Towards monolithic low-loss silicon nitride waveguides on a mature 200 mm CMOS platform

Abstract

Silicon nitride photonics has enabled a broad class of low-loss integrated devices and chip-scale solutions that benefit from transparency over a wide wavelength range and compatibility with complementary metal-oxide-semiconductor process, allowing applications of tele/datacom, artificial intelligence, sensing and bio-photonics. As a complimentary platform to silicon-on-insulator photonics, low-loss silicon nitride waveguide technology was present to extend the capabilities of silicon photonics platform. Silicon nitride films prepared by low pressure chemical vapor deposition have low intrinsic loss and good repeatability, but silicon nitride film is prone to crack when the thickness is no less than 300 nm. In order to reduce high stress, the wafer-level silicon nitride waveguides with 400 nm thickness were fabricated by two-step deposition method on 200-mm complementary metal-oxide-semiconductor pilot-line. Due to the different linewidth change between single-stripe and multiple-stripe structure after the same layer etch process, the layout compensation is needed to correct this deviation. But the linewidth sensitivity for silicon nitride waveguides is relatively low, propagation losses in the C-band were slightly reduced from 0.66 dB/cm for 0.9 µm width down to 0.62 dB/cm for 1 µm width.