Fracture toughness, adhesion and mechanical properties of low-K dielectric thin films measured by nanoindentation

The semiconductor industry is gradually moving from well-established Al/SiO2 technology to the new Cu/low-k interconnects, which brings a challenge in terms of poor thermal and/or mechanical properties of low-K dielectric films. Extensive nanoindentation studies have been undertaken on organo-silicate glass (OSG) low-K films to explore their mechanical and fracture properties. A cube corner indentation method was used to measure the fracture toughness of the OSG films, which ranges from 0.01 to 0.05 MPa(.)m(1/2). Film fracture was also observed during superlayer indentation adhesion testing. Interfacial cracks kinked into the film itself, indicating competition between adhesive and cohesive failure mechanisms. Given that the crack propagates through the low-K, critical stress intensities on the order of 0.05 MPa(.)m(1/2) are estimated. This is also consistent with the upper bound calculations of 0.06 MPa(.)m(1/2), based on spontaneous film fracture at a critical film thickness of 3 mum due to tensile residual film stress relief. (C) 2003 Elsevier Science B.V. All rights reserved.