Integration issues for polymeric dielectrics in large area electronics [TFTs]

The issues concerning the integration of polymeric low-permittivity (low-k) dielectrics in amorphous Si (a-Si) thin-film transistor (TFT) arrays have been investigated. A photosensitive spin-on polymer, photo-benzocyclobutene (PBCB), has been studied for integration as interlevel dielectric between the transistor and pixel levels in TFT arrays. The dielectric films were characterized by permittivity, stress, and planarization measurements. The dielectric constant was found to be in the range of 2.5-3.5. The degree of planarization was > 90%, and the film stress was about 60 MPa. Process parameters have been optimized for integration in TFT arrays. Measurements on test structures showed low leakage current and good electrical contact at via interconnections.