Integration of Electroplated CoFe in Trench Type Flux Guides for Magnetic MEMS Applications

Abstract

For a magnetic MEMS application, the integration of soft magnetic flux guides with high saturation flux density is often needed. A complex form including a trench in substrate was designed to achieve its flux guide function. Electroplating CoFe with followed Chemical-mechanical Polishing (CMP) process was chosen as fabrication technology. Pulse current was selected as power supply for electrodeposition process. Experimental results show, that fine tuned pulse current parameters are necessary for electroplating high magnetic performance, low residual stress CoFe films into a trench form without any formation of cracks and voids. For the further system integration a planarization step is required. Since the CoFe layers show a strong response to the chemical attack causing etching, the mere mechanical polishing process is adequate for the planarization of CoFe. Furthermore, the application of alumina abrasives shows very good results regarding surface quality.