Deposition of Cu films from supercritical fluids using Cu(I) ?-diketonate precursors
Cu films were deposited onto planar and etched silicon substrates by the hydrogen-assisted reduction of a series of copper(I)(1,1,1,5,5,5-hexafluoro-2,4-acetylacetonate)L compounds [Cu(I)(hfac)L] where L is (2-butyne), (1,5-cyclooctadiene), (vinyltrimethylsilane) or (2-methyl-1-hexene-3-yne) in supercritical solvents using a cold wall, high pressure reactor. At substrate temperatures of 225C and a pressure of 200 bar, H2 reduction of Cu(I)(hfac)(2-butyne) in CO2 yielded high purity films with exceptional step coverage in features as narrow as 100 nm with an aspect ratio of eight. Planar films deposited by H2 reduction of each of the precursors in supercritical CO2 and Cu(I)(hfac)(2-butyne) in supercritical C2F6 exhibited little carbon or oxygen contamination. Attempts to deposit high purity Cu films by the thermal disproportionation of the Cu(I)(hfac)L precursors in supercritical CO2 in the absence of H2 at 225C were unsuccessful and yielded highly oxidized Cu films in each case. Thermal disproportionation of Cu(I)(hfac)(2-butyne) in supercritical C2F6 also yielded poor quality films, although oxygen contamination was less severe than in CO2.
supercritical fluids copper metallization chemical fluid deposition