Photosensitive polynorbornene based dielectric. II. Sensitivity and spatial resolution

Abstract

Photodefinable poly(decylnorbornene-co-ep- oxidenorbornene) copolymer has been developed as a di- electric material for electronic packaging applications. The photodefinition properties of the polymer are affected by the copolymer composition, the concentration of photoactive compound and the process conditions. In particular, ultra- high contrast conditions were found to promote the fabrica- tion of vertical sidewall structures. For photodefined struc- tures, the vertical sidewalls were obtained at specific formu- lations and process conditions. Under different conditions, non-vertical features were observed. Rutherford backscat- tering analysis (RBS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were used to study the photodefinition properties. In this article, a mechanism based on the diffusion of photoactive compounds from the exposed area to the unexposed area is presented. The trans- port of photoactive compounds takes place through the free volume that results from solvent evaporation. The diffusion of the photoactive compounds to the surface of the polymer film results in a higher concentration of photogenerated acid at the surface. The movement of the photoactive compounds occurs in both the in-plane and through-plane directions. © 2004 Wiley Periodicals, Inc.