Sub-100 nm lines produced by direct laser ablation in polyimide

Phillips, H. M.; Callahan, D. L.; Sauerbrey, R.; Szabó, Gábor; Bor, Zs.

doi:10.1063/1.104778

Cited by 96 publications

(26 citation statements)

References 9 publications

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“…Specifically, at 80 mJ cm 2 , 0.7-m-wide grooves are found, while 0.85-m-wide grooves are observed at 240 mJ cm 2 . This has been previously reported and attributed to the ablation threshold [357,358], which will cause wider areas to be ablated at the higher fluences. Assuming a Gaussian laser intensity profile, the diameter of the beam with intensities above a constant threshold increases with increasing energy.…”

Section: Resultsmentioning

confidence: 82%

“…In addition, multipulse techniques seem to have problems with the quality of the gratings. Sometimes, substructures on top of the remaining ridges are detected [357,358], or the grooves are wider than the remaining ridges [359]. Using laser ablation as a fabrication technique provides the unique advantage that the grating depth can be varied continuously by adjusting the laser power.…”

Section: Resultsmentioning

confidence: 99%

“…A completely different approach uses a photocurable monomer and a contact mask (using the volume contraction of the polymer and diffusion of the monomer into the polymerization area) [355]. Faster techniques for highly reproducible gratings use phase masks [356,357], Talbot interferometers [358,359], transmission gratings with imaging optics [360], and Michelson interferometers [361]. All of these techniques use laser fluences above a certain material-dependent threshold.…”

Section: Introductionmentioning

confidence: 99%

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Laser Application of Polymers

Lippert

2004

Polymers and Light

150

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Laser ablation of polymers has been studied with designed materials to evaluate the mechanism of ablation and the role of photochemically active groups on the ablation process, and to test possible applications of laser ablation and designed polymers. The incorporation of photochemically active groups lowers the threshold of ablation and allows high-quality structuring without contamination and modification of the remaining surface. The decomposition of the active chromophore takes place during the excitation pulse of the laser and gaseous products are ejected with supersonic velocity. Time-of-flight mass spectrometry reveals that a metastable species is among the products, suggesting that excited electronic states are involved in the ablation process. Experiments with a reference material, i.e., polyimide, for which a photothermal ablation mechanism has been suggested, exhibited pronounced differences. These results strongly suggest that, in case of designed polymers which contain photochemically active groups, a photochemical part in the ablation mechanism cannot be neglected. Various potential applications for laser ablation and the special photopolymers were evaluated and it became clear that the potential of laser ablation and specially designed material is in the field of microstructuring. Laser ablation can be used to fabricate three-dimensional elements, e.g., microoptical elements.Keywords Laser ablation · Ablation mechanism · Photopolymers · Polyimide · Spectroscopy This was not always true, of course. For many years, the laser was viewed as "an answer in search of a question". That is, it was seen as an elegant device, but one with no real useful application outside of fundamental scientific research. In the last two to three decades however, numerous laser applications have moved from the laboratory to the industrial workplace or the commercial market. Lasers are unique energy sources characterized by their spectral purity, spatial and temporal coherence, and high average peak intensity. Each of these characteristics has led to applications that take advantage of these qualities: -Spatial coherence: e.g., remote sensing, range finding and many holographic techniques. -Spectral purity: e.g., atmospheric monitoring based on high-resolution spectroscopies. -and of course the many other applications in communication and storage, e.g., CDs.All of these high-tech applications have come to define everyday life in the late twentieth century. One property of lasers, however, that of high intensity, did not immediately lead to "delicate" applications but rather to those requiring "brute force". That is, the laser was used in applications for removing material or heating. The first realistic applications involved cutting, drilling, and welding, and the laser was little more advanced than a saw, a drill, or a torch. In a humorous vein A.L. Schawlow proposed and demonstrated the first "laser eraser" in 1965 [4], using the different absorptivities of paper and ink to remove the ink without damaging the und...

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Section: Resultsmentioning

confidence: 82%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Laser Application of Polymers

Lippert

2004

Polymers and Light

150

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“…For the fs results on PET (A~250 nm, 0 = 0 °) the equations fit well with n = 1. In contrast to the ns experiments [10,12], the results obtained with fs and PI (A,~100 nm, 0--0 °) cannot be calculated from these equations if n= 1 is employed. These results also demonstrate, for the first time, that with some polymers structures k S IIP can dominate.…”

Section: Discussionmentioning

confidence: 74%

“…The periodicity of such structures is of the order of the wavelength of the light and depends on the angle of incidence of the laserbeam. Ripple formation has been observed on various polymers, including Polylmide (PI) and PolyEthylene Terephthalate (PET), at laser fluences below [6-8] and above [9 11] the ablation threshold ~th" On PI, coherent structures with linewidths below 100 nm have also been obtained by means of an excimerlaser interference technique [11][12][13].Non-coherent structures with a periodicity in the micrometer range are frequently observed in polymers. These structures are either regular spaced naps, or joining or branching walls with a preferred direction (similar to Fig.…”

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confidence: 98%

Femtosecond excimer-laser-induced structure formation on polymers

et al. 1994

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Abstract. Structure formation upon 500 fs 248 nm KrFlaser irradiation of PolyEthylene Terephthalate (PET) and Polylmide (PI) has been investigated. The results obtained with fs pulses have been compared to those with ns pulses. 42.55, 81.40, 82.65 Irradiation of polymers with pulsed UV-laser light and pulse lengths of, typically, 1-50 ns frequently results in surface-structure formation [1][2][3]. These structures are often periodic or quasi-periodic in the sense that either the one-or two-dimensional lateral Fourier transform of the structure height h (x, y) corresponds to a single frequency or a relative narrow group of frequencies, respectively. The structures can be classified according to two groups: coherent and non-coherent structures. PACS:Coherent laser-induced surface structures such as ripples and dots are due to interference between the incident laser light and surface-scattered waves [4,5]. The periodicity of such structures is of the order of the wavelength of the light and depends on the angle of incidence of the laserbeam. Ripple formation has been observed on various polymers, including Polylmide (PI) and PolyEthylene Terephthalate (PET), at laser fluences below [6-8] and above [9 11] the ablation threshold ~th" On PI, coherent structures with linewidths below 100 nm have also been obtained by means of an excimerlaser interference technique [11][12][13].Non-coherent structures with a periodicity in the micrometer range are frequently observed in polymers. These structures are either regular spaced naps, or joining or branching walls with a preferred direction (similar to Fig. 1). For uniaxially and biaxially stretched foils wall-and nap-type structures, respectively, have been observed [14][15][16][17]. The internal stress-fields are related to either the production process of the polymer foil itself or/and to post-fabrication stretching.Non-periodic microstructures on excimer-laser irradiated PET have been reported in [18]. These structures consist of branched dendrites that have a lateral dimension in the micrometer range and a height of 5-30 nm.Femtosecond UV excimer-laser ablation was investigated for polymers [19][20][21], LiNbO3 [22], superconductors [23], and fused silica [24]. Ultra-short pulses require lower threshold fluences for ablation than ns pulses and yield an improved surface quality within the ablated areas.In this paper we study the formation of structures induced by femtosecond excimer-laser pulses on polymer surfaces.

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