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High-aspect-ratio photoresist processing for fabrication of high resolution and thick micro-windings
Anthony, Ricky; Laforge, Elias; Casey, Declan P.; Rohan, James F.; Ó Mathúna, S. Cian
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.
Keyword(s): High aspect ratio; High resolution; MEMS; Integrated magnetics; Photolithography
Publication Date:
Type: Journal article
Peer-Reviewed: Yes
Language(s): English
Institution: University College Cork
Citation(s): 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
Publisher(s): IOP Publishing
File Format(s): application/pdf
Related Link(s):
First Indexed: 2019-03-22 06:30:51 Last Updated: 2019-03-22 06:30:51