DEPOSITION OF COPPER-FILMS ON SILICON SUBSTRATES - FILM PURITY AND SILICIDE FORMATION

Deposition of copper films on silicon substrates by the radio-frequency plasma reduction of spin-coated copper formate films in hydrogen and oxygen plasma discharges has been investigated further. The atomic compositions of these films, determined by Auger electron and x-ray photoelectron spectroscopy, were found to be a strong function of the processing conditions, especially power density and temperature. Rutherford backscattering studies (RBS) of the silicon-copper interface revealed the formation of copper silicide at deposition temperatures that are nominally as low as 40-degrees-C. The silicide formation was further investigated by depositing pure copper films on silicon substrates by thermal evaporation. The Cu/Si interface was analyzed before and after in situ annealing at 300-degrees-C and 10(-8) Torr and compared with the results for the plasma deposited films. RBS data show that diamondlike carbon films are excellent diffusion barriers between Si and Cu.