Highly Bendable Planar Hall Resistance Sensor

Abstract

A set of planar Hall resistance (PHR) sensors was fabricated on rigid and flexible substrates. High signal-to-noise ratio, low offset voltage, nearly zero hysteresis of signal, and excellent linearity were demonstrated for sensors, based on Ta (5 nm)/NiFe (10 nm)/IrMn (10 nm)/Ta (5 nm) thin films, grown on polydimethylsiloxane (PDMS) and parylene C polymeric substrates. The effect of bending on the performance of the PHR sensors was studied. The effect of bending deformation on the performance characteristics of the fabricated PHR sensors is reversible until the bending angle reaches a critical one. The critical bending angle is shown to depend on the substrate composition. An irreversible deformation of a sensor's film, accompanied by the formation of wrinkles and cracks, occurs when the bending angle exceeds the critical one. This deformation originates from the difference between the values of Young's modulus of the substrate and the film. The bending stability of a PHR sensor, grown on PDMS substrate, was improved by deposition of 1 µm of parylene C as a buffer and as a capping layer. The performance characteristics of the designed bendable PHR sensors are compatible with requirements for applications in wearable electronics and medical diagnostic devices.