Novel Low-Dielectric Constant Photodefinable Polyimides for Low-Temperature Polymer Processing

Abstract

A novel hexafluoroisopropanol (HFA)-substituted aromatic polyimide is reported that is prepared by chemical imidization of a poly(amic-acid) precursor obtained by polymerization of an HFA-substituted diamine and 6FDA. The HFA substituted polyimide shows good solubility in common organic casting solvents and 0.26 N TMAH alkaline developer. The HFAcontaining side-group can be easily removed thermally at temperatures above 280 o C, which results in a dramatic decrease in the polyimide dielectric constant from 3.20 to 2.60 (at 1 MHz). A photosensitive composition based on 20 wt% THBP inhibitor loaded into the HFA-substituted polyimide is shown to produce good positive-tone imaging using I-line lithography. This strategy of incorporating thermally removable side-groups into polyimides to enhance solvent solubility and allow for solution processing while also permitting aqueous development enables production of low-k polymers that can be processed at significantly lower temperatures than conventional poly(amic acid) polymers and patterned using standard lithographic processing.