The Investigation Of The AMR Linear Magnetic Sensor

With the development of science and technology,magnetic field sensors have become an indispensable part of today’s social life.Among many magnetic field sensors,the AMR effect magnetic field sensor has become a hot spot for magnetic field sensor research because of its high sensitivity,simple preparation process,ease of integration and low cost.This paper studies magnetic field sensors based on the AMR effect.First of all,the preparation process of magnetoresistive thin films with AMR effect was explored.In this paper,magnetoresistive sputtering method is used to prepare a magnetoresistive thin film on a silicon substrate with 300nm SiO₂ on the surface and a Ta/NiFe/Ta three-layer structure.The first layer of Ta is used as a buffer layer to provide NiFe thin film growth on a silicon substrate.A good substrate,the second layer of Ni Fe film is the core functional film of the AMR effect,the quality of the NiFe film directly affects the AMR performance of the entire magnetoresistive film,and the third layer of Ta acts as a protective layer of the magnetoresistive film to protect the magnetoresistive film.No external oxidation and damage.In this paper,magnetoresistive films with NiFe film thicknesses of 8nm,10nm,11nm,12nm and 14nm were prepared.The influence of different NiFe thickness on the performance of AMR films was analyzed.The best thickness of NiFe film was 11nm,and the corresponding AMR value was obtained.At1.243%,the maximum magnetic sensitivity of the magnetoresistive film was 0.282%/Oe.In this paper,magnetoresistive thin films with thickness of 3nm,4nm,5nm and 6nm are prepared.The thickness of NiFe film is 11nm.The influence of different thickness of Ta buffer layer on the performance of AMR films is analyzed to obtain the best Ta buffer.The thickness of the layer is 5 nm,the corresponding AMR value obtained is 1.31%,and the maximum magnetic sensitivity of the magnetoresistive film is 0.419%/Oe.Then the influence of the process conditions of vacuum magnetic annealing on the AMR effect of NiFe magnetoresistive thin film was investigated.For the magnetoresistive film with a thickness of 5 nm and a Ni buffer film thickness of 5 nm,the influence of the vacuum magnetic field annealing temperature and time on the performance of the AMR line was analyzed.In this paper,the annealing temperatures of300℃,350℃,400℃,and 450℃ were analyzed.The best vacuum magnetic field annealing temperature was 350℃,the corresponding AMR value was 1.35%,and the maximum magnetic sensitivity of the magnetoresistive thin film was 0.259%/Oe..In this paper,annealing conditions of 3h,3.5h,4h and 4.5h annealing time were analyzed.After the vacuum magnetic field annealing time was more than 3h,the AMR value of the magnetoresistive film was about 1.35%,no change.Secondly,the Barber electrode current bias effect was explored.Through COMSOL software,the effect of Barber electrode tilt angle and Barber electrode spacing on current bias was simulated.This paper simulates the current bias direction when the Barber electrode tilt angle is 45o.It is found that when the spacing between the electrodes is smaller,the direction of the current bias is closer to 45o,but the small spacing will reduce the AMR performance of the sensor.Simulation and analysis of the current bias direction when the Barber electrode tilt angle is 50°was performed.It was found that when the Barber electrode aspect ratio is 2,the current bias effect is the best,the current bias direction approaches 45°,and the optimal current offset can be achieved.Set effect.Finally,an AMR linear magnetic field sensor was designed and prepared.A strip-shaped magnetoresistive bar with sharp corners at both ends was designed as the core functional part.The Wheatstone bridge was used as the main sensor structure,and Barber electrodes with 45°and 50°tilt angles were used as the current bias to pass the light.The AMR linear magnetic field sensor was successfully fabricated by preparing the sensor pattern by etching and growing Al as a Barber electrode material by electron beam evaporation.The sensor performances of Barber electrodes with Al thickness of 200nm,300nm,400nm,500nm,600nm,700nm,800nm,and 900nm were investigated.The best Al thickness was 800nm.The best Barber electrode tilt angle was 50°corresponding to the AMR linearity.The linear interval width of the magnetic field sensor is 16Oe,the linear correlation coefficient of the linear interval is 0.99741,and the sensitivity of the sensor is 0.25mV/V/Oe.