Fundamental Properties of Organic Low-k Dielectrics Usable in the Cu Damascene Process

The material parameters for organic low-k dielectrics usable in the damascene process were studied using two different types of polymers with similar low dielectric constants, namely, the PQ-600 thermoplastic polymer and the SiLK thermosetting polymer. The resistibility of these polymers in the damascene process was investigated through hard-mask (SiO2) deposition, etching and chemical mechanical polishing (CMP) processes using scanning probe microscopy (SPM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and a modified edge liftoff test (m-ELT). For the PQ-600 film, damage was observed in the deposition process and dissolution of the film occurred during chemical cleaning in the etching process. On the other hand, the SiLK film was combinable with the Cu damascene process and usable as an interlayer dielectric (ILD) in one-level Cu wiring. A high glass transition temperature (Tg) and chemical resistance resulting from the thermosetting structure are considered to be the essential properties required for the desired organic low-k dielectrics. In eddition, the electrical properies of the SiLK film were investigated using a one-level test element group (TEG) formed through a single Cu damascene process. The dielectric constant of the SiLK film extracted from the Cu damascene TEG compared with that of bulk SiO2 was reduced by 24%. The leakage current measured at 1 MV/cm between the adjoining Cu lines at the TEG pattern with a hard mask was 9.7×10-10 A/cm2, and dielectric breakdown occurred at 5.5 MV/cm.