Micro-patterning of NdFeB and SmCo magnet films for integration into micro-electro-mechanical-systems |
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Authors: | A Walther C Marcoux R Grechishkin NM Dempsey |
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Institution: | a CEA Léti-MINATEC, 17 rue des Martyrs, 38054 Grenoble, France b Institut Néel, CNRS-UJF, 25 rue des Martyrs, 38042 Grenoble, France c Laboratory of Magnetoelectronics, Tver State University, 170000 Tver, Russia |
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Abstract: | The integration of high-performance RE-TM (NdFeB and SmCo) hard magnetic films into micro-electro-mechanical-systems (MEMS) requires their patterning at the micron scale. In this paper we report on the applicability of standard micro-fabrication steps (film deposition onto topographically patterned substrates, wet etching and planarization) to the patterning of 5-8 μm thick RE-TM films. While NdFeB comprehensively fills micron-scaled trenches in patterned substrates, SmCo deposits are characterized by poor filling of the trench corners, which poses a problem for further processing by planarization. The magnetic hysteresis loops of both the NdFeB and SmCo patterned films are comparable to those of non-patterned films prepared under the same deposition/annealing conditions. A micron-scaled multipole magnetic field pattern is directly produced by the unidirectional magnetization of the patterned films. NdFeB and SmCo show similar behavior when wet etched in an amorphous state: etch rates of approximately 1.25 μm/min and vertical side walls which may be attributed to a large lateral over-etch of typically 20 μm. Chemical-mechanical-planarization (CMP) produced material removal rates of 0.5-3 μm/min for amorphous NdFeB. Ar ion etching of such films followed by the deposition of a Ta layer prior to film crystallization prevented degradation in magnetic properties compared to non-patterned films. |
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Keywords: | NdFeB films SmCo films Integration MEMS |
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