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. The process does not require sintering and therefore the temperatures required are lower. Enhanced resolution also enables visible light nanophotonics. Researchers report their findings in Science.
Printing micro- and ultra-nanometer-scaled structures of quartz glass from pure silicon oxide opens many new 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. Dr. Jens Bauer, head of KIT’s Institute of Nanotechnology INT, has developed a process that produces transparent quartz glass at lower temperatures with high resolution and good mechanical properties.
Hybrid Polymer Resins as Feedstock
Bauer, the Emmy Noether Junior Research Group leader at KIT and his collaborators from the University of California Irvine, Edwards Lifesciences, and Irvine’s Edwards Lifesciences Company, describe the process. Science. The feedstock is a hybrid inorganic-organic polymer. This liquid resin is composed of molecules known as polyhedral, oligomeric silsesquioxane(POSS), which are small, cage-like silicon oxide molecules 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. The POSS cages are also coalescing to form a continuous nanostructure or microstructure. This temperature is half that required for nanoparticle sintering processes.
Structures remain stable even under challenging chemical and temperature conditions
Bauer explains: “The lower temperatures enable the free-form-printing of robust optical-grade glasses structures with the necessary resolution for visible light nanophotonics on semiconductor chips,” Bauer explains. The quartz glass is not only excellent in optical quality but also has good mechanical properties.
The researchers in Karlsruhe and Irvine have used POSS resin to create various nanostructures. These include photonics crystals that stand alone, with beams 97nm wide, parabolic lenses, and a multiple-lens objective with nanostructured components. Bauer says, “Our process creates structures that are 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 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 jointly run by KIT, Heidelberg University and the University of Heidelberg. 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.