Oxidation Resistant Dilute Copper (Boron) Alloy Films Prepared by DC-Magnetron Cosputtering

Abstract

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% H2, pure Ar, vacuum, and air ambients in the temperature range of 200–500°C. Sheet resistance, Rutherford backscattering, x-ray diffraction measurements were made to characterize the films. The residual resistivity of the as-deposited alloy films was found to be 5.3 μΩ-cm/at %. To obtain sufficiently low working resistivity, an alloy content 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.