Collective Die-to-Wafer Bonding Enabling Low-Loss Evanescent Coupling for Optically Interconnected System-on-Wafer

In this article, we present a collective photonic integrated circuits (PICs) die-to-wafer dielectric bonding process, enabling silicon nitride (SiN) waveguide-based die-to-wafer evanescent coupling with insertion losses (ILs) of <inline-formula> <tex-math notation="LaTeX">$0.16~\pm 0.06$ </tex-math></inline-formula> dB at optical O-band 1310 nm wavelength. This SiN evanescent coupling is of great significance and offers integration flexibility to effectively reduce optical coupling lossand enable higher density optical connectivity compared to conventional edge coupling optical fiber arrays. The collective die-to-wafer (collective D2W, CoD2W) bonding process enhances manufacturing efficiency by enabling high throughput, reducing handling steps, and lowering overall production costs. Besides, the evanescent coupling misalignment tolerance is up to <inline-formula> <tex-math notation="LaTeX">$2~\mu $ </tex-math></inline-formula>m, which can mitigate alignment sensitivity and packaging difficulties. This advancement supports high-volume, low-latency, lower energy-consumption optical I/O, paving the way for optically interconnected 300-mm wafer-scale multi-XPU compute systems for high-performance artificial intelligence/machine-learning (AI/ML) computing.