Mechanism of radiation‐induced degradation of poly(methyl methacrylate) as studied by ESR and electron spin echo methods

Ichikawa, Tsuneki; Yoshida, Hiroshi

doi:10.1002/pola.1990.080280519

Cited by 61 publications

(23 citation statements)

References 25 publications

(4 reference statements)

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“…It is known by electron paramagnetic resonance study [13] that the weakly bound electron is stable below 170 K, probably the transition temperature, where the local molecular motions are frozen, and the enhancement of I3 is also observed below the temperature [3][4][5][6][7][8]. Moreover, the visible light, the energy of 2~ 3 eV, can bleach the weakly bound electrons even below 170 K [13]. The bounding energy of the weakly bound electrons should be less than 2 3 eV.…”

Section: I3mentioning

confidence: 99%

The Effect of Visible Light Irradiation on Positronium Formation in Polyethylene at Low Temperature

et al. 1999

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The effect of visible light exposing on the ortho-positronium formation in polyethylene was studied. Lifetime spectra of positrons in polyethylene were measured in the temperature range between 50 K and 370 K. It was observed that the visible light quenches the enhancement of ortho-positronium intensity (I3) at lower temperature than ca. 250 K -the glass transition temperature of polyethylene. On the other hand, the lifetime of ortho-positronium component (T3) was not affected by the presence of the visible light.

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Section: I3mentioning

confidence: 99%

The Effect of Visible Light Irradiation on Positronium Formation in Polyethylene at Low Temperature

et al. 1999

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“…143,191) An excited state of PMMA is also formed through the recombination of an electron with its parent radical cation. The radical cations, 192) radical anions, 193,194) and excited PMMA molecules [195][196][197] are reported to decompose. In either case, the side chain first detaches and a macroradical is formed.…”

Section: Methacrylate Polymermentioning

confidence: 99%

Radiation Chemistry in Chemically Amplified Resists

Kozawa

Tagawa

2010

Jpn. J. Appl. Phys.

333

319

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Historically, in the mass production of semiconductor devices, exposure tools have been repeatedly replaced with those with a shorter wavelength to meet the resolution requirements projected in the International Technology Roadmap for Semiconductors issued by the Semiconductor Industry Association. After ArF immersion lithography, extreme ultraviolet (EUV; 92.5 eV) radiation is expected to be used as an exposure tool for the mass production at or below the 22 nm technology node. If realized, 92.5 eV EUV will be the first ionizing radiation used for the mass production of semiconductor devices. In EUV lithography, chemically amplified resists, which have been the standard resists for mass production since the use of KrF lithography, will be used to meet the sensitivity requirement. Above the ionization energy of resist materials, the fundamental science of imaging, however, changes from photochemistry to radiation chemistry. In this paper, we review the radiation chemistry of materials related to chemically amplified resists. The imaging mechanisms from energy deposition to proton migration in resist materials are discussed.

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“…12 Illumination of the sample with visible light for 30 min leads to the complete disappearance of the anion radicals and the increase of methyl radicals by following reactions. 10 • 12 -…”

mentioning

confidence: 99%

Thermal and Photo-Induced Reactions of Polymer Radicals in γ-Irradiated Poly(alkyl methacrylate)

Tanaka

Yoshida

Ichikawa

1990

Polym J

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ABSTRACT:Thermal and photo-induced reactions of radical species generated by y-irradiation of poly(methyl methacrylate) and poly(ethyl methacrylate) have been investigated by means of ESR spectroscopy. The y-irradiation at cryogenic temperature leads to the formation of three major radical species, side chain ---COOC.H 2 • + 1 · -anion radicals and---COOCHC._ 1 H 2 • _ 1 radicals, and main chain -CH-radicals. Cation radicals are immediately converted to the neutral radicals by proton transfer to the polymer molecules. Illumination of the polymer anion radicals with visible light leads to electron detachment or the elimination of ester alkyl groups to form alkyl radicals. Illumination with UV light leads to the conversion of the ---COOCHC. _ 1 H 2• _ 1 radicals to acyl-type-C = 0 radicals. Both the---COOCHC. _ 1 H 2.-1 and the-C = 0 radicals are the precursor of scission-type ·qCH3)(COOC.H2.+ 1)CH 2-radicals.KEY WORDS Poly(methyl methacrylate) / Poly(ethyl methacrylate) /Resist/ Lithography / Radiolysis / Degradation / Chain scission / Radical / ESR / Since poly(alkyl methacrylate)s are typical positive-resist materials in deep UV, electron beam and X-ray lithography, many studies have been carried out for clarifying the mechanism of radiation-induced degradation of poly(alkyl methacrylate)s. It is well known that the irradiation of poly(alkyl methacrylate)s with Ionizing radiations results in the formation of scission-type radicals 1 -3 ·c-(CH3)(COOC.H2.+ 1)CH 2-. The formation of the scission-type radicals strongly suggests that the degradation is induced by the reaction of polymer radicals.Since ionization is the main action of ionizing radiations, radiation-generated positive and negative ion radicals are thought to play important roles in the degradation of the polymers. A considerable amount of spectroscopic studies have been carried out for elucidating the nature and the roles of primary ion rad-* To whom correspondence should be addressed. icals in the degradation of the polymers. 4 -10 However, there have been few consistencies between investigators even for the spectroscopic assignment of the ion radicals. We have recently made the pulse radiolysis studies of poly(alkyl methacrylate) solutions, and determined the optical absorption bands of the polymer anion radicals. 11 We have also made the ESR and electron spin echo studies of yirradiated poly(methyl metacrylate) (PMMA) and found that the y-irradiation at cryogenic temperature leads to the formation of three major radical species, side chain -COOCH 3 ·-anion radials and -COOCH 2 radicals, and main chain -CH-radicals. 12 Upon annealing the polymer to room temperature, the -COOCH 2 radicals were disappeared accompanied by the formation of scission-type ·qcH 3 )(COOCH 3 )CH 2 -radicals, which suggests that the -COOCH2 radicals are respon-835

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Mechanism of radiation‐induced degradation of poly(methyl methacrylate) as studied by ESR and electron spin echo methods

Cited by 61 publications

References 25 publications

The Effect of Visible Light Irradiation on Positronium Formation in Polyethylene at Low Temperature

The Effect of Visible Light Irradiation on Positronium Formation in Polyethylene at Low Temperature

Radiation Chemistry in Chemically Amplified Resists

Thermal and Photo-Induced Reactions of Polymer Radicals in γ-Irradiated Poly(alkyl methacrylate)

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