Over the last couple of decades, the Giant Magneto-Impedance (GMI) effect has become a well-known phenomenon, especially for its use in magnetic field sensing applications. Discussed in this paper will be a comprehensive summary of the fundamental theory behind the GMI effect, as well as the design, fabrication, and test of multilayer thin film GMI sensors. In recent research, multilayer GMI sensors have been shown to obtain GMI sensitives ranging from 10 – 100 times more than that of currently in industry Giant Magnetoresistance (GMR) sensors, comparable to that of its bulk microwire counterpart. To investigate this, a tri-layer film stack sensor, consisting of a conductive Copper layer sandwiched between two ferromagnetic Permalloy layers, was designed and fabricated in RIT’s SMFL. Sensor performance relied heavily on two main components: structural design of the sensors (i.e. geometry and materials) and the ability to induce transverse anisotropic magnetic domain alignment. Standard CMOS processing techniques were used during fabrication to induce this transverse domain alignment. This discussion will highlight some of the challenges faced during processing and their impact on sensor performance. Despite these challenges, sensors were successfully fabricated with an added step to incorporate a Titanium seed layer beneath the first layer of Permalloy. With process modifications to consider, a maximum GMI Ratio of 0.028% and sensitivity of 0.010%/Oe for a frequency of 10 MHz was obtained. While sensor performance was less than optimal, the overall goal of qualifying and quantifying the GMI effect in multilayer thin film sensors was achieved.
Heinze, Sean H.
"Giant Magneto-Impedance Effect in Multilayer Thin Film Sensors,"
Journal of the Microelectronic Engineering Conference: Vol. 23:
1, Article 17.
Available at: https://repository.rit.edu/ritamec/vol23/iss1/17