Ultra-low-loss photonic integrated chips on an 8-inch anomalous-dispersion Si₃N₄-SiO₂-Si wafer

We report the fabrication of 8-inch crack-free, dispersion-engineered Si₃N₄-SiO₂-Si wafers fully compatible with industrial foundry silicon photonics fabrication lines. By combining these wafers with a developed amorphous silicon (a-Si) hardmask etching technique, we achieve ultra-low-loss Si₃N₄ photonic integrated circuits (PICs) with intrinsic quality factors exceeding 22×10⁶ using standard ultraviolet stepper photolithography, corresponding to a low propagation loss of 1.54 dB/m. We demonstrate the generation of a soliton frequency comb on these high-quality Si₃N₄ PICs, corroborating the designed anomalous dispersion. These results establish the feasibility of mass-manufacturing high-performance, dispersion-engineered Si₃N₄ PICs using standard foundry-grade processes, opening new pathways for applications in optical communications, nonlinear optics, and quantum optics.