Copper Films Prepared by Metal Organic Chemical Vapor Deposition (MOCVD) Process Using Copper (Acetylacetonate) and Water Vapor as Reactants: The Impact of Water Vapor

ABSTRACTBy using the strong reductive potential of copper acetylacetone (Cu(acac)2) when Cu(acac)2) was thermally decomposed, copper metal films were prepared by metal organic chemical vapor deposition (MOCVD) process using sublimed Cu(acac)2 vapor and water vapor as reactants, at one atmosphere pressure. According to thermodynamic calculations, Cu films could be prepared by MOCVD process with a high ratio of partial pressures for water vapor and Cu(acac)2 vapor (PH2O/Pcu(acac)2>30) In this paper, the impacts of MOCVD processing parameters such as watervapor partial pressure, total carrier gas flow rate, and precursor partial pressure on film composition and microstructure were investigated. Deposition temperature is the primary processing parameter affecting film stoichiometry. In a specific deposition temperature window, from 370°C to 400°C, polycrystalline Cu films with Cu [111] preferential orientation were deposited. ER and XRD results indicated that films deposited at temperature lower than 350°C contain copper oxide phase with poor crystal structure. By comparing the values of X-ray Auger Electron Spectroscopy (XAES) and Auger parameter (αAu) from photoelectrons of Cu films and standards from reference compounds, die principle oxidation state of copper in these films was determined as Cu(0). The deposition results indicated that a water vapor partial pressure above 10 torr is necessary to produce Cu films. As indicated by SEM, Increasing the carrier gas flow rate, above 600 sccm, can reduce the average temperature profile in the thermal boundary layer above the substrate surface, retard the gas phase reaction rate, presumably eliminate the homogeneous nucleation, and deposit smooth Cu films.