Microfabrication

Bilayer lift-off process for aluminum metallization

[+] Author Affiliations
Thomas E. Wilson

Marshall University, Department of Physics, One John Marshall Drive, Huntington, West Virginia 25755, United States

Konstantin A. Korolev

Marshall University, Department of Physics, One John Marshall Drive, Huntington, West Virginia 25755, United States

Nathaniel A. Crow

Marshall University School of Medicine, 1600 Medical Center Drive, Huntington, West Virginia 25701, United States

J. Micro/Nanolith. MEMS MOEMS. 14(1), 014501 (Jan 20, 2015). doi:10.1117/1.JMM.14.1.014501
History: Received October 14, 2014; Accepted December 15, 2014
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Abstract.  Recently published reports in the literature for bilayer lift-off processes have described recipes for the patterning of metals that have recommended metal-ion-free developers, which do etch aluminum. We report the first measurement of the dissolution rate of a commercial lift-off resist (LOR) in a sodium-based buffered commercial developer that does not etch aluminum. We describe a reliable lift-off recipe that is safe for multiple process steps in patterning thin (<100nm) and thick aluminum devices with micron-feature sizes. Our patterning recipe consists of an acid cleaning of the substrate, the bilayer (positive photoresist/LOR) deposition and development, the sputtering of the aluminum film along with a palladium capping layer and finally, the lift-off of the metal film by immersion in the LOR solvent. The insertion into the recipe of postexposure and sequential develop-bake-develop process steps are necessary for an acceptable undercut. Our recipe also eliminates any need for accompanying sonication during lift-off that could lead to delamination of the metal pattern from the substrate. Fine patterns were achieved for both 100-nm-thick granular aluminum/palladium bilayer bolometers and 500-nm-thick aluminum gratings with 6-μm lines and 4-μm spaces.

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© 2015 Society of Photo-Optical Instrumentation Engineers

Citation

Thomas E. Wilson ; Konstantin A. Korolev and Nathaniel A. Crow
"Bilayer lift-off process for aluminum metallization", J. Micro/Nanolith. MEMS MOEMS. 14(1), 014501 (Jan 20, 2015). ; http://dx.doi.org/10.1117/1.JMM.14.1.014501


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