It’s a terascale world after all

Melinda Rose, melinda.rose@photonics.com

Using high-resolution optical lithography techniques that are 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.

With CMOS fabrication tools, scientists at the Photonics Research Group, a laboratory of Ghent University that is associated with the Interuniversity Microelectronics Center (IMEC), put the map in a corner of an 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 map is viewed through a scanning electron microscope. Images ©Photonics Research Group-University of Ghent 2009.

The smallest features resolved on the map are about 100 nm, a size that is still several times larger than 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 fabrication process consisted of 30 steps, including layer depositions and chemical etching on a silicon-on-insulator wafer. Four different layer thicknesses were resolved, and these corresponded to four different images, or mask layers, that had to be patterned separately.

The terascale world map, created using high-resolution optical lithography techniques, is hidden in the bottom right corner of a photonic chip.

The silicon photonic technology developed with these chips integrates optical circuits onto a small chip: Light can be manipulated on a submicrometer scale in tiny strips of silicon called waveguides or photonic wires, which means that these silicon photonic circuits can pack a million times more components into the same space than today’s commercial glass-based photonics can.

The circuits developed on this 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, as with an optical fiber, to the wires on a chip.

The small map is viewed through an optical microscope. The different colors are caused by interference effects in the different layer thicknesses of silicon.

Located in Leuven, Belgium, the Photonics Research Group works to build on technologies developed for the microelectronics industry to create smart photonic chips for health care, communications, identification and biosciences.