Characterisation of combined positive-negative photoresists by excimer laser ablation

Wei, Jiang; Hoogen, N.; Lippert, Thomas; Hahn, Ch.; Nuyken, Oskar; Wokaun, Alexander

doi:10.1007/s003390051545

Cited by 9 publications

(9 citation statements)

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“…Introducing a functional ester group that enables selective photocrosslinking without destruction of the polymer backbone can improve the stability of the polymers without changing the sensitivity to direct laser structur-ing [128]. These polymers can function as positive (laser ablation) as well as conventional negative resists.…”

Section: Introductionmentioning

confidence: 98%

“…To overcome this limitation, novel photopolymers have been developed which can be used as classical negative (cross-linking) resists, but still exhibit very high sensitivity towards laser direct structuring. These polymers are based on polyesters containing cinnamylidene malonic acid groups (CM polymers) which undergo photocrosslinking upon irradiation at l>395 nm and laser direct structuring at l=308 nm [128]. The CM polymers are also specially designed for excimer laser lithography using the XeCl excimer laser (308 nm) and pass the fundamental test for laser resists described in the previous chapter [126].…”

Section: Introductionmentioning

confidence: 99%

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Laser Application of Polymers

Lippert

2004

Polymers and Light

148

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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: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Laser Application of Polymers

Lippert

2004

Polymers and Light

148

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“…These polymers allow an investigation of the influence of cross‐linking and the influence of the linear absorption coefficient by varying R in the chemical structures (Figure 17 and 18). 50–53…”

Section: Discussionmentioning

confidence: 99%

Interaction of Photons with Polymers: From Surface Modification to Ablation

Lippert

2005

Plasma Processes & Polymers

137

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Summary: This work reviews the interaction of photons with polymers with an emphasis on UV laser ablation and surface modification using VUV lamps. Laser ablation of polymers is an established process in industrial applications, but the mechanisms of ablation are still controversial. Different polymers, such as poly(methyl methacrylate), polyimides and specially designed polymers are used as examples to show that the mechanism is a mixture of photochemical and photothermal features which are closely related to the polymer structure and properties. Different approaches to probe the ablation mechanisms and to improve ablation are discussed. Photoactive groups have been introduced into the polymer structure to improve the quality of ablation and to elucidate the ablation mechanisms. The experimental techniques to probe the ablation mechanism range from time‐resolved measurements, such as shadowgraphy, ToF‐MS, and ns‐surface interferometry to variations of the irradiation wavelengths and pulse lengths. The necessity for a critical evaluation of the experimental procedures and analysis is discussed exemplary for polyimides. The data for different types of polyimides are mixed up and some experimental procedures are possibly causing problems for the data evaluation. Various recent trends for laser ablation, such as ultrafast ablation or VUV ablation are also discussed. Surface modifications of polymers using VUV photons from lamps are discussed for oxidation and nitriding of poly dimethylsiloxane (PDMS) and polyolefines. The mechanism of the PDMS surface oxidation is presented in detail.

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“…structuring at k = 308 nm. [9] The CM polymers are also special designed for excimer laser lithography using the XeCl excimer laser (308 nm). The polymers reveal a high absorption coefficient at 308 nm, decompose into gaseous species which do not contaminate the surface, and exhibit a high sensitivity to laser ablation.…”

Section: Introductionmentioning

confidence: 99%