Oxidation resistant dilute copper (boron) alloy, films prepared by DC-magnetron cosputtering

To enhance the corrosion resistance and reliability of the proposed copper interconnections in silicon integrated circuits, alloying with small amounts thermodynamically favorable elements has been pursued In the present investigation dilute copper (boron) alloy thin films (in boron concentration range of 0-4 at % in copper) were deposited by DC magnetron co-sputtering using a high purity copper and Cu-4 at % B targets. Films were then annealed in Ar-3% H-2, pure Ar,vacuum and air ambients in the temperature range of 200-500 degrees C. Sheet resistance, Rutherford backscattering, x-ray diffraction measurements were made to characterize the films. The residual resistivity of the as-deposited ahoy films was found to be 5.3 mu Omega-cm/at %. To obtain sufficiently low working resistivity, an alloy cement below 0.5 at % is suggested for application as a potential metallization material. The addition of boron, which is the common dopant in Si, to the copper films offers considerable oxidation protection The resulting oxidation rates are considerably lower than that for pure copper films. All this will be presented and discussed.