Identification of Materials in Integrated Circuit Interconnects Using X-Ray Absorption Near Edge Spectroscopy
Zachary H. Levine, Bruce D. Ravel
Most integrated circuit interconnects are principally composed of a few metals, including aluminum alloyed with copper, tungsten, titanium, A13 Ti, and A12Cu, 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 LI, LII, and LIII edges, and the Ti LII, and LIII, and compare to experiment when possible. The signal -to- noise ratio required to distinguish among the aluminum compounds from the A1 K edge spectra is shown to be about one order of magnitude higher than that needed to detect elemental aluminum.