Reactive deposition of conformal palladium films from supercritical carbon dioxide solution

High-purity palladium films were deposited onto Si wafers and polyimide by the reduction of organopalladium compounds in supercritical CO2 solution using a batch process at temperatures between 40 and 80 degrees C and pressures between 100 and 140 bar. Hydrogenolysis of pi-2-methylallyl(cyclopentadienyl)palladium(II) in CO2 at 60 degrees C is complete in less than 2 min, yielding continuous, 100-200 nm thick, reflective films and the benign, fully hydrogenated ligand decomposition products, cyclopentane and isobutane. Analysis of the deposited films by X-ray photoelectron spectroscopy indicates that they are free of ligand-derived contamination. Deposition of thin films on patterned silicon wafers having feature sizes as small as 0.1 mu m wide by 1.0 mu m deep is strictly conformal, including uniform coverage of the lower corners and bottoms of the trenches. Deposition by hydrogenolysis of palladium(II) hexafluoroacetylacetonate also yields high-quality films while deposition using pi-allyl-(2,4-pentanedionato)palladium(II) is sensitive to fluid-phase decomposition of the precursor and yields nonuniform deposits.