Fabrication and Packaging of Edge Coupled Silicon Nitride Photonic Integrated Circuits on Glass Substrates for High Performance Interposers

Silicon nitride photonic integrated circuits were fabricated on glass substrates for the first time using reactive ion etched edge facets, demonstrating a minimum propagation loss of 2.4 ± 0.36 dB/cm and minimum edge coupling loss of 2.17 ± 0.79 dB. Two sets of processes were developed: one including high temperature steps (T > 350°C) common to complimentary-metal-oxide-semiconductor (CMOS) foundry front-end-of-line tools and one including low temperature steps (T < 350°C) compatible with CMOS foundry back-end-of-line tools. For both the high and low temperature samples, a CMOS foundry compatible process was also established for dry etching edge facets > 85 𝜇m deep into SiO2 substrates using magnetically enhanced reactive ion etching with amorphous silicon hard masks without metal. Results show the viability of this glass interposer to help achieve Pbps co-packaged optics switch performance by addressing the material limitations of organic or silicon based interposers and enabling pick-and-place assembly of photonic die to package level integrated photonic waveguides.