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Lift-off technology for thick metallic microstructures
Krátký, Stanislav ; Horáček, Miroslav ; Meluzín, Petr ; Kolařík, Vladimír ; Matějka, Milan ; Oulehla, Jindřich ; Pesic, Z.
This paper deals with a method enabling the preparation of thick metallic microstructures on metal substrates. Such metallic microstructures can be used as a resolution samples to characterize various microanalysis techniques, such as X-ray fluorescence (XRF) or X-ray photoelectron spectroscopy (XPS). Moreover, the\npatterned samples could be used as anodes to characterize focusing properties of X-ray tubes for micro CT systems. Considering that the standard lift-off technique is designated for structures with the thickness of several hundred nanometers at most, we had to modify lift-off technique to be possible to use it for preparation of very thick metal layers (several microns) with spatial resolution of a few microns. The mask with the desired pattern for UV exposure was prepared by e-beam lithography. SU-8 photoresist was used for a lift-off because of its aspect ratio ability, process purity and high resistance to heating. We used a thin layer of PMMA under the SU-8 masking layer to guarantee the photoresist would lift-off correctly. Thick aluminum layer was deposited by thermal evaporation. The dependence of metal layer thickness as a function of required exposed\nline width was determined. The final lift-off process was carried out in acetone ultrasonic bath. Generally, this technology can be used for the evaporate deposition of various materials with several microns thick layer in\nmicron resolution.
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