Deposition of Cu–Ag Alloy Film by Supercritical Fluid Deposition

Abstract

Cu–Ag alloy films for microelectronics interconnects were deposited by H2 reduction of bis(2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II) [Cu(tmhd)2] and (1,5-cyclooctadiene) (hexafluoroacetylacetonato)silver(I) [Ag(hfac)(COD)] in supercritical carbon dioxide (scCO2). By varying Ag precursor concentration from 0.001 to 0.003 mol %, while keeping Cu precursor concentration constant, the maximum Ag content in the film can be adjusted from 1.2 to 7.8 at. %. Silver in the films was concentrated near the substrate, because Ag deposition could be initiated first during the deposition process. X-ray diffraction (XRD) analysis showed that a strong Cu(111) texture was formed for all the deposited films including pure Cu film. It was also found that Ag alloying by supercritical fluid deposition (SCFD) would not deteriorate surface quality of Cu film. The electrical resistivity of Cu–Ag film was determined to be between 3.7 and 5.0 µΩ·cm.