Efficient proximity effect correction method based on multivariate adaptive regression splines for grayscale e-beam lithography

Mi, Wujun; Nillius, Peter

doi:10.1116/1.4875955

Cited by 5 publications

(2 citation statements)

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“…The discs used to build up Stacked Prism Lenses are fabricated using focused UV lithography 33 , for which a UV lens is employed to shape the UV beam and pattern the photoresist, instead of the binary photomask used in conventional UV lithography. The UV lens is fabricated with grayscale e-beam lithography 38 . The negative photoresist, SU-8 2100, The applied photoresist is exposed with focused UV lithography.…”

Section: Resultsmentioning

confidence: 99%

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A stacked prism lens concept for next-generation hard X-ray telescopes

Nilius

Pearce

et al. 2019

Nat Astron

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Effective collecting area, angular resolution, field of view and energy response are fundamental attributes of X-ray telescopes. The performance of state-of-the-art telescopes is currently restricted by Wolter optics, especially for hard X-rays. In this paper, we report the development of a new approach -the Stacked Prism Lens, which is lightweight, modular and has the potential for a significant improvement in effective area, while retaining high angular resolution. The proposed optics is built by stacking discs embedded with prismatic rings, created with photoresist by focused UV lithography. We demonstrate the SPL approach using a prototype lens which was manufactured and characterized at a synchrotron radiation facility. The design of a potential satellite-borne X-ray telescope is outlined and the performance is compared to contemporary missions.Since the first orbiting X-ray telescope, the Einstein Observatory, was launched in 1978, focusing X-ray telescopes (XRTs) have provided new knowledge on the universe by observing remote objects in the X-ray spectrum 1, 2 . The performance of XRTs is mainly determined by the optics. State-of-the-art focusing XRTs rely on Wolter optics, for which X-rays that are nearly parallel to the nested mirrors are collected by total external reflection. This has been successfully employed in several telescopes (e.g. Chandra 3 , XMM-Newton 4 , Swift 5 and the planned ATHENA mission 6 ), for X-rays in the energy range of 0.1 to 10 keV with high values of efficiency, angular resolution and sensitivity. However, for X-ray energies higher than 10 keV, using the same technique compromises spatial resolution and efficiency since the grazing angle quickly decreases with energy, making the focal length of the system impractically long and the field of view (FoV) very small. Moreover, the efficiency of the mirrors decreases, and nesting becomes more difficult. To mitigate this issue, it is possible to use multi-layered coatings and Bragg-reflection from depthgraded multi-layers to increase the grazing angle in the hard X-ray energy range 7, 8 . Current hard X-ray focusing telescopes such as NuSTAR 9 and Astro-H 10, 11 are designed this way. Although this provides a significant improvement in performance for hard X-rays, the long focal length is challenging when designing missions, and the small effective collecting area and narrow FoV limits the scientific return from missions. In addition, the angular resolution is severely influenced by 1 arXiv:2002.02299v1 [astro-ph.IM] 6 Feb 2020 figure error, surface roughness and assembly precision 2 .At present, refractive 12, 13 and diffractive transmissive X-ray optics 14 have been used in a wide range of applications [15][16][17] , such as biology 18 , chemistry 19 and lithography 20,21 . Several novel zone plates 14 , such as multilayer zone plates 22-25 , interlaced zone plates 26 and stacked zone plates 27 , as well as refractive optics, such as commercially available compound refractive X-ray lenses 13 , have been developed for hard X-ray ima...

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Section: Resultsmentioning

confidence: 99%

“…Lithographic process for the UV lens. The fabrication method for the UV lens is grayscale ebeam lithography 33,38 . The e-beam resist SML 1000 was used as structural material.…”

Section: Methodsmentioning

confidence: 99%