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The role of van der Waals forces in adhesion of micromachined surfaces

Nature Materials volume 4, pages 629–634 (2005)Cite this article

Abstract

Interfacial adhesion and friction are important factors in determining the performance and reliability of microelectro- mechanical systems. We demonstrate that the adhesion of micromachined surfaces is in a regime not considered by standard rough surface adhesion models. At small roughness values, our experiments and models show unambiguously that the adhesion is mainly due to van der Waals dispersion forces acting across extensive non-contacting areas and that it is related to 1/Dave2, where Dave is the average surface separation. These contributions must be considered because of the close proximity of the surfaces, which is a result of the planar deposition technology. At large roughness values, van der Waals forces at contacting asperities become the dominating contributor to the adhesion. In this regime our model calculations converge with standard models in which the real contact area determines the adhesion. We further suggest that topographic correlations between the upper and lower surfaces must be considered to understand adhesion completely.

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Figure 1: Cantilever fabrication process and nomenclature.
Figure 2: Interferograms of cantilever beams at an actuation voltage of Vpad = 50 V.
Figure 3: Experimental and FEM beam deflections for an actuation voltage of Vpad = 40 V.
Figure 4
Figure 5: The numerical surface-separation routine uses actual AFM images of the landing-pad and structural polysilicon layers to calculate the adhesion energy.
Figure 6: A histogram of the adhesion contributions versus pixel separation (2 nm bin size).

References

  1. Van Kessel, P. F., Hornbeck, L. J., Meier, R. E. & Douglass, M. R. MEMS-based projection display. Proc. IEEE 86, 1687–1704 (1998).

    Article  Google Scholar 

  2. Chau, K. H. L. & Sulouff, R. E. Technology for the high-volume manufacturing of integrated surface-micromachined accelerometer products. Microelectr. J. 29, 579–586 (1998).

    Article  Google Scholar 

  3. Yao, J. J. RF MEMS from a device perspective. J. Micromech. Microeng. 10, R9–R38 (2000).

    Article  CAS  Google Scholar 

  4. Eldada, L. Advances in telecom and datacom optical components. Opt. Eng. 40, 1165–1178 (2001).

    Article  Google Scholar 

  5. Maboudian, R. & Howe, R. T. Critical review: adhesion in surface micromechanical structures. J. Vac. Sci. Technol. B 15, 1–20 (1997).

    Article  CAS  Google Scholar 

  6. Maboudian, R. & Carraro, C. Surface chemistry and tribology of MEMS. Annu. Rev. Phys. Chem. 55, 35–54 (2004).

    Article  CAS  Google Scholar 

  7. Srinivasan, U., Houston, M. R., Howe, R. T. & Maboudian, R. Alkyltrichlorosilane-based self-assembled monolayer films for stiction reduction in silicon micromachines. J. Microelectromech. Syst. 7, 252–260 (1998).

    Article  CAS  Google Scholar 

  8. Kim, B. H., Chung, T. D., Oh, C. H. & Chun, K. A new organic modifier for anti-stiction. J. Microelectromech. Syst. 10, 33–40 (2001).

    Article  CAS  Google Scholar 

  9. Ashurst, W. R. et al. Alkene based monolayer films as anti-stiction coatings for polysilicon MEMS. Sensors Actuat. A 91, 239–248 (2001).

    Article  CAS  Google Scholar 

  10. London, F. The general theory of molecular forces. Trans. Faraday Soc. 33, 8–26 (1937).

    Article  CAS  Google Scholar 

  11. Israelachvili, J. & Tabor, D. The measurement of van der Waals dispersion forces in the range 1.5 to 130 nm. Proc. R. Soc. Lond. A 331, 19–38 (1972).

    Article  CAS  Google Scholar 

  12. Tabor, D. & Winterton, R. H. S. The direct measurement of normal and retarded van der Waals forces. Proc. R. Soc. Lond. A 312, 435–450 (1969).

    Article  CAS  Google Scholar 

  13. Casimir, H. B. G. & Polder, D. The influence of retardation on the London – van der Waals forces. Phys. Rev. 73, 360–372 (1948).

    Article  CAS  Google Scholar 

  14. Serry, F. M., Walliser, D. & Maclay, G. J. The role of the Casimir effect in the static deflection and stiction of membrane strips in microelectromechanical systems (MEMS). J. Appl. Phys. 84, 2501–2506 (1997).

    Article  Google Scholar 

  15. Anandarajah, A. & Chen, J. Single correction function for computing retarded van der Waals attraction. J. Colloid Interface Sci. 176, 293–300 (1995).

    Article  CAS  Google Scholar 

  16. Fuller, K. N. G. & Tabor, D. The effect of surface roughness on the adhesion of elastic solids. Proc. R. Soc. Lond. A 345, 327–342 (1975).

    Article  Google Scholar 

  17. Maugis, D. On the contact and adhesion of rough surfaces. J. Adhes. Sci. Technol. 10, 161–175 (1996).

    Article  CAS  Google Scholar 

  18. Buks, E. & Roukes, M. L. Stiction, adhesion energy, and the Casimir effect in micromechanical systems. Phys. Rev. B 63, 033402 (2001).

    Article  Google Scholar 

  19. Houston, M. R., Howe, R. T. & Maboudian, R. Effect of hydrogen termination on the work of adhesion between rough polycrystalline silicon surfaces. J. Appl. Phys. 81, 3474–3483 (1997).

    Article  CAS  Google Scholar 

  20. Komvopoulos, K. & Yan, W. A fractal analysis of stiction in microelectromechanical systems. J. Tribol. 119, 391–400 (1997).

    Article  CAS  Google Scholar 

  21. De Boer, M. P. & Michalske, T. A. Accurate method for determining adhesion of cantilever beams. J. Appl. Phys. 86, 817–827 (1999).

    Article  CAS  Google Scholar 

  22. Rogers, J. W., Mackin, T. J. & Phinney, L. M. A thermomechanical model for adhesion reduction of MEMS cantilevers. J. Microelectromech. Syst. 11, 512–520 (2002).

    Article  CAS  Google Scholar 

  23. Jones, E. E., Begley, M. R. & Murphy, K. D. Adhesion of micro-cantilevers subjected to mechanical point loading: modeling and experiments. J. Mech. Phys. Solids 51, 1601–1622 (2003).

    Article  Google Scholar 

  24. Sniegowski, J. J. & de Boer, M. P. IC-compatible polysilicon surface micromachining. Annu. Rev. Mater. Sci. 30, 299–333 (2000).

    Article  CAS  Google Scholar 

  25. Sze, S. M. (ed.) VLSI Technology (McGraw-Hill, New York, 1983).

  26. Knapp, J. A. & de Boer, M. P. Mechanics of microcantilever beams subject to combined electrostatic and adhesive forces. J. Microelectromech. Syst. 11, 754–764 (2002).

    Article  CAS  Google Scholar 

  27. De Boer, M. P., Knapp, J. A., Michalske, T. A., Srinivasan, U. & Maboudian, R. Adhesion hysteresis of silane coated microcantilevers. Acta Mater. 48, 4531–4541 (2000).

    Article  CAS  Google Scholar 

  28. Xiao, X. & Linmao, Q. Investigation of humidity-dependent capillary force. Langmuir 16, 8153–8158 (2000).

    Article  CAS  Google Scholar 

  29. He, M. et al. Critical phenomenon of water bridges in nanoasperity contacts. J. Chem. Phys. 114, 1355–1360 (2001).

    Article  CAS  Google Scholar 

  30. De Boer, M. P., Clews, P. J., Smith, B. K. & Michalske, T. A. Adhesion of polysilicon microbeams in controlled humidity ambients. Mater. Res. Soc. Symp. Proc. 518, 131–136 (1998).

    Article  CAS  Google Scholar 

  31. Hertz, H. The contact of elastic solids. J. Reine Angew. Math. 92, 156–171 (1881).

    Google Scholar 

  32. Israelachvili, J. Intermolecular and Surface Forces (Academic, New York, 1992).

    Google Scholar 

  33. Brzoska, J. B., Ben Azouz, I. & Rondelez, F. Silanization of solid substrates: a step toward reproducibility. Langmuir 10, 4367–4373 (1994).

    Article  CAS  Google Scholar 

  34. Johnson, K. L., Kendall, K. & Roberts, A. D. Surface energy and the contact of elastic solids. Proc. R. Soc. Lond. A 324, 301–313 (1971).

    Article  CAS  Google Scholar 

  35. Perutz, S., Wang, J., Kramer, E. J. & Ober, C. K. Synthesis and surface energy measurement of semi-fluorinated, low-energy surfaces. Macromolecules 31, 4272–4276 (1998).

    Article  CAS  Google Scholar 

  36. Jensen, B. D., de Boer, M. P., Masters, N. D., Bitsie, F. & LaVan, D. A. Interferometry of actuated microcantilevers to determine material properties and test structure nonidealities in MEMS. J. Microelectromech. Syst. 10, 336–346 (2001).

    Article  Google Scholar 

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Acknowledgements

Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the US Department of Energy’s National Nuclear Security Administration under contract DE AC04-94AL85000. The authors would like to thank A. Corwin for help in collecting experimental data and B. McKenzie for the SEM images.

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Authors and Affiliations

  1. Department of Mechanical Engineering, University of Colorado, Boulder, Colorado, 80309, USA

    Frank W. DelRio & Martin L. Dunn

  2. Radiation and Reliability Physics Department, Sandia National Laboratories, Albuquerque, New Mexico, 87185, USA

    Frank W. DelRio & Maarten P. de Boer

  3. Radiation-Solid Interactions Department, Sandia National Laboratories, Albuquerque, New Mexico, 87185, USA

    James A. Knapp

  4. Material Mechanics Department, Sandia National Laboratories, Albuquerque, New Mexico, 87185, USA

    E. David Reedy Jr

  5. Microelectronics Operations Department, Sandia National Laboratories, Albuquerque, New Mexico, 87185, USA

    Peggy J. Clews

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  1. Frank W. DelRio
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Correspondence to Maarten P. de Boer.

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DelRio, F., de Boer, M., Knapp, J. et al. The role of van der Waals forces in adhesion of micromachined surfaces. Nature Mater 4, 629–634 (2005). https://doi.org/10.1038/nmat1431

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