Foundry compatible fabrication of Si3N4 microring resonators for 15-plex biosensing at 1310nm

The advent of the SARS-CoV-2 pandemic has rekindled the demand for inexpensive, point-of-care and at-home diagnostic systems that offer high degrees of scalability, sensitivity, and specificity. While several options of sensing modalities have been researched and subsequently commercialized, these sensing systems are yet to simultaneously satisfy the spiked demand for higher accuracy and scalable manufacturing. In this context, the prospect of integrated photonics-enabled biosensors has garnered immense attention from both scientific and business communities. However, realizing low group indices of the photonic structures required for higher bulk sensitivities at commonly used telecom operation wavelengths is typically achieved using design approaches incompatible with foundry process constraints. Siphox Inc., founded in 2020, developed an ensemble biosensing platform by merging the benefits of CMOS-friendly integrated photonic structures with proprietary biochemical assays to realize low-cost, highly sensitive, label and label-free, multiplexed diagnostic system. As a first demonstration, we present our results of 15-plex biosensing utilizing low-loss (<3.5dB/cm) Si3N4 strip-waveguide ring resonators fabricated using 248 nm deep UV (DUV) stepper lithography. We describe the design, simulation, and measurement results of bulk and surface sensitivities and detection limits for our TE-polarized waveguide resonator structures operating at O-band (1310 nm). We demonstrate a bulk sensitivity of >117 nm/RIU and an intrinsic limit of detection of 1.87x10(-4) RIU.