Electron beam writing of continuous resist profiles for optical applications

Stauffer, J. M.

doi:10.1116/1.586051

Cited by 23 publications

(11 citation statements)

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“…Blazed diffractive elements can be fabricated either by a series of photolithography processes that approximate the surface relief with a multilevel structure [1][2][3][4] or by direct-write technologies, such as single-point laser beam writing in photoresist, 5 single-point diamond turning, 6 or single-point electronbeam (e-beam) writing in polymers. [7][8][9] In this paper we are concerned with the synthesis and the fabrication of diffractive elements composed of binary subwavelength pillars etched in a high-index material deposited on a glass substrate for visible-light operation. Their principle of operation relies on the analogy between periodic subwavelength-structured surfaces and artificial dielectric materials.…”

Section: Introductionmentioning

confidence: 99%

Design and fabrication of blazed binary diffractive elements with sampling periods smaller than the structural cutoff

et al. 1999

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International audienceWe report here on the theoretical performance of blazed binary diffractive elements composed of pillars carefully arranged on a two-dimensional grid whose period is smaller than the structural cutoff. These diffractive elements operate under unpolarized light. For a given grating geometry, the structural cutoff is a period value above which the grating no longer behaves like a homogeneous thin film. Because the grid period is smaller than this value, effective-medium theories can be fully exploited for the design, and straightforward procedures are obtained. The theoretical performance of the blazed binary elements is investigated through electromagnetic theories. It is found that these elements substantially outperform standard blazed échelette diffractive elements in the resonance domain. The increase in efficiency is explained by a decrease of the shadowing effect and by an unexpected sampling effect. The theoretical analysis is confirmed by experimental evidence obtained for a 3λ-period prismlike grating operating at 633 nm and for a 20°-off-axis diffractive lens operating at 860 nm

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Section: Introductionmentioning

confidence: 99%

Design and fabrication of blazed binary diffractive elements with sampling periods smaller than the structural cutoff

et al. 1999

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“…This causes exposed resist to be soluble for wet development so that it can be etched down to the substrate while unexposed resist remains virtually intact. In constrast to this process, which produces a bi-level topography in resist, GEBL relies on a lateral gradient of M w imparted in the resist to produce a multi-level topography following a timed wet development (Stauffer et al 1992). Illustrated in Figure 4, this is achieved using a dose-modulated electron exposure where doses D 1 < D 2 < D 3 give rise to local average molecular weights M w,1 > M w,2 > M w,3 , and if D 3 is large enough to clear the resist, local resist thicknesses h 1 > h 2 > h 3 = 0 following wet development.…”

Section: Thermally Activated Selective Topography Equilibration (Taste)mentioning

confidence: 99%

Extreme Ultraviolet and Soft X-Ray Diffraction Efficiency of a Blazed Reflection Grating Fabricated by Thermally Activated Selective Topography Equilibration

McCoy

McEntaffer²,

Miles

2020

ApJ

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Future observatories utilizing reflection grating spectrometers for extreme ultraviolet (EUV) and soft x-ray (SXR) spectroscopy require high-fidelity gratings with both blazed groove facets and custom groove layouts that are often fanned or feature a slight curvature. While fabrication procedures centering on wet anisotropic etching in mono-crystalline silicon produce highly-efficient blazed gratings, the precision of a non-parallel groove layout is limited by the cubic structure of the silicon crystal. This motivates the pursuit of alternative techniques to grating manufacture, namely thermally activated selective topography equilibration (TASTE), which uses grayscale electron-beam lithography to pattern multi-leveled structures in resist followed by an optimized polymer thermal reflow to smooth the 3D patterns into continuous surface relief profiles. Using TASTE, a mold for a reflection grating with a periodicity of 400 nm and grooves resembling an asymmetric sawtooth was patterned in 130 nmthick poly(methyl methacrylate) resist on a silicon substrate over a 50 mm by 7.5 mm area. This structure was coated with 15 nm of gold by electron-beam physical vapor deposition using titanium as an adhesion layer and then tested for EUV and SXR diffraction efficiency at beamline 6.3.2 of the Advanced Light Source synchrotron facility. Results demonstrate a quasi-blaze response characteristic of a 27 • blaze angle with groove facets smooth to 1.5 nm RMS. Absolute peak order efficiency ranges from 75% to 25% while total relative efficiency measures 90% across the measured bandpass of 15.5 nm > λ > 1.55 nm.

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“…As an alternative to traditional photo-lithography that employs UV light to pattern photo-resist, electron-beam lithography uses a beam of electrons to generate patterns in the resist 46,47 . The primary advantage of this technique is that it can improve on the diffraction limit of light and make features in the nano-meter regime.…”

Section: E-beam-lithography Technologymentioning

confidence: 99%