Micro-structuring of thick NdFeB films using high-power plasma etching for magnetic MEMS application

This paper describes the micro-patterning of thick NdFeB magnetic films using a high-power plasma etching method. The effects of RF bias power and gas composition on the selectivity and etching rate are experimentally studied. A maximum etching rate of 60 nm min^-1 is achieved with an inductively coupled plasma power of 500 W and a RF bias power of 200 W. A maximum selectivity of 0.26 between hard baked AZP4903 photoresist and NdFeB magnetic films is achieved when volumetric Cl₂ concentration is 2.5%. NdFeB micro-magnets as thick as 4.2 μm are achieved by using AZP4903 photoresist. Magnetic film as thick as 10 μm can be patterned by using SU-8 photoresist with a thickness of 100 μm as the mask. The magnetic property of patterned microstructures is characterized using a vibrating sample magnetometer and the magnetic field distribution is measured using a Hall effect sensor IC. The characterization results indicate that the patterned magnetic microstructures have a high magnetic remanance of 1.0 T, which is comparable to that of the non-patterned NdFeB films.