Publisher : The Korean Society of Mechanical Engineers
DOI : 10.3795/KSME-A.2016.40.8.731
Title & Authors
Hybrid UV Lithography for 3D High-Aspect-Ratio Microstructures Park, Sungmin; Nam, Gyungmok; Kim, Jonghun; Yoon, Sang-Hee;
Three-dimensional (3D) high-aspect-ratio (HAR) microstructures for biomedical applications (e.g., microneedle, microadhesive, etc.) are microfabricated using the hybrid ultraviolet (UV) lithography in which inclined, rotational, and reverse-side UV exposure processes are combined together. The inclined and rotational UV exposure processes are intended to fabricate tapered axisymmetric HAR microstructures; the reverse-side UV exposure process is designed to sharpen the end tip of the microstructures by suppressing the UV reflection on a bottom substrate which is inevitable in conventional UV lithography. Hybrid UV lithography involves fabricating 3D HAR microstructures with an epoxy-based negative photoresist, SU-8, using our customized UV exposure system. The effects of hybrid UV lithography parameters on the geometry of the 3D HAR microstructures (aspect ratio, radius of curvature of the end tip, etc.) are measured. The dependence of the end-tip shape on SU-8 soft-baking condition is also discussed.
Barber, R. L., Ghantasala, M. K., Divan, R., Vora, K. D., Harvey, E. C. and Mancini, D. C., 2005, "Optimisation of SU-8 Processing Parameters for Deep X-ray Lithography," Microsys. Technol., Vol. 11, pp. 303-310.
Park, J. H., Allen, M. G. and Prausnitz, M. R., 2005, "Biodegradable Polymer Microneedles: Fabrication, Mechanics and Transdermal Drug Delivery," J. Control. Release, Vol. 104, pp. 51-66.
Behrmann, G. P. and Duignan, M. T., 1997, "Excimer Laser Micromachining for Rapid Fabrication of Diffractive Optical Elements," Appl. Opt., Vol. 36, pp. 4666-4676.
Yoon, Y. K., Park, J. H. and Allen, M. G., 2006, "Multidirectional UV Lithography for Complex 3-D MEMS Structures," J. Microelectromech. Syst., Vol. 15, pp. 1121-1130.
Park, J. H. and Prausnitz, M. R., 2010, "Analysis of Mechanical Failure of Polymer Microneedles by Axial Force," J. Korean Phys. Soc., Vol. 56, No. 4, pp. 1223-1227.
Dill, F. H., Hornberger, W. P., Hauge, P. S. and Shaw, J. M., 1975, "Characterization of Positive Photoresist," IEEE Trans. on Electron Devices, Vol. ED-22, No. 7, pp. 445-452.
William, J. D. and Wang, W., 2004, "Study on the Postbaking Process and the Effects on UV Lithography of High Aspect Ratio SU-8 Microstructures," J. Microlithogr. Microfabr. Microsyst., Vol. 3, No. 4, pp. 563-568.
Lin, C.-H., Yeh, W.-T., Chan, C.-H. and Lin, C.-C., 2012, "Influence of Graphene Oxide on Metal-insulator Semiconductor Tunneling Diodes," Nanoscale Res. Lett., Vol. 7, No. 1, p. 343.
Campo, A. D. and Greiner, C., 2007, "SU-8: a Photoresist for High-aspect-ratio and 3D Submicron Lithography," J. Micromech. Microeng, Vol. 17, pp. R81-R95.
Liu, G., Tian, Y. and Kan, Y., 2005, "Fabrication of High-aspect-ratio Microstructures Using SU-8 Photoresist," Microsys. Technol., Vol. 11, pp. 343-346.
Becnel, C., Desta, Y. and Kelly, K., 2005, "Ultradeep X-ray Lithography of Densely Packed SU-8 Features: I. An SU-8 Casting Procedure to Obtain Uniform Solvent Content with Accompanying Experimental Results," J. Micromech. Microeng, Vol. 15, pp. 1242-1248.