CSL researchers develop novel low cost photolithographic technique

A novel low cost photolithographic (writing with light) technique has been developed by CSL Professor James Gary Eden, Illinois ECE Post-Doctoral Research Associate Andrey Mironov, and Engineering Teaching Lab Coordinator Dane Joseph Sievers. A startup company licensed this technology and started manufacturing low cost high resolution photolithographic tools for universities and R&D.

This technology offers the potential to significantly advance microfabrication, microfluidics, polymer optics, and other fields. In their work, a simple photolithographic system operating at 172 nm has been demonstrated at a fraction of the cost of the old lamp systems. This new system offers a resolution that is a factor of two smaller than the best resolution offered by the mercury lamp systems. Compared to the newer, deep-UV lasers systems, the cost of the 172 nm lamp technology is less expensive by a factor of at least 1,000-10,000 (3-4 orders of magnitude).

Photolithography is the process by which circuits and electronic devices are "patterned" (i.e., laid out) in sophisticated chips such as those manufactured by Intel, AMD, and Qualcomm. Photolithography allows one to specify where transistors, for example, and other electronic components are located on the chip and how electrical current will be routed.

Unfortunately, the race to build smaller and smaller electronic devices has resulted in the cost of photolithographic systems rising so rapidly that they are now accessible to only a few of the largest companies worldwide. The "long and the short" of this situation is that small companies and researchers have had little access to photolithographic technology for quite a while. In addition to improving the resolution and significantly lowering the cost of a photolithigraphic system, this technique allows for a  substitution of low cost safe polymers for toxic and expensive chemicals.

Currently, researchers use clean rooms and complicated processes to fabricate microfluidic devices, diffraction gratings, and other microstructures in polymers. The 172 nm

photolithography technique allows for a precise selective removal or polymers with Vacuum Ultraviolet light outside a cleanroom and does not require expensive or toxic materials. This means that small universities (no clean room access) and even high schools can now fabricate complicated 3D microstructures of ~1 micrometer size in polymers for educational and research purposes.

Additionally, their technique allows one to use a variety of low-cost, eco-friendly and non-toxic polymers as a photoresist and does not require a conventional development step. Therefore, no toxic chemicals are required for this photolithography process and significantly less waste is generated compared to conventional lithography steps. This would be extremely valuable for small laboratories, R&D companies, and even progressive high schools. Students, for example, can now make high quality diffraction gratings, fresnel lenses, microfluidic devices, and other components in acrylics in minutes.

At the same time, the developed process may be advantageous to large industrial companies. It eliminates several conventional photolithography steps and, as a result, significantly reduces generated chemical and water waste. In addition, it allows for large wafers (300 and 400 mm in diameter) to be processed in a single exposure step, which substantially increases the throughput.