SMILE · 3D Silicon Micromachining with Infrared ultrafast LasErs

3D Silicon Micromachining with Infrared ultrafast LasErs

"The famous physicist Richard Feynman said, ""There is plenty of room at the bottom."", and is often quoted to highlight the successes of modern fabrication techniques. The continual progress in these enables new technologies we enjoy daily. In this respect, silicon, the bedrock of modern computers, mobile communications, and Si-photonics, has proven to be extremely capable. The material is incorporating ever more speed, usually described with Moore's law. Precisely due to these amazing successes, one may be surprised to hear that virtually none of these are taking advantage of the vast space available, below the surface, inside silicon wafers. In this sense, electronics and Si-photonics continue to live in Flatland. What more could be achieved, if the bulk of Si was opened to usage? A team of scientists now found a way to pack various laser-written structures deep inside silicon chips (Tokel, et. al. Nature Photonics, 11, 639, 2017). In this novel approach, they use a focused infrared laser which exploits the inherent optical response of Si to create 1-μm-resolution building blocks in a sliver of silicon. For the first time, the researchers demonstrate arbitrary 3D fabrication in silicon. But this was the first hurdle the researchers had to overcome. Next, they convert these 3D architectures into functional optical devices, such as lenses, waveguides, holograms. ""We achieve this by exploiting dynamics arising from nonlinear interactions, leading to controllable building blocks,"" says Dr. Onur Tokel of the Department of Physics at Bilkent. ""In any 3D fabrication method, there is a trade-off between speed, resolution, and complexity. With our approach, we are hitting the sweet spot. The critical realization is noticing that most practical components can be made out of needle-like building blocks. Our method enables creating such blocks, while also preserving a width of 1 µm for each block. Better yet, the rods can be combined to create a 2D layer, or even 3D shapes."" A further outcome is related to 3D printing or sculpting. They found that by exposing modified areas to a specific chemical, it is possible to realize 3D sculpturing. They demonstrated various micro-components, such as microchannels, thru-Si vias, and micropillars. ""I should note that this is a direct-laser writing approach, inexpensive compared to conventional lithography,"" notes Dr. Serim Ilday, of the Department of Physics, one of the coauthors of the paper. Inspired by the successes of ""on-chip"" devices, the team coined the term ""in-chip"", as a descriptor for this new class of components based on direct 3D fabrication. ""The possibilities are endless. It is likely that the method will enable entirely new in-chip devices, such as Si-photonics components, or microfluidic channels that may be used to efficiently cool electronic chips"", observed Prof. Ömer Ilday, another co-author of the paper from Bilkent. (Adapted from dissemination: https://www.eurekalert.org/pub_releases/2017-10/bufo-sil100717.php)"

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