A micromachined wide-bandwidth magnetic field sensor based on all-PMMA electron tunneling transducer

Abstract

All-PMMA-based tunneling magnetic sensors were fabricated by hot embossing replication with silicon templates. The silicon templates had smooth surfaces, positive profiles, and pyramid-like pits with a high aspect ratio. With this fast (20 min), simple (one-step), and repeatable method, the all-PMMA tunneling sensor platform yielded sharp tunneling tips with 75 m in baseline and 50 m in depth. The sensors were assembled and fixed with measurement circuits, after their electrodes were patterned with modified photolithography and Co film was deposited with e-beam evaporation. A natural frequency response of 1.3 kHz was observed, and a tunneling barrier height of 0.713 eV was tested. Due to the quadratic relation between magnetic force and the field, the sensor field response (7 0 10 6 V T 2 ) was also quadratic. The noise voltage at 1 kHz is 0.2 mV, corresponding to a magnet field of 0 46 10 6 T. The bandwidth of this senor is 18 kHz. This new type of sensor platform is promising for the next generation of microsensing applications.