Imaging material components of an integrated circuit interconnect

Two regions of interest on a copper/tungsten integrated circuit interconnect were imaged using two techniques: (a) the absorption spectrum was measured at 15 x-ray energies between 1687 and 1897 eV, and (b) the x-ray fluorescence spectrum was recorded with incident photon energies of 1822, 1797, and 1722 eV. The energies were chosen to optionally excite tungsten and tantalum above their M-5 edges yet stay below the silicon K edge. Four materials in the circuits, tantalum, tungsten, silica, and copper were mapped using both techniques. The two sets of images agree in their main features, but differ for finer features. (C) 2004 American Institute of Physics.