Reaction paths and kinetics of aluminide formation in Al/epitaxial-W(001) model diffusion barrier systems
Single‐crystal bcc W(001) layers, 140 nm thick, were grown on MgO(001) substrates by ultrahigh‐vacuum (UHV) magnetron sputter deposition at Ts=600 °C. Al overlayers, 190 nm thick with strong (001) and (011) preferred orientation and an average grain size of 200 nm, were then deposited at Ts=100 °C without breaking vacuum. Changes in bilayer sheet resistance Rs were monitored continuously as a function of time ta and temperature Ta during UHV annealing. In addition, Rutherford backscattering spectroscopy, x‐ray diffraction, transmission electron microscopy (TEM), and scanning TEM, in which cross‐sectional specimens were analyzed by energy‐dispersive x‐ray analysis with a 1 nm resolution, were used to follow area‐averaged and local interfacial reaction paths as well as microstructural changes as a function of annealing conditions. The initial reaction products were discontinuous regions of monoclinic‐structure WAl4 which exhibit a crystallographic relationship with the underlying W layer. bcc WAl12 forms at...
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 〈00l〉 substrates was studied. The W layer was 〈00l〉 oriented and rotated 45° 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 A, and the in-plane parameter was 3.153 A, 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, 〈016〉 and 〈3 9 11〉, which were twinned with multiple placements on the epitaxial W layer. The driving force for the tilted 〈001〉 and 〈011〉 orientations of Al on W is due to strain minimization through ...
Thin film diffusion of platinum in gold
Abstract Several Au-based conductor metallization schemes involve a layer of Pt underneath the Au film. The present work was done in order to determine the diffusion of Pt in Au films using electrical resistivity measurements, X-ray diffraction and transmission electron microscope examination of the diffused gold layer. The samples consisted of approximately 5500 A of Au on about 2000 A Pt on oxidized silicon wafers. The metal films were electron-beam evaporated onto unheated substrates and then isothermally aged at various temperatures ranging from 325°C (12 days) to 600°C (8 h). In the range 0–10 at. %Pt, the resistivity of the alloyed Au film increases by approximately 0.9 micro ohms cm per. at %Pt. Beyond 10 at. %Pt, the resistivity increase is greater than that predicted by a linear composition dependence. The temperature dependence of the estimated diffusion constant D follows an Arrhenius relationship of the type D =6.6×10 −8 exp (−0.95/ kT ). At 350°C , D is over three orders of magnitude higher than that expected from bulk diffusion data. This fact, as well as a thermal activation energy of about 1 eV, indicates a grain boundary controlled diffusion in Au-Pt thin film couples.