EP-4741859-A2 - SYSTEMS, METHODS, AND STRUCTURES FOR IMPROVING MAGNETIC FIELD SENSOR PERFORMANCE

EP4741859A2EP 4741859 A2EP4741859 A2EP 4741859A2EP-4741859-A2

Abstract

Disclosed are example systems, methods, and structures for improving magnetic field sensor performance. In particular, described are example systems, methods, and structures for improving magnetic field sensor performance in applications where magnetic field sensing elements detect a deflection of a magnetic field generated by a magnet. Systems, methods, and structures disclosed herein may provide a sensor device that includes magnetic field sensing elements and a plurality of magnet structures embedded in a semiconductor die. In some embodiments, the plurality of magnet structures may be configured to generate a magnetic field corresponding to a layout of the magnetic field sensing elements in the semiconductor die.

Inventors

LASSALLE-BALIER, Rémy

Assignees

Allegro MicroSystems, LLC

Dates

Publication Date: 20260513
Application Date: 20250903

Claims (20)

A sensor device, comprising: a plurality of magnetic field sensing elements formed into bridge circuits on a first side of a semiconductor die; and a plurality of magnet structures embedded in a second side of the semiconductor die.
The sensor device of claim 1, wherein the plurality of magnetic field sensing elements comprise one or more giant magnetoresistance (GMR) elements, one or more tunneling magnetoresistance (TMR) elements, or one or more Hall plate elements.
The sensor device of claim 1, wherein the plurality of magnet structures generate a magnetic field that biases the plurality of magnetic field sensing elements along a first axis, and wherein the plurality of magnetic field sensing elements are maximally sensitive to the magnetic field along a second axis that is orthogonal to the first axis.
The sensor device of claim 1, wherein a first magnet structure of the plurality of magnet structures has a first volume and a second magnet structure of the plurality of magnet structures has a second volume different than the first volume.
The sensor device of claim 1, wherein the semiconductor die has a first axis and the plurality of magnet structures are symmetrical about the first axis.
The sensor device of claim 5, wherein the semiconductor die has a second axis and the plurality of magnet structures are symmetrical about the second axis.
The sensor device of claim 6, wherein the first axis is orthogonal to the second axis.
The sensor device of claim 1, wherein walls of the semiconductor die surround the plurality of magnet structures.
The sensor device of claim 1, wherein at least some of the plurality of magnet structures have dimensions that differ from others of the plurality of magnet structures.
The sensor device of claim 1, wherein the plurality of magnet structures generate a magnetic field, and wherein the plurality of magnetic field sensing elements comprise at least four magnetic field sensing elements configured to sense a deflection of the magnetic field caused by a target that rotates in proximity to the sensor device.
The sensor device of claim 10, wherein each of the magnetic field sensing elements comprises a first segment and a second segment, and the magnetic field applies a bias that is the same along a first axis of the first segments of each of the at least four magnetic field sensing elements on average over a period of a rotation of the target.
The sensor device of claim 10, wherein the magnetic field applies no bias along a second axis of each of the at least four magnetic field sensing elements on average over a period of a rotation of the target.
The sensor device of claim 10, wherein the magnetic field generated by the plurality of magnet structures applies a constant bias across a region of the first side of the semiconductor die on average over a period of rotation of the target.
The sensor device of claim 10, wherein the magnetic field generated by the plurality of magnet structures applies a bias across each of at least four regions of the first side of the semiconductor die, and wherein the bias applied to each of the at least four regions is constant across that region on average over a period of rotation of the target.
The sensor device of claim 1, wherein each of the plurality of magnet structures is formed in a respective cavity in the second side of the semiconductor die.
The sensor device of claim 15, wherein at least one of the cavities has a top along the second side of the semiconductor die and a bottom within the semiconductor die, wherein the at least one cavity is formed with an undercut such that the bottom is wider than the top.
A method, comprising: identifying regions of a first side of a semiconductor die for placement of magnetic field sensing elements; dimensioning a plurality of magnet structures for a second side of the semiconductor die; generating a mask for etching cavities into the second side of the semiconductor die based at least in part on the dimensioning of the plurality of magnet structures; and causing the cavities to be etched into the second side of the semiconductor die based on the mask.
The method of claim 17, further comprising causing the magnetic field sensing elements to be formed onto the regions of the first side of the semiconductor die.
The method of claim 18, wherein the magnetic field sensing elements comprise at least one of a giant magnetoresistance (GMR) element, a tunneling magnetoresistance (TMR) element, or a Hall plate element.
The method of claim 19, wherein the magnetic field sensing elements are configured to be biased by a magnetic field generated by the plurality of magnet structures along a first axis, and to be maximally sensitive to the magnetic field along a second axis orthogonal to the first axis.

Description

BACKGROUND Sensor devices are often used to monitor parameters of a system. For example, sensor devices may be used to measure speed and/or direction of rotation of a rotation object, such as of a wheel. The speed and/or direction measurements may then be used, such as in the implementation of driver assistance applications. As another example, sensor devices may be used to measure a position or angle of rotation of a rotation object, such as of a rotor of an electric motor. The measurement information may then be used to control the motor. For example, a controller may continuously receive a measured angle of rotation of the rotor, and may use this information to commutate the motor. That is, the measured angle information may be used by the controller to switch currents in motor windings, producing magnetic fields that cause the rotor to rotate. The controller can then control aspects of the motor, such as speed and torque, based on the measured angle information. Numerous applications, spanning from industrial automation and robotics, to self-parking and power steering applications in automobiles, may require monitoring of a rotation speed, direction, angle, or position of a rotating object. SUMMARY Disclosed are example systems, methods, and structures for improving magnetic field sensor performance. In particular, described are example systems, methods, and structures for improving magnetic field sensor performance in applications where magnetic field sensing elements detect a deflection of a magnetic field generated by a magnet. Systems, methods, and structures disclosed herein may provide a sensor device that includes magnetic field sensing elements and a plurality of magnet structures embedded in a semiconductor die. In some embodiments, the plurality of magnet structures may be configured to generate a magnetic field corresponding to a layout of the magnetic field sensing elements in the semiconductor die. Using systems, methods, and structures disclosed herein, a sensor device may be provided that is less susceptible to misalignment, that has improved resistance to temperature cycling, that has improved resolution, that has improved noise characteristics, that has better immunity to magnetic stray fields, that has less temperature dependence, that is easier to install in a system, that has reduced magnetic offset, and/or that is more compact. In accordance with some embodiments, there is provided a sensor device. The sensor device comprises a plurality of magnetic field sensing elements formed into bridge circuits on a first side of a semiconductor die. The sensor device further comprises a plurality of magnet structures embedded in a second side of the semiconductor die. In some embodiments, the plurality of magnetic field sensing elements comprise one or more giant magnetoresistance (GMR) elements, one or more tunneling magnetoresistance (TMR) elements, or one or more Hall plate elements. In further embodiments, the plurality of magnet structures generate a magnetic field that biases the plurality of magnetic field sensing elements along a first axis, and the plurality of magnetic field sensing elements are maximally sensitive to the magnetic field along a second axis that is orthogonal to the first axis. In still further embodiments, a first magnet structure of the plurality of magnet structures has a first volume and a second magnet structure of the plurality of magnet structures has second volume different than the first volume. In some embodiments, the semiconductor die has a first axis and the plurality of magnet structures are symmetrical about the first axis. In further embodiments, the semiconductor die has a second axis and the plurality of magnet structures are symmetrical about the second axis. In still further embodiments, the first axis is orthogonal to the second axis. In some embodiments, the walls of the semiconductor die surround the plurality of magnet structures. In further embodiments, at least some of the plurality of magnet structures have dimensions that differ from others of the plurality of magnet structures. In still further embodiments, the plurality of magnet structures generate a magnetic field, and the plurality of magnetic field sensing elements comprise at least four magnetic field sensing elements configured to sense a deflection of the magnetic field caused by a target that rotates in proximity to the sensor device. In some embodiments, each of the magnetic field sensing elements comprises a first segment and a second segment, and the magnetic field applies a bias that is the same along a first axis of the first segments of each of the at least four magnetic field sensing elements on average over a period of a rotation of the target. In further embodiments, the magnetic field applies no bias along a second axis of each of the at least four magnetic field sensing elements on average over a period of a rotation of the target. In still further embodiments, the magn