Photosensitive Poly(benzoxazole) via Poly(o-hydroxy azomethine) II. Environmentally Benign Process in Ethyl Lactate

Abstract

ABSTRACT:The synthesis and photosensitivity of poly(o-hydroxyazomethine) (PHAM) from isophthalaldehyde (IPA) and 4,4 0 -(hexafluoroisopropylidene)bis(o-aminophenol) (6FAP) in an environmentally friendly solvent, ethyl lactate (EL) was investigated. Polycondensation of IPA and 6FAP proceeded in EL, giving PHAM with a number average molecular weight more than ten thousands. The solution of PHAM in EL showed a good stability for hydrolysis. The photosensitive film cast from the solution of PHAM and 25 wt % 1-{1,1-bis[4-(2-diazo-1-(2H)-naphthalenone-5-sulfonyloxy)phenyl]methylethylgbenzene (S-DNQ) in EL showed a sensitivity (D 0 ) of 250 mJ/cm 2 and a contrast ( 0 ) of 2.5 with 436 nm light (g-line), respectively. A fine positive image featuring 10 mm line-and-space pattern was observed on the film of the photoresist exposed to 200 mJ/cm 2 of g-line by the contact-printing mode. The positive image was successfully converted to a poly(benzoxazole) (PBO) pattern by thermal treatment. The optically estimated dielectric constant of the PBO is 2.76. [DOI 10.1295/polymj.36.489] KEY WORDS Poly(benzoxazole)s / Poly(o-hydroxyazomethine) / Environmentally Friendly Process / High Temperature Material / Photosensitive Material / Photoresist / Low Dielectric Constants / Poly(benzoxazole)s (PBOs) are an important class of macromolecules that have outstanding mechanical, thermal, and chemical properties.1-5 Photosensitive PBOs (PSPBOs) have been developed 6-11 as alternative materials to photosensitive polyimides (PSPIs), which are widely used in constructing protection and insulation layers in semiconductor manufacturing. 12The precursors of PSPIs, poly(amic acid)s (PAAs) are very soluble in 2.38 wt % aqueous tetramethylammonium hydroxide (TMAHaq), an industrial standard aqueous alkaline developer. The dissolution rate, however, is too high to get a sufficient dissolution contrast between the exposed and unexposed areas. Thus, the dissolution rate of PAAs has to be reduced by either prebaking or post-exposure-baking. While these methods do not afford reliable dissolution contrasts, precursors of PSPBOs, poly(o-hydroxyamide)s (PHAs) [6][7][8][9][10][11] have an appropriate dissolution rate in TMAHaq due to the presence of a phenolic OH moiety. PBOs are generally prepared from PHAs and poly (o-hydroxy imide) 13,14 via thermal cyclization. Recently, a novel route of formulation for PSPBOs has been reported, based on poly(o-hydroxyazomethine)s (PHAMs) and diazonaphothoquinones (DNQs). 15 Compared to the synthesis of PHA derived from dicarboxylic active diester and bis(o-aminophenol) derivatives, PHAM is an attractive precursor for PSPBO because of its facile synthesis from dialdehyde and bis(o-aminophenol) derivatives, and the leaving group in the synthesis of PHAM is just water, environmentally advantageous to phenol in PHA synthesis. Furthermore, the direct photosensitive polymer formulation from the polymerization solution is possible by simply adding DNQ.In industrial engineering an environmentally benign process for photosens...

Synthesis and characterization of fluorinated poly(azomethine ether)s from new core-fluorinated azomethine-containing monomers

“…The structure of the synthesized azomethine-containing monomers 4, 5, 9, and 10 was confirmed by FTIR, 1 H, 13 C, 19 F NMR, and UV-vis spectrometry techniques (see the Supporting Information).…”

“…[6][7][8] PAMs can be synthesized in a traditional approach (also known as polyazomethine route) by a reaction of dialdehydes with diamines. [4,[9][10][11][12][13][14][15][16] Unfortunately, the produced polymers are characterized by limited solubility in the most of common organic solvents. [3,4,6] The growing macromolecular chains of PAMs precipitate from the solution during the polycondensation reaction.…”

Recent Development of Photosensitive Polybenzoxazoles

“…15 EL in particular is known to be a non-toxic, biodegradable organic fluid made from renewable carbohydrates such as cornstarch.…”

Highly Transparent Photosensitive Polybenzoxazole: Poly(o-hydroxy amide) Derived from 4,4′-(Hexafluoroisopropylidene)bis(o-aminophenol) and o-Substituted Dicarboxylic Acid Chlorides

“…2 Thus, the photosensitive polybenzoxazole (PSPBO) is attracting great attention as substitute for conventional PSPI in recent years. [3][4][5][6][7][8][9][10][11][12] The commercially available PSPBO is based on poly(o-hydroxy amide) (PHA), which is usually prepared by polycondensation of 4,4 0 -(hexafluoroisopropylidene)bis(o-aminophenol) (12) and 4,4 0 -oxybis-(benzoic acid) (8a) using a condensation agent, because of its high transparency at 365 nm wavelength (i-line). 13,14 There is an increasing demand for thicker films for small package to act as a buffer layer andray shielding applications, 15,16 consequently, it is quite important to develop a novel photosensitive polymer with higher transparency for UV lithography.…”