Identification of materials in integrated circuit interconnects using x-ray absorption near-edge spectroscopy

Most integrated circuit interconnects are principally composed of a few metals, including aluminum alloyed with copper, tungsten, titanium, Al3Ti, and Al2Cu, in a silica matrix. Integrated circuit interconnects have recently been proposed as a candidate system for visualization by computerized microtomography using absorption in the soft x-ray region. In this work, we demonstrate the feasibility of materials identification using volume-resolved x-ray absorption near edge spectra (XANES) obtained by tomographic reconstruction. A similar experiment could be performed with an energy-resolved high-voltage transmission electron microscope. We calculate the XANES for interconnect materials near the Al K edge, the Cu L-I, L-II, and L-III edges, and the Ti L-II and L-III, and compare them to experiment when possible. The signal-to-noise ratio required to distinguish among the aluminum compounds from their Al K edge spectra is shown to be about one order of magnitude higher than that needed to detect elemental aluminum. [S00218979(99)04701-5].