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

Abstract

Abstract 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°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 (i‐line) and developed with an aqueous alkaline developer (aqueous tetramethylammonium hydroxide and iso ‐propanol, TMAHaq/ i PrOH). A clear negative image with 8‐µm features was produced by contact‐printing and converted into the PI‐2 pattern upon heating at 200°C, confirming the results obtained by Scanning electro microscopy (SEM) imaging and infrared spectroscopy. Copyright © 2006 John Wiley & Sons, Ltd.