Electrodeposition of Permalloy in Deep Silicon Trenches Without Edge-Overgrowth Utilizing Dry Film Photoresist

An electrodeposition process for embedding NiFe alloys in deep silicon trenches (100 mum) without edge-overgrowth was developed by utilizing dry film photoresist as a sacrificial trench top. The dry film photoresist prevented high concentration of current flux at the trench edges during electrodeposition leading to planar deposition topographies. In addition, the effect of the applied current density on material composition of the electrodeposited NiFe film was investigated, and the composition for permalloy (Ni₈₀Fe₂₀) was obtained with a current density of 100 mA/cm². Furthermore, the B-H response of the electrodeposited permalloy films exhibited a saturation magnetic flux density and relative permeability of 1.23 Tesla and 82, respectively. The electrodeposition technique developed in this work was utilized to fabricate a free-standing MEMS electromagnetic linear actuator composed of silicon and permalloy structures.