AVS 50th International Symposium
    Magnetic Interfaces and Nanostructures Monday Sessions
       Session MI-MoA

Paper MI-MoA9
Arrays of Magnetoresistive Sensors for Non-destructive Testing

Monday, November 3, 2003, 4:40 pm, Room 316

Session: Magnetic Recording and Magnetoresistive Structures
Presenter: A.V. Nazarov, National Institute of Standards and Technology
Authors: A.V. Nazarov, National Institute of Standards and Technology
F.C.S. da Silva, National Institute of Standards and Technology
P. Kabos, National Institute of Standards and Technology
D.P. Pappas, National Institute of Standards and Technology
Correspondent: Click to Email
Magnetic field mapping is a powerful tool that can provide high sensitivity and high spatial resolution for current localization.@footnote 1@ In this work, we used magnetic field mapping to non-destructively analyze the current distribution in integrated circuit chips and localize wiring defects. The magnetic field produced by current distributions was simultaneously measured with arrays of magnetoresistive (MR) sensors in order to increase the effective speed of the scan. Arrays of eight permalloy barber-pole type MR sensors were fabricated using a two step lift-off lithography process. The sensors were 40 µm long, 4 µm wide, and separated by 210 µm. The nominal resistance of the sensors was in the 24.9 to 25.2 @ohm@ range and the MR change was 1.8 %. A broadband, simultaneous, 8-channel, computer-based digital lock-in technique was developed for data acquisition and analysis. The measured magnetic field distributions were directly converted to current images using normalized discrete 1-d Fourier transforms. Measurements of test structures show the absence of cross-talk between sensors and that the spatial resolution is approximately z/2 where z is the distance between current plane and the sensor. This work was supported by the National Institute of Standards and Technology Office of Law Enforcement Standards, the Federal Bureau of Investigation, the National Security Agency, the National Institute of Justice, and the Advanced Technology Program. @FootnoteText@ @footnote 1@S. Chatraphorn, E. F. Fleet, F. C. Wellstood, L. A. Knauss, and T. M. Eiles, Appl. Phys. Lett. 76, 2304 (2000).