Femtosecond uv excimer laser ablation

Küper, S.; Stuke, M.

doi:10.1007/bf00692122

Cited by 315 publications

(98 citation statements)

References 14 publications

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“…Ablation at 308 nm was done in air atmosphere with the set up described in detail [4]. Before ablation, the sample was placed under a contact mask with 200 gm holes and irradiated for 40 s with the fusion systems UV lamp.…”

Section: Methodsmentioning

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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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: Methodsmentioning

confidence: 99%

“…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].…”

mentioning

confidence: 99%

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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“…In addition, if the focus position of the ultrafast laser beam is set inside a transparent material, then multiphoton absorption can be confined to a region near the focal volume to implement internal modification and 3D micro-and nanofabrication of transparent materials [7][8][9]. Thus, since the first demonstration of femtosecond laser ablation in 1987 [10,11], research and development with regard to ultrafast laser processing has rapidly advanced. Figure 1 shows the evolution of the number of papers related to ultrafast laser processing presented at the SPIE LAMOM conference each year.…”

Section: Introduction and Historymentioning

confidence: 99%

Progress in ultrafast laser processing and future prospects

Sugioka

2017

Nanophotonics

170

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Abstract:The unique characteristics of ultrafast lasers have rapidly revolutionized materials processing after their first demonstration in 1987. The ultrashort pulse width of the laser suppresses heat diffusion to the surroundings of the processed region, which minimizes the formation of a heat-affected zone and thereby enables ultrahigh precision micro-and nanofabrication of various materials. In addition, the extremely high peak intensity can induce nonlinear multiphoton absorption, which extends the diversity of materials that can be processed to transparent materials such as glass. Nonlinear multiphoton absorption enables three-dimensional (3D) micro-and nanofabrication by irradiation with tightly focused femtosecond laser pulses inside transparent materials. Thus, ultrafast lasers are currently widely used for both fundamental research and practical applications. This review presents progress in ultrafast laser processing, including micromachining, surface micro-and nanostructuring, nanoablation, and 3D and volume processing. Advanced technologies that promise to enhance the performance of ultrafast laser processing, such as hybrid additive and subtractive processing, and shaped beam processing are discussed. Commercial and industrial applications of ultrafast laser processing are also introduced. Finally, future prospects of the technology are given with a summary.

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“…16 Much of the later work has been devoted to explaining departures from this behavior by means of more sophisticated models which include such aspects as thermal diffusion and/or nonlinear absorption within the material, screening of the incoming radiation by the ablation plume, and incubation effects. [17][18][19][20][21][22][23] Further insights into the ablation mechanism have been obtained by a variety of techniques, including spectroscopy of the ablation products and high speed photography. 24 The modeling work to date has resulted in a comprehensive picture of laser ablation by a single illuminating beam at normal incidence.…”

Section: Introductionmentioning

confidence: 99%

Excimer laser ablation of microstructures: A numerical model

Paterson

Holmes

Smith

1999

Journal of Applied Physics

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A new model for the ablation of microstructures with excimer laser radiation is presented. The model is based on an interactive two-step approach. The local distribution of the light over the developing structure is evaluated for each pulse. This distribution is then used to calculate the local etch rate, and hence the change to the structure. Despite the assumptions inherent in the model, in particular assumptions made about the propagation of the light through a developing structure and about the etching behavior of the materials, results from the model agree with actual aspects of ablated structures. The model has been used with some success to predict the wall angles of trench structures ablated using partially coherent illumination from a fly's eye homogenizer. Predictions of the model show good agreement with the experiment results. In particular, the model correctly predicts the variation of the wall angles with incident fluence and also predicts structures with well defined wall angles over depths much greater than the depth of focus of the image.

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Femtosecond uv excimer laser ablation

Cited by 315 publications

References 14 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

Progress in ultrafast laser processing and future prospects

Excimer laser ablation of microstructures: A numerical model

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