Characterization of a Dissociative Excited State in the Solid State: Photochemistry of Poly(methyl methacrylate). Photochemical Processes in Polymeric Systems. 5

Gupta, Amitava; Liang, Ranty H.; Tsay, Fun Dow; Moacanin, J.

doi:10.1021/ma60078a060

Cited by 112 publications

(88 citation statements)

References 3 publications

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“…The shift in the wavenumber of both ester absorption bands is in contrast to the observations of earlier workers [11 ] who reported a earbonyl shift and only a decrease of the C -O stretch upon irradiation of PMMA with 266nm laser light. Clearly, in our experiments a different type of ester is formed in the photolysis of PMMA, although it would be speculative to assign a structure from these UV and infrared spectra alone.…”

Section: Discussioncontrasting

confidence: 99%

“…The band at 2104 cm -~ cannot be assigned unambiguously from the IRspectrum alone. Most likely, carbon monoxide is formed, but also ketene has been postulated as a photoproduct of PMMA before [11].…”

Section: Discussionmentioning

confidence: 99%

“…In earlier studies [7][8][9][10][11] other researchers have observed an increasing UV absorption upon irradiation of PMMA with a 253.7 nm mercury lamp or 266 nm laser radiation. The increasing UV absorption was attributed mainly to the formation of carbonyl or unsaturated species [10], which, however, were not detected in the infrared spectrum.…”

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confidence: 91%

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UV-excimer-laser ablation of polymethylmethacrylate at 248 nm: Characterization of incubation sites with Fourier transform IR- and UV-Spectroscopy

1989

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Abstract. Ultraviolet and Fourier transform infrared (FTIR) spectroscopic experiments with thin films of polymethylmethacrylate (PMMA) are reported. During the incubation with 248 nm excimer laser light or continuous (cw) UV light sources PMMA exhibits a rapidly increasing, broad UV absorption. This is caused by the production of unsaturated species, which are detected in the infrared spectrum of irradiated PMMA films. The spectral data explain the incubation process preceding the ablation of PMMA at 248 nm. Taking advantage of the increased UV absorption, cw light incubated PMMA films can be selectively ablated by standard 308 nm excimer laser pulses. PACS: 33.20, 81.40, 82.30 Surfaces can be structured by ablation with intense UV laser light [-1,2]. A wide variety of polymers with different penetration depths for UV laser light show for certain fluence ranges high removal rates of material on the order of micrometers per pulse, along with little thermal damage to the edges. Thus the surfaces of many polymers have been patterned with a resolution down to less than one micrometer [3]. While this technique is already applied in industry and surgery, many effects ofphotoablation still have to be explained and a detailed understanding of the ablation process remains a challenge.In a wide fluence range polymethylmethacrylate (PMMA) does not start ablation with the first laser pulse, but requires a number of incubation pulses [-4, 5] before a steady ablation regime is reached. During these incubation pulses the material is believed to suffer damage in its chemical structure. The etch curve of PMMA (cf. Fig. 2 of [4]) with 248 nm excimer laser pulses shows for higher fluences a leveling off and reaches a saturation plateau, where a further increase in fluence does not yield a significantly higher etch rate. This effect had been attributed to a shielding of the PMMA surface by the ablation plume I-5,6]. Our model calculations [-4] showed, however, that this alone could not fully explain the effect. Assuming a dynamic absorption coefficient, depending on the irradiation dosis and the intensity of the laser light, the etch rate and the number of incubation pulses could be predicted quantitatively for the ablation of PMMA with excimer laser pulses of 16 ns duration at 248 nm. This paper will discuss the origin of the increase in absorption due to the irradiation dosis.Infrared and UV spectra provide valuable information about the excimer laser induced photochemistry of PMMA. In earlier studies [7][8][9][10][11] other researchers have observed an increasing UV absorption upon irradiation of PMMA with a 253.7 nm mercury lamp or 266 nm laser radiation. The increasing UV absorption was attributed mainly to the formation of carbonyl or unsaturated species [10], which, however, were not detected in the infrared spectrum.In the following we shall describe ultraviolet-and infrared-spectroscopic experiments with PMMA, irradiated with light from a 248 nm (16 ns) excimer laser and various continuous light sources. The light in...

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Section: Discussioncontrasting

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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UV-excimer-laser ablation of polymethylmethacrylate at 248 nm: Characterization of incubation sites with Fourier transform IR- and UV-Spectroscopy

1989

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“…The G-value of acid generation is 1.4 without any acid generators. 124) Although the counteranion has not been identified, it is possibly a formic 198) or acetic 196) anion. The main chain scission of PMMA is also induced by UV light.…”

Section: Methacrylate Polymermentioning

confidence: 99%

Radiation Chemistry in Chemically Amplified Resists

Kozawa

Tagawa

2010

Jpn. J. Appl. Phys.

336

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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“…But these three masses are a leading contribution only for the more interesting first peak. A more detailed analysis of 16 further selected masses (partially measured also in [6,20]) indicate that the second peak above 250°C is dominated by a series of small fragments typically for a total degradation of the polymer film.…”

Section: Resultsmentioning

confidence: 99%

Hardening of smooth pulsed laser deposited PMMA films by heating

et al. 2009

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Smooth poly(methyl methacrylate) (PMMA) films without any droplets were pulsed laser deposited at a wavelength of 248 nm and a laser fluence of 125 mJ/cm 2 . After deposition at room temperature, the films possess low universal hardness of only 3 N/mm 2 . Thermal treatments up to 200°C, either during deposition or afterwards, lead to film hardening up to values of 200 N/mm 2 . Using a combination of complementary methods, two main mechanisms could be made responsible for this temperature induced hardening effect well above the glass transition temperature of 102°C. The first process is induced by the evaporation of chain fragments and low molecular mass material, which are present in the film due to the ablation process, leading to an increase of the average molecular mass and thus to hardening. The second mechanism can be seen in partial cross-linking of the polymer film as soon as chain scission occurs at higher temperatures and the mobility and reactivity of the polymer material is high enough.

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Characterization of a Dissociative Excited State in the Solid State: Photochemistry of Poly(methyl methacrylate). Photochemical Processes in Polymeric Systems. 5

Cited by 112 publications

References 3 publications

UV-excimer-laser ablation of polymethylmethacrylate at 248 nm: Characterization of incubation sites with Fourier transform IR- and UV-Spectroscopy

UV-excimer-laser ablation of polymethylmethacrylate at 248 nm: Characterization of incubation sites with Fourier transform IR- and UV-Spectroscopy

Radiation Chemistry in Chemically Amplified Resists

Hardening of smooth pulsed laser deposited PMMA films by heating

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