CHEMICAL-VAPOR-DEPOSITION OF SILVER

The complexes [Ag(hfac)(PRs)] and [Ag(fod)(PR(3))] (hfac 1,1,1,5,5,5-hexafluoropentanedionato; fod = 2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octanedionato; R = CH3, C2H5) have been prepared by displacement of olefin from [Ag(hfac)(alkene)] compounds by the phosphines PR(3) or by direct reaction of silver(I) oxide, PR(3) and the respective beta-diketone. The complex [Ag(fod)(PEt(3))] melts at 26-28 degrees C and so can act as a liquid CVD precursor above this temperature. Unlike several other silver(I) hfac complexes, these phosphine derivatives are monomeric, as shown by an X-ray structure determination of [Ag(hfac)(PMe(3))], and they are volatile. Each complex has been shown to be an excellent precursor for the thermal chemical vapor deposition of silver films at temperatures of 250-350 degrees C. The resulting films are shown by XPS and EDX analysis to contain silver with some carbon impurity. Pure silver films are formed by CVD from [Ag(fod)(PR(3))] at 300 degrees C by using moist hydrogen as carrier gas. The SEM image of a film grown from [Ag(hfac)(PMe(3))] at 350 degrees C shows a rough surface with average grain size of 1-2 mu m, but smoother films with grain sizes of 0.1-0.25 mu m are formed by CVD from [Ag(fod)(PR(3))] under H-2.