a1 Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8520
Part I [D.J. Morris and R.F. Cook, J. Mater. Res. 23, 2429 (2008)] of this two-part work explored the instrumented indentation and fracture phenomena of compliant, low-dielectric constant (low-κ) films on silicon substrates. The effect of film thickness and probe acuity on the fracture response, as well as the apparent connection of this response to the perceived elastic modulus, were demonstrated. These results motivate the creation of a fracture model that incorporates all of these variables here in Part II. Indentation wedging is identified as the mechanism that drives radial fracture, and a correction is introduced that adjusts the wedging strength of the probe for the attenuating influence of the relatively stiff substrate. An estimate of the film fracture toughness can be made if there is an independent measurement of the film stress; if not, a critical film thickness for channel-cracking under the influence of film stress may be estimated.
(Received February 5 2008)
(Accepted May 16 2008)