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

A negative‐type photosensitive polyimide (PSPI) based on semialicyclic poly(amic acid) (PAA), poly(trans‐1,4‐cyclohexylenediphenylene amic acid), and {[(4,5‐dimethoxy‐2‐nitrobenzyl)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′,4,4′‐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/cm² 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‐μm line and space pattern was printed on a film, which was exposed to 500 mJ/cm² 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′,4,4′‐biphenyltetracarboxylic dianhydride and 4,4′‐oxydianiline. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1317–1323, 2010     

Three‐component negative‐type photosensitive polyimide precursor based on poly(amic acid), a crosslinker,and a photoacid generator

A new negative‐working and alkaline‐developable photosensitive polyimide precursor based on poly(amic acid) (PAA), 4,4′‐methylenebis[2,6‐bis(hydroxymethyl)]phenol (MBHP) as a crosslinker, and a photoacid generator (5‐propylsulfonyloxyimino‐5H‐thiophen‐2‐ylidene)‐2‐(methylphenyl)acetonitrile (PTMA) has been developed. PAA was prepared by ring‐opening polymerization of pyromellitic dianhydride with 4,4′‐oxydianiline. The photosensitive polyimide precursor containing PAA (65 wt %), MBHP (25 wt %), and PTMA (10 wt %) showed a clear negative image featuring 10 μm line and space patterns when it was exposed to 436 nm light at 100 mJ·cm^?2, post‐exposure baked at 130 °C for 3 min, followed by developing with a 2.38 wt % aqueous tetramethylammonium hydroxide solution at 25 °C. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 593–599, 2005     

Alkaline-developable positive-type photosensitive polyimide with high mechanical strength and high resolution based on chain extendable poly(amic acid), thermally degradable cross-linker and photoacid generator

A positive-type photosensitive polyimide ( PSPI ) based on a chain extendable poly(amic acid) ( PAA ), a thermally degradable cross-linker 1,3,5-tris[(2-vinyloxy)ethoxy]benzene ( TVEB ), and a photoacid generator (PAG) (5-propylsulfonyloxyimino-5H-thiophene-2-ylidene)-(2-methylphenyl)acetonitrile ( PTMA ) has been developed. The chain extendable PAA was prepared from 3,3′,4,4′-biphenyltetracarboxylic dianhydride ( BPDA ) and 4,4′-oxydianiline ( ODA ) and end-capped with di-tert-butyl dicarbonate ( DIBOC ) in N-methyl-2-pyrrolidone (NMP), which has a controlled molecular weight for developing in a 2.38 wt% tetramethyl ammonium hydroxide aqueous solution ( TMAH _aq ) and undergoes a chain extending reaction during curing stage. The photosensitive resist solution was formulated with the polymerization solution (30 wt% in NMP), TVEB (15 wt% for the polymer), and PAG (4.5 wt% for the polymer). The PSPI showed a sensitivity of 47 mJ cm⁻² and a contrast of 5.8 when exposed to 365-nm light, followed by postexposure baking at 90 °C for 10 min and development with the 2.38 wt% TMAH _aq at room temperature. A fine-positive image with 3-μm line-and-space patterns was obtained on a 3-μm thick film exposed to UV light at 365 nm in the contact-printed mode. After thermal curing at 350 °C for 1 hr, the resulting PSPI features excellent mechanical strength and elongation.     

Negative‐type photosensitive poly(phenylene ether) based on poly(2,6‐dimethyl‐1,4‐phenylene ether), a crosslinker,and a photoacid generator

A negative‐type photosensitive poly(phenylene ether) (PSPPE) based on poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPE), a novel crosslinker 4,4′‐methylene‐bis [2,6‐bis(methoxymethyl)phenol] (MBMP) having good compatibility with PPE, and diphenylidonium 9,10‐dimethoxy anthracene‐2‐sulfonate (DIAS) as a photoacid generator (PAG) has been developed. This resist consisting of PPE (73 wt %), MBMP (20 wt %) and DIAS (7 wt %) showed a high sensitivity (D_0.5) of 58 mJ/cm² and a contrast (γ_0.5) of 9.5 when it was exposed to i‐line (365 nm wavelength light), postexposure baked at 145 °C for 10 min, and developed with toluene at 25 °C. A fine negative image featuring 6 μm line‐and‐space pattern was obtained on the film exposed to 300 mJ/cm² of i‐line by a contact‐printed mode. The resulting polymer film cured at 300 °C for 1 h under nitrogen had a low dielectric constant (ε = 2.46) comparable to that of PPE and a higher T_g than that of PPE. In addition, the cured PSPPE film was pretty low water absorption (<0.05%) as same as PPE. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4949–4958, 2008     

Photosensitive polybenzoxazole based on a poly(o‐hydroxy amide), a dissolution inhibitor,and a photoacid generator

A positive‐type photosensitive polybenzoxazole (PSPBO), based on a poly(o‐hydroxy amide) (PHA), the dissolution inhibitor (DI) 9,9‐bis(4‐tert‐butoxycarbonyloxyphenyl)fluorene (t‐Boc BHF), and the photoacid generator (5‐propylsulfonyloxyimino‐5H‐thiophene‐2‐ylidene)‐(2‐methylphenyl)acetonitrile (PTMA), was developed. Several new tert‐butoxycarbonylated compounds as DIs for PSPBOs were prepared from phenolic compounds having a cardolike structure with di‐tert‐butyl dicarbonate in the presence of 4‐dimethylaminopyridine. Among them, t‐Boc BHF and 5,5′,6,6′‐tetra(tert‐butoxycarbonyl)‐3,3,3′,3′‐tetramethyl‐1,1′‐spirobiindane acted as excellent DIs, giving a large dissolution contrast between the exposed and unexposed areas in a 2.38 wt % tetramethylammonium hydroxide solution (TMAHaq)/5 wt % iso‐propanol (i‐PrOH). The dissolution behavior of this PSPBO system was studied in relation to the PTMA and t‐Boc BHF loadings and postexposure baking temperature. A PSPBO consisting of PHA (77 wt %), t‐Boc BHF (20 wt %), and PTMA (3 wt %) exhibited a sensitivity of 34 mJ/cm² and a contrast of 5.8 when exposed to 365‐nm light (i‐line) and developed with an aqueous alkaline developer, 2.38 wt % TMAHaq/5 wt % i‐PrOH. A clear, positive image with 6‐μm features and a 10‐μm‐thick pattern with high sensitivity and contrast was produced by contact printing and converted into polybenzoxazole patterns upon heating at 350 °C for 1 h. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 661–668, 2007     

Preparation of a chemically amplified photosensitive polyimide based on norbornene‐end‐capped poly(amic acid ethoxymethylester)

A positive‐working chemically amplified photosensitive polyimide (PSPI) developable with basic aqueous solutions was obtained from poly(amic acid ethoxymethylester) (PAAE) as a polyimide precursor and diphenyliodonium 5‐hydroxynaphthalene‐1‐sulfonate (DINS) as a photoacid generator. The norbornene‐end‐capped PAAE based on 4,4′‐oxydiphthalic anhydride and 4,4′‐oxydianiline exhibited high transparency at 365 nm. The protection ratio of the ethoxymethyl groups was optimized to maximize the difference between the dissolution rates of the exposed and unexposed areas. The acid generated from DINS in the UV‐exposed region effectively deprotected the ethoxymethyl groups of PAAE by a chemical amplification mechanism. A 10‐μm‐thick film of the PSPI precursor system containing 16 wt % DINS exhibited a sensitivity (D^o) of 1100 mJ cm^?2 when developed with a 2.38 wt % aqueous tetramethyl ammonium hydroxide solution at room temperature. A fine, positive, 5‐μm line‐and‐space pattern was fabricated in a 15‐μm‐thick film with 1500 mJ cm^?2 of UV exposure. This resolution is excellent in comparison with those previously reported for chemically amplified PSPIs, and such a film can thus be used as a buffer coating in semiconductor packaging. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5520–5528, 2005     

Alkaline-developable and negative-type photosensitive polyimide with high sensitivity and excellent mechanical properties using photo-base generator

An alkaline developable and negative-type PSPI with a high sensitivity and excellent mechanical properties based on a poly(amic acid) (PAA) and a photo-base generator has been developed. The PAA was prepared by the polycondensation of p-phenylenediamine (PDA) with an equimolar of 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6-FDA) and converted thermally to the corresponding polyimide, PI(PDA-BPDA/6-FDA). PI(PDA-BPDA/6-FDA) showed the high thermal and mechanical properties and the dimensional stability such as the thermal decomposition temperature of 530°C, glass transition temperature of 369°C, linear coefficient of thermal expansion of 28 ppm/K, ultimate tensile strength of 148 MPa, elongation at break of 25% and dielectric constant of 2.8. The PSPI was formulated directly from PAA(PDA-BPDA/6-FDA) with a photo-base generator (PBG), (E)-3-(2-hydroxy-4-methoxyphenyl)-1-(piperidin-1-yl)prop-2-en-1-one (HMPP) (10 wt% to PAA) and the optimized parameters for photolithographic process were investigated including the PBG content, post-exposure bake (PEB) temperature, and PEB time. The PSPI based on PAA(PDA-BPDA/6-FDA) and HMPP (10 wt% to PAA) showed a sensitivity of 114 mJ/cm² and contrast of 1.29 when exposed to 365-nm light (i-line), post-exposure baked at 160°C for 5 min, and developed with an aqueous solution of 2.38 wt% tetramethylammonium hydroxide and iso-propanol. A clear negative 8-μm features pattern was obtained by contact-printing and converted into the PI pattern upon heating at 250°C, confirming by scanning electron microscopy and infrared spectroscopy.     

Synthesis of a highly transparent poly(o‐hydroxyamide) in the i‐line region and its application to photosensitive polymers

A novel poly(σ‐hydroxyamide) (PHA) based photosensitive polymer that exhibits high transparency at 365 nm wavelength (i‐line) has been developed. Time‐dependent density functional theory (TD‐DFT) calculations using the B3LYP hybrid functional were performed to predict the transparencies of various hydroxyamides in the i‐line region. Based on the calculations, 4,4′‐sulfonylbis(σ‐aminophenol) (SAP) was prepared and polymerized with 4,4′‐oxybis(benzoyl chloride) (OBBC), and the resulting PHA, which is abbreviated as PHA‐S, showed a high transparency comparable to that of PHA derived from 4,4′‐(hexafluoroisopropylidene)bis(σ‐aminophenol). Positive‐type photosensitive PHA was then formulated based on PHA‐S with a crosslinker 1,3,5‐tris[(2‐vinyloxy)ethoxy]benzene (TVEB) and a photoacid generator (5‐propylsulfonyloxyimino‐5H‐thiophen‐2‐ylidene)‐2‐(methylphenyl)acetonitrile (PTMA) (17:3:1 in weight ratio), and demonstrated photosensitivity and contrast of 14 mJ/cm² and 2.7, respectively, when the resist film was prebaked at 120 °C for 5 min, irradiated by i‐line, post exposure baked at 120 °C for 5 min, developed with an 2.38 wt% TMAH solution for 5 s. A clear positive image featuring 10‐μm line‐and‐space was also printed in a film which was exposed to 50 mJ/cm² of i‐line by contact‐printing. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2527–2535, 2005     

Synthesis of alkaline‐developable,photosensitive hyperbranched polyimides through the reaction of carboxylic acid dianhydrides and trisamines

Hyperbranched polyimides (HBPI)s with high glass‐transition temperatures and excellent thermal stability were synthesized through the reaction of commercially available carboxylic acid dianhydrides with tris[4‐(4‐aminophenoxy)phenyl]ethane (TAPE). In particular, hyperbranched polyimide HBPI(TAPE‐DSDA), prepared through the reaction of TAPE with 3,3′,4,4′‐diphenylsulfonetetracarboxylic dianhydride (DSDA), showed higher thermal stability and good solubility. Furthermore, alkaline‐developable, photosensitive HBPI(TAPE‐DSDA)‐MA‐CA was prepared through the reaction of HBPI(TAPE‐DSDA) with glycidyl methacrylate with tetrabutylammonium bromide as a catalyst in N‐methyl‐2‐pyrrolidinone (NMP) followed by the addition reaction of cis‐1,2,3,6‐tetrahydrophthalic anhydride with triphenylphosphine as a catalyst in NMP. The glass‐transition temperatures of HBPI(TAPE‐DSDA)‐MA‐CA were greater than 300 °C. A resist composed of 74 wt % HBPI(TAPE‐DSDA)‐MA‐CA, 22.2 wt % trimethylpropane triacrylate, and 3.8 wt % Irgacure 907 as a photoinitiator achieved a resolution of a 55‐μm line pattern and a 275‐μm space pattern by UV irradiation (1000 mJ/cm²). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3697–3707, 2004     

Three‐component,negative‐type,alkaline‐developable,thermally stable,and photosensitive polymer based on poly(2,6‐dihydroxy‐1,5‐naphthalene), a crosslinker,and a photoacid generator

A negative working and chemically amplified photosensitive polymer has been developed, which is based on poly(2,6‐dihydroxy‐1,5‐naphthalene) (PDHN), the crosslinker 4,4′‐methylenebis[2,6‐bis(hydroxymethyl)]phenol, and the photoacid generator (5‐propylsulfonyloxyimino‐5H‐thiophen‐2‐ylidene)‐(2‐methylphenyl)acetonitrile. PDHN, with a number‐average molecular weight of 25,000, was prepared by the oxidative coupling polymerization of 2,6‐dihydroxynaphthalene with di‐μ‐hydroxo‐bis[(N,N,N′,N′‐tetramethylethylenediamine)copper(II)] chloride in 2‐methoxyethanol at room temperature. The resulting PDHN showed a 5% weight loss temperature of 440 °C in nitrogen and a low dielectric constant of 2.82. The resist showed a sensitivity of 8.3 mJ cm^?2 and a contrast of 11 when it was exposed to 436‐nm light, followed by postexposure baking at 100 °C for 5 min and development with a 2.38 wt % aqueous tetramethylammonium hydroxide solution at 25 °C. A fine negative image featuring 10‐μm line‐and‐space patterns was obtained on a film 3 μm thick exposed to 10 mJ cm^?2 of ultraviolet light at 436 nm in the contact‐printed mode. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2235–2240, 2004     

Pattern formation of polyimide by using photosensitive polybenzoxazole as a top layer

A versatile method for positive-type patterning of polyimide (PI) based on a two-layer photosensitive poly(benzoxazole) (PSPBO) and poly(amic acid) (PAA) film has been developed to provide a promising material in the field of microelectronics. This patterning system consisted of a pristine PAA thick bottom-layer and a poly(o-hydroxy amide) (PHA) thin top layer with 9,9-bis[4-(tert-butoxycarbonyl-methyloxy)phenyl]fluorene (TBMPF) as a dissolution inhibitor, and (5-propylsulfonyloxyimino-5H-thiophene-2-ylidene)-(2-methylphenyl)-acetonitrile (PTMA) as a photoacid generator (PAG). The PHA and PAA were prepared from 4,4′-(hexafluoroisopropylidene)-bis(o-aminophenol) and 4,4′-oxybis(benzoic acid) derivatives, and 3,3′,4,4′-biphenyltetracarboxylic dianhydride and 4,4′-oxydianiline, respectively, in N,N-dimethylacetamide. This two-layer system based on PHA (150-nm thickness) and PAA (1.5-μm thickness) showed high sensitivity of 35 mJ/cm² and high contrast of 10.3 when exposed to a 365 nm line (i-line), post-baked at 100 °C for 2 min, and developed in a 2.38 wt.% tetramethylammonium hydroxide aqueous solution/5 wt.% iso-propanol at 25 °C. A clear positive image of a 4-μm line-and-space pattern was printed on a film which was exposed to 100 mJ/cm² of i-line by a contact-printing mode and fully converted to the corresponding PBO/PI pattern upon heating at 350 °C, confirmed by FT-IR spectroscopy. This two-layer system could be applied to the patterning of various PAAs.     

The improved photosensitivity of photosensitive polyimides containing o-nitrobenzyl ether groups induced by the addition of photoacid generator

In this article, photosensitive polyimides (PSPIs) with photosensitive groups, o-nitrobenzyl ether groups (Nb), were successfully synthesized based on 2,2′-dihydroxy benzophenone-3,3′,4,4′-tetracarboxylic dianhydride and on diamine containing ethylene glycol chains (ODA). Also, a series of polyimide (PI), ODA-1-PI, ODA-3-PI, and ODA-5-PI with a number of ethylene glycol chains of 1, 3, and 5 were prepared to investigate the relationship between structure and solubility. Interestingly, ODA-5-PI, which possesses a large number of ethylene glycols, exhibited the most excellent solubility. Therefore, due to the good solubility of ODA-5-PI in organic solvents and alkaline solutions, a PSPI, poly(1,4-phenyleneoxy-3,6,9,12,15-pentaoxaoctane-1,4-phenylene-2,2′-di[2-nitrobenzyloxy]benzophenone-3,3′,4,4′-tetracarboxdiimide), named ODA-5-PSPI, was synthesized by linking Nb, which is a photosensitive group. Aiming at producing positive tone patterns, the synthesized ODA-5-PSPI was exposed to UV irradiation and then to a post-exposure bake. Afterward, it was developed using a 2.38 wt% tetramethylammonium hydroxide solution. Furthermore, a photoacid generator (PAG) was additionally incorporated for a micropatterning process. Notably, in the presence of the PAG, the photocleavage of ODA-5-PSPI occurred not only by the intramolecular rearrangement of Nb but also by its hydrolysis reaction. As a result, due to the synergistic effect of photocleavage, the micropatterning of ODA-5-PSPI with PAG could be clearly obtained with less energy (2.0 J/cm²) compared with that without PAG (3.6 J/cm²). Therefore, through the addition of PAG, the photosensitivity was improved by 45%.     

Synthesis and micropatterning properties of a novel base‐soluble,positive‐working,photosensitive polyimide having an o‐nitrobenzyl ether group

A novel positive‐working, photosensitive polyimide, poly[1,4‐phenyleneoxy‐1,4‐phenylene‐2,2′‐di(2‐nitrobenzyloxy)benzophenone‐3,3′,4,4′‐tetracarboxdiimide] (OPI‐Nb), developable with an aqueous base was prepared by the o‐nitrobenzylation of a polyimide, poly(1,4‐phenyleneoxy‐1,4‐phenylene‐2,2′‐dihydroxybenzophenone‐3,3′,4,4′‐tetracarboxdiimide) (OPI), derived from 2,2′‐dihydroxy‐3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (DHBA) and 4,4′‐oxydianiline, and it micropatterning properties were investigated. The o‐nitrobenzylation of OPI to OPI‐Nb was conducted with o‐nitrobenzyl bromide in N‐methyl‐2‐pyrrolidinone containing Et₃N. The DHBA monomer was synthesized by exhaustive KMnO₄ oxidation of bis(2‐dimethoxy‐3,4‐dimethylphenyl)methane obtained by etherification of bis(2‐hydroxy‐3,4‐dimethylphenyl)methane with iodomethane, followed by deprotection of the methoxy groups and cyclodehydration of the obtained 2,2′‐dihydroxy‐3,3′4,4′‐benzophenonetetracarboxylic acid. The intermediate bis(2‐hydroxy‐3,4‐dimethylphenyl)methane was prepared by the condensation of 2,3‐dimethylphenol with paraformaldehyde. The degree of o‐nitrobenzylation was determined to be over 94 mol % from ¹H NMR absorption of benzylic CH₂ protons. The aromatic OPI was perfectly soluble in a dilute aqueous NaOH solution and tetramethylammonium hydroxide (TMAH), whereas OPI‐Nb was not even swellable in them. In the micropatterning process, OPI‐Nb showed a line‐width resolution of 0.4‐μm and a sensitivity of 5.4 J/cm² when its thin films were irradiated with 365‐nm light and developed with a 2.38% aqueous TMAH solution at room temperature for 90 s. The thickness loss of OPI‐Nb films measured after postbaking at 350 °C was in the 8–9% range. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 776–788, 2007     

Synthesis and characterization of photosensitive benzocyclobutene‐functionalized siloxane thermosets

Two methylphenylsiloxane monomers with crosslinkable benzocyclobutene functionalities at the terminal positions, 1,1,5,5‐dimethyldiphenyl‐1,1,5,5‐di[2′‐(4′‐benzocyclobutenyl)vinyl]‐3,3‐diphenyltrisiloxane (BCB‐1) and 1,1,3,3‐dimethyl‐diphenyl‐1,1,3,3‐di[2′‐(4′‐benzocyclobutenyl)vinyl]disiloxane (BCB‐2) were prepared and characterized. By heating the solution of BCB‐1 and BCB‐2 in mesitylene, two partially polymerized resins of BCB‐1B and BCB‐2B with high molecular weight were also achieved. The monomers and their oligomers fully cured at temperatures above 250 °C. Cured BCB‐1 and BCB‐2 exhibited high T_g (257 and 383 °C) and good thermal stability (T_5% > 472 °C both in N₂ and in air). They also demonstrated low dielectric constants (2.69 and 2.66), low dissipation factors (2.36 and 2.23), and low water absorptions (0.20% and 0.17%). Moreover, a negative photosensitive formulation derived from BCB‐1B in combination with 2,6‐bis(4‐azidobenzylidene)‐4‐methylcyclohexanone (BAC‐M) as a photosensitive agent has been developed. The photosensitive composition, BCB‐1B containing 5 wt % BAC‐M, showed a sensitivity of 550 mJ/cm² and a contrast of 1.96 when it was exposed to a 365 nm light (i‐line) and developed with cyclohexanone at 25 °C. A fine negative image of 10 μm line‐and‐space pattern was also printed in a film which was exposed to 700 mJ/cm² of i‐line by contact‐printing mode. The negative image can be maintained without any pattern deformation in the curing process. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6246–6258, 2009     

A positive-working photosensitive alkaline-developable polyimide with a highly dimensional stability and low dielectric constant based on poly(amic acid) as a polyimide precursor and diazonaphthoquinone as a photosensitive compound

A positive-working photosensitive polyimide precursor based on fluorinated poly(amic acid) (FPAA) and 2,3,4-tris(1-oxo-2-diazonaphthoquinon-4-ylsulfonyloxy)benzophenone (D4SB) as a photosensitive compound has been developed. FPAA was prepared by ring-opening polyaddition of dianhydrides, pyromellitic dianhydride and biphenyltetracarboxylic dianhydride, with diamine, 2,2′-bis(trifluoromethyl)benzidine, in methanol. The FPAA film showed excellent transparency to UV light and good solubility in a wide range of organic solvents. The dissolution behavior of FPAA containing 30 wt % D4SB after exposure was studied, and it was found that the difference of dissolution rate between exposed and unexposed parts was enough to get high contrast due to the photochemical reaction of D4SB in the polymer film. The photosensitive fluorinated polyimide (FPI) precursor containing 30 wt % D4SB showed a sensitivity of 80 mJ cm⁻² and a contrast of 7.8 with 365 nm light when it was developed with 0.3% aqueous tetramethyl ammonium hydroxide solution at room temperature. The FPI film cured up to 360°C had a low coefficient of thermal expansion of 10.3 ppm °C⁻¹ and a low dielectric constant of 3.04. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2261–2267, 1998     

Synthesis and positive‐imaging photosensitivity of soluble polyimides having pendant carboxyl groups

Polyimides having pendant carboxyl groups were prepared by a direct one‐pot polycondensation of 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA) with 3,5‐diaminobenzoic acid (DABz) and bis[4‐(3‐aminophenoxy)phenyl]sulfone (m‐BAPS) in the presence of a γ‐valerolactone/pyridine catalyst system using N‐methyl‐2‐pyrrolidone (NMP)/toluene mixture as a solvent at 180 °C. The obtained polyimides were soluble in dipolar aprotic solvents such as dimethylformamide, dimethyl sulfoxide, and NMP as well as in tetrahydrofuran and aqueous basic solution. The solubility of the polyimides was dependent on the diamine composition. Photosensitve polyimide (PSPI) systems composed of the polyimides and diazonaphthoquinone compound as a photosensitive material gave positive‐tone behavior by UV irradiation, followed by development with aqueous tetramethylammonium hydroxide (TMAH) solution. The scanning electron microscopic photograph of the resulting image showed 10‐μm line/space resolution with about 15 μm of film thickness. The PSPIs baked at 350 °C for a short time had excellent thermal resistance comparable to the original polyimides. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 934–946, 2001     

New synthetic route for photosensitive poly(benzoxazole)

A new positive working photosensitive poly(benzoxazole) (PBO) precursor based on poly(o‐hydroxyazomethine) ( 3 ) and 1‐{1,1‐bis[4‐(2‐diazo‐1‐(2H)naphthalenone‐5‐sulfonyloxy)phenyl]ethyl}‐4‐{1‐[4‐(2‐diazo‐1(2H)naphthalenone‐5‐sulfonyloxy)phenyl]methylethyl}benzene (S‐DNQ) as a photosensitive compound was developed. 3 was prepared by the condensation of 2,2‐bis(3‐amino‐4‐hydroxyphenyl)hexafluoropropane with isophthalaldehyde in 1‐methyl‐2‐pyrrolidinone/toluene under azeotropic conditions. The photosensitive PBO precursor containing 30 wt % S‐DNQ showed a sensitivity of 120 mJ cm^?2 and a contrast of 2.2 when it was exposed to 436‐nm light and developed with a 2.38 wt % aqueous tetramethylammonium hydroxide solution at room temperature. A fine positive image featuring 10‐μm line and space patterns was observed on the film of the photoresist exposed to 200 mJ cm^?2 ultraviolet light at 436 nm by the contact mode. The positive image was successfully converted into the PBO pattern by a thermal treatment. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3399–3405, 2002     

Novel positive‐working and aqueous‐base‐developable photosensitive poly(imide benzoxazole) precursor

A novel positive‐working and aqueous‐base‐developable photosensitive poly(imide benzoxazole) precursor based on a poly(amic acid hydroxyamide) bearing phenolic hydroxyl groups and carboxylic acid groups, a diazonaphthoquinone (DNQ) photosensitive compound, and a solvent was developed. Poly(amic acid hydroxyamide) was prepared through the polymerization of 2,2‐bis(3‐amino‐4‐hydroxyphenyl)hexafluoropropane, trimellitic anhydride chloride, and 4,4′‐oxydibenzoyl chloride. Subsequently, the thermal cyclization of the poly(amic acid hydroxyamide) precursor at 350 °C produced the corresponding poly(imide benzoxazole). The inherent viscosity of the precursor polymer was 0.17 dL/g. The cyclized poly(imide benzoxazole) showed a high glass‐transition temperature of 372 °C and 5% weight loss temperatures of 535 °C in nitrogen and 509 °C in air. The structures of the precursor polymer and the fully cyclized polymer were characterized with Fourier transform infrared and ¹H NMR. The photosensitive polyimide precursor containing 25 wt % DNQ photoactive compound showed a sensitivity of 256 mJ/cm² and a contrast of 1.14 in a 3‐μm film with a 0.6 wt % tetramethylammonium hydroxide developer. A pattern with a resolution of 5 μm was obtained from this composition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5990–5998, 2004     

Synthesis of photosensitive and thermosetting poly(phenylene ether) based on poly[2,6‐di(3‐methyl‐2‐butenyl)phenol‐co‐2,6‐dimethyl‐phenol] and a photoacid generator

A chemically amplified photosensitive and thermosetting polymer based on poly[2,6‐di(3‐methyl‐2‐butenyl)phenol (15 mol %)‐co‐2,6‐dimethylphenol (85 mol %)] ( 3c ) and a photoacid generator [(5‐propylsulfonyloxyimino‐5H‐thiophen‐2‐ylidene)‐(2‐methylphenyl)acetonitrile] was developed. Poly[2,6‐bis(3‐methyl‐2‐butenyl)phenol]‐co‐2,6‐dimethylphenol)] ( 3 ) with high molecular weights (number‐average molecular weight ～ 24,000) was prepared by the oxidative coupling copolymerization of 2,6‐di(3‐methyl‐2‐butenyl)phenol with 2,6‐dimethylphenol in the presence of copper(I) chloride and pyridine as the catalyst under a stream of oxygen. The structures of 3 were characterized with IR, ¹H NMR, and ¹³C NMR spectroscopy. 3 was crosslinked by a thermal treatment at 300 °C for 1 h under N₂. The 5% weight loss temperatures and glass‐transition temperatures of the cured copolymers reached around 420 °C in nitrogen and 300 °C, respectively. The average refractive index of the cured copolymer ( 3c ) film was 1.5452, from which the dielectric constant at 1 MHz was estimated to be 2.6. The resist showed a sensitivity of 35 mJ cm^?2 and a contrast of 1.6 when it was exposed to 436‐nm light, postexposure‐baked at 145 °C for 5 min, and developed with toluene at 25 °C. A fine negative image featuring 8‐μm line‐and‐space patterns was obtained on a film exposed to 100 mJ cm^?2 with 436‐nm light in the contact‐printed mode. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 149–156, 2005     

Efficient gel‐type electrolyte with bismaleimide via in situ low temperature polymerization in dye‐sensitized solar cells

This study reports the characteristics of gel‐type dye‐sensitized solar cells (DSSCs), fabricated with gel‐type electrolyte containing poly‐1,1′‐(methylenedi‐4,1‐phenylene)bismaleimide (PBMI), or poly‐1,1′‐(3,3′‐dimethyl‐1,1′‐biphenyl‐4,4′‐diyl)bismaleimide (PDBBMI), or poly‐N,N′‐(4‐methyl‐1,3‐phenylene)bismaleimide (PMPBMI), prepared by in situ polymerization of the corresponding monomer without an initiator at 30 °C. Incorporating 0.3 wt % content of exfoliated alkyl‐modified nanomica (EAMNM) into PBMI‐gelled electrolyte leads to higher short‐circuit current density (J_sc = 17.14 mA cm^?2) and efficiency (η = 7.02%) than that of neat PBMI‐gel electrolyte (J_sc = 15.32 mA cm^?2, η = 6.41%). Incorporating 0.3 wt % EAMNM into PBMI‐gelled electrolyte results in remarkably stable device performance under continuous light soaking under one sun (100 mW cm^?2) at 55 °C. The efficiency of DSSCs based on PBMI/0.3 wt % EAMNM‐gelled electrolyte drops by only 1.7% (η = 6.93%) after 500 h of continuous light soaking. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010