Fall 2010 IAB
September 15 to 17
MEMS-enhanced Magnetoresistive Sensors
Magnetoresistive (MR) sensors are highly sensitive magnetic field sensors but suffer from large 1/f noise. We have developed a new approach for reducing the 1/f noise in MR sensors by using a MEMS resonator to mechanically modulate the magnetic field signal to a high frequency, where the 1/f noise vanishes. This mechanism improves the MR element sensitivity by 2-3 orders of magnitude in the low frequency sensing range. A fully integrated fabrication process was developed, where the MR sensor is fabricated first on the surface of a SOI wafer and the MEMS actuators are fabricated last. Our first generation device, reported at previous IAB meetings, integrated electrostatic MEMS and magnetic tunnel junction (MTJs) MR sensors. A second generation device is under development, consisting of a highly sensitive spin valve (SV) MR sensor and two AlN piezoelectric cantilevers with integrated magnetic flux concentrators. This new approach should bring the SV sensitivity down to the picoTesla range, making this hybrid device suitable for use in medical imaging, bionics, and any other application where ultra low magnetic sensing may be required.