VHF Piezoelectric Aluminum Nitride on Silicon Lamb Wave Mode Micromechanical Lorentz Force Magnetometers

Description

This proposal aims to experimentally demonstrate a new device concept under the frameworkof microelectromechanical systems (MEMS) Lorentz force magnetic field sensors (otherwisereferred to as MEMS magnetometers). MEMS Lorentz force magnetometers are μm-scalesensors fabricated in the same processes used to manufacture MEMS inertial sensors that arefound in every smartphone. MEMS inertial sensors are responsible for measuring motion andare now mature technologies. MEMS Lorentz force magnetometers on the other hand are stillin development with great interest in applying them as electronic compasses in smartphones.MEMS Lorentz force magnetometers measure magnetic fields by coupling the Lorentz forceto an oscillating structure and detecting the resulting effects. Combining magnetometers withinertial sensors will allow the capability for personal navigation from smartphones. ExistingMEMS magnetometers either have to be sealed in vacuum (thus adding to both complexityand cost of manufacturing) or burn additional power as a tradeoff for being able to operate inair. This proposal aims to address these bottlenecks to advance the state-of-art.The novelty of our proposed approach lies in applying piezoelectric lamb wave modes ofresonance to Lorentz force detection with the aim of significantly increasing sensitivity whenoperating the device in air. The expected increase in sensitivity stems from (1) increasing theefficiency of converting the effect of the Lorentz force to an output electrical signal by usinga piezoelectric transducer and (2) reducing the impact of viscous damping on the oscillatingsensing structure in air by exploiting lamb wave modes. The first research objective is thus todemonstrate an experimental proof of concept. Our analysis has suggested that scaling upfrequency benefits sensitivity in the particular case of piezoelectric lamb wave modes. Thisscaling law of frequency versus sensitivity is the very opposite to trends observed in existingsilicon MEMS magnetometers. The difference appears to stem from our choice to change thetransducer interface and device topology. The second research objective aims to verify thisscaling law of frequency versus sensitivity. The last research objective aims to measure thelimits of sensitivity of the proposed approach by embedding the sensors in a closed loop.This proposal leverages on our previous work on conventional MEMS magnetometer deviceconcepts combined with our recent achievements in very high frequency (VHF) piezoelectriclamb wave mode resonators for radio frequency applications. We are well positioned to leadthis project and deliver on all the proposed research objectives.?