MEMS microbridge vibration monitoring using spin-valve sensors

• Published in: IEEE transactions on magnetics Vol. 38; no. 5; pp. 3371 - 3373
• Main Authors: Haohua Li, Gaspar, J., Freitas, P.P., Chu, V., Conde, J.P.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01-09-2002; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Bridge circuits; Electronics; Exact sciences and technology; Gas detectors; Magnetism; Micro- and nanoelectromechanical devices (mems/nems); Microelectromechanical systems; Micromechanical devices; Monitoring; Semiconductor device measurement; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Sensor systems; System-on-a-chip; Vibration measurement; Voltage; Spin valve; spin-valve sensors; Measurement sensor; Microequipment; MEMS; micromagnets; Experimental study; Microelectromechanical device
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2002.802288

Spin-valve sensors were used to measure on chip, the vibration of microelectromechanical systems microbridges excited by dc + ac voltages. A spin-valve sensor (10 /spl times/ 2 /spl mu/m/sup 2/, MR = 6.5%) was placed 3 /spl mu/m away and 2.6 /spl mu/m below the central region of an a-Si:H/Al bridge, with a 1-/spl mu/m air gap. This sensor detects the fringe field created by a Co/sub 78/Pt/sub 22/ micromagnet deposited on top of the bridge. The bridge movement was controlled by an applied voltage on the gate. An unforeseen capacitance coupling effect was found between the control gate and the spin-valve sensor, affecting all ac measurements. Once this coupling was isolated and taken into account, bridge oscillation at joint dc + ac excitation voltages was monitored. Bridge vibration amplitudes of several tens of angstroms peak to peak were detected for dc and ac gate voltages up to 30 V.