researchers from bilkent university and middle east technical university, both in ankara, turkey, have described a novel method for writing 3-d structures inside the silicon chips using a focused infrared laser beam, according to a report from bilkent.

researchers used a laser to create 3-d structures on silicon.
(wikimedia commons)

the report explained, “a focused infrared laser beam exploits the inherent optical response of silicon to create 1-μm-resolution (one-hundredth of the human hair) building blocks in a sliver of silicon.”

in order to make the 3-d structures functional as optical devices, the scientists precisely built rod- or needle-like building blocks by optimizing the speed and resolution of the laser as it scanned across the silicon.

“a further outcome of the method is related to 3d printing or sculpting. the researchers found that by exposing the laser-modified areas to a specific chemical etchant, it is possible to realize 3d sculpturing of the entire wafer,” the article added.

“they demonstrated various microscopic components, such as microchannels, thru-si vias, cantilevers, and micropillars. creation of some of these is prohibitively difficult with other methods.”

this method, researchers claimed, is also more cost-effective than previous attempts at creating 3-d structures that have used reactive ion etching or e-beam lithography. the optical and mems devices that were created are also compatible with established cmos fabrication methods.

“inspired by the successes of ‘on-chip’ devices on silicon and other materials,” the article continued, “the team coined the term ‘in-chip’ devices, as a shorthand descriptor for this new class of components based on direct 3d laser-fabrication.”

the research was recently published in nature photonics. the abstract stated:

“silicon is an excellent material for microelectronics and integrated photonics, with untapped potential for mid-infrared optics. despite broad recognition of the importance of the third dimension, current lithography methods do not allow the fabrication of photonic devices and functional microelements directly inside silicon chips.

“even relatively simple curved geometries cannot be realized with techniques like reactive ion etching. embedded optical elements, electronic devices and better electronic–photonic integration are lacking. here, we demonstrate laser-based fabrication of complex 3d structures deep inside silicon using 1-µm-sized dots and rod-like structures of adjustable length as basic building blocks.

“the laser-modified si has an optical index different to that in unmodified parts, enabling the creation of numerous photonic devices. optionally, these parts can be chemically etched to produce desired 3d shapes.

“we exemplify a plethora of subsurface—that is, ‘in-chip’—microstructures for microfluidic cooling of chips, vias, micro-electro-mechanical systems, photovoltaic applications and photonic devices that match or surpass corresponding state-of-the-art device performances.”