Strategies and process optimization for microfabrication of magnetic pillars
Briukhanova, Daria (2023)
Briukhanova, Daria
2023
Master's Programme in Photonics Technologies
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2023-06-13
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202305236085
https://urn.fi/URN:NBN:fi:tuni-202305236085
Tiivistelmä
In this thesis, fabrication techniques toward the realization of magnetic microsurfaces were developed and implemented. Microsurfaces were fabricated with the help of photolithography and electrochemical deposition. As a result, arrays of square and circular nickel micropillars with lateral dimensions of 6 μm, 11 μm, and 21 μm and height up to 10 μm were obtained. Micropillar arrays were characterized with scanning electron microscopy, optical microscopy, profilometry, and vibrating sample magnetometry. Micropillars with straight vertical walls and a maximum aspect ratio of 1.7 were achieved. Also, mushroom-shaped structures were attained by overplating the metal.
Maskless lithography was used to pattern photoresist. The effect of the wavelength of the laser source, exposure dose, and focal point shift on the transferred pattern was experimentally studied. The choice of the wavelength and the dose require serious consideration, especially for small-size structures, while adjustment of a focal point does not show a significant effect on the microsurface quality. Nickel was deposited on a patterned photoresist via electroplating. Current and time were optimized for depositing around 10 μm of magnetic metal. Magnetic pillars of various sizes and shapes were fabricated and imaged. The smallest lateral dimensions of 6 μm were attained, but smaller size pillars are also possible. The developed fabrication process is a fast and simple way to obtain micrometers high magnetic pillars or structures of different geometry. It is suitable for rapid prototyping and can be further fine-tuned for more specific fabrication requirements.
Furthermore, two alternative approaches for fabrication of magnetic micropillars were pursued and reported. The first one involves polishing, photolithography, and wet chemical etching of bulk CoFe-alloy magnet. The second approach deals with forming micropillars in silicon with deep reactive ion etching, followed by sputtering of CoFeB alloy. Fabricated microsurfaces can be potentially used for diamagnetic levitation of particles.
Maskless lithography was used to pattern photoresist. The effect of the wavelength of the laser source, exposure dose, and focal point shift on the transferred pattern was experimentally studied. The choice of the wavelength and the dose require serious consideration, especially for small-size structures, while adjustment of a focal point does not show a significant effect on the microsurface quality. Nickel was deposited on a patterned photoresist via electroplating. Current and time were optimized for depositing around 10 μm of magnetic metal. Magnetic pillars of various sizes and shapes were fabricated and imaged. The smallest lateral dimensions of 6 μm were attained, but smaller size pillars are also possible. The developed fabrication process is a fast and simple way to obtain micrometers high magnetic pillars or structures of different geometry. It is suitable for rapid prototyping and can be further fine-tuned for more specific fabrication requirements.
Furthermore, two alternative approaches for fabrication of magnetic micropillars were pursued and reported. The first one involves polishing, photolithography, and wet chemical etching of bulk CoFe-alloy magnet. The second approach deals with forming micropillars in silicon with deep reactive ion etching, followed by sputtering of CoFeB alloy. Fabricated microsurfaces can be potentially used for diamagnetic levitation of particles.