Abstract
A technique to measure the yield strength of thin films has been developed which combines experimental observations of deflection and plastic deformation with finite element predictions of stress. This technique relies on integrated circuit technology to build bridge and cross beam test structures with a range of dimensions. Each structure is deflected in increments of 1 μm until the structure no longer elastically recovers upon release. In tandem with experimentally verified numerical predictions of force and stress, the yield strength of the thin film can be bounded between the highest elastic stress result and the lowest plastic stress result. For our test material of copper, this method provides a yield strength between 2.80 and 3.09 GPa, a value significantly larger than that for bulk copper, but consistent with thin film theory.
Similar content being viewed by others
References
Gan, L. andBen-Nissan, B., “The effects of mechanical properties of thin films on nano-indentation data: Finite element analysis,”Comp. Mat. Sci.,8,273 (1997).
Greek, S. andEricson, F., “Young's modulus, yield strength and fracture strength of microelemints determined by tensile testing,”Mat. Res. Soc. Symp. Proc.,518,51 (1998).
Koehler, J.S., “Attempt to Design a Strong Solid,”Phys. Rev. B,2-2,547 (1970).
Lehoczky, S.L., “Strength enhancement in thin-layered Al−Cu laminates,”J. Appl. Phys.,49–11,5479 (1978).
Li, L., Huang, B., Qiao, Q., Gordon, M.H., Schmidt, W.F., andAng, S.S., “A technique for determining the mechanical behavior and electrical performance of thin films,”MEMS, Vol1, ASME IMECE Proceedings 545 (1999).
Merz, M.D. andDahlgren, S.D., “Tensile Strength and Work Hardening of Ultrafine-Grained High-Purity Copper,”J. Appl. Phys.,46–8,3235 (1975).
Obermeier, E., “Mechanical and thermophysical properties of thin films for MEMS: Techniques and devices,”Mat. Res. Soc. Symp. Pro.,444,39 (1997).
Read, D.T., “Silicon-framed tensile specimens: techniques and results,”Mat. Res. Soc. Symp. Proc.,518,167 (1998).
Read, D.T. andDally, J.W., “Mechanical Behavior of Aluminum and Copper Thin Films,”Mechanics and Materials for Electronic Packaging,2,41 (1994).
Rudd, J.A., Josell, D., andSpaepen, F., “A New Method for Tensile Testing of Thin Films,”J. Mater. Res.,8–1,112 (1993).
Son, D., Lee, Y., Ahn, J., andKwon, D., “Evaluation of Young's modulus and yield strength of thin film structural material using nanoindentation technique,”Mat. Res. Soc. Symp. Proc.,562,201 (1999).
Strojny, A., **a, X., Tsou, A., andGerberich, W.W., “Techniques and considerations for nanoindentation measurements of polymer thin film constitutive properties,”J. Adhesion Sci. Technol.,12–12,1299 (1998).
Wasa, K. andHayakawa, S., Handbook of Sputter Deposition Technology, Noyes Publications, Park Ridge, New Jersey (1992).
Weihs, T.P., Hong, S., Bravman, J.C., andNix, W.D., “Mechanical deflection of cantilever microbeams: A new technique for testing the mechanical properties of thin films,”J. Mater. Res.,3–5,931 (1988).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Gordon, M.H., Schmidt, W.F., Qiao, Q. et al. A simple technique for determining yield strength of thin films. Experimental Mechanics 42, 232–236 (2002). https://doi.org/10.1007/BF02410977
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF02410977