Synthesis and characterization of poly(acrylate amic acid) and its application as negative-tone photosensitive polyimides

Abstract

The dianhydride monomer 3,3′,4,4′ - benzophenone tetracarboxylic acid dianhydride and two diamine monomers, 4,4′ - diamino - 3,3′ -biphenyldiol (HAB) and 2,4 - diaminophenol dihydrochloride (DAP), were used to synthesize a series of poly(hydroxyl amicacid). Further functionalization by grafting acrylate groups yields the correspondingpoly(acrylate amic acid) that underwent a crosslinking reaction on exposure to UV-light and was used as a negativetone photosensitive polyimide (PSPI). The analysis of chemical composition and molecular weight of these poly(amic acid)s determined by nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared spectroscopy, and gel permeation chromatography revealed that the molecular weight of the poly(hydroxyl amic acid) increased with the molar content of HaB in the feedstock, because HAB exhib-ited higher polymerization reactivity than DAP. Moreover, the degree of grafting acrylate groups onto poly(hydroxyl amic acid) was determined by 1H-NMR spectroscopy. The photoresist was formulated by adding 2-benzyl-2-N,N-dime- thylamino-1(4-morpholinophenyl) butanone (IRG369) and isopropylthioxanthone as a photoinitiator, tetra (ethylene glycol) diacrylate as a crosslinker, and tribromomethyl phenyl sulfone as a photosensitizer. The PSPI precursor exhibited a photosensitivity of 200 mJ/cm2 and a contrast of 1.78. A pattern with a resolution of 10 μm was observed in an optical micrograph after thermal imidization at 300°C. © 2009 Wiley Periodicals, Inc.