Ultralow-loss photonic integrated chips on 8-inch anomalous-dispersion Si$_3$N$_4$-SiO$_2$-Si Wafer

TL;DR

This paper demonstrates the fabrication of ultra-low-loss, dispersion-engineered Si3N4 photonic chips on 8-inch wafers compatible with industrial foundry processes, enabling high-quality frequency combs for advanced optical applications.

Contribution

It introduces a scalable fabrication process for high-Q Si3N4 PICs on large wafers using standard foundry techniques, including a novel hardmask etching method.

Findings

Intrinsic quality factors exceeding 25 million achieved.

Successful demonstration of frequency-comb generation.

Compatibility with industrial silicon photonics foundry processes.

Abstract

We report the fabrication of 8-inch crack-free, dispersion-engineered Si$_3$N$_4$-SiO$_2$-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 Si$_3$N$_4$ photonic integrated circuits (PICs) with intrinsic quality factors exceeding $25 \times 10^6$ using electron beam lithography and $24 \times 10^6$ using standard ultraviolet stepper photolithography. Frequency-comb generation is demonstrated on these high-quality Si$_3$N$_4$ PICs, corroborating the designed anomalous dispersion. These results establish the feasibility of mass-manufacturing high-performance, dispersion-engineered Si$_3$N$_4$ PICs using standard foundry-grade processes, opening new pathways for applications in optical communications, nonlinear optics, and quantum optics.