Stress-released SiN fabrication process for dispersion-engineered integrated silicon photonics.

We develop a stress-released stoichiometric silicon nitride (SiN) fabrication process for dispersion-engineered integrated silicon photonics. To relax the high tensile stress of a thick SiN film grown by low-pressure chemical vapor deposition (LPCVD) process, we grow the film in two steps and introduce a conventional dense stress-release pattern onto a ∼400nm-thick SiN film in between the two steps. Our pattern helps minimize crack formation by releasing the stress of the film along high-symmetry periodic modulation directions and helps stop cracks from propagating. We demonstrate a nearly crack-free ∼830nm-thick SiN film on a 4" silicon wafer. Our SiN photonic platform enables dispersion-engineered, waveguide-coupled microring and microdisk resonators, with cavity sizes of up to a millimeter. Specifically, our 115µm-radius microring exhibits an intrinsic quality (Q)-factor of ∼2.0×10 for the TM mode and our 575µm-radius microdisk demonstrates an intrinsic Q of ∼4.0×10 for TM modes in 1550nm wavelengths.