Low-Temperature Deposition of Conformal Copper Films in Supercritical CO2 by Catalytic Hydrogen Reduction of Copper Hexafluoroacetylacetonate

Conformal copper films were deposited onto various copper diffusion barrier layers with catalytic hydrogen reduction of copper(II) hexafluoroacetylacetonate, Cu(hfa)2, in supercritical CO2. In the presence of 2-5 at. % of Pd(hfa)2 (relative to Cu(hfa)2), device quality copper films (resistivity 2.1 × 10-6 -cm) could be obtained at temperatures as low as 70 C. The amounts of Pd in the Cu films were found to be very low (~0.2 at. %) throughout the bulk of the Cu films. Adhesion of Cu films onto barrier layers was strong despite no Cu seed layer being used. The bottom-up supercritical fluid deposition mechanism allowed Cu films to fill up small features patterned on Si wafers