Low‐CTE photosensitive polyimide based on semialicyclic poly(amic acid) and photobase generator

Abstract

A negative-type photosensitive polyimide (PSPI) based on semialicyclic poly(amic acid) (PAA), poly(trans-1,4cyclohexylenediphenylene amic acid), and {[(4,5-dimethoxy-2nitrobenzyl)oxy]carbonyl} 2,6-dimethylpiperidine (DNCDP) as a photobase generator has been developed as a next-generation buffer coat material. The semialicyclic PAA was synthesized from 3,3 0 ,4,4 0 -biphenyltetracarboxylic dianhydride and trans-1,4-cyclohexyldiamine in the presence of acetic acid, and the PAA polymerization solution was directly used for PSPI formulation. This PSPI, consisting of PAA (80 wt %) and DNCDP (20 wt %), showed high sensitivity of 70 mJ/cm 2 and high contrast of 10.3, when it was exposed to a 365-nm line (i-line), postexposure baked at 190 C for 5 min, and developed with 2.38 wt % tetramethylammonium hydroxide aqueous solution containing 20 wt % isopropanol at 25 C. A clear negative image of 6-lm line and space pattern was printed on a film, which was exposed to 500 mJ/cm 2 of i-line by a contact printing mode and fully converted to poly(trans-1,4-cyclohexylenebiphenylene imide) pattern upon heating at 250 C for 1 h. The PSPI film had a low coefficient of thermal expansion of 16 ppm/K compared to typical PIs, such as prepared from 3,3 0 ,4,4 0 -biphenyltetracarboxylic dianhydride and 4,4 0 -oxydianiline.

Origin of dielectric response and conductivity of some alicyclic polyimides

“…These characteristics come from their low molecular density and polarity, low probability of undergoing intermolecular CT, and even lower probability of main chain scission, because of the presence of multibonds which increase main chain rigidity [16]. According to this literature review, one of the methods for designing of soluble and transparent polyimide is the incorporation of alicyclic groups and flexible linkages for the control of chain flexibility and segmental mobility, so that to reduce the intermolecular interactions, by disrupting co‐planarity and conjugation, reducing symmetry, separating electronic segment [17] inhibiting packing, and reducing the intensity of the yellow color [18].…”

Formation of Fine Pattern by Reaction Development Patterning Using Photo-Base Generator and Acidic Developers

“…Photosensitive polymers used in the harsh environment such as buffer coat layers [1], interlayer dielectric films [2] and optical waveguides [3] require good thermal and mechanical properties like engineering plastics. Conventional photosensitive polymers for such applications vary their solubility in developer by polymer reaction under photoirradiation.…”

Semi-Alicyclic Polyimides: Insights into Optical Properties and Morphology Patterning Approaches for Advanced Technologies

“…incorporation of alicyclic dianhydride: Epiclon (98% purity, Merk) to increase the solubility (due to the less polymer-polymer interactions) and thermal stability (due to the multibond and rigidity of the alicyclic structure) [27]; -incorporation of flexible linkages (-O-, -CH2-, -(CH2)2-) to introduce "kinks" to the polymer chain which decrease the rigidity, inhibit the packing, reduce the intermolecular interactions, weaken the intensity of the yellow color, and increase the solubility [28].…”