Interconnect Process Technology Using Perfluorocyclobutane (PFCB)

A novel polymer dielectric derived from tris-perfluorocyclobutene(PFCB) monomer has been investigated as a thin film dielectric. The dielectric constant of this material has been measured at 2.35. PFCB is applied from a hydrocarbon solvated solution using conventional spin coating equipment onto the substrate and produces highly uniform films after curing at 300 °C. This paper describes the processing and properties of films derived from PFCB, and examines the interactions between the polymer and metals at the interfaces. In particular, the interfaces formed by the deposition of Cr or Co onto PFCB are unchanged after 30 minutes at 390 °C. The interface formed by the application of the polymer onto Ta is similarly unaffected by high temperatures. The interfaces formed by the deposition of Ta or Ti onto the polymer surface did not remain intact, with substantial quantities of the metals permeating the polymer after high temperature exposures. This behavior is discussed relative to the thermo-physical properties of the metal fluorides.