Hall Plate Research Articles

A novel diagnosis method for a Hall plates-based rotary encoder with a magnetic concentrator.

In the last few years, rotary encoders based on two-dimensional complementary metal oxide semiconductors (CMOS) Hall plates with a magnetic concentrator have been developed to measure contactless absolute angle. There are various error factors influencing the measuring accuracy, which are difficult to locate after the assembly of encoder. In this paper, a model-based rapid diagnosis method is presented. Based on an analysis of the error mechanism, an error model is built to compare minimum residual angle error and to quantify the error factors. Additionally, a modified particle swarm optimization (PSO) algorithm is used to reduce the calculated amount. The simulation and experimental results show that this diagnosis method is feasible to quantify the causes of the error and to reduce iteration significantly.

Extracting 3D Magnetic Field Components With Two Hall Plates on a Piezoelectric Nano Rotary Positioner System

In light of a 3-D Hall sensor that is being designed at the Magnet Section of the Paul Scherrer Institute (PSI), a new calibration scheme is under development. As a preparation to this, a single Hall plate is calibrated for perpendicular and in-plane field directions by rotation of the Hall plate in a calibration magnet. A piezoelectric nano rotary positioner system that fits into the 38 mm aperture of the calibration magnet will be applied. In addition, two Hall plates glued back-to-back and rotated 90 ° around the normal axis with respect to each other are used which have the clear advantage that the planar Hall effect is nearly cancelled out. It will be shown that the full 3-D field vector of a magnetic field can be extracted by rotation of the probe(s) in the to-be-measured magnetic field. Hence, the setup can be used efficiently to measure the (inhomogeneous) magnetic field of large aperture magnets. The paper describes the calibration results and the scheme to measure the full field vector using a piezoelectric nano rotary positioner system.

A novel CMOS Hall effect sensor

This paper reports on a new technique for sensing the Hall effect in an integrated CMOS device. Contrary to traditional Hall plates where sensor contacts comprise of highly doped, low ohmic contacts, the proposed sensor makes use of a parasitic vertical pnp bipolar junction transistor (BJT) to sense and amplify the Hall current caused by the Lorentz force in the presence of a perpendicular magnetic field. The Hall effect appears as a current through the emitter of the BJT. The BJT forward gain implies a direct gain of at least β+1 in the measured signal in comparison to traditional methods.

Modelling of micro-Hall sensors for magnetization imaging

This paper presents a numerical model for the study of micro-Hall magnetometry applications, aiming at evaluating the sensitivity of semiconductor miniaturized devices to the stray field of permalloy nanostructures with ring and disk geometry. The procedure couples a micromagnetic code, for the calculation of the stray field generated by the nanomagnet, to a 2D classical transport model for the determination of the electric potential distribution inside the Hall plate. The model is applied to study the sensitivity of a micro-Hall device in the detection of magnetization switching processes characterized by vortex state, focusing on the influence of magnetic nanostructure position.

霍尔芯片关键技术及发展趋势分析

本文首先概述了霍尔芯片的分类、应用和市场前景。然后，分析了霍尔芯片的设计难点，并从霍尔盘和信号处理电路两个方面阐述了解决霍尔芯片温度漂移和失调电压的方案，同时也对不同解决方案的进行了对比。基于霍尔芯片的设计难点和应用，总结出霍尔芯片呈现高集成度、低温度性漂移、高灵敏度、低失调电压、新型的霍尔元件结构、微型化等发展趋势。The classification, application and market prospect of the Hall chip are introduced in this paper. The design difficulties are analyzed. The paper presents how to solve the temperature drift and offset voltage of the Hall chips in two aspects of Hall plates and signal processing circuits. Meanwhile, different solutions are also compared. Based on the design difficulties and the application, the developing trends such as high degree of integration, low temperature drift, high sensitivity, low offset voltage, new Hall plate structure and miniaturization are summarized.

Package Stress Monitor to Compensate for the Piezo-Hall Effect in CMOS Hall Sensors

Package-induced stress changes the sensitivity of planar Hall plates via the piezo-Hall effect. In this paper, we present a novel stress sensor that allows us to compensate for this undesired mechanical cross-sensitivity. The new CMOS-compatible sensor is based on a Wheatstone bridge built of eight appropriately arranged n- and p-doped piezoresistors. The differential output signal $V_{\rm bridge}$ of the sensor is proportional to the sum of in-plane normal stresses $\sigma_{xx}+\sigma_{yy}$ with the sensitivity $S_{{\rm bridge},\sigma}=\partial\left(V_{\rm bridge}/V_{\rm bias}\right)/\partial\left(\sigma_{xx}+\sigma_{yy}\right)=-0.047~{\rm GPa}^{-1}$ . Doping concentrations larger than $10^{19}~{\rm cm}^{-3}$ for both the n- and p-type resistors are used to minimize the parasitic resistor mismatch due to the junction field effect. Simultaneously, the highly doped resistors keep the relative thermal cross-sensitivity of the sensor as small as $74~{\rm ppm~K}^{-1}$ . In contrast to conventional sensor rosettes, the new sensor has the advantage of offering a differential output signal. The measured signal is successfully used to decrease the stress-impact on the sensitivity of CMOS Hall sensors by a factor of five.

Contact-Less Speed Probe Based on Eddy Currents

In this work, we present a technique for the speed measurement of a metallic body with flat surface and without marks, using a contact-less probe. Basically, the measurement system is made with a permanent magnet for the magnetic field generation and a Hall plate as pick-up sensor. The contact-less probe geometry, the electronic circuit and the devices used for the output signal treatment, including a suitable signal processing applied to increase the signal noise ratio are described. In addition, a theoretical analysis of the probe sensitivity is proposed. In order to show the practical performance of the speed measurement proposed, a series of experimental tests is presented.

Method for electric field and potential calculations in Hall plates

Electrostatic field problems occurring in Hall plates are difficult to solve, mainly because of a non-standard boundary condition defining an oblique angle of the electric field w.r.t. an isolating boundary. A new approach for solving Hall-related field problems is presented. Compared to prior approaches, the technique leads more easily to closed-form expressions for the electric field, and allows obtaining voltage-related Hall characteristics in numerically well conditioned forms.

A THEORY OF MAGNETIC ANGLE SENSORS WITH HALL PLATES AND WITHOUT FLUXGUIDES

Magnetic angle sensors detect the angular position of a permanent magnet attached to a rotating shaft. The magnet is polarized diametrically to the rotation axis. No soft magnetic ∞ux guides are present. The semiconductor die is placed on and orthogonal to the rotation axis. There are two kinds of systems: (i) perpendicular systems detect the fleld components perpendicular to the rotation axis, and (ii) axial systems detect the component parallel to the rotation axis. The former use magneto-resistive sensors or vertical Hall efiect devices; the latter use Hall plates. This paper focuses on axial systems, derives their conceptual limitations, and compares them with perpendicular systems. An optimized system and optimum shapes of magnets are reported. Angle errors due to assembly tolerances of magnet and sensor versus shaft are explained. It is proven that assembly tolerances of optimized axial systems give three times larger errors than perpendicular systems.

A lateral double-diffused magnetic sensitive metal-oxide-semiconductor field-effect transistor with integrated n-type Hall plate

A magnetic sensitive device, lateral double-diffused magnetic sensitive metal-oxide-semiconductor field-effect transistor (LD MagFET), combining the sensory operation of conventional magnetic sensitive metal-oxide-semiconductor field-effect transistors (MagFETs) and Hall plates is proposed. The sensor device is fully compatible with a high-voltage complementary metal-oxide-semiconductor (CMOS) technology. It is found that the LD MagFET with integrated Hall plate exhibits an order of magnitude higher relative magnetic sensitivity in comparison with the split-drain silicon MagFETs in standard CMOS.

A CMOS Magnetic Hall Sensor Using a Switched Biasing Amplifier

A compact CMOS magnetic Hall sensor that includes both a Hall plate and readout circuit is proposed. In order to achieve a low-noise and low-power operation, the sensor employs a switched biasing amplifier with a chopper. The prototype has been implemented and fabricated in a high-voltage 0.18 CMOS process and occupies 0.624 mm2. Owing to the switched biasing amplifier, the input-referred noise is reduced from 41 μT√Hz to 25 μT/ √Hz. The entire sensor consumes 4.5 mW with a 3.3 V supply voltage.

A Highly Sensitive CMOS Digital Hall Sensor for Low Magnetic Field Applications

Integrated CMOS Hall sensors have been widely used to measure magnetic fields. However, they are difficult to work with in a low magnetic field environment due to their low sensitivity and large offset. This paper describes a highly sensitive digital Hall sensor fabricated in 0.18 μm high voltage CMOS technology for low field applications. The sensor consists of a switched cross-shaped Hall plate and a novel signal conditioner. It effectively eliminates offset and low frequency 1/f noise by applying a dynamic quadrature offset cancellation technique. The measured results show the optimal Hall plate achieves a high current related sensitivity of about 310 V/AT. The whole sensor has a remarkable ability to measure a minimum ±2 mT magnetic field and output a digital Hall signal in a wide temperature range from −40 °C to 120 °C.

Characterization of magnetic field rotation of steel sheet under uniaxial stress

The rotation of magnetic field strength on a steel plate caused by uniaxial stress has been known for years. However, previous study investigated this phenomenon rather experimentally using hall plates and searching coils. This paper presents a fundamental study of magnetic anisotropy based on an analytic model using magnetic scalar potential. The magnetic field strength of the steel sheet can be solved mathematically by performing a special coordinate transformation. The calculated angular displacement due to stress induced magnetic anisotropy was later found to be highly consistent with FEM simulation results. Finally, the quantization of magnetic field rotation of an electrical sheet (ES) under variable tension stress was performed. Using 50CS470 ES sheet as the testing sample, it was discovered the rotation as much as 25° occurred when 50MPa tension load was applied, corresponding to a permeability ratio of 2.8.

In-Situ Analysis of Deformation and Mechanical Stress of Packaged Silicon Dies With an Array of Hall Plates

A technique is presented that allows to simultaneously measure stress and deformation of packaged silicon dies. Required is a test chip with an array of Hall plates assembled in a package made of nonmagnetic materials. Exploiting the highly anisotropic magnetic sensitivity of the integrated Hall plates in an external magnetic field, makes it possible to measure the deformation. Moreover, the piezoresistive and piezo-Hall effect allow for measurements of several stress components without extra sensor elements. An optical measurement verifies the new technique, and a standard plastic package is exemplarily analyzed at different temperatures, under the influence of an external force, and at moisture load. The combined knowledge of stress and deformation allows for deeper insight into the mechanical impact of packaging on integrated circuits.

An Improved Equivalent Simulation Model for CMOS Integrated Hall Plates

An improved equivalent simulation model for a CMOS-integrated Hall plate is described in this paper. Compared with existing models, this model covers voltage dependent non-linear effects, geometrical effects, temperature effects and packaging stress influences, and only includes a small number of physical and technological parameters. In addition, the structure of this model is relatively simple, consisting of a passive network with eight non-linear resistances, four current-controlled voltage sources and four parasitic capacitances. The model has been written in Verilog-A hardware description language and it performed successfully in a Cadence Spectre simulator. The model’s simulation results are in good agreement with the classic experimental results reported in the literature.

2D Simulator for Eddy Current Field Filters

Hall devices are magnetic field current sensors based on the Hall effect. A bias current is applied via contacts through the Hall plates which are placed along magnetic field. High frequency components affect the Hall plates in a non- linear manner, disturbing the uniform biasing current flow. This problem can be alleviated by the development of a flux shaping device. A CAD tool is presented here, which can simulate the behavior of shields with different shape in order to choose the one that may be optimally used.

Investigation of impact of neutron irradiation on properties of InSb-based hall plates

Hall sensors based on InSb thin film layers are presently being evaluated as one of the options for ITER ex-vessel steady state magnetic sensors. The compatibility with vacuum vessel baking temperature of 220°C and with the maximum life time neutron fluence of 1018cm−2 has to be demonstrated. Recently, the InSb Hall sensors with operational temperature up to 350°C were developed. We investigated stability of these sensors type when exposed to neutron irradiation on experimental fission reactor LVR-15, and during short term post-irradiation temperature cycling. Parameters of the samples were measured before and after irradiation up to the total neutron fluence of 1017cm−2. Stability of parameters, within a few percents, of the InSb sensors highly doped by Sn was observed. Novel approach to further stabilization of sensors properties based on shielding thermal neutrons and curing the damage caused by fast neutrons by proper annealing was proposed and tested.

Piezo-Hall characterization of integrated hall sensors using a four-point bending bridge

This paper reports on the characterization of the stress-dependent magnetic sensitivity of CMOS-based Hall devices, i.e. crossshaped four-terminal n-wells and field effect transitors (FET) with four source-drain contacts, using a novel experimental setup. The setup comprises a four-point bending bridge used to apply well-defined mechanical in-plane stress to silicon strips, combined with permanent magnets for the application of controlled magnetic fields up to ±240 mT. Measurements of both nwell-based Hall plates and FET-based Hall plates are performed. The piezo-Hall coefficient P12 extracted from stress measurements under vertical magnetic fields from the n-well sensors is in excellent agreement with previously reported values while the FET-based devices exhibit a clearly reduced coefficient.

Modeling Package-Induced Effects on Molded Hall Sensors

The consideration of package-induced effects during the design process of microelectromechanical systems (MEMS) sensors is still of major importance in order to estimate its influence on performance and reliability. A method for predicting the influence of the packaging and assembly process on the performance of a Hall sensor is described. The geometry of the device, the behavior of the packaging materials, as well as the packaging process are regarded using this method. At first, the complex material behavior of adhesives and molding compounds was investigated. It is shown, that for modeling the influence of the packaging on the sensor performance correctly, the nonlinear temperature- and time-dependent material behavior has to be taken into account. Differences of the coefficients of thermal expansion of the packaging materials lead to thermo-mechanical stress in the package. Due to the time-dependent material properties, this results in a change of the offset and the sensitivity of the sensor over time and may lead to a sensor working outside its specification. The piezoresistive and piezo-Hall coefficients of semiconductor Hall plates were measured; thereby the stress- and temperature-dependency of the Hall plates were determined. According to the results, package-induced stresses lead to a change of the offset voltage up to 80% of the full-scale while the sensitivity changes by plusmn4 percentage.

Fractional quantization of Hall resistance as a consequence of mesoscopic feedback

A nonlinear single-particle model is introduced, which captures the characteristic of systems in the quantum Hall regime. The model involves the magnetic Schrodinger equation with spatially variable magnetic flux density. The distribution of flux is prescribed via the postulates of the mesoscopic mechanics (MeM) introduced in my previous articles (cf. [9, 10]). The model is found to imply exact integer and fractional quantitzation of the Hall conductance. In fact, Hall resistance is found to be RH = (h/e2)(M/N) at the filling factor value N/M. The assumed geometry of the Hall plate is rectangular. Special properties of the magnetic Schrodinger equation with the mesoscopic feedback loop allow us to demonstrate quantization of Hall resistance as a direct consequence of charge and flux quantization. I believe results presented here shed light at the overall status of the MeM in quantum physics, confirming its validity.