Thermal annealing of buried Al barrier layers to passivate the surface of copper films

Abstract
Annealed metallic bilayers consisting of Cu/Al/SiO2 are studied from the perspective of providing both surface passivation and diffusion barrier/adhesion promoter function for advanced copper based metallization. Upon annealing this bilayer film at 400 °C or higher, enough Al dissolves into the Cu to provide substantial oxidation resistance at the copper surface. The resistivity of these annealed films is approximately 4.5 μΩ cm. Compared to films of pure copper, these bilayer films are much more adherent to SiO2 and much more stable (both morphology and diffusion) on SiO2.

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