Performance Optimization Of AMR Linear Magnetoresistive Sensor

The wide applications of magnetic field sensors have been closely related to huaman our daily life.In recent year,with the rapid development of integrated circuit technology,anisotropic magnetoresistance(AMR)sensors with high sensitivity,low power consumption and easy integration have become a research hotspot of magnetic field sensors.Since the magnetic film is the key part of the AMR sensor,its anisotropic magnetoresistance effect and sensitivity are closely related to the performance of the AMR sensors.Therefore,the processes of the NiFe film are optimized first,and the thin films with high AMR value are obtained.Based in this material,the angles between the Barber electrode and the magnetoresistive strip are optimized.Highly sensitive and high linearity AMR magnetoresistive field sensor are fabricated.The following work has been carried out in this thesis:Firstly,we proposed to use the Ta/Nb multilayer as the buffer layer for NiFe thin films.A series of NiFe films with Ta/Nb buffer layer and NiFe films with Ta and Nb buffer layers were prepared by high-throughput material chips.The films with the three structures were analyzed.The results show that at the same NiFe thickness,the AMR values of the thin films with a single layer of Ta and Nb as the buffer layer increase with the increase of the thickness of the buffer layer,and the performance of the Nb/NiFe/Ta sample is better than Ta/NiFe/Ta.In contrast,the film with the Ta/Nb buffer layer has the largest grain size and the smallest resistivity,so it can reach a high anisotropic magnetoresistance value and sensitivity.The corresponding values are 1.19% and 0.25%/Oe,respectively.At the same time,the buffer layer can improve the soft magnetic properties of the NiFe film and reduce the coercive force and the saturation magnetic moment.Then,the effects of different thickness of Ta/Nb buffer layer on the NiFe film were studied.Ta/Nb/NiFe/Ta structure films with different thicknesses of Ta and Nb were prepared.The results show that the AMR of the multilayer film is optimal at Ta(5nm)/Nb(3nm),and the anisotropic magnetoresistance reaches the maximum value of 1.74%,and the sensitivity of 0.29%/Oe.Finally,we use Barber electrodes to change the current direction to achieve a linear output,and use the Wheatstone bridge to ensure the stability and sensitivity of the magnetoresistive film current.AMR sensors with Ta(5nm)/Nb(3nm)/NiFe(24nm)/Ta(2n m)as a magnetoresistive film were prepared.The results show that the Barber electrode can effectively bias the current and realize the linear output of the magnetoresistive film.The influence of the angle between the Barber electrode and the magnetoresistive strip on the linearity of the sensor output was also studied.AMR sensors with Barber electrode orientations of 45o,50o and 55o were prepared.The AMR sensor has the best output linearity when the angle between the Barber electrode and the magnetoresistive strip is 50°.