is half that required for nanoparticle sintering processes.
Structures remain stable even under challenging chemical and thermal conditions
Bauer explains that “the lower temperature allows the free-form print of robust, optical grade glass structures with the required resolution for visible-light Nanophotonics directly on semiconductor chip,” Bauer says. The quartz glass is not only excellent in optical quality but has good mechanical properties.
Researchers in Karlsruhe and Irvine have used POSS resin to create various nanostructures. These include photonics crystals that stand alone, with beams 97nm wide, microlenses parabolic, and a nanostructured multi-lens objective. Bauer says that the process Bauer uses produces structures stable even in harsh chemical or temperature conditions.
Oliver Kraft Vice President Research of KIT says, “The INT Group headed by Jens Bau is associated with 3DMM2O Cluster of Excellence.” “The results of the research, which have been published in Science, are just one example of how early stage researchers are supported by the cluster.” 3D Matter Made to Order (or 3DMM2O) is a Cluster of Excellence that KIT and Heidelberg University have jointly established. By combining engineering and natural sciences, it pursues an interdisciplinary approach. The goal is to take 3D additive manufacturing to the next stage, from molecules to macro-scale dimensions.