Buffer layer structure for measuring the elastic properties of brittle thin films by nanoindentation with application on nanoporous low-k dielectrics

Abstract

Nanoindentation technique is widely employed in the semiconductor industry to characterize the mechanical properties of thin film materials. Low dielectric constant (low-k) materials, commonly used as interlayer dielectrics of the on-chip interconnects, are structurally fragile and prone to fracture and delamination when subject to concentrated stresses during nanoindentation. Characterization of their mechanical properties by nanoindentation technique is complicated not only by the well-known substrate effect arising from the elastic mismatch between the low-k film and the substrate but also by the potential material damages. This paper demonstrates the use of a buffer layer structure augmented with a novel analysis procedure to overcome these challenges, allowing us to extend the nanoindentation technique to even thinner films and improve measurement accuracy. The demonstrated approach is not restricted to low-k dielectrics, but is expected to be generically useful for other material systems given proper choice of the buffer layer.