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Multiphoton photoresists giving nanoscale resolution that is inversely dependent on exposure time

Nature Chemistry volume 3, pages 223227 (2011) | Download Citation



Recent advances in materials science have made it possible to perform photolithography at the nanoscale using visible light. One approach to visible-light nanolithography (resolution augmentation through photo-induced deactivation) uses a negative-tone photoresist incorporating a radical photoinitiator that can be excited by two-photon absorption. With subsequent absorption of light, the photoinitiator can also be deactivated before polymerization occurs. This deactivation step can therefore be used for spatial limitation of photopatterning. In previous work, continuous-wave light was used for the deactivation step in such photoresists. Here we identify three broad classes of photoinitiators for which deactivation is efficient enough to be accomplished by the ultrafast excitation pulses themselves. The remarkable properties of these initiators result in the inverse scaling of lithographic feature size with exposure time. By combining different photoinitiators it is further possible to create a photoresist for which the resolution is independent of exposure over a broad range of fabrication speeds.

  • Compound C23H26N2O


  • Compound C18H21O3P

    Ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate

  • Compound C23H25ClN2

    N-[4-[[4-Dimethylamino)phenyl]phenylmethylene]-2,5-cyclohexadien-1-ylidene]-N-methylmethanaminium chloride

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The authors acknowledge the support of the Maryland NanoCenter and its NispLab. The NispLab is supported in part by the National Science Foundation (NSF) as a Materials Research Science and Engineering Center (MRSEC) Shared Experimental Facility. This work was supported in part by the UMD-NSF-MRSEC (grant DMR 05-20471). The authors are grateful to A. Mullin and D. Falvey for helpful discussions.

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  1. Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA

    • Michael P. Stocker
    • , Linjie Li
    • , Rafael R. Gattass
    •  & John T. Fourkas
  2. Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA

    • John T. Fourkas
  3. Center for Nanophysics and Advanced Materials, University of Maryland, College Park, Maryland 20742, USA

    • John T. Fourkas
  4. Maryland NanoCenter, University of Maryland, College Park, Maryland 20742, USA

    • John T. Fourkas


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M.S., L.L. and J.T.F. conceived and designed the experiments. M.S., L.L. and R.R.G. performed the experiments. M.S. and L.L. analysed the data. M.S. and J.T.F. co-wrote the paper.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to John T. Fourkas.

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