Exploration of Chemical Precursors for Deposition of Wurtzite-Structured Ferroelectric Aluminum Nitride-Based Thin Films (ExPreFAN)

• Applicants: Professorin Dr. Anjana Devi; Dr. Uwe Schröder
• Subject Area: Synthesis and Properties of Functional Materials ; Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering ; Solid State and Surface Chemistry, Material Synthesis
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 563108379

The discovery of ferroelectric Sc-substituted aluminum nitride (AlN) in 2019 broadened the application spectrum of wurtzite-structured nitride semiconductors. Widening the range of cation-substituted ferroelectric nitrides can significantly contribute to a comprehensive understanding of the structural and chemical origin of their ferroelectric properties. Atomic layer deposition (ALD) and metal-organic chemical vapor deposition (MOCVD) processes are preferred by industry because they allow cost-effective depositions on 300 mm substrates and better conformality. Ferroelectricity has been observed in Sc-substituted AlN grown by MOCVD, but no demonstration has emerged for crystalline growth by ALD. The greatest challenges for the deposition of AlN thin films doped with rare earths are the low vapor pressures and the reactivity of the dopant precursors. Therefore, the interdisciplinary joint project ExPreFAN between IFW and NaMLab gGmbH aims at developing new precursors for Scandium and Ytterbium for ALD and MOCVD processes while also testing unexplored compositions using commercial precursors for dopants such as Zirconium and Hafnium to grow cation-substituted ferroelectric AlN thin films of high wurtzite-structure quality for next generation of nonvolatile memories. During ExPreFAN, IFW will develop the new precursors and the MOCVD processes based on them. NaMLab will focus on the ALD process development of ferroelectric AlN with different cation-substituent elements using commercially available precursors and the new precursors from IFW. Both project partners will collaborate on film fabrication, as well as structural and chemical characterization using their state-of-the-art cleanroom and research facilities. The ferroelectric properties of the ALD and MOCVD-grown films will be evaluated at NaMLab through capacitor structures. Critical metrics for nonvolatile memory applications, such as cycling enedurance and retention, will be evaluated for the most promising ferroelectric films. Theoretical simulations from Tyndall will support the precursor synthesis and electrical characterization. By combining the complementary expertise of the project partners, ExPreFAN aims to explore new precursors for ALD and MOCVD growth of ferroelectric cation-substituted AlN films for next generation of nonvolatile memory technologies. At the same time, a detailed characterization promotes a better understanding of the film properties and the knowledge transfer between young researchers in the fields of materials science, electrical engineering and theoretical modeling.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2477: Nitrides4Future – Novel Materials and Device Concepts