Mechanistic Role of H2O and the Ligand in the Chemical Vapor Deposition of Cu, Cu2O, CuO, and Cu3N from Bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)copper(II)

Abstract

The mechanism of chemical vapor deposition of Cu, Cu2O, CuO, and Cu3N from Cu(hfacac)(2)(H2O) was studied by XRD, MS, FTIR, XPS, SIMS, and NMR techniques. The molecular structure of the precursor was established by a single-crystal X-ray diffraction experiment. Crystallographic data (-165 degrees C): triclinic space group P1, a = 9.402(3) Angstrom, b = 11.068(3) Angstrom, c = 7.958(2) Angstrom, alpha = 105.71(2)degrees, beta = 100.99(2)degrees, gamma = 76.27(2)degrees, V = 767.31 Angstrom(3), Z = 2, R = 0.0303, R(w) = 0.0312. In the presence of excess water in the process gas stream, a facile release of free Hhfacac ligand from the copper complex is activated by a proton transfer from coordinated water. Ligand-mediated reduction of the metal from CU2+ to Cu+ and from Cu+ to Cu-0 oxidation states occurs in the absence of an external reducing agent at temperatures of 280 and 400 degrees C, respectively. Evidence for this ligand-mediated reduction is seen in the presence of the two major ligand-oxidation products (CF3COOH and CF3C(OH)(2)CH(OH)(2)) in the effluent from the deposition reaction. A labeling experiment using (H2O)-O-18 proved that oxygen in copper oxide films deposited from Cu(hfacac)(2) onto insulating substrates is derived from water and not the hfacac ligand. As an example of benefits that can be derived from this mechanistic knowledge, we have also shown that replacing H2O with NH3 leads to the formation of Cu3N.