Integration of fluorinated amorphous carbon as low-dielectric constant insulator: Effects of heating and deposition of tantalum nitride

We investigated the effects of heating and deposition of tantalum nitride o n fluorinated amorphous carbon (a-C:F) thin films, deposited by a cosputter ing process using polytetrafluoroethylene and graphite targets. Carbon is o bserved by x-ray photoelectron spectroscopy (XPS) in four distinct chemical states, C-C, C-F, C-F-2, C-F-3, and the relative intensity of C-F-x to C-C increases with increasing fluorine content and decreasing deposition tempe rature. Heat treatment of this material in vacuum up to 450 degrees C resul ts in reduction of the intensities of C-F-x relative to that of C-C. The pr edominant desorbing masses detected by a mass spectrometer were consistent with CF3, CF, C3F5, CF2, COF, COF2, and Ar. The temperature at which desorb ing CFx species are detected increases with decreasing fluorine concentrati on and increasing deposition temperature. This improved thermal stability i s attributed to the decreasing amount of volatile, small molecular weight C Fx species and more C-C crosslinking in the less fluorinated film. To integ rate with copper metallization, the interface between a-C:F and tantalum ni tride was studied by depositing tantalum nitride on a a-C:F films and monit oring the interfacial chemical reactions in situ using XPS. Substantial def luorination was observed upon deposition of tantalum nitride. This leads to the formation of tantalum fluoride, whose relatively high vapor pressure a nd susceptibility to hydrolysis could lead to delamination. (C) 1999 Americ an Vacuum Society. [S0734-2101(99)06505-7].