Advanced diffuser-based grayscale lithography

M. Christophersen; C. C. Cheung

doi:10.1117/12.2673182

26 September 2023 Advanced diffuser-based grayscale lithography

M. Christophersen, C. C. Cheung

Proceedings Volume 12667, Laser Beam Shaping XXIII; 126670C (2023) https://doi.org/10.1117/12.2673182
Event: SPIE Optical Engineering + Applications, 2023, San Diego, California, United States

Abstract

Grayscale lithography produces three-dimensional (3D) photoresist profiles versus the standard two-dimensional lithography. Grayscale lithography is fully compatible with standard nano- and micro-fabrication deposition and etching techniques, enabling a wide range of applications, e.g., micro-lenses or micro-fluidic ramps. In order for grayscale lithography to work, the resist is only exposed partially (versus fully for standard lithography). This partial exposure can be achieved by various methods; two examples are: (i) the use of a so-called high-energy beam sensitive (HEBS) photomask, or (ii) a grayscale photomask with a projection stepper. Diffuser-based grayscale lithography, as shown in our original work [1], circumvents many of these disadvantages, but our earlier method has a fundamental limitation: sharp resist edges cannot be patterned because the diffuser will “smear” out any edge feature causing rounding in the resist profile. In this paper, we extend our original method to enable transfer of grayscale resist profiles into substrates with sharp edges and corners. The basic idea of the newly proposed advanced approach is rather straightforward and effective: adding a buried metal mask to the diffuser-based gray-scale method. Furthermore, we decrease the roughness of the resist by using holographic diffusers; these are diffractive optical elements that transform beams into a defined shape with homogenized distribution.

(2023) Published by SPIE. Downloading of the abstract is permitted for personal use only.

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M. Christophersen and C. C. Cheung "Advanced diffuser-based grayscale lithography", Proc. SPIE 12667, Laser Beam Shaping XXIII, 126670C (26 September 2023); https://doi.org/10.1117/12.2673182

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KEYWORDS

Diffusers

Grayscale lithography

Metals

Etching

Silicon

Lithography

Profilometers

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