Fabrication of three-dimensional millimeter-height structures using direct ultraviolet lithography on liquid-state photoresist for simple and fast manufacturing

Jungkwun Kim; Yong-Kyu Yoon

doi:10.1117/1.JMM.14.3.033504

15 July 2015 Fabrication of three-dimensional millimeter-height structures using direct ultraviolet lithography on liquid-state photoresist for simple and fast manufacturing

Jungkwun Kim, Yong-Kyu Yoon

Author Affiliations +

Funded by: NSF

Journal of Micro/Nanolithography, MEMS, and MOEMS, Vol. 14, Issue 3, 033504 (July 2015). https://doi.org/10.1117/1.JMM.14.3.033504

Abstract

A rapid three-dimensional (3-D) ultraviolet (UV) lithography process for the fabrication of millimeter-tall high aspect ratio complex structures is presented. The liquid-state negative-tone photosensitive polyurethane, LF55GN, has been directly photopatterned using multidirectionally projected UV light for 3-D micropattern formation. The proposed lithographic scheme enabled us to overcome the maximum height obtained with a photopatternable epoxy, SU8, which has been conventionally most commonly used for the fabrication of tall and high aspect ratio microstructures. Also, the fabrication process time has been significantly reduced by eliminating photoresist-baking steps. Computer-controlled multidirectional UV lithography has been employed to fabricate 3-D structures, where the UV-exposure substrate is dynamically tilt-rotating during UV exposure to create various 3-D ray traces in the polyurethane layer. LF55GN has been characterized to provide feasible fabrication conditions for the multidirectional UV lithography. Very tall structures including a 6-mm tall triangular slab and a 5-mm tall hexablaze have been successfully fabricated. A 4.5-mm tall air-lifted polymer-core bowtie monopole antenna, which is the tallest monopole structure fabricated by photolithography and subsequent metallization, has been successfully demonstrated. The antenna shows a resonant radiation frequency of 12.34 GHz, a return loss of 36 dB, and a 10 dB bandwidth of 7%.

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Jungkwun Kim and Yong-Kyu Yoon "Fabrication of three-dimensional millimeter-height structures using direct ultraviolet lithography on liquid-state photoresist for simple and fast manufacturing," Journal of Micro/Nanolithography, MEMS, and MOEMS 14(3), 033504 (15 July 2015). https://doi.org/10.1117/1.JMM.14.3.033504

Published: 15 July 2015

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KEYWORDS

Ultraviolet radiation

Photoresist materials

Lithography

Antennas

Photomasks

Liquids

Polyurethane

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