Facile formulation of alkaline-developable positive-type photosensitive polyimide based on fluorinated poly(amic acid), poly(amic acid), and fluorinated diazonaphthoquinone

An alkaline-developable, positive-type, and photosensitive polyimide (PSPI) based on fluorinated poly(amic acid) (FPAA), poly(amic acid) (PAA), and fluorinated diazonaphthoquinone (FDNQ-1) as a photoactive compound has been successfully developed. The solution of FPAA, PAA, and FDNQ-1 was spin-coated on a silicon wafer and prebaked. The two phase-separated layers, a thin top layer of FPAA containing FDNQ-1 and a thick bottom layer of PAA, were formed due to the high polarity difference between PAA and FPAA containing FDNQ-1. This phase separation was directly observed in an SEM image. The upper thin layer acted as a photosensitive layer, and a fine pattern was formed in the bottom layer. The PSPI containing PAA (85 wt%), FPAA (15 wt%), and FDNQ-1 (25 wt% to polymers) showed an excellent sensitivity of 60 mJ cm(-2) and a high contrast of 3.3 when it was exposed to 365 nm wavelength light (i-line) and developed with a 0.238 wt% tetramethylammonium hydroxide aqueous solution (TMAHaq) at 25 degrees C. A fine positive pattern having a 6 mm resolution on the 1.0 mm film was obtained by exposure to 100 mJ cm(-2) i-line in the contact-printed mode. The resulting polymer film was converted to the corresponding PI cured at 300 degrees C. This novel positive patterning PI system can be one of the candidates for the next generation microchip fabrication process which provides a facile formulation of PSPI.