Electroplated metal microstructures embedded in fusion-bonded silicon: conductors and magnetic materials

Fabrication methods for integrating thick (tens or hundreds of micrometers) electroplated metallic microstructures inside fusion-bonded silicon wafers are proposed and validated. Cu and Ni₈₀Fe₂₀ (permalloy) test structures were embedded inside of cavities in silicon wafers, which were fusion-bonded at 500°C for 4h with nearly 100% yield. Resistance tests validated the electrical integrity of the metals after annealing, and magnetic measurements indicated the Ni-Fe maintained its magnetic performance after annealing. Additional mechanical tests verified a strong, uniform bond, and that the presence of the metals does not degrade the bond strength. These results demonstrate the ability to integrate conductive and magnetic materials in wafer-bonded silicon, a method useful for a variety of multiwafer, MEMS devices.