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

Modeling of Three-Axis Hall Effect Sensors Based on Integrated Magnetic Concentrator

IEEE Sensors Journal, 2020

In this paper, we develop computational model to analyze the magnetic concentrating effect of integrated magnetic concentrator (IMC) on surrounding external magnetic field. We present an IMC-based three-axis Hall sensor model that enables to measure both inclination angles and absolute strength of a random external magnetic field. An IMC changes surrounding parallel magnetic components into perpendicular components, and therefore allows the horizontal Hall plates to measure both the strength and inclination angles of parallel external magnetic fields. We develop a finite element method (FEM) based model in COMSOL Multiphysics for the three-axis Hall sensor. Key factors influencing IMC's magnetic concentrating effect, including material property and sensor structure, are investigated and discussed using the developed model. Comparing to traditional IMC-based three-axis angular sensors, a reference permanent magnet is no longer needed in the sensor. A measurement accuracy of 0.8 and 1.2 degrees are achieved respectively for the angles of α and θ of external magnetic field.

High resolution Hall magnetic sensors

The resolution of a magnetic sensor depends on its intrinsic noise, offset instability and the magnetic sensitivity. Both noise and offset can be substantially reduced by the spinning current technique. The effective magnetic sensitivity can be increased by the application of a magnetic flux concentrator. The physical limit of magnetic sensitivity is estimated. Values of sensitivity, noise and offset of various discrete and integrated horizontal and vertical Hall devices, and of sensor systems are given. High resolution integrated Hall sensors are currently mostly used as compass in mobile phones.

Novel Hall sensors developed for magnetic field imaging systems

Journal of Magnetism and Magnetic Materials, 2007

We report here on the fabrication and application of novel planar Hall sensors based on shallow InGaP/AlGaAs/GaAs heterostructure with a two-dimensional electron gas (2DEG) as an active layer. The sensors are developed for two kinds of experiments. In the first one, magnetic samples are placed directly on the Hall sensor. Room temperature experiments of permalloy objects evaporated onto the sensor are presented. In the second experiment, the sensor scans close over a multigranular superconducting sample prepared on a YBCO thin film. Large-area and high-resolution scanning experiments were performed at 4.2 K with the Hall probe scanning system in a liquid helium flow cryostat.

Technology and properties of a vector hall sensor

Microelectronics Journal, 2006

Symmetrical four-sided 12−mm−highpyramidswith301−tiltedsideswererevealedbytheetchingofsemi−insulating(100)GaAssubstratesin1H3PO4:A^H2O2:8H2Oat12-mm-high pyramids with 301-tilted sides were revealed by the etching of semi-insulating (1 0 0) GaAs substrates in 1H 3 PO 4 : Â H 2 O 2 :8H 2 O at 12−mm−highpyramidswith301−tiltedsideswererevealedbytheetchingofsemi−insulating(100)GaAssubstratesin1H3PO4:A^H2O2:8H2Oat25 1C via sacrificial /0 0 1S-oriented Ti/GaAs/AlAs (100/2000/100 nm) etching mask patterns. The pyramids, MOCVD overgrown with InGaP/AlGaAs/GaAs heterostructure pyramids, were used as the base for magnetic field vector sensors. Each sensor consisted of three Hall probes defined on the sides of a pyramid. The device processing was realized via AZ5214-E layers deposited conformally over the pyramids by draping from water surface. While the planar reference 5 Â 5-mm 2-sized Hall probes exhibited a sensitivity of 930VAAˋ1TAˋ1at298K,thesensitivityofthoseonthe301−tiltedfacetswasimpossibletodeterminebecausetheyhadaresistanceof930 VA À1 T À1 at 298 K, the sensitivity of those on the 301-tilted facets was impossible to determine because they had a resistance of 930VAAˋ1TAˋ1at298K,thesensitivityofthoseonthe301−tiltedfacetswasimpossibletodeterminebecausetheyhadaresistanceof100 kO at 298 K. Further work is necessary to optimize the InGaP/AlGaAs/GaAs heterostructure growth and dopant incorporation on the 301-tilted pyramidal facets.

Highly sensitive Hall magnetic sensor microsystem in CMOS technology

IEEE Journal of Solid-State Circuits, 2002

A highly sensitive magnetic sensor microsystem based on a Hall device is presented. This microsystem consists of a Hall device improved by an integrated magnetic concentrator and new circuit architecture for the signal processing. It provides an amplification of the sensor signal with a resolution better than 30 V and a periodic offset cancellation while the output of the microsystem is available in continuous time. This microsystem features the overall magnetic gain of 420 V/T.

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.