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Journal of Micro/Nanolithography, MEMS, and MOEMS

Grayscale lithography—automated mask generation for complex three-dimensional topography
Author(s): James Loomis; Dilan Ratnayake; Curtis McKenna; Kevin M. Walsh
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Paper Abstract

Grayscale lithography is a relatively underutilized technique that enables fabrication of three-dimensional (3-D) microstructures in photosensitive polymers (photoresists). By spatially modulating ultraviolet (UV) dosage during the writing process, one can vary the depth at which photoresist is developed. This means complex structures and bioinspired designs can readily be produced that would otherwise be cost prohibitive or too time intensive to fabricate. The main barrier to widespread grayscale implementation, however, stems from the laborious generation of mask files required to create complex surface topography. We present a process and associated software utility for automatically generating grayscale mask files from 3-D models created within industry-standard computer-aided design (CAD) suites. By shifting the microelectromechanical systems (MEMS) design onus to commonly used CAD programs ideal for complex surfacing, engineering professionals already familiar with traditional 3-D CAD software can readily utilize their pre-existing skills to make valuable contributions to the MEMS community. Our conversion process is demonstrated by prototyping several samples on a laser pattern generator—capital equipment already in use in many foundries. Finally, an empirical calibration technique is shown that compensates for nonlinear relationships between UV exposure intensity and photoresist development depth as well as a thermal reflow technique to help smooth microstructure surfaces.

Paper Details

Date Published: 23 March 2016
PDF: 10 pages
J. Micro/Nanolith. 15(1) 013511 doi: 10.1117/1.JMM.15.1.013511
Published in: Journal of Micro/Nanolithography, MEMS, and MOEMS Volume 15, Issue 1
Show Author Affiliations
James Loomis, The Univ. of Auckland (New Zealand)
Dilan Ratnayake, Univ. of Louisville (United States)
Curtis McKenna, Univ. of Louisville (United States)
Kevin M. Walsh, Univ. of Louisville (United States)


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