Texture of Al thin films deposited by magnetron sputtering onto epitaxial W(001)

• Highly textured epitaxial metallizations will be required for the next generation of devices with the main driving force being a reduction in electromigration. Herein a model system of 190 nm of Al on a 140 nm layer of W grown on MgO less than 00l greater than substrates was studied. The W layer was less than 00l greater than oriented and rotated 45 degrees with respect to the MgO substrate to minimize the misfit; the remaining strain was accommodated by dislocations, evident in transmission electron microscopy images. From high-resolution x-ray diffraction (XRD) measurements, the out-of-plane lattice parameter was determined to be 3.175 Angstrom, and the in-plane parameter was 3.153 Angstrom, i.e., the W film sustained a strain resulting in a tetragonal distortion of the lattice. XRD pole figures showed that the Al had four fold symmetry and two dominant orientations, less than 016 greater than and less than 3 9 11 greater than, which were twinned with multiple placements on the epitaxial W layer. The driving force for the tilted less than 001 greater than and less than 011 greater than orientations of Al on W is due to strain minimization through lattice matching. These results show that less than 00l greater than Al deposited at ambient conditions onto W is difficult to achieve and implies that electromigration difficulties are inherent.

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