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Experimental and Finite Element Study of Tribological Characteristics of SU-8 Thin Film

실험 및 유한요소해석에 의한 SU-8 박막의 Tribological 특성 연구

  • 양우열 (한남대학교 기계공학과) ;
  • 신명근 (한남대학교 기계공학과) ;
  • 김형만 (한남대학교 기계공학과) ;
  • 한상철 (한남대학교 기계공학과) ;
  • 성인하 (한남대학교 기계공학과)
  • Received : 2012.07.17
  • Accepted : 2012.12.02
  • Published : 2013.04.01

Abstract

In this study, two-dimensional finite element models were developed and experiments were conducted using an atomic force microscope to investigate the tribological characteristics of an SU-8 layer coated on a patterned wafer for microsystem applications. The results revealed that both the adhesion and the friction forces measured by the atomic force microscope were lower for the SU-8 coated surface than for the bare silicon surface. This is attributed to the hydrophobicity of SU-8. Another important result derived from the finite element analysis was the critical load required to fracture the SU-8 film with respect to the thickness. The critical loads for thicknesses of 200, 400, and 800 nm were approximately 13, 22, and 28 mN, respectively, which corresponded to a Hertzian contact pressure of 1.2-1.8 GPa. These results will aid in the design of a suitable SU-8 thickness for microsystem components that are in contact with one another.

Keywords

SU-8 Photoresist;Friction;Adhesion;Finite Element Analysis;Atomic Force Microscope;Critical Load

Acknowledgement

Supported by : 한국연구재단

References

  1. Rymuza, Z., 2007, "Tribology of Polymers," Archives of Civil and Mechanical Engineering, Vol. VII, No. 4, pp.177-184.
  2. Yamaguchi, Y., 1990, Tribology of Plastic Materials, Tribology Series, Vol. 16, Elsevier, New York.
  3. Imperial College Press ed., Polymer Tribology, Chapter 1, World Scientific Publishing, 2009.
  4. Hammerschmidt, J. A., Gladfelter, W. L. and Haugstad, G., 1999, "Probing Polymer Viscoelastic Relaxations with Temperature-Controlled Friction Force Microscopy," Macromolecules, Vol. 32, pp. 3360-3367. https://doi.org/10.1021/ma981966m
  5. Forrest, J. A., Dalnoki-Veress, K. and Dutcher, J. R., 1997, "Interface and Chain Confinement Effects on the Glass Transition Temperature of Thin Polymer Films," Physical Review E, Vol. 56, pp. 5705-5716. https://doi.org/10.1103/PhysRevE.56.5705
  6. Yu, H., Balogun, O., Li, B., Murray, T. W., and Zhang, X., 2006, "Fabrication of Three-Dimensional Microstructures Based on Singled-Layered SU-8 for Lab-on-Chip Applications," Sensors and Actuators A: Physical, Vol. 127, No. 2, pp. 228-234. https://doi.org/10.1016/j.sna.2005.08.033
  7. Yu, H., Balogun, O., Li, B., Murray, T. W., and Zhang, X., 2004, "Building Embedded Microchannels Using a Single Layered SU-8 and Determining Young's Modulus Using a Laser Acoustic Technique," Journal of Micromechanics and Microengineering, Vol. 14, No. 11, pp. 1576-1584. https://doi.org/10.1088/0960-1317/14/11/020
  8. Singh, R. A., Satyanarayana, N., Kustandi, T. S. and Sinha, S. K., 2011, "Tribo-Functionalizing Si and SU8 Materials by Surface Modification for Application in MEMS/NEMS Actuator-Based Devices," Journal of Physics D: Applied Physics, Vol. 44, 015301. https://doi.org/10.1088/0022-3727/44/1/015301
  9. Son, Y., Lim, T. W., Yang, D. Y., Yi, S. W., Kong, H. J. and Park, S. H., 2008, "Study on Process Parameters of a SU-8 Resin in Two-Photon Stereolithography for the Fabrication of Robust Three-dimensional Microstructures," Journal of the Korean Society of Precision Engineering, Vol. 25, No. 1, pp. 130-137.
  10. Choi, I., Wang, H., Choi, K. S. and Kim, H. M., 2010, "Numerical Analysis-Based Design of PEMFC Channel, Fabrication of Channels, and Performance Test Using SU-8," Trans. Korean Soc. Mech. Eng. B, Vol. 34, No. 4, pp. 349-354. https://doi.org/10.3795/KSME-B.2010.34.4.349
  11. Lawrence, C. J., 1988, "The Mechanics of Spin Coating of Polymer Films," Physics of Fluids, Vol. 31, No. 10, pp. 2786-2795. https://doi.org/10.1063/1.866986
  12. Sader, J. E., Chon, J. W. M. and Mulvaney, P., 1999, "Calibration of Rectangular Atomic Force Microscope Cantilevers," Review of Scientific Instruments, Vol. 70, pp. 3967-3969. https://doi.org/10.1063/1.1150021
  13. Green, C. P., Lioe, H., Cleveland, J. P., Proksch, R., Mulvaney, P. and Sader, J. E., 1995, "Normal and Torsional Spring Constants of Atomic Force Microscope Cantilevers," Review of Scientific Instruments, Vol. 75, pp. 1988-1996.
  14. Ogletree, D. F., Carpick, R. W. and Salmeron, M., 1996, "Calibration of Frictional Forces in Atomic Force Microscopy," Review of Scientific Instruments, Vol. 67, pp. 3298-3306. https://doi.org/10.1063/1.1147411
  15. De, S., Hong, J. and Bathe, K., 2003, "On the Method of Finite Spheres in Applications: Towards the use with ADINA and in a Surgical Simulator," Computational Mechanics, Vol. 31, No. 1, pp. 27-37. https://doi.org/10.1007/s00466-002-0390-3
  16. Cappella, B. and Dietler, G., 1999, Force-Distance Curves by Atomic Force Microscopy, Surface Science Reports, Vol. 34, No. 1-3, pp. 5-104.
  17. Waltman, R. J. and Guo, X.-C., 2012, "AFM Force-Distance Curves for Perfluoropolyether Boundary Lubricant Films as a Function of Molecular Polarity," Tribology Letters, Vol. 45, No. 2, pp. 275-289. https://doi.org/10.1007/s11249-011-9887-2
  18. Williams, J. A. and Le, H. R., 2006, "Tribology and MEMS," Journal of Physics D: Applied Physics, Vol. 39, pp. 201-204. https://doi.org/10.1088/0022-3727/39/12/R01
  19. Kim, D.E., Cha, K. H. and Sung, I. H., 2002, "Design of Surface Micro-Structures for Friction Control in Micro-Systems Applications," CIRP Annals, Vol. 51, No. 1, pp. 495-498. https://doi.org/10.1016/S0007-8506(07)61569-8
  20. Baumgart, P., Krajnovich, D. J., Nguyen, T. A. and Tam, A. C., 1995, "A New Laser Texturing Technique for High Performance Magnetic Disk Drives," IEEE Transactions on Magnetics,Vol. 31, pp. 2946-2951. https://doi.org/10.1109/20.490199
  21. Abgrall, P., Conedera, V., Camon, H., Gue, A. M. and Nguyen, N. T., 2007, "SU-8 as a Structural Material for Labs-on-Chips and Microelectromechanical Systems," Electrophoresis, Vol. 28, pp. 4539-4551. https://doi.org/10.1002/elps.200700333
  22. Foulds, I. G. and Parameswaran, M., 2006, "A Planar Self-Sacrificial Multilayer SU-8-Based MEMS Process Utilizing a UV-Blocking Layer for the Creation of Freely Moving Parts," Journal of Micromechanics and Microengineering, Vol. 16, pp. 2109-2115. https://doi.org/10.1088/0960-1317/16/10/026
  23. Tay, N. B., Minn, M. and Sinha, S. K., 2011, "Polymer Jet Printing of SU-8 Micro-Dot Patterns on Si Surface: Optimization of Tribological Properties," Tribology Letters, Vol. 42, pp. 215-222. https://doi.org/10.1007/s11249-011-9765-y
  24. Tay, N. B., Minn, M. and Sinha, S. K., 2011, "A Tribological Study of SU-8 Micro-Dot Patterns Printed on Si Surface in a Flat-on-Flat Reciprocating Sliding Test," Tribology Letters, Vol. 44, pp. 167-176. https://doi.org/10.1007/s11249-011-9835-1
  25. Jiguet, S., Judelewicz, M., Mischler, S., Hofmann, H., Bertsch, A. and Renaud, P., 2006, "SU-8 Nanocomposite Coatings with Improved Tribological Performance for MEMS," Surface & Coatings Technology, Vol. 201, No. 6, pp. 2289-2295. https://doi.org/10.1016/j.surfcoat.2006.03.041