Nanosystem Manufacturing Center
Dr. Jack Wolfe
Prof. Weichuan Shih
Prof. John A. Dani (Chair, Department of Neuroscience, UPenn)
Prof. D. Litvinov
Prof. Gopathy Purushothman (Vanderbilt School of Medicine)
Prof. Deborah Rodrigues
Prof. P. Ruchhoeft
Prof. Jarek Wosik
Prof. Cunjiang Yu
Prof. Wanda Zagozdzon-Wosik
The mission of the Nanosystem Manufacturing Center is to develop technology for manufacturing integrated nanosystems. Support from the National Science Foundation in 2008 continued the development of an advanced neutral beam printer and supporting mask-making hardware for a high throughput lithograph in the sub-100 nm regime. Other projects by these center researchers include a proof of concept tool for removing photoresist from 300 mm silicon wafers through a collaboration with Axcelis Technologies Inc., as well as the development of two new concepts for fabricating water filters that are currently being evaluated by potential investors. Researchers also demonstrated, for the first time, the ability to fabricate nanoscale structures in 3-D. Among the main accomplishments of the center:
Neutral beam lithography: This is a proximity printing technique where a stencil mask (a membrane with open transmission windows) is flooded by a broad beam of energetic (e.g. 30 keV) helium atoms and transmitted beamlets expose resist on a substrate. The major accomplishments last year included a careful study of the advantages of this technique vis-Ã -vis ion beam proximity lithography, the development of a mechanical nanostepping capability with sub-nanometer pattern placement accuracy, and the development of advanced source technology. Our work is summarized in an invited review article in Journal of Physics D (Jan.-Feb., 2008).
Photoresist ashing: Resist masks are used in every level of integrated circuit manufacturing. We solved the long standing residue problem in ashing high dose, ion implanted photoresist, thus eliminating several expensive cleaning cycles in integrated circuit manufacturing. Because of this advance, we were contracted by Axcelis Technologies Inc. to build a proof-of-concept tool for ashing 300 mm silicon wafers. The tool is now undergoing shake-down tests before starting an evaluation program with several major integrated circuit chip manufacturing companies. Through this project, we developed a new way to measure substrate loss during resist ashing in collaboration with Axcelis and Professor Wolfgang Donner in the department of physics. The approach has unprecedented accuracy—about 0.5 angstroms or just 1/4 of an atomic layer.
3-D lithography: A novel plasma enhanced resist coating process was developed with NSF sponsorship that unlocks the potential of ion and neutral beam proximity lithography for patterning 3-D surfaces. The technique is expected to find wide application in microelectromechanical systems (MEMS). The technique enabled the fabrication of multichannel cuff electrodes about 10 times smaller than what exists today. We used the cuffs to monitor neuronal signals in a grasshopper. This research is part of a larger program with Professor Richard Liu the UH Department of Electrical and Computer Ennineering and Professor Fabrizio Gabianni in the Neuroscience Department at the Baylor College of Medicine. Profs. John A. Dani, Gopathy Purushothman, Weichuan Shih, and Jack Wolfe have applied the technology to fabricate neural probes with integrated conductor wiring on ultra-thin optical fibers that provide significantly better localization of neuronal signals and displace 90% less brain tissue than state-of-the-art competitors. The probes are being used to map neural circuits in the brain.