GOALI: High Permeability Ferrite Cores for Micro-Inductors

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Magnetic materials have unique properties that are driving their integration with microelectronic and micro-electro-mechanical (MEM) devices. Various microfabrication technologies are being pursued aggressively. In this proposal, it is proposed to develop a novel technique to deposit oxide magnetic material films applicable to micro magnetic devices. The magnetic materials chosen for the proposed study are low coercivity soft ferrites (manganese zinc and nickel zinc ferrites) with initial permeability ranging from 1,000-10,000. The films will find extensive applications in micro inductors, micro transformers and other on chip magnetic devices. These films will be deposited by electrophoresis i.e electrodeposition from nano to micron size ferrite particles suspended in a solution. The ferrite powders will be prepared by jet milling technique in conjunction with a ferrite company Ferronics and the Center for Advanced Ceramic Technology (CACT) at Alfred University.An electrochemical process will be developed to get uniform deposition of magnetic films on silicon wafers. The films will be characterized for their magnetic properties, thickness uniformity and adhesion. Subsequently, a lithographic technique will be developed to pattern ferrite films to form the cores of micro inductors. Fundamental investigations will be made to understand the effect of particle size distribution and electrodeposition in confined regions on the film morphology by modeling the deposition process. The magnetic properties will be measured on these films and structures. These film structures will be integrated with copper micro-inductors on semiconductor substrates. Inductors will be designed and modeled analytically and using an electromagnetic software. The fabrication will be carried out utilizing the IC fabrication facility at Rochester Institute of Technology (RIT). Electrical measurements such as inductance and Q-factor will be done using network analyzer and impedance meters. The optimized structures will then be fabricated with circuitry on silicon wafers.This will be a multidisciplinary experimental and theoretical research program between Microelectronic Engineering, Electrical Engineering, Physics and Electrochemistry. In addition, there is support from industry and the CACT center. The project will enable fabrication of on-chip magnetic components for micro-inductors and micro magnetics. The proposed process can also be utilized to integrate other magnetic materials such as hard ferrites and microwave ferrites.