Photonic Chip Holds World Map

Using high-resolution optical lithography techniques important in microelectronics fabrication, researchers in Belgium have produced a terascale world map with a circumference of only 40 µm, or about half the width of a human hair.

Scale of the world map created using high-resolution optical lithography techniques. It is hidden in the bottom right corner of a photonic chip. (Images copyright ©Photonics Research Group-University of Ghent 2009)

Using CMOS fabrication tools, the Photonics Research Group of Ghent University-IMEC put the map in a corner of a optical silicon chip designed for one of the group's research projects on nanophotonic integrated circuits. The world map was defined on a silicon photonics test chip in IMEC's cleanroom for 200-mm processing.

The small world as seen through an optical microscope. The different colors are caused by interference effects in the different layer thicknesses of silicon.

The fabrication consisted of a 30-step process including layer depositions and chemical etching steps on a silicon-on-insulator wafer. Four different layer thicknesses can be resolved, corresponding to four different images, or mask layers, that have to be patterned separately.

The smallest features resolved on the map are about 100 nm, which is still a several times larger than the today’s state-of-the-art transistors. However, the scale reduction enables more complex optical functions on a single chip for applications in telecommunications, high-speed computing, biotechnology and health care, the researchers said.

The silicon photonics technology that is being developed with these chips integrates optical circuits onto a small chip: Light can be manipulated on submicrometer scale in tiny strips of silicon called waveguides or photonic wires. Using the unique properties of silicon, combined with state-of-the-art manufacturing technology, these silicon photonic circuits can pack a million times more components on the same footprint as today’s commercial glass-based photonics.

The small map as seen through a scanning electron microscope.

The circuits developed on this particular chip were used to demonstrate photonic wires with the lowest propagation losses, the researchers said. Also, structures were developed to improve the efficiency of coupling light from the outside world (like an optical fiber) to the wires on chip.

The Photonics Research Group, a laboratory of Ghent University, is associated with IMEC, the Interuniversity Microelectronics Center, located in Leuven, Belgium. The group focuses on the research and development of smart photonic chips for future application in communications, identification, biosciences and health care, building on technologies developed for the microelectronics industry. The use of silicon and microelectronics fabrication can drastically reduce the size, power consumption and cost of photonic chips, bringing them closer to integration with consumer electronics, cell phones, smart distributed sensor networks and point-of-care diagnostics.

For more information, visit: http://photonics.intec.ugent.be/