Multi-axis integrated Hall magnetic sensors (original) (raw)

High magnetic field amplification for improving the sensitivity of Hall sensors

IEEE Sensors Journal, 2000

This paper describes the design of two magnetic concentrators that can be used to intensify the magnetic field in the active region of magnetic sensors, such as Hall sensors. The literature provides many examples of magnetic amplification, but magnetic gains never exceed 100 typically (Drljaca et al.2001. We demonstrate that a larger magnetic field amplification ( 1000 and even higher) can be achieved. Magnetic field amplification can even exceed the theoretical value fixed by the relative permeability of the material. Thus, the effective sensitivity of Hall sensors can be improved by at least three orders of magnitude by implementing them inside an especially tailored magnetic concentrator; noise-equivalent magnetic induction spectral density (National Electronics Manufacturing Initiative spectral density) down to 10 pT Hz should be reached, using a good conditioning electronic.

From Three-Contact Vertical Hall Elements to Symmetrized Vertical Hall Sensors with Low Offset

Sensors and Actuators A: Physical, 2016

 We analyze the operation principle of three-contact vertical Hall elements as building blocks for symmetric vertical Hall sensors.  We demonstrate the inherent symmetry of the fully symmetric vertical Hall sensor by its resistance and offset characteristic.  We further develop an advanced version of the sensor by orthogonally coupling four fully symmetric vertical Hall sensors into an ultra-low offset vertical Hall sensor.  The signal-to-offset ratio of the fully symmetric vertical Hall sensor is improved by a factor of more than 10 compared to the previous state-of-the-art device. By further orthogonal coupling the ultra-low offset vertical Hall sensor achieves an equivalent magnetic offset field in the range of the earth's magnetic field which represents to our knowledge the best data achieved for a standalone vertical Hall sensor.

Highly sensitive Hall sensor in CMOS technology

Sensors and Actuators A: Physical

We present a highly sensitive Hall device fabricated in a standard CMOS technology and combined with integrated flux concentrators acting as magnetic amplifiers. The active area of the Hall plate is in a buried n-well with a shape optimized by removing the parts less sensitive to the magnetic field. The effect of the shape of the concentrators is studied. This results in the design of elliptical shape integrated concentrators for the optimization of the sensitivity, and of the measurement range, as well as for the decrease of the overall chip size. The CMOS sensor combined with the optimized concentrators has a sensitivity of 2.1 VrT with a 4 V bias, the lowest detectable field is 0.2 mT in a frequency range of 10 y3-10 Hz and the linearity is better than 1% in a "16 mT measurement range.

Optimal geometry of CMOS voltage-mode and current-mode vertical magnetic hall sensors

2015 IEEE SENSORS, 2015

Four different geometries of a vertical Hall sensor are presented and studied in this paper. The current spinning technique compensates for the offset and the sensors, driven in current-mode, provide a differential signal current for a possible capacitive integration over a defined time-slot. The sensors have been fabricated using a 6-metal 0.18-μm CMOS technology and fully experimentally tested. The optimal solution will be further investigated for bendable electronics. Measurement results of the four structures over the 10 available samples show for the best geometry an offset of 41.66 ± 8 μT and a current-mode sensitivity of 9 ± 0.1 %/T. Since the figures widely change with geometry, a proper choice secures optimal performance.

Vector Magnetometer Based on a Single Spin-Orbit-Torque Anomalous-Hall Device

Physical Review Applied

In many applications, the ability to measure the vector information of a magnetic field with high spatial resolution and low cost is essential, but it is still a challenge for existing magnetometers composed of multiple sensors. Here, we report a single-device based vector magnetometer, which is enabled by spinorbit torque, capable of measuring a vector magnetic field using the harmonic Hall resistances of a superparamagnetic ferromagnet (FM)/heavy metal (HM) bilayer. Under an ac driving current, the first and second harmonic Hall resistances of the FM/HM bilayer show a linear relationship with the vertical and longitudinal component (along the current direction) of the magnetic field, respectively. By employing a L-shaped Hall device with two orthogonal arms, we can measure all the three field components simultaneously, so as to detect both the amplitude and direction of magnetic field in a threedimensional space. As proof of concepts, we demonstrate both angular position sensing on the three coordinate planes and vector mapping of magnetic field generated by a permanent magnet, both of which are in good agreement with the simulation results. Crosstalk between vertical and longitudinal field components at large field is discussed using theoretical models.

Optimisation of Spin-Valve Planar Hall Effect Sensors for Low Field Measurements

IEEE Transactions on Magnetics, 2012

In this paper are presented results of galvanomagnetic measurements and micromagnetic simulations performed on low-field magnetic sensors based on the planar Hall effect (PHE). Disc-shaped structures of the type Co/Cu/Ni80Fe20, 4 mm diameter, deposited by magnetron sputtering onto Si substrate, were used to build magnetic sensors. At this stage of study, no uniaxial anisotropy axes were defined during the samples deposition. Two types of applications have been considered: (i) magnetic field measurements and (ii) rotation sensing. In order to obtain a coherent rotation of the magnetization inside the PHE sensor under the action of an applied magnetic field, H appl , DC or AC magnetic biasing fields were used. By these means the magnetic sensitivity and the hysteresis width of the PHE signal can be tuned. Sensitivities between 0.07 and 0.17 V1A 01 1m have been obtained for a driving current of 10 mA. Micromagnetic simulations were used to explain some field angular behavior of these sensors.

Current trends in planar Hall effect sensors: evolution, optimization and applications

2021

The benefits conferred by the thermal stability, very low detection limit, and high sensitivity of planar Hall effect (PHE) sensors have supported up-to-date diversity of applications like nT magnetometer, current sensing, or low magnetic moments detection in lab-on-a-chip devices. Herein, we demonstrate in this review the implications linked to planar Hall effect sensors, initiating from the backbone of PHE and its evolution throughout the recent few decades. Key parameters affecting sensors' performance such as noise different sources, thermal stability, and magnetoresistance magnitude are discussed. The progression of sensor junction from disk, cross to bridge, ring, and ellipse configuration is delivered. Moreover, the logical sequence of structure from a single magnetoresistive layer to bi-, trilayers, and spin-valves is briefly investigated. Research contributions to the development of these sensors are highlighted with the focus on microfluidics and flexible sensorics areas. The conclusions extracted from this review are beneficial for the production, development, and performance quality validation of planar Hall effect-based devices and microfluidics and future expectations. Not at least, this review can be a valuable source of information for scientists that intend to use PHE for fundamental research or to develop new applications and devices.

Three-Axis Teslameter With Integrated Hall Probe

IEEE Transactions on Instrumentation and Measurement, 2007

The first commercially available teslameter with a fully integrated three-axis Hall probe is described. The Hall probe chip contains horizontal and vertical Hall elements, analog electronics, and a synchronization circuit. A horizontal Hall element measures the perpendicular component, and two vertical Hall devices measure the two in-plane components of a magnetic flux density vector. Current spinning in the Hall devices cancels offset, 1/f noise, and the planar Hall voltage. The analog electronic module of the teslameter cancels the residual offset and compensates temperature dependence and nonlinearity of the Hall voltages. The digital module provides analog-to-digital conversion and communication to a computer.

Integrated semiconductor magnetic field sensors

Proceedings of the IEEE, 1986

A magnetic field sensor is an entrance transducer that converts a magnetic field into an electronic signal. Semiconductor magnetic held sensors exploit the galvanomagnetic effects due to the Lorentz force on charge carriers. Integrated semiconductor, notably silicon, magnetic field sensors, are manufactured using integrated orcuit technologies. lntegrated sensors are being increasingly developed for a variety of applications in view of the advantage offered by the integration of the magnetic field sensitive element together with support and signal processing circuitry on the same semiconductor chip. The ultimate goal is to develop a broad range of inexpensive batch-fabricated high-performance sensors interfaced with the rapidly proliferating microprocessor. This review aims at the recent progress in integrated silicon magnetic devices such as integrated Hall plates, magnetic field-effect transistors, vertical and lateral bipolar magnetotransistors, magnetodiodes, and current-domain magnetometers. The current development of integrated magnetic field sensors based on 111-V semiconductors is described as well. Bulk Hall-effect devices are also reviewed and serve to define terms of performance reference. Magnetic device modeling and the incorporation of magnetic devices into an integrated circuit offering in situ amplification and compensation of offset and temperature effects are further fopics of this paper. Silicon will continue to be aggressively exploited in a variety of magnetic (and other) sensor applications, complementary to its traditional role as integ,vted circuit material.