07 Jun 2023
Low-temperature process developed at KIT delivers a variety of high-resolution optics products.Karlsruhe Institute of Technology (KIT), Germany, produces nanometer-fine quartz glass structures that can be printed directly onto semiconductor chips.
A hybrid organic-inorganic polymer resin serves as the starting material for the 3D printing of silicon dioxide. Since the process does not require sintering, the temperatures required are significantly lower. At the same time, higher resolution enables nanophotonics with visible light. The work is described in Science.
The printing of quartz glass made of pure silicon dioxide in micro- and nanometer-fine structures opens up new possibilities for many applications in optics, photonics and semiconductor technology. However, until now, techniques based on traditional sintering have dominated.
The temperatures required for the sintering of silicon dioxide nanoparticles are over 1,100 degrees Celsius – far too hot for direct deposition on semiconductor chips. A research team led by Dr. Jens Bauer from the KIT Institute of Nanotechnology (INT) has now developed a new process to produce transparent quartz glass with high resolution and excellent mechanical properties at significantly lower temperatures.
Bauer, who heads the Emmy Noether junior research group "Nanoarchitected Metamaterials" at KIT, and his colleagues from the University of California Irvine and the medical technology company Edwards Lifesciences in Irvine present the method in the journal Science.
Hybrid organic-inorganic polymer resin
A specially developed hybrid organic-inorganic polymer resin serves as the starting material. This liquid resin consists of so-called polyhedral oligomeric silsesquioxane molecules (POSS): tiny cage-like silicon dioxide molecules are equipped with organic functional groups.
Once formed, the fully 3D printed and networked nanostructure is heated in air to a temperature of 650 degC. In the process, the organic components are expelled and, at the same time, the inorganic POSS cages combine, resulting in a continuous fused silica micro- or nanostructure. The required temperature is only half that of processes based on the sintering of nanoparticles.
“The lower temperature makes it possible to print robust, transparent and free-form optical glass structures directly onto semiconductor chips with the resolution required for visible-light nanophotonics," explains Bauer. In addition to the excellent optical quality, the quartz glass produced in this way has excellent mechanical properties and is easy to process.
The team from Karlsruhe and Irvine printed many different nanoscale structures with the POSS resin, including photonic crystals of free-standing 97-nanometer beams, parabolic microlenses, and a multilens microlens with nanostructured elements. “Our process enables structures that also withstand difficult chemical or thermal conditions,” said Bauer.
“The group at INT headed by Jens Bauer belongs to the Cluster of Excellence 3DMM2O,” said Professor Oliver Kraft, VP Research at KIT. “The research results now published in Science are just one example of how well the consistent promotion of young talent within the cluster works.”
The 3D Matter Made to Order cluster of excellence, a joint cluster of KIT and Heidelberg University, is combination of natural and engineering sciences a strongly interdisciplinary approach. His goal is to take 3D additive manufacturing processes to the next level – from the molecular level to macroscopic dimensions.