High-aspect-ratio microstructures for magnetoelectronic applications

Tao Wang; Andrew B. McCandless; Sean M. Ford; Kevin W. Kelly; Richard Lienau; Dale Hensley; Yohannes M. Desta; Zhong-geng Ling

doi:10.1117/12.472792

15 January 2003 High-aspect-ratio microstructures for magnetoelectronic applications

Tao Wang, Andrew B. McCandless, Sean M. Ford, Kevin W. Kelly, Richard Lienau, Dale Hensley, Yohannes M. Desta, Zhong-geng Ling

Author Affiliations +

Proceedings Volume 4979, Micromachining and Microfabrication Process Technology VIII; (2003) https://doi.org/10.1117/12.472792
Event: Micromachining and Microfabrication, 2003, San Jose, CA, United States

Abstract

This paper describes a process to fabricate three-dimensional multilevel high-aspect-ratio microstructures (HARMs) for magnetoelectronic devices using aligned x-ray lithography in conjunction with electrodeposition. In this process, x-ray masks were constructed on a seed layer coated polyimide membrane with ultraviolet (UV) patterned and electrodeposited gold absorbers. The optically transparent polyimide allows one to align and print large areas (>4 inch in diameter) with high alignment accuracies. Patterns that contain 5-10 μm diameter posts and 7-10 μm wide lines were printed to 100-120 μm polymethyl methacrylate (PMMA) resist prepared on silicon wafers using x-ray lithography. Nickel-iron was electroplated to form ferromagnetic HARMs, while electroplated gold formed circuits. The composition profile measured with an electron probe x-ray microanalyzer (EPMA) suggested that iron content increases as NiFe plating proceeds inside the recess. The electrodeposition resulted in well-defined NiFe structures with aspect-ratios up to 20:1, smooth sidewalls and top surfaces. To isolate the magnetic structures and circuits, both wet chemical etching and sputter etching were explored to remove seed layer, and the latter yielded complete removal without noticeable damage to the features. A complete aligned x-ray exposure and electrodeposition protocol applicable to universal multilevel microstructures was established.

Citation Download Citation

Tao Wang, Andrew B. McCandless, Sean M. Ford, Kevin W. Kelly, Richard Lienau, Dale Hensley, Yohannes M. Desta, and Zhong-geng Ling "High-aspect-ratio microstructures for magnetoelectronic applications", Proc. SPIE 4979, Micromachining and Microfabrication Process Technology VIII, (15 January 2003); https://doi.org/10.1117/12.472792

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