Despite the widespread adoption of silicon photonics, fiber coupling remains a major challenge for large-scale manufacturing. Our group has previously demonstrated integrated microlens couplers (IMCs) as an efficient, broadband, and polarization-insensitive solution for wafer-scale fiber-to-chip coupling, achieving a free-space coupling loss as low as 0.6 dB.
In this project, we replace polymer-based IMCs with hard-material SiON microlenses formed by transferring the lens profile from photoresist (PR) to SiON using anisotropic etching. By optimizing the oxide-to-nitride ratio, we minimized film stress while maintaining the desired refractive index. We successfully deposited extra-thick (>20 µm), low-stress (wafer bow <50 µm) SiON films via PECVD. In addition, we developed etch recipes with controlled PR-to-SiON selectivity to ensure high-fidelity pattern transfer. The microlenses have been successfully fabricated and achieved a coupling loss of 1.0 dB.
These advancements significantly improve IMC durability during packaging, paving the way for a robust, pluggable fiber-to-chip connector for scalable silicon photonics integration.
Project is currently funded by: Industry Sponsored Research