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Accurate layer thickness control and planarization for multilayer SU-8 structures

[+] Author Affiliations
Novak E. S. Farrington

e2v technologies (UK) Plc., Carholme Road, Lincoln, LN1 1SF, United Kingdom

Stavros Iezekiel

University of Cyprus, Department of Electrical and Computer Engineering, Nicosia 1678, Cyprus

J. Micro/Nanolith. MEMS MOEMS. 10(1), 013019 (March 29, 2011). doi:10.1117/1.3563599
History: Received August 24, 2010; Revised January 13, 2011; Accepted January 26, 2011; Published March 29, 2011; Online March 29, 2011
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A technique is developed to enable accurate layer thickness control and planarization in a multilayer SU-8 2000 micromachining process, while maintaining a high quality surface finish. Relying on carefully controlled mechanical lapping and polishing stages, layer thicknesses from 30–400 μm have been routinely achieved to an accuracy of ±3 μm with excellent planarity. High-aspect ratio structures (intended for use in a millimeter-wave engineering application) with up to five layers and of 770-μm thickness have been fabricated using this method. The quality of the resulting surfaces has been investigated and characterized using scanning probe microscopy: a typical rms surface roughness of around 10 nm has been measured. The problem of air-bubble formation and migration encountered during the lapping stage has been documented along with a technique for their elimination. It is also shown that the common problem of the expansion of the lower layers in a multilayer structure due to solvent reabsorption can be effectively eliminated through careful process optimization.

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© 2011 Society of Photo-Optical Instrumentation Engineers (SPIE)

Citation

Novak E. S. Farrington and Stavros Iezekiel
"Accurate layer thickness control and planarization for multilayer SU-8 structures", J. Micro/Nanolith. MEMS MOEMS. 10(1), 013019 (March 29, 2011). ; http://dx.doi.org/10.1117/1.3563599


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