Ni80Fe20 V-shaped magnetic core for high performance MEMS sensors and actuators

Development of integrated ferromagnetic materials structure as magnetic core is crucial for high performance MEMS sensors and actuators. A core structure is able to improve the magnetic flux linkage and concentrate the magnetic flux density in the magnetic device resulting high magnetic field generation. Previous research has utilized various ferromagnetic materials of different structures embedded into the silicon substrate as MEMS magnetic core. This paper presents fabrication of V-shaped magnetic core by anisotropic wet etching of 30 percent potassium hydroxide (KOH) at 75 °C to produce V-shaped silicon cavity structure. Filling process of Permalloy (Ni₈₀Fe₂₀) into the cavity is done by DC electroplating technique. Low current density of 10 mA/cm² is used to electrodeposit Ni₈₀Fe₂₀ magnetic film in this study. Saccharin addition into the electrolyte composition produced a bright and crack free structure as internal stress in the electrodeposited film is reduced. This effect is essential to have good magnetic properties of the magnetic core. Thicker structure of electroplated Ni₈₀Fe₂₀ is observed at the sharp edges of the V-shaped cavity tip. The reason of this effect to happen is because high current flux density occurrence at those edges. From this work, fabrication of V-shaped Ni₈₀Fe₂₀ magnetic core has been successfully demonstrated. This magnetic core is expected to give superior magnetic performance for on chip MEMS device applications.