Application of Magnetic Ferrite Electrodeposition and Copper Chemical Mechanical Planarization for On-Chip Analog Circuitry

Inductors are important components of analog circuit designs, from matching circuitry to passive filters. In this study, the application of electrophoretically deposited nano-ferrite material has been investigated as a technique to increase the inductance of integrated copper planar inductors fabricated using copper plating and chemical mechanical planarization. Sintered Mn-Zn ferrite particles are suspended in a medium of isopropyl alcohol with magnesium nitrate and lanthanum nitrate salts. The transportation of the particles to the substrate surface is assisted by applied electric field and particles adhere to the substrate surface by a glycerol based surfactant. Electrophorectic deposition process forms a self aligned polymeric thin film on the surface of a p-type silicon substrate selectively with respect to copper. This ferrite deposition method yields high selectivity to the inductor coils and patterned silicon substrates compatible with standard silicon technology.