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

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 mu m 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 mu m/min and vertical side walls which may be attributed to a large lateral over-etch of typically 20 mm. Chemical-mechanical-planarization (CMP) produced material removal rates of 0.5-3 mu m/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. (C) 2008 Elsevier B. V. All rights reserved.