Ultra-high-Q α-Tantalum resonators on 300-mm silicon wafers

Mitigating material losses is essential for improving coherence in superconducting quantum circuits. While prior research has predominantly focused on minimizing interface losses, other losses remain less explored. In this work, we demonstrate α-phase tantalum thin films grown on 300 mm Si wafers and fabricate resonators that achieve internal quality factors consistently above 40 million at single-photon excitation. By systematically tuning dielectric energy participation ratio, we find that Q-factors scale with participation and identify other limits than the pure interface losses. Based on our learning, a realistic path should exist towards Q factors potentially even exceeding 100 million. Our results highlight the importance of optimizing overall material properties for the continuous improvement of coherence times in superconducting quantum circuits.