We describe the synthesis, characterization, and lithographic performance of positive-working chemically amplified photosensitive polybenzoxazoles (PSPBOs) composed of partially tert-butoxycarbonyl (t-BOC) protected hyperbranched poly(o-hydroxyamide)s (HB-tbocPHAs) and diphenyliodonium 9,10-dimethoxyanthracene-2-sulfonate (DIAS) as a photo-acid generator (PAG). The HB-tbocPHAs as precursors of PSPBOs were synthesized from hyperbranched poly(o-hydroxyamide)s (HBPHAs), which were prepared by self-polycondensation of an AB2 type monomer. A series of HB-tbocPHAs having the t-BOC content of 8−100 mol % were successfully prepared by controlling the feed amount of di-tert-butyl dicarbonate (DTBDC). HB-tbocPHAs had adequate dissolution rate in tetramethylammonium hydroxide (TMAH) aqueous solution as well as excellent solubility in common organic solvents. HB-tbocPHA having 39 mol % t-BOC group showed the optimum dissolution rate in 2.38 wt % TMAH aqueous solution and good adhesion on a silicon wafer. The thermal deprotection of the t-BOC group and conversion to polybenzoxazole (PBO) of HB-tbocPHA in the presence of strong acid such as p-toluenesulfonic acid (p-TsOH) were investigated by using FT-IR, DSC, and TGA to examine the acid effect. Both the deprotection of t-BOC groups and the conversion to PBO were accelerated in the presence of p-TsOH. The photolithographic performance of the resist formulated with HB-tbocPHA and 20 wt % of DIAS was evaluated. The resist showed 115 mJ/cm2 of sensitivity and 2.2 of contrast with 365 nm light when it was developed in 2.38 wt % TMAH aqueous solution at room temperature. The fine positive pattern was obtained at the 200 mJ/cm2 of i-line exposure. The patterned film was successfully converted to polybenzoxazole without any distortion by thermal treatment at 300 °C for 1 h.
ABSTRACT:The novel AB 2 and A 2 B type monomers for hyperbranched polybenzoxazoles (HBPBOs) containing one (or two) hydroxy amine and two (or one) carboxylic acid groups in the aromatic backbones were prepared starting from 5-methoxyresorcinol and 4-fluorobenzonitrile for AB 2 and 3,5-dihydroxybenzoic acid and 3-fluoro-6-nitrophenol for A 2 B monomer. Hyperbranched poly(o-hydroxyamide)s (HBPHAs) as precursors of HBPBOs were synthesized by self-polycondensation of the AB x type monomers in the presence of (2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphonic acid diphenyl ester (DBOP) as a condensing agent at room temperature. The terminal groups of free carboxylic acid or amine were chemically modified with 2-amino-4-tert-butylphenol or 3,5-dimethylbenzoic acid. End-capped HBPHAs had good solubility in aprotic solvents and tetrahydrofuran (THF) having the weight average molecular weight (M w ) in the range of 27000-131000. The conversion of HBPHA to HBPBO was carried out by thermal and chemical cyclization methods. HBPBOs prepared by chemical cyclization of HBPHAs in polyphosphoric acid (PPA) were soluble in aprotic solvents such as N-methyl-2-pyrrolidinone (NMP), N,N-Dimethylacetamide (DMAc), Dimethyl Formamine (DMF), and THF, whereas thermally cyclized ones were insoluble in any organic solvents.1 H NMR and IR analyses indicated that the chemical cyclization proceeded quantitatively. The weight-average molecular weights (M w ) of soluble HBPBOs were found to be 23000-97000 by gel permeation chromatography (GPC) measurement with standard polystyrene calibration. Both of HBPBOs prepared by thermal and chemical cyclization methods showed excellent thermal stability having the 10 wt% weight loss (T 10 ) in the range of 488-537• C under nitrogen.KEY WORDS Polybenzoxazoles / Hyperbranched Polymer / Cyclodehydration / Poly(o-hydroxyamide)s / One-pot Polymerization / AB 2 Monomer / The aliphatic polybenzoxazoles (PBOs) were first synthesized through the melt polycondensation of 3,3 -diaminobenzidine tetrahydrochloride and sebacic acid by Brinker et al. in 1959. 1 Six years later, linear aromatic polybenzoxazoles (PBOs) were first reported by Imai et al. 2 and have since been under widespread investigation. For a few decades, both of AA-BB and AB type monomer systems have been studied in the synthesis of linear polybenzoxazoles having good thermal and mechanical properties. 3-7 Fibers prepared from this polymer have superior tensile strength and flame retardance. PBO fibers were used in high-performance composites and comfortable protective garments. However, in spite of these attractive properties, their application has been somewhat limited since their poor processability. The processability or solubility of these polymers could be improved by the introduction of the flexible units or bulky pendant groups to the main chain. [8][9][10][11] Nowadays, It is well known that dendritic macromolecules such as dendrimers or hyperbranched polymers have unusual properties compared to their linear analogues like as better solubility...
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