High-aspect-ratio photoresist processing for fabrication of high resolution and thick micro-windings

No Thumbnail Available
9605.pdf(1.28 MB)
Accepted version
Anthony, Ricky
Laforge, Elias
Casey, Declan P.
Rohan, James F.
Ó Mathúna, S. Cian
Journal Title
Journal ISSN
Volume Title
IOP Publishing
Research Projects
Organizational Units
Journal Issue
DC winding losses remain a major roadblock in realizing high efficiency micro-magnetic components (inductors/transformers). This paper reports an optimized photoresist process using negative tone and acrylic based THB-151N (from JSR Micro), to achieve one of the highest aspect ratio (17:1) and resolution (~5 µm) resist patterns for fabrication of thick (~80 µm) micro-winding using UV lithography. The process was optimized to achieve photoresist widths from 5 µm to 20 µm with resist thickness of ~85 µm in a single spin step. Unlike SU-8, this resist can be readily removed and shows a near-vertical (~91°) electroplated Cu side-wall profile. Moreover, the high resolution compared to available resist processes enables a further reduction in the footprint area and can potentially increase the number of winding thereby increasing the inductance density for micro-magnetic components. Resistance measurements of electroplated copper winding of air-core micro-inductors within the standard 0402 size (0.45 mm2 footprint area) suggested a 42% decrease in resistance (273 mΩ–159 mΩ) with the increase in electroplated Cu thickness (from 50 µm to 80 µm). Reduction of the spacings (from 10 µm to 5 µm) enabled further miniaturisation of the device footprint area (from 0.60 mm2 to 0.45 mm2) without significant increase in resistance.
High aspect ratio , High resolution , MEMS , Integrated magnetics , Photolithography
Anthony, R., Laforge, E., Casey, D. P., Rohan, J. F. and O’Mathuna, C. (2016) 'High-aspect-ratio photoresist processing for fabrication of high resolution and thick micro-windings', Journal of Micromechanics and Microengineering, 26(10), 105012 (9 pp). doi: 10.1088/0960-1317/26/10/105012
© 2016 IOP Publishing Ltd. This is an author-created, un-copyedited version of an article accepted for publication in Journal of Micromechanics and Microengineering. The publisher is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/0960-1317/26/10/105012