Fracture characterization of thin-films by dual tip indentation

The continuous process of miniaturization in the microelectronics industry requires the introduction of new, thinner interlayer dielectric (ILD) materials with poorer mechanical properties. As a consequence, new mechanical characterization techniques are needed in the industry to evaluate very thin films. This work presents a new fracture characterization technique for thin films, called "dual tip indentation" (DTI). The technique takes advantage of a particular geometry of the indentation tip to provoke shallow and controlled cracking on the targeted brittle thin film. The technique is applied to the fracture characterization of two different ILD with four thicknesses, ranging from 100 nm to 500 nm. Further fractographic analysis, along with finite element modeling, shows that it is possible to extract intrinsic fracture properties from the fracture load. The technique allows one to discriminate between the ILD and, for both materials, 100 nm films show lower strength. No effect of film thickness on strength is observed in the range between 200 and 500 nm. The results from DTI compare well with those previously obtained for the same materials from membrane testing, taking into account the differences in volume tested. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.