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Innovative SU-8 Lithography Techniques and Their Applications
Open AccessArticle

Performance of SU-8 Membrane Suitable for Deep X-Ray Grayscale Lithography

Research Center for Ubiquitous MEMS and Micro Engineering (UMEMSME), National Institute of Advanced Industrial Science and Technology (AIST), 1-2-1 Namiki, Tsukuba, Ibaraki 305-8564, Japan
Academic Editor: Arnaud Bertsch
Micromachines 2015, 6(2), 252-265; https://doi.org/10.3390/mi6020252
Received: 8 December 2014 / Accepted: 4 February 2015 / Published: 9 February 2015
(This article belongs to the Special Issue 15 Years of SU8 as MEMS Material)
In combination with tapered-trench-etching of Si and SU-8 photoresist, a grayscale mask for deep X-ray lithography was fabricated and passed a 10-times-exposure test. The performance of the X-ray grayscale mask was evaluated using the TERAS synchrotron radiation facility at the National Institute of Advanced Industrial Science and Technology (AIST). Although the SU-8 before photo-curing has been evaluated as a negative-tone photoresist for ultraviolet (UV) and X-ray lithographies, the characteristic of the SU-8 after photo-curing has not been investigated. A polymethyl methacrylate (PMMA) sheet was irradiated by a synchrotron radiation through an X-ray mask, and relationships between the dose energy and exposure depth, and between the dose energy and dimensional transition, were investigated. Using such a technique, the shape of a 26-μm-high Si absorber was transformed into the shape of a PMMA microneedle with a height of 76 μm, and done with a high contrast. Although during the fabrication process of the X-ray mask a 100-μm-pattern-pitch (by design) was enlarged to 120 μm. However, with an increase in an integrated dose energy this number decreased to 99 μm. These results show that the X-ray grayscale mask has many practical applications. In this paper, the author reports on the evaluation results of SU-8 when used as a membrane material for an X-ray mask. View Full-Text
Keywords: SU-8; X-ray lithography; X-ray mask; grayscale; tapered trench etching; PMMA; synchrotron radiation SU-8; X-ray lithography; X-ray mask; grayscale; tapered trench etching; PMMA; synchrotron radiation
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Mekaru, H. Performance of SU-8 Membrane Suitable for Deep X-Ray Grayscale Lithography. Micromachines 2015, 6, 252-265.

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