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Ion Beam Milling for Structuring of Tunnel-Magneto-Resistance Sensors

Abstract
We demonstrate that high quality tunnel-magneto-resistance (TMR) sensors composed of CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) can be produced by using ion beam etching to structure the layer stack with a scia Mill 200. Background information about the MTJs functionality as well as sample preparation and the ion beam milling process are given. Required tool capability, such as helium backside cooling and etching uniformity, are analyzed. Finally, the MTJs were characterized by measuring the electrical resistance in a magnetic field.

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