The Karlsruhe Institute of Technology has developed a new process that allows printing of nanometer scale quartz glass structures directly on semiconductor chips. 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.
The printing of nano- and micrometer-scaled structures in quartz glass from pure silicon dioxide has many applications for optics, semiconductors and photonics. The processes used so far have relied on conventional 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.
Feedstock for Hybrid Polymer Resins of Organic and Inorganic Composition
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. As a feedstock, they use a hybrid polymer resin that is organic and inorganic. This liquid resin consists primarily of polyhedral, oligomeric silicon dioxide (POSS) molecule. These are small, cage-like molecules of silicon dioxide with organic functional groupings.
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. At the same moment, the POSS cages inorganic coalesce to form a continuous nanostructure or microstructure. The temperature required to achieve this is less than half of the temperature necessary for processes that rely on sintering nanoparticles.
Structures Stay Stable Under Challenging Thermal and Chemical 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. Quartz glass has excellent mechanical properties, and is easy to process. It also offers an excellent optical quality.
Researchers from Karlsruhe and Irvine printed various nanostructures using the POSS resin, including free-standing photonic crystals with 97 nm beams and parabolic microlenses. They also created a micro objective that had nanostructured elements and multiple lenses. Bauer says that the process Bauer uses produces structures stable under extreme chemical or thermal conditions.
Oliver Kraft, Vice president Research at KIT, says that the INT group led by Jens Bauer belongs to the 3DMM2O Cluster of Excellence. The research results published in Science show how clusters can support early-stage researchers. 3D Matter Made to Order (or 3DMM2O) is a Cluster of Excellence that KIT and Heidelberg University have jointly established. The project combines natural sciences with engineering to create a highly inter-disciplinary approach. The goal is to take 3D additive manufacturing to the next stage, from molecules to macro-scale dimensions.