Research on Subwavelength Microphtonic Sensors for In-situ Monitoring with High Spatial and Temporal Resolution in Manufacturing Environments

Micron-sized subwavelength structured photonic sensors could allow critical thermomechanical phenomena in manufacturing processes to be monitored, while offering tremendous advantages. To implement these novel sensors into real manufacturing processes, the microring sensors can be embedded at critical locations in metallic structures, which are heavily used in hostile manufacturing environments. This paper presents our research progress on fabrication, embedding, and application of integrated mciroring sensors. For fundamental study, microring resonators have been microfabricated on-chip with silicon-on-insulator wafer substrates. The fabricated optical resonators offer Qs on the order of 20,000, enabling significantly improved temporal sensing and detection of high-frequency strain variation. A new approach to fabricate metal embedded photonic structures was developed. Various thin film photonic materials were studied for embedded microphotonic sensors. Effect of process parameters on refractive index of silicon nitride/silicon oxynitride films was studied. Issues on design and implementation of micro sensors for Chemical Mechanical Planarization (CMP) were studied and a grafting process was designed to embed micro sensors into polishing pads. A preliminary design for the sensor and its installation into a continuous casting mold was also developed.