Magnetic actuation and MOS-transistor sensing for CMOS-integrated resonators

We present a magnetic actuation scheme combined with a piezoresistive MOS-transistor sensing technique for CMOS-integrated resonators. It was developed for a cantilever resonator with on-chip amplifier, but is broadly applicable. The high efficiency of electromagnetic actuation significantly reduces the required operation power and allows for the use in portable devices. By use of stress-sensitive PMOS-transistors as active loads, the size of the piezoresistive Wheatstone bridge is significantly reduced. Thirdly, the post-processing sequence of the cantilever resonator has been optimized, so that only one photolithography step is necessary to release the whole mechanical structure. This facilitates the fabrication, increases yield and, thus, reduces fabrication cost.