Poly-SiGe-based MEMS Xylophone Bar Magnetometer

Abstract

This paper presents the design, fabrication and preliminary characterization of highly sensitive MEMS-based Xylophone Bar Magnetometers (XBMs) realized in imec's polySiGe MEMS technology. Key for our Lorentz force driven capacitively sensed resonant sensor are the combination of reasonably high Q-factor and conductivity of imec's poly-SiGe, our optimized multiphysics sensor design targeting the maximization of the Q-factor in a wide temperature range as well as our proprietary monolithic above-CMOS integration and packaging schemes. Prototypes 3-axis devices were fabricated and characterized. We present optical vibrometer and electrical S-parameter measurements of XBMs performed in vacuum with a reference magnet at increasing sensor separation. The optical oscillation amplitude is well correlated with the magnetic field amplitude. The electrical 2-port measurements, 1 st port as Lorentz force actuator and 2 nd port as capacitive sensor, also reproduces the designed magnetic field dependence. This opens the way towards the on-chip integration of small footprint extremely sensitive magnetometers.

A Test Setup for the Characterization of Lorentz-Force MEMS Magnetometers

“…Laser Doppler Vibrometers (LDV) are generally used in works where the characterization of the mechanical performance of the device is disclosed, as it provides information on the rotor displacement in units of meters [30], [31], [32], [33]. This instrument, though, is usually combined with other strategies that provide electrical characterization: in [30], a LDV is combined with a differential amplifier that provides a capacitive sensing characterization, and [32] combines the LDV with a VNA. The work in [33] deserves a special mention, as it uses a lockin amplifier to filter the noisy LVD output.…”