Nanoscale elastic imaging and mechanical modulus measurements of aluminum/low-k dielectric interconnect structures

Shekhawat, G. S. and Briggs, G. Andrew D. and Kolosov, Oleg and Geer, R. E. (2001) Nanoscale elastic imaging and mechanical modulus measurements of aluminum/low-k dielectric interconnect structures. In: Characterization and metrology for ULSI Technology 2000, International Conference. American Institute of Physics, GAITHERSBURG, pp. 449-452. ISBN 156396967X

Abstract

One of the most difficult challenges in low-k integration in IC processing concerns the significant mismatch of mechanical properties between metals and most low-k dielectrics. Previously, it has not been possible to image on a nanometer length scale the local variation of mechanical properties near dielectric/liner and liner/metal interfaces. Such an ability would greatly facilitate thermal and bias-stress reliability analysis of single and multi-level low-k metallization structures by locating variations in local material modulus due to local compositional variations, stress concentration, etc... Pursuant to this, we report the development of a new technique to image such properties based on ultrasonic force microscopy (UFM). UFM utilizes an ultrasonic excitation vibration combined with conventional scanning atomic force microscopy (AEM) to probe elastic variations of a broad range of materials.