Tetramethylammonium Hydroxide Aqueous Solution Research Articles

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

AbstractA 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

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

Fluoropolymer Resists: Fundamentals and Lithographic Evaluation

Hexafluoroisopropanol (HFA) extensively utilized in the design of 157 nm resists provides attractive but complex dissolution characteristics. Poly(norbornene hexafluoroalcohol) (PNBHFA), which is equivalent to polyhydroxystyrene for 248 nm lithography, exhibits linear dissolution kinetics in 0.26 N tetramethylammonium hydroxide (TMAH) aqueous solution while weaker developers could induce swelling, resulting in multi-stage dissolution. We have found that the dissolution rate of PNBHFA in 0.26 N TMAH (3,000-8,000 A/sec) is not controlled by polymer molecular weights but affected more significantly by the endo/exo isomer ratio of NBHFA employed in polymerization.PNBHFA with a higher exo concentration dissolves more slowly and exhibits less hydrogen-bonding. The H-bonding interaction is not affected by molecular weight. The HFA OH in the exo isomer interacts more strongly with an acid generator and ester. Dissolution of exo-enriched PNBHFA is more strongly inhibited by addition of an acid generator. Lithographic performance of our PNBHFA blend resist is affected by the endo/exo ratio of NBHFA. Copolymers of two similar TFMAs with NBHFA and vinyl ether bearing norbornane hexafluoroalcohol (VENBHFA) exhibit very different surface segregation when blended with PNBHFA. The hydrophilicity of our TBTFMA copolymer system has been vastly improved by incorporating a polar comonomer carrying two HFA groups, which has decreased the 157 nm absorption to 0.9-1.1/μm. The transparency can be further increased by using such co- and terpolymers as a dissolution inhibitor or contrast booster of the most transparent vendor fluoropolymers.

Positive-type Photosensitive Polyimide with Low Modulus based on Soluble Block Copoly(imide-siloxane)

A novel positive-type photosensitive polyimide with low modulus based on soluble block copoly(imide-siloxane) with hydroxyl group and diazonaphthoquinone as a photoreactive compound has been developed. The base block copoly(imide-siloxane) was prepared by a direct one-pot polycondensation of biphenyltetracarboxylic dianhydride(BPDA) 2,2-Bis(3-amino-4-methyl)phenylhexafluoropropane(Bis-AP-AF) and diamino(poly)siloxane in the presence of a γ-valerolactone and pyridine catalyst system using dipolar aprotic solvent such as N-methyl-2-pyrrolidone(NMP). The base block copoly(imide-siloxane) consists of aromatic polyimide unit as a hard segment, and polysiloxane unit as a soft segment.The polysiloxane unit contributed to the resulting poly(imide-siloxane) film with not only colorlessness and transparency which are the important factors for a photosensitive polyimide but also low modulus. Due to the low modulus, it can reduce the residual wafer stress caused by the CTE (coefficient of thermal expand) mismatch between silicon wafer (3ppm/K) and polyimide (30∼60ppm/K), and prevent semiconductor devices from physical and electric damage. Photosensitive block copoly(imide-siloxane) containing 20wt% Ester of 2,3,4,4'-trihydrobenzophenone with 1,2-naphthoquinone-(2)-diazide-5-sulfonic acid (4NT-300) showed a sensitivity of 350mj/cm2 and a contrast of 1.95 when it was exposed to UV light, followed by development with 2.38% tetramethylammonium hydroxide (TMAH) aqueous solution containing 10wt% isopropyl alcohol (IPA) at room temperature.

New Positive-type Photosensitive Polyimide Having Sulfo Groups 2. Polyimides from 2,2'-oxy(or thio)bis(5-aminobenzenesulfonic acid) 4,4'-oxydianiline, and 4,4'-hexafluoro propylidene-bis(phthalic anhydride)

New positive-working photosensitive polyimides (PSPIs) based on polyimides bearing sulfo groups (PISs) 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 have been developed. PISs were prepared by ring-opening polyaddition of 2,2'-oxybis(5-aminobenzenesulfonic acid) (OBAS) or, 2,2'-thiobis(5-aminobenzenesulfonic acid) (TBAS) and 4,4'-oxydianiline (ODA), with 4,4'-hexafluoropropylidenebis(phthalic anhydride) (6FDA), followed by thermal cyclization in m-cresol. PIS containing 30wt% of S-DNQ showed a sensitivity of 100 mJ cm-2 and a contrast of 2.6, when it was exposed to 365-nm light followed by developing with 2.38 wt % aqueous tetramethylammonium hydroxide (TMAH) solution at room temperature. A fine positive image featuring 20μm line and space patterns was observed on the film of the photoresist exposed to 200 mJ cm-2 of UV-light at 365 nm by the contact mode. The positive image was successfully converted to the polyimide pattern by thermal treatment.

Characterization of Positive-type Photosensitive Polyimide Films Formed by Electrodeposition Coating

Soluble polyimides having pendant carboxyl groups were prepared by 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 γ-valerolactone/pyridine catalyst system using N-methyl-2-pyrrolidone (NMP)/toluene mixture as a solvent, and used for the electrodeposition coating. Positive-type photosensitive polyimide compositions for electrodeposition coating consisted of the pendant carboxyl-containing polyimide, NMP and cyclohexanone as solvents, N-methylmorpholine as a neutralizing agent, deionized water and diazonaphthoquinone(DNQ) compound(PC-5®) as a photosensitive material. The electrodeposition coating under a fixed voltage provided photosensitive polyimide films with high levels of appearance and smoothness on a copper foil. These photosensitive polyimide films formed by electrodeposition coating gave positive-tone behavior by UV irradiation and following development in an aqueous tetramethylammonium hydroxide(TMAH) or ethanolamine-containing solution. The scanning electron microscopic photographs of the resulting images showed fine and sharp line/space patterns.

A study of the passivation peak current density for (1 0 0) oriented silicon in tetramethylammonium hydroxide (TMAH): effect of temperature, concentration and carrier type

A detailed study into the effect of temperature and concentration on the peak current density for p- and n-type (1 0 0) oriented silicon (Si) in aqueous tetramethylammonium hydroxide (TMAH) solutions is described. The peak current density data was obtained from linear sweep voltammograms carried out at a sweep rate of 5 mV s −1. The temperature range used was 30–80 °C and the concentration range employed was 5–25 wt.% TMAH. The peak current density was found to increase with temperature for both p(1 0 0) and n(1 0 0) Si at every concentration investigated. A general decrease in the peak current density was observed with increasing concentration for the two carrier types at every temperature investigated. The effect of carrier type was also investigated and how this effect varied with concentration and temperature. Peak current density data was used to estimate the activation energy for the dissolution of the Si(1 0 0) plane in TMAH. This appears to be a valid alternative method to the use of etch rate data for estimating these activation energies. The activation energy for n(1 0 0) Si (0.600–0.616 eV) was found to be consistently higher than that of its p(1 0 0) counterpart (0.521–0.578 eV). The results presented confirm that a close relationship between the peak current density and the etch rate exists.

New positive-type photosensitive polyimide having sulfo groups

A new positive-working photosensitive polyimide (PSPI) has been developed, which is based on polyimide bearing sulfo groups (PIS) 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. PIS was prepared by ring-opening polyaddition of 1,3-phenylenediamine-4-sulfonicacid (PDAS), 4,4′-oxydianiline (ODA), and 4,4′-hexafluoropropylidenebis(phthalic anhydride) (6FDA), followed by thermal cyclization in m-cresol. PIS containing 30 wt% of S-DNQ showed a sensitivity of 100 mJ cm −2 and a contrast of 1.7, when it was exposed to 365 nm light followed by developing with 2.38 wt% aqueous tetramethylammonium hydroxide (TMAH) 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 of UV-light at 365 nm by the contact mode. The positive image was successfully converted to the polyimide pattern by thermal treatment.

Chemically Amplified Photosensitive Polybenzoxazoles Based on tert-Butoxycarbonyl Protected Hyperbranched Poly(o-hydroxyamide)s

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 AB 2 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/cm 2 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/cm 2 of i-line exposure. The patterned film was successfully converted to polybenzoxazole without any distortion by thermal treatment at 300 °C for 1 h.

Effect of preswelling on radiation degradation of cotton cellulose

Cotton cellulose was swollen in aqueous solutions of sodium hydroxide and tetramethylammonium hydroxide (TMAH), respectively, in the presence of air. Samples after neutralization and drying were irradiated in open air (3, 10, and 20 kGy) in dry form (water content about 8–10%). Degree of polymerization (DP) and FTIR spectra were determined as a function of base concentration. Decrease of DP during irradiation was restrained by base pretreatment of cellulose probably due to the crosslinks developed. This effect was observed at low concentration as well where no crystal transition occurs. In the FTIR spectra absorbances belonging to the intermolecular H bonds decreased with increasing base concentration. High-energy irradiation resulted in a further decrease of intermolecular hydrogen bonds. It was assumed that crosslinking was assisted by the increased mobility of molecular chains in the amorphous part of base-treated cellulose. Effect of preswelling was more significant for TMAH-treated samples.

"Mercerization" of Cotton with Tetramethylammonium Hydroxide

Bleached cotton fabric is treated with an aqueous solution of tetramethylammonium hydroxide (TMAH) or with sodium hydroxide in various concentrations with or without tension. The degree of "mercerization" is characterized by the crystallinity, iodine sorp tion capacity, water retention values before and after drying, dye uptake, and color strength. The shrinkage of the slack mercerized fabrics is also measured. The "mercer izing" effect of TMAH is higher than that of NaOH, and all changes caused by swelling are significantly reduced by tension.

A New Positive-working Alkaline developable Photoresist Based on Partially O-tert-butoxycarbonylmethylated-tetra-C-methylcalix[4]resorcinarene and a Photoacid Generator.

A new positive-working low-molecular-weight photoresist has been developed. The photoresist consisted of the matrix, tetra-C-methylcalix[4]resorcinarene (p-t-BM-C4-R) in which the OH groups were protected with tert-butoxycarbonylmethyl groups (protecting ratio: 27 ∼ 60%), and a photoacid generator (PAG), 5-(propylsulfonyloxyimino-5H-thiophen-2-ylidene)-2-methylphenyl-acetonitrile (PTMA). The p-t-BM-C4-R (protecting ratio: 40%) containing PTMA (2 wt%) showed a high sensitivity (10 mJ/cm2) and a contrast 11 after the irradiation with g-line, post-exposure baking at 120 °C at 60 sec, and developing with 2.38 wt% tetramethylammonium hydroxide aqueous solution (TMAHaq) at 20 °C for 10 sec.

Chemically Amplified Photosensitive Poly(benzoxazole)

A novel chemically amplified photosensitive poly (benzoxazole) (PBO) precursor based on partially tert-buthoxycarbonylated (t-BOC) poly (o-hydroxyamide) having norbornene end-capping groups 5 and diphenyliodonium-9, 10-dimethoxyantracene-2-sulfonate (DIAS) as a photo-acid generator has been developed. The resist showed a sensitivity of 60 mJ cm-2 and a contrast of 2.5 when it was exposed to 365 nm light, followed by post-baking at 120°C for 5min and developing with 2.38 wt% aqueous tetramethylammonium hydroxide (TMAH) solution at 25°C. A fine positive image featuring 10μm line and space patterns was obtained on the film exposed to 100 mJ cm-2 of UV-light at 365 nm by the contact mode. By heat treatment at 350°C for 1h, this positive image gave the cross-linked PBO retaining its original shape that indicated high durability during thermal process.

A New Photoresist Materials for 157nm Lithography-3: Poly [2-hydroxy-3-pinanyl vinyl sulfonate-co-4-(1,1,1,3,3,3-hexafluoro-2-hydroxypropyl)styrene

A new photoresist for 157 nm lithography on the basis of poly[(2-hydroxy-3-pinanyl vinyl sulfonate)-co-4-(1, 1, 1, 3, 3, 3-hexafluoro-2-hydroxypropyl)styrene] [poly(VSO3Pina73-co-HFISt27)] and triphenylsulfonium perfluoro-1-butanesulfonate (TPS-Nf) as a photoacid generator (PAG) has been developed. Poly(VSO3Pina-co-HFISt)s were prepared by free radical polymerization of VSO3Pina with HFISt. The photoresist consisting of poly(VSO3Pina73-co-HFISt27) and 4 wt% TPS-Nf showed a sensitivity of 10 mJ cm-2 and a contrast of 6, when it was exposed to 157 nm laser and developed with 0.6 wt% aqueous tetramethylammonium hydroxide (TMAH) solution at 25 °C. A fine positive image of 140 nm line and space patterns was printed in a film, which was exposed to 15 mJ cm-2 by a contact printed mode. The resist film showed an optical density (OD) value of 3.6 μm-1 at 157 nm wavelength.

Photosensitive poly(benzoxazole) based on precursor from diphenyl isophthalate and bis( o-aminophenol)

A new synthetic method for the preparation of poly(benzoxazole) (PBO) precursor, poly( o-hydroxyamide) ( 7) from bis( o-aminophenol) ( 5) and diphenyl isophthalate ( 6) has been developed. Polymer 7 was prepared by the polycondensation of 5 and 6 in 1-methyl-2-pyrrolidinone (NMP) at 185–205 °C. Model reactions were carried out in detail to elucidate appropriate conditions for the formation of 2-hydroxybenzanilide ( 3) from o-aminophenol ( 1) and phenyl benzoate ( 2). The photosensitive (PBO) precursor based on polymer 7 containing a 22% of benzoxazole unit and 30 wt% 1-{1,1-bis[4-(2-diazo-1-(2 H)naphthalenone-5-sulfonyloxy)phenyl]ethyl}-4-{1-[4-(2-diazo-1(2 H)naphthalenone-5-sulfonyloxy)phenyl]methylethyl}benzene (S-DNQ) showed a sensitivity of 110 mJ cm −2 and a contrast of 5.0 when it was exposed to 436 nm light followed by developing with a 2.38 wt% aqueous tetramethylammonium hydroxide solution at room temperature. A fine positive image featuring 8 μm line and space patterns was observed on the film of the photoresist exposed to 200 mJ cm −2 of UV-light at 436 nm by the contact mode.

New synthetic route for photosensitive poly(benzoxazole)

AbstractA 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

Preparation and characterization of CuO–ZrO2 nanopowders

Nanosized copper oxide–zirconia particles containing 10–30 mol% of copper were prepared by using a precipitation technique in aqueous tetramethylammonium hydroxide solutions. Two methods, in situ (INS) and step-by-step (SBS), which differed in the time when the copper salt was introduced to the synthesis procedure, were used, and this allowed a comparison of the properties of the final powders produced using the two modes of preparation. The surface areas and phase compositions were different for the samples prepared from the two different methods after calcination at 500 °C. A surface area of 168 m2 g−1 was obtained for the sample prepared with the SBS method and 121 m2 g−1 for the INS method, both contain 30 mol% copper. Tetragonal ZrO2 was observed from X-ray diffraction patterns for all samples prepared with the SBS method, however, no separate phase of copper or copper oxide was observed. It is proposed that all of the copper is finely distributed on the surface of the ZrO2 particles with the SBS method. For the samples prepared from the INS method, tetragonal ZrO2 was obtained at a low copper content and the peaks indexed to tetragonal ZrO2 shifted to higher angle with the increase of copper content, indicating copper ions being incorporated into the lattice. An amorphous compound was obtained at high copper content (30 mol%). The phase change with the calcination temperature was also investigated for the INS sample containing 30 mol% copper. The studies show that tetragonal ZrO2 and copper oxide were present after calcination at 400 °C, and tetragonal ZrO2 with a small amount of monoclinic ZrO2, as well as copper oxide, formed after calcination at 700 °C. However, after heating at 500 °C, amorphous compounds were obtained, suggesting that 500 °C could be a phase transition point. The incorporation of copper in the ZrO2 lattice resulted in a loss of order in the ZrO2 structure when calcined at 500 °C, with a further increase in the calcination temperature leading to the phase change.

A Study on Reclaimed Photoresist Developer Using an Electrodialysis Method

Photoresist developer reclamation technology and systems have been investigated and characteristics of the reclaimed developer were evaluated. High-purity tetramethylammonium hydroxide (TMAH) aqueous solution adjusted to an appropriate concentration is generally used as the photoresist developer in the lithography step for large scale integration (LSI) and liquid crystal display (LCD) manufacturing processes. TMAH was recovered by an electrodialysis (ED) method from developer waste (spent developer), and purified by ion exchange (IE) technologies. The reclaimed developer was analyzed and found to feature the same purity as fresh commercial developer and no differences in their characteristics as developer material could be determined. Our experimental reclamation system recovered more than 80% of stable TMAH from waste and, moreover, achieved large reductions in operating costs, which amounted to total cost reductions of 55–75% for LSI and 65–85% for LCD compared with the conventional systems without reclamation studied by us. In addition, environmental load was reduced.

New positive‐type photosensitive polymer based on poly(2,6‐dihydroxy‐1,5‐naphthylene) and diazonaphthoquinone

AbstractA positive working photosensitive polymer based on poly(2,6‐dihydroxy‐1,5‐naphthylene) (PDHN) with 1‐(1,1‐bis{4‐[2‐diazo‐1(2H)naphthalene‐5‐sulfonyloxy]phenyl}ethyl)‐4‐(1‐{4‐[2‐diazo‐1(2H)naphthalene‐5‐sulfonyloxy]phenyl}methylethyl) benzene (S‐DNQ) as a photosensitive compound has been developed. PDHN (number‐average molecular weight: 13,000; polydispersity index: 1.9) was prepared by oxidative coupling polymerization of the 2,6‐dihydroxynaphthalene‐benzylamine complex using iron(III) chloride hexahydrate in the solid state. A 10 wt % loss temperature of PDHN was 450 °C in air, and the film of 1 μm thickness showed excellent transparency above 400 nm. The resist system consisting of PDHN and S‐DNQ gave a clear positive pattern when it was exposed to 436 nm of light, followed by development with a 0.50 wt % aqueous tetramethylammonium hydroxide solution at 25 °C. The sensitivity (D) and contrast (γ) were 300 mJ/cm2 and 2.1, respectively. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 393–398, 2002

Synthesis and characterization of norbornene-based polymers with 7,7-dimethyloxepan-2-one acid labile groups for chemically amplified photoresists

The present paper describes a novel class of norbornene-based copolymers containing 7,7-dimethyloxepan-2-one acid labile groups. Poly(3-(bicyclo[2.2.1]hept-5-en-2-ylhydroxymethyl)-7,7-dimethyloxepan-2-one-co-5-((2-decahydronaphthyl)oxycarbonyl)-norbornene-co-5-norbornene-2-carboxylic acid- co-maleic anhydride) was synthesized and evaluated as a potential chemically amplified resist for ArF lithography. The 7,7-dimethyloxepan-2-one group of the matrix polymer was readily cleaved and the carboxylic acid functionality was formed by acid-catalyzed ring-opening reaction in the exposed region after post-exposure bake. The resist patterns of 0.12 μm feature size were obtained at a dose of 10 mJ cm −2 with a conventional developer, 2.38 wt% tetramethylammonium hydroxide aqueous solution, using an ArF excimer laser stepper.