Ultra-Low Loss Dispersion-Engineered Silicon Nitride Waveguides on 300 mm Wafers

Ultra-low loss silicon nitride waveguides have become ubiquitous in integrated photonics, spanning applications in frequency comb generation, spontaneous four-wave mixing photon sources, and high quality factor (Q-factor) cavities for laser self-injection locking. Silicon nitride is an ideal material due to its compatibility with standard complementary metal-oxide-semiconductor (CMOS) processing, broadband transparency from the visible to mid-IR, and high index contrast with silicon dioxide for high waveguide confinement. However, nonlinear applications require thick (> 600 nm) silicon nitride films for proper waveguide dispersion engineering, which poses a serious challenge for large wafer sizes due to the high induced stress. Here, we demonstrate the first low-loss silicon nitride waveguides in a 300 mm silicon photonics process with a thickness > 700 nm. We entirely mitigate stress-induced cracking by opting for a Damascene fabrication process rather than standard subtractive etching. We experimentally characterize the fabricated chips by measuring various microresonators across the wafer, observing highly uniform propagation loss and Q-factors in the telecommunication bands. In the O-band, we observe Q-factors as high as 976,000 and propagation loss as low as 0.485 dB/cm; in the C-band, we observe Q-factors as high as 1,041,000 and propagation loss as low as 0.348 dB/cm. Furthermore, by characterizing the group velocity dispersion (GVD) from the resonator free spectral range (FSR), we show that this platform can provide broadband anomalous GVD with proper waveguide width engineering and thus support nonlinear phenomena such as soliton Kerr comb generation. Notably, we tailor the fabrication process to be fully compatible with the standard AIM Photonics active process, providing future prospects for integrating low-loss dispersion-engineered silicon nitride devices alongside high-speed carrier-based silicon devices and germanium photodetectors. This novel demonstrated platform opens a wealth of opportunities in integrated photonics including high-speed data communications, quantum information, and optical sensing.