Photosensitive Polyimide Precursor Research Articles

Negative-tone photosensitive polyimide with high transparency

Negative-tone photosensitive polyimides (n-PSPI) with high transparency at visible wavelength region (400–700 nm) were prepared by dissolving photosensitive polyimide precursor -poly(amide ester)(PAE) resins, photoinitiator, photocrosslinker and other additives in organic solvents. The PAE resins were synthesized by polycondensation of a fluorinated aromatic diamine with an aromatic diester dichloride or its mixture. The n-PSPI coating solutions showed good photolithographic performance with resolution of 8 µm (via) and 7 µm (line) at 5 µm of the thermally cured film thickness. After thermally cured at 350 °C/1h, the typical PSPI film exhibited excellent thermal properties with Tg of 344 °C and Td5 of 525 °C, respectively. The mechanical properties with elongation at breakage of as high as 42.2% and tensile strength of 133.7 MPa were also measured. Additionally, the thermally cured PSPI films exhibited excellent transparency with UV cuttoff wavelength of 362 nm, transmittance of 90.5% at 450 nm, and 95.5% at 550 nm, as well as yellowness indices of less than 6.55. Furthermore, theoretical simulations were used to prove that trifluoromethyl group in the backbone structure of PSPI precursor resin can effectively improve the transparency of PSPI films.

A water-borne photo-sensitive polyimide precursor for an eco-friendly process of preparing organic thin film transistors

A water-borne photo-sensitive poly(amic acid) salt for the micropatterned polyimide layer of a microelectronic device.

Preparation and properties of thermally conductive photosensitive polyimide/boron nitride nanocomposites

AbstractA new thermally conductive photoresist was developed. It was based on a dispersion of boron nitride (BN) nanoflakes in a negative‐tone photosensitive polyimide (PSPI) precursor. 3‐Mercaptopropionic acid was used as the surfactant to modify the BN nanoflake surface for the dispersion of BN nanoflakes in the polymer. The thermal conductivity of the composite films increased with increasing BN fraction. The thermal conductivity of the PSPI/BN nanocomposite was up to 0.47 W m−1 K−1 for a mixture containing 30 wt % nanosized BN filler in the polyimide matrix. Patterns with a resolution of 30 μm were obtained from the PSPI/BN nanocomposites. The PSPI/BN nanocomposites had excellent thermal properties. Their glass‐transition temperatures were above 360°C, and the thermal decomposition temperatures were over 460°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

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

AbstractThe 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 amic acid). Further functionalization by grafting acrylate groups yields the corresponding poly(acrylate amic acid) that underwent a crosslinking reaction on exposure to UV‐light and was used as a negative‐tone 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 exhibited 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‐dimethylamino‐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. J Appl Polym Sci, 2009

Preparation and properties of conductive silver/photosensitive polyimide nanocomposites

AbstractA new electrically conductive photoresist has been developed. It is based on the dispersion of silver nanoflakes in a negative‐tone photosensitive polyimide (PSPI) precursor. 2‐Mercaptopropionic acid was used as the surfactant to modify the silver nanoflake surface for the dispersion of silver nanoflakes in the polymer. The silver/PSPI nanocomposites showed electrical conductivity at a low silver content of 10 wt %. The electrical conductivity of the silver/PSPI nanocomposites ranged from 10 to 104 S/cm, which was dependent on the silver weight fraction in the resist formulation. Patterns with a resolution of 30 μm were obtained from the silver/PSPI nanocomposites. The silver/PSPI nanocomposites had excellent thermal properties. Their glass transition temperatures were above 360 °C and thermal decomposition temperatures were over 420 °C. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1575–1583, 2009

Novel Partial Esterification Reaction in Poly(amic acid) and Its Application for Positive-Tone Photosensitive Polyimide Precursor

We found novel quantitative esterification in poly(amic acid) (PAA) by reacting with N,N-dimethylformamide dialkyl acetals (DFAs). Different alkyl ester was obtained by changing the alkyl group in DFAs. The esterification ratio was determined by amount of DFAs. The reaction proceeds under mild condition without any catalysis. It has not been reported such a kind of quantitative partial esterification before. The partial esterification allowed us to control the solubility of PAA to alkaline solutions. The strict solubility rate control to alkaline solution of PAA was quite important for positive tone photosensitive polyimide (posi PSPI). The partial esterification of PAA gave us a way to strict dissolution control. By using it, we could obtain posi PSPI just mixing with diazonaphthoquinone compound.

Synthesis and characterization of a photosensitive polyimide precursor and its photocuring behavior for lithography applications

Photosensitive polyimide (PSPI) is of great interest, especially in microelectronic industry and potentially in the photonics and MEMS applications. Here we report on our studies for optimization of synthesis conditions for a PSPI which can be used in lithography. The direct polymerization method using phenyl phosphonic dichloride (PPD) as an activator was used to synthesize poly(amic ester) (PAE) from pyromellitic dianhydride (PMDA), 4,4′-oxydianiline (ODA) and 2-hydroxyethylmethacrylate (HEMA). Main parameters of the synthesis procedure were investigated by differential scanning calorimetry (DSC) analyses. From that, synthesis conditions were determined. Characteristics of the synthesized PAE and the imidized film were studied by the means of DSC, thermalgravimetric analyses (TGA) and Fourier transform infrared spectroscopy (FTIR). The glass transition temperature and the thermal stability of the imidized film were determined. Additionally, formulations of photo-PAE and the Irgacure 369 as photoinitiator were prepared and photocuring was tested by lithography. The results show that the images can be transferred to the PAE film by selective exposure.

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

AbstractA 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 (Do) 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

New Negative-type Photosensitive Alkaline-developable Semi-aromatic Polyimides with Low Dielectric Constants Based on Poly(amic acid) from Aromatic Diamine Containing Adamantyl Units and Alicyclic Dianhydrides, A Cross-linker, and A Photoacid Generator

A new negative-working and alkaline-developable photosensitive polyimide precursor based on semi-aromatic poly(amic acid)s (4), 4,4′-methylenebis[2,6-bis(hydroxymethyl)]phenol (MBHP) as a cross-linker, and a photoacid generator (5-propylsulfonyloxyimino-5H-thiophen-2-ylidene)-2-(methylphenyl)acetonitrile (PTMA) has been developed. Novel polymers 4 were prepared by ring-opening polyadditions of alicyclic dianhydrides (1), 1,2,3,4-cyclobutanetetracarboxylic dianhydride (1a), bicyclo[2.2.2]oct-7-ene-2,3;5,6-tetracarboxylic dianhydride (1b), and bicyclo[2.2.1]heptane-2-methanecarboxylic-3,5,6-tricarboxylic-2,3:5,6-dianhydride (1c) with 1,3-bis(4-aminophenoxy)adamantane (3). Polymers 4 were converted to corresponding poly(imide)s (5) by thermal treatment. The dielectric constants (ε) of 5 estimated from the refractive indices were 2.72–2.74. The photosensitive polyimide precursor containing 4 (60 wt %), MBHP (30 wt %), and PTMA (10 wt %) cast from 2-methoxyethanol solution showed a clear negative image featuring 15 μm line and space patterns when it was exposed to 436 nm light, post-exposure baked at 110 °C for 3 min, followed by developing with 2.38 wt % aqueous tetramethylammonium hydroxide (TMAH) solution at 25 °C for 40 s.

An Organic Thin-Film Transistor with a Photoinitiator-Free Photosensitive Polyimide as Gate Insulator

This investigation deals with the synthesis and detailed study of a photoinitiator-free photosensitive polyimide gate insulator for organic thin-film transistors (OTFTs), one of the most important components of active-matrix displays on plastic substrates. The photosensitive polyimide precursor poly(amic acid) is prepared from the aromatic dianhydride 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) and the novel aromatic diamine 7-(3,5-diaminobenzoyloxy)coumarine (DACM). The photosensitivity of the poly(amic acid) film is investigated using a high-pressure mercury lamp at 280-310 nm. The pattern resolution of the photocured film was about 50 μm. The surface morphology of the films before and after the photopatterning process is also investigated. In addition, we have fabricated pentacene OTFTs with the photoinitiator-free photosensitive polyimide as gate insulator. The OTFT characteristics are discussed in more detail with respect to the electrical properties of the photosensitive polyimide thin film.

Low Temperature Curing of Polyimide Precursors by Variable Frequency Microwave

Polyimides are commonly used as a thermally stable insulator for semiconductors. To assure adequate chemical or physical properties, a layer of their precursors has to be cured in a convection oven at more than 300 °C. In this paper, we compare variable frequency microwave (VFM) heating with convection heating for curing various polyimide precursors and a photosensitive polyimide precursor. Then, we demonstrate that the use of VFM enables us to cure the precursor lower than the standard convection cure temperature while maintaining necessary film properties such as cyclization, Tg, Td, and elongation.

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

AbstractA 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

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

New Fabrication Method of Self-written Waveguide by Using Photosensitive Polyimide

A Photosensitive polyimide (PSPI) precursor for light-induced self-written (LISW) waveguide based on a poly(amic acid) (PAA) and 1,4-dihydropyridine derivatives (DHP)s has been developed. The PAA was prepared by ring-opening polyaddition of aromatic fluorinated tetracarboxylic dianhydrides and diamines. Upon exposing the PSPI precursor to laser light, a self-focusing effect induced by the difference in refractive index between the exposed and unexposed portions was observed. Thermal treatment of the laser exposed PSPI precursor gave a polyimide LISW wave guide with no other processing steps. The coupling loss between two multimode fibers with a 0.5 mm gap, was decreased from 5.2 dB in air to 0.7 dB by insertion of the PSPI LISW waveguide. This simple new fabrication method of LISW waveguide structures allows convenient and easy alignment of optical waveguide components.

Synthesis and characterization of novel negative-working aqueous base developable photosensitive polyimide precursors

Through molecular designing, three poly(amic esters) (PAEs) have been synthesized from pyromellitic dianhydride (PMDA), 2,2′-bis-(3-amino-4-hydroxyphenyl) hexafluoropropane (BisAPAF), 4,4′-diaminodiphenyl ether (4,4′-ODA) and 2-hydroxyethyl methacrylate (HEMA). Due to the introduction of photosensitive acrylate groups and aqueous base soluble phenolic hydroxyl groups in the backbone, these poly(amic esters) can be used as the precursors of negative-working, aqueous base developable photosensitive polyimides (PSPIs). These poly(amic esters) were prepared by direct polymerization by using phenyl phosphonic dichloride (PPD) as an activator. The inherent viscosities of these polymers were 0.20 (dL/g). Their structures were characterized by Fourier transform infrared spectroscopy (FTIR) and 1H NMR. In order to improve the photolithographic performance of these PSPIs, different photosensitizers, photoinitiators and a crosslinker have been added in the PSPI formulations. Among them, the Michler's ketone (MK)/tribromomethyl phenyl sulfone (TBPS) system gave the best results. Using a 2.38 wt% aqueous TMAH solution as a developer, patterns with a resolution of 10 μm were obtained from these PSPI formulations. In addition, the effects of the molecular structure of the precursors and the concentration of developer on the photosensitivity of the PSPI formulations were also discussed.

Novel positive‐working aqueous‐base developable photosensitive polyimide precursors based on diazonaphthoquinone‐capped polyamic esters

AbstractNovel positive‐working aqueous‐base developable photosensitive polyimide (PSPI) precursors based on partially diazonaphthoquinone (DNQ)‐capped polyamic esters bearing phenolic hydroxyl groups and a DNQ photosensitive compound (PIC‐3) were developed. The partially DNQ capped polyamic esters were prepared from an esterification reaction of 1,2‐naphthoquinone diazide‐5‐sulfonyl chloride with the polyamic esters. The partially DNQ capped polyamic esters decreased the dark film loss effectively in the aqueous‐base developer and were able to make thicker film resists compared to the uncapped polyamic esters. The 25 mol % DNQ‐capped BisAPAF–PMDA polyamic ester and BisAPAF–ODPA polyamic ester containing 25 wt % PIC‐3 photosensitive compound showed a sensitivity of 176 and 185 mJ/cm2, and a contrast of 1.68 and 1.02, respectively, in a 3‐μm film with 1.25 wt % tetramethylammonium hydroxide developer. A pattern with a resolution of 5 μm was obtained from both PSPI precursor compositions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2293–2300, 2003

Effects of reactive end-capper on mechanical properties of chemical amplified photosensitive polyimide

Photosensitive polyimide (PSPI) was synthesized and characterized to replace the conventional polyimide buffer layer because direct patterning with PSPI could reduce the processing procedure to the half. Since PSPI should be dissolved in alkaline aqueous solution and have good mechanical properties after imidization, low molecular weight of PSPI was synthesized with reactive end-capper, which could extend the chain length of PSPI during imidization. Therefore norbornene end-capped PSPI precursor was synthesized with various 5-norbornene-2,3-dicarboxylic anhydride (NDA) content. Although molecular weight of PSPI decrease with increasing NDA content, the elongation at break and the glass transition temperature ( T g) of PSPI films imidized at 300 °C increased with increasing NDA content. On the other hand, elongation at break of PSPI films imidized at 350 °C decreased but T g of those increased with increasing NDA content. Above T g, thermal expansion coefficient decreased dramatically by introducing NDA end-capper. From mechanical and thermal properties of PSPI, it appears that low molecular weight of PSPI can be chain-extended and crosslinked during imidization.

Synthesis and characterization of a positive‐working, aqueous‐base‐developable photosensitive polyimide precursor

AbstractA positive‐working, aqueous‐base‐developable photosensitive polyimide precursor based on poly(amic ester)‐bearing phenolic hydroxyl groups and a diazonaphthoquinone photosensitive compound was developed. The poly(amic ester) was prepared from a direct polymerization of 2,2′‐bis‐(3‐amino‐4‐hydroxyphenyl)hexafluoropropane and bis(n‐butyl)ester of pyromellitic acid in the presence of phenylphosphonic dichloride as an activator. Subsequently, the thermal imidization of the poly(amic ester) precursor at 300°C produced the corresponding polyimide. The inherent viscosity of the precursor polymer was 0.23 dL/g. The cyclized polyimide showed a glass‐transition temperature at 356°C and a 5% weight loss at 474°C in nitrogen. The structures of the precursor polymer and the fully cyclized polymer were characterized by Fourier transform infrared spectroscopy and 1H‐NMR. The photosensitive polyimide precursor containing 25 wt % diazonaphthoquinone photoactive compound showed a sensitivity of 150 mJ/cm2 and a contrast of 1.65 in a 3 μm film with 1.25 wt % tetramethylammonium hydroxide developer. A pattern with a resolution of 10 μm was obtained from this composition. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 352–358, 2002

A New Positive-Type Photosensitive Alkaline-Developable Alicyclic Polyimide Based on Poly(amic acid silylester) as a Polyimide Precursor and Diazonaphthoquinone as a Photosensitive Compound

A new positive working photosensitive alicyclic polyimide precursor based on poly(amic acid tert-butyldimethylsilylester) (3) and 2,3,4-tris[2-diazo-1-(2H)-naphthalenone-4-sulfonyloxy]benzophenone ...

Development of Photosensitive Polyimide with Low Dielectric Constant.

A negative-working photosensitive polyimide (PI) precursor based on a low dielectric polyimide precursor having a low coefficient of thermal expansion (CTE) and 1, 4-dihydropyridine (DHP) as a photosensitive compound has been developed. Co-polyamic acid(Co-PAA)s were prepared by ring-opening polyaddition of aromatic dianhydrides with diamines. The dissolution behavior of Co-PAAs containing DHP after exposure was studied and it was found that the difference of dissolution rate between the exposed and unexposed parts was enough to get a high contrast due to the photochemical reaction of DHP in the polymer film. The cured Co- PI film at 380°C showed the low coefficient of thermal expansion of 20ppm and the low dielectric constant of 2.7 at 1MHz.