MIT researchers and engineers at NY Creates have developed a scalable manufacturing platform to produce flexible, transparent silicon-photonics chips on 300-millimeter wafers, MIT reported.
Silicon photonics transmits and processes data using light rather than electrical currents. Standard semiconductor foundries routinely produce rigid, opaque 300-millimeter wafers that contain billions of nanoscale optical devices. While previous laboratory demonstrations yielded individual flexible or transparent photonic chips, those earlier techniques could only produce a few devices at a time.
Wafer-scale thinning
The fabrication sequence begins on a traditional rigid silicon wafer. The team patterns optical waveguides onto the substrate before bonding a temporary silicon support wafer directly to the top surface. Workers then invert the assembly to strip away the original silicon base material from above.
Fabrication engineers managed wafer stress by restricting processing temperatures to 500 degrees Celsius or below. Thinning a 300-millimeter wafer down to several microns without temperature controls causes the disk to bow, which risks rippling the surface or shattering the wafer on the tool line. The team deployed standard industrial thinning techniques followed by a selective chemical etch, leaving behind an oxide and waveguiding layer thinner than a tenth of a human hair.
The team then adhered a thin, transparent polyester film to the exposed optical layers and de-bonded the temporary silicon carrier from the bottom. This leaves a flexible, transparent wafer measuring only a few microns thick.
Durability and vision tests
Researchers evaluated the finished platform through waveguiding, mechanical flexing, and transparency experiments. In durability trials, a single chip underwent thousands of bends around cylinders of various sizes down to the diameter of a small screw with no loss in optical performance. The chip only began to degrade after repeated bending around a toothpick.
The team positioned a chip in front of a bionic eye to measure optical clarity. Looking through the device produced minimal haze and no noticeable image distortion, demonstrating its suitability for curved augmented-reality visors or conformal medical monitors.
Lead author Tal Sneh and senior author Jelena Notaros published the findings in the journal Optica alongside co-authors Andres Garcia Coleto, Thomas Dyer, Kevin Fealey, and Milica Notaros. NY Creates carried out wafer processing at the Albany NanoTech Complex, while chip dicing occurred at MIT.nano. The team plans to integrate more complex components, increase waveguide efficiency, and refine transparency in future work.
