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Originally published in Science Express on 9 April 2009
Science 15 May 2009:
Vol. 324. no. 5929, pp. 913 - 917
DOI: 10.1126/science.1167610
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Reports

Two-Color Single-Photon Photoinitiation and Photoinhibition for Subdiffraction Photolithography

Timothy F. Scott,1,* Benjamin A. Kowalski,2 Amy C. Sullivan,2,{dagger} Christopher N. Bowman,1 Robert R. McLeod2,{ddagger}

Controlling and reducing the developed region initiated by photoexposure is one of the fundamental goals of optical lithography. Here, we demonstrate a two-color irradiation scheme whereby initiating species are generated by single-photon absorption at one wavelength while inhibiting species are generated by single-photon absorption at a second, independent wavelength. Co-irradiation at the second wavelength thus reduces the polymerization rate, delaying gelation of the material and facilitating enhanced spatial control over the polymerization. Appropriate overlapping of the two beams produces structures with both feature sizes and monomer conversions otherwise unobtainable with use of single- or two-photon absorption photopolymerization. Additionally, the generated inhibiting species rapidly recombine when irradiation with the second wavelength ceases, allowing for fast sequential exposures not limited by memory effects in the material and thus enabling fabrication of complex two- or three-dimensional structures.

1 Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO 80309–0424, USA.
2 Department of Electrical and Computer Engineering, University of Colorado, Boulder, CO 80309–0425, USA.

* Present address: Center for Bioengineering, Department of Mechanical Engineering, University of Colorado, Boulder, CO 80309–0427, USA.

{dagger} Present address: Department of Physics and Astronomy, Agnes Scott College, Decatur, GA 30030, USA.

{ddagger} To whom correspondence should be addressed. E-mail: robert.mcleod{at}colorado.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Two Beams Squeeze Feature Sizes in Optical Lithography.
J. W. Perry (2009)
Science 324, 892-893
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