Direct patterning of poly(amic acid) and low-temperature imidization using a photo-base generator

A negative-type photosensitive polyimide (PSPI) based on poly(amic acid) (PAA) and a photo-base generator (PBG) has been developed. PAA-2, the polyimide precursor, was prepared from oxydianiline (ODA) and 4,4'-biphthalic dianhydride (BPDA) in N,N-dimethylacetamide (DMAc), and used directly for lithographic evaluations. Since a photo-generated base, dimethyl piperidine (DMP), was effective for the imidization of PAA-2 to the corresponding PI-2 at temperatures up to 200 degrees C, the dissolution behavior of this system was studied in relation to PBG content, bake-temperature dependence, and composition of the aqueous alkaline developer. The PSPI using 85 wt% PAA-2 and 15 wt% synthesized PBG showed a sensitivity of 220 Mj/cm(2) and contrast of 11.7 when exposed to 365-nm light G-line) and developed with an aqueous alkaline developer (aqueous tetramethylammonium hydroxide and iso-propanol, TMAHaq/iPrOH). A clear negative image with 8-mu m features was produced by contact-printing and converted into the PI-2 pattern upon heating at 200 degrees C, confirming the results obtained by Scanning electro microscopy (SEM) imaging and infrared spectroscopy. Copyright (c) 2006 John Wiley & Sons, Ltd.