Abstract
A technique was developed to obtain the subcritical crack growth velocity in a 4-point bending sample by analyzing the load-displacement curve. This was based on the observation that the compliance of a beam increases as the crack grows. Beam theory was used to analyze the general configuration where two cracks propagated in the opposite directions. A simple equation relating the crack velocity to the load and displacement was established, taking advantage of the fact that the compliance was linearly proportional to the crack lengths; thus the absolute crack length was not important. Two methods of obtaining crack velocity as a function of load were demonstrated. First, by analyzing a load-displacement curve, a corresponding velocity curve was obtained. Second, by changing the displacement rate and measuring the corresponding plateau load, a velocity value was calculated for each plateau load. While the former was capable of obtaining the dependence of crack velocity versus load from a single test, the latter was found to be simpler and more consistent. Applications were made to a CVD SiO2 system. In both cases of crack propagation either inside the SiO2 layer or along its interface with a TiN layer, the crack growth velocity changed with the stress intensity at the crack tip exponentially. As a result, a small crack will grow larger under essentially any tensile stresses typically existing in devices, provided that chemical agents facilitating stress corrosion mechanisms are also present.
Similar content being viewed by others
References
T. A. Michalske and B. C. Bunker, J. Am. Ceram. Soc. 76, 2613 (1993).
Q. Ma, H. Fujimoto, P. Flinn, V. Jain, F. Adibi-Rizi, F. Moghadam, and R. H. Dauskardt, in Materials Reliability in Microelectronics V, edited by A. S. Oates, W. F. Filter, R. Rosenberg, A. L. Greer, and K. Gadepally (Mater. Res. Soc. Symp. Proc. 391, Pittsburgh, PA, 1995), pp. 91–96.
P. G. Charalambides, H. C. Cao, J. Lund, and A. G. Evans, Mechanics of Materials 8, 269 (1990).
P. G. Charalambides, J. Lund, A. G. Evans, and R. M. McMeeking, J. Appl. Mech. 111, 77 (1989).
M. R. Turner, B. J. Dalgleish, M. Y. He, and A. G. Evans, Acta Metall. Mater. 43, 3459 (1995).
R. M. Cannon, B. J. Dalgleish, R. H. Dauskardt, T. S. Oh, and R. O. Ritchie, Acta Metall. Mater. 39, 2145 (1991).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Ma, Q. A four-point bending technique for studying subcritical crack growth in thin films and at interfaces. Journal of Materials Research 12, 840–845 (1997). https://doi.org/10.1557/JMR.1997.0122
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1557/JMR.1997.0122