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Silicon Strength Testing for Mesoscale Structural Applications

Published online by Cambridge University Press:  10 February 2011

Kuo-Shen Chen ,
Arturo A. Ayon  and
S. Mark Spearing
Kuo-Shen Chen
Affiliation:
Massachusetts Institute of Technology Cambridge, MA 02139 U.S.A.
Arturo A. Ayon
Affiliation:
Massachusetts Institute of Technology Cambridge, MA 02139 U.S.A.
S. Mark Spearing
Affiliation:
Massachusetts Institute of Technology Cambridge, MA 02139 U.S.A.
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Abstract

The development of power MEMS, such as the Microengine being developed at MIT, requires highly stressed structures to achieve high power densities. Material strength is, therefore, a critical issue for the design of such devices. Due to the stochastic nature of the strength of brittle materials, the length scales of the test specimens should be close to those of the structure in order to avoid excessive extrapolation of the test data. In this paper, strength characterization and supporting analysis of mesoscale biaxial flexure and radiused hub flexure single crystal silicon specimens are presented. The Weibull reference strength' of planar biaxial flexure specimens was found to lie in the range 1.2 to 4.6 GPa, depending on the surface quality. The local strength at stress concentrations was obtained by testing radiused hub flexure specimens. For the case of deep reactive ion etched (DRIE) specimens, the strength at fillet radii was found to be significantly lower than that measured from planar biaxial flexure specimens due to the inferior surface quality in such regions. It was found that strength could be significantly increased by the introduction of an additional isotropic etch after the DRIE step. The test results reported herein have important implications for the development of highly stressed microfabricated structures. The sensitivity of the mechanical strength to surface processing and etching techniques must be accounted for in the design cycle, particular with regard to the selection of the appropriate fabrication route. Furthermore, in the design of highly stressed MEMS devices, it is important to account for the stochastic nature of the material strength.

Keywords

strength testsiliconMEMSfractureetching
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 518: Symposium N – Microelectromechanical Structures for Materials Research , 1998 , 123
Copyright
Copyright © Materials Research Society 1998

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References

[1] , Epstein et al. , “Micro-Heat Engines, Gas Turbines, and Rocket Engines- The MIT Microengine Project-” 28th AIAA Fluid Dynamics Conference and 4th AIAA shear flow conference, June 1997.Google Scholar
[2] Ayon, A. A., Lin, C.C., and Schmidt, M.A.: “Characterization of an Inductivity Coupled Plasma Etcher,” Submitted to Journal of Vacuum Science and Technology.Google Scholar
[3] Spearing, S.M. and Chen, K. S., “Micro-Gas Turbine Engine Materials and Structures,” Ceramic Engineering and Science Proceedings, Vol. 18, no.4, pp. 11–18, August 1997.Google Scholar
[4] Timoshenko, S. and Goodier, J., ”Theory of Elasticity, 3rd edition”, McGraw-Hill, New York, 1970.Google Scholar
[5] Weibull, Weibull W., “A Statistical Theory of the Strength of Materials,” Ing. Vetenskaps Akad. Handl., No. 151, pp. 45, 1939.Google Scholar
[6] Wilson, C. J. and Beck, P. A., “Fracture Testing of Bulk Silicon Microcantilever Beams Subject to a Side Load,” J. Microelectromechanical Systems, 5(3), pp. 142–150, 1996.Google Scholar
[7] Ericson, F. and Schweitz, J.,”Micromechanical Fracture Strength of Silicon,” J. Appl. Phys., Vol. 68, no.11, pp. 5840–5844, 1990 Google Scholar
[8] Hu, S. M., “Critical Stress in Silicon Brittle Fracture, and Effect of Ion Implantation and Other Surface Treatments”, J. of Applied Physics, 53(5), pp. 3576–3580, 1982.Google Scholar
[9] ABAQUS ABAQUS/Standard 5.5 Users Manual, Hibbit, Karlsson & Sorensen, Inc., Pawtucket, RI, 1996.Google Scholar
[10] Brantley, W. A., “Calculated Elastic Constants for Stress Problems Associated with Semiconductor Devices,” J. Appl. Phys., Vol. 44, pp. 534–535, 1973.Google Scholar
[11] Chao, L.Y. and Shetty, D. K., “Time-Dependent Strength Degradation and Reliability of an Alumina Ceramic Subject to Biaxial Flexure,” Life Prediction Methodologies and Data for Ceramic Materials, ASTM STP 1201, Brinkman, C. R. and Duffy, S. F. eds., American Socity for Testing and Materials, Philadelphia, PA, 1993.Google Scholar