Current Perspectives: Micro-patterning of NdFeB and SmCo magnet films for integration into micro-electro-mechanical-systems

• Published in: Journal of magnetism and magnetic materials Vol. 321; no. 6; pp. 590 - 594
• Main Authors: Walther, A, Marcoux, C, Desloges, B, Grechishkin, R, Givord, D, Dempsey, N M
• Format: Journal Article
• Language: English
• Published: 01.03.2009
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2008.09.028

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 mum 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 mum/min and vertical side walls which may be attributed to a large lateral over-etch of typically 20 mum. Chemical-mechanical-planarization (CMP) produced material removal rates of 0.5-3 mum/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.