Tilt segmented anisotropic magnetoresistive angle sensor
阅读说明:本技术 倾斜分段式的各向异性磁阻角度传感器 (Tilt segmented anisotropic magnetoresistive angle sensor ) 是由 拜伦·乔恩·罗德里克·沙尔弗 李德元 于 2018-06-26 设计创作,主要内容包括:一种集成式AMR传感器包含:具有两个电阻器的半电桥、具有四个电阻器的惠斯通电桥,或具有呈正交配置的四个电阻器的第一惠斯通电桥以及具有呈正交配置的四个电阻器的第二惠斯通电桥,所述第二惠斯通电桥相对于所述第一惠斯通电桥定向成45度。每一电阻器(204)包含:第一磁阻区段(284),其电流流动方向(288)相对于所述电阻器(204)的参考方向(206)定向成第一倾斜角;及第二磁阻区段(286),其电流流动方向(290)相对于所述参考方向(206)定向成第二倾斜角。所述倾斜角经选择以有利于抵消由于所述磁阻区段(284、286)的形状各向异性所致的角度误差。在另一实施方案中,一种方法识别抵消由于所述磁阻区段(284、286)的形状各向异性所致的角度误差的倾斜角。(An integrated AMR sensor comprising: a half bridge with two resistors, a wheatstone bridge with four resistors, or a first wheatstone bridge with four resistors in an orthogonal configuration and a second wheatstone bridge with four resistors in an orthogonal configuration, the second wheatstone bridge oriented at 45 degrees with respect to the first wheatstone bridge. Each resistor (204) includes: a first magnetoresistive section (284) having a current flow direction (288) oriented at a first tilt angle relative to a reference direction (206) of the resistor (204); and a second magneto-resistive section (286) having a current flow direction (290) oriented at a second oblique angle relative to the reference direction (206). The tilt angle is selected to facilitate cancellation of angular errors due to shape anisotropy of the magnetoresistive segments (284, 286). In another implementation, a method identifies a tilt angle that cancels an angular error due to shape anisotropy of the magnetoresistive segments (284, 286).)
1. An integrated Anisotropic Magnetoresistive (AMR) sensor, comprising:
a first resistor having a first reference direction; the first resistor includes: first magnetoresistive sections each having a first current flow direction oriented at a first tilt angle relative to the first reference direction; and second magnetoresistive sections each having a second current flow direction oriented at a second oblique angle relative to the first reference direction; and
a second resistor having a second reference direction perpendicular to the first reference direction, the second resistor comprising: first magnetoresistive sections each having a first current flow direction oriented at the first tilt angle relative to the second reference direction; and second magnetoresistive sections each having a second current flow direction oriented at the second tilt angle relative to the second reference direction;
wherein the first tilt angle has a positive value and the second tilt angle has a negative value, wherein angular errors of the integrated AMR sensor due to shape anisotropy are cancelled out.
2. The integrated AMR sensor of claim 1, wherein:
the first resistor is electrically coupled in series between a first bias terminal and a sense terminal; and is
The second resistor is electrically coupled in series between the sense terminal and a second bias terminal.
3. The integrated AMR sensor of claim 1, further comprising:
a third resistor having a third reference direction perpendicular to the first reference direction, the third resistor comprising: first magnetoresistive sections each having a first current flow direction oriented at the first tilt angle relative to the third reference direction; and second magnetoresistive sections each having a second current flow direction oriented at the second tilt angle relative to the third reference direction; and
a fourth resistor having a fourth reference direction perpendicular to the third reference direction, the fourth resistor comprising: first magnetoresistive sections each having a first current flow direction oriented at the first tilt angle relative to the fourth reference direction; and second magnetoresistive sections each having a second current flow direction oriented at the second oblique angle relative to the fourth reference direction.
4. The integrated AMR sensor of claim 3, wherein:
the first resistor is electrically coupled in series between a first bias terminal and a first sense terminal;
the second resistor is electrically coupled in series between the first sense terminal and a second bias terminal;
the third resistor is electrically coupled in series between the first bias terminal and a second sense terminal; and is
The fourth resistor is electrically coupled in series between the second sense terminal and the second bias terminal.
5. The integrated AMR sensor of claim 3, further comprising:
a fifth resistor having a fifth reference direction oriented at 45 degrees relative to the first reference direction, the fifth resistor comprising: first magnetoresistive sections each having a first current flow direction oriented at the first tilt angle relative to the fifth reference direction; and second magnetoresistive sections each having a second current flow direction oriented at the second tilt angle relative to the fifth reference direction;
a sixth resistor having a sixth reference direction perpendicular to the fifth reference direction, the sixth resistor comprising: first magnetoresistive sections each having a first current flow direction oriented at the first tilt angle relative to the sixth reference direction; and second magnetoresistive sections each having a second current flow direction oriented at the second tilt angle relative to the sixth reference direction;
a seventh resistor having a seventh reference direction perpendicular to the fifth reference direction, the seventh resistor comprising: first magnetoresistive sections each having a first current flow direction oriented at the first tilt angle relative to the seventh reference direction; and second magnetoresistive sections each having a second current flow direction oriented at the second tilt angle relative to the seventh reference direction; and
an eighth resistor having an eighth reference direction perpendicular to the seventh reference direction, the eighth resistor comprising: first magnetoresistive sections each having a first current flow direction oriented at the first tilt angle relative to the eighth reference direction; and second magnetoresistive sections each having a second current flow direction oriented at the second oblique angle relative to the eighth reference direction.
6. The integrated AMR sensor of claim 5, wherein:
the first resistor is electrically coupled in series between a first bias terminal and a first sense terminal;
the second resistor is electrically coupled in series between the first sense terminal and a second bias terminal;
the third resistor is electrically coupled in series between the first bias terminal and a second sense terminal;
the fourth resistor is electrically coupled in series between the second sense terminal and the second bias terminal;
the fifth resistor is electrically coupled in series between a third bias terminal and a third sense terminal;
the sixth resistor is electrically coupled in series between the third sense terminal and a fourth bias terminal;
the seventh resistor is electrically coupled in series between the third bias terminal and a fourth sense terminal; and is
The eighth resistor is electrically coupled in series between the fourth sense terminal and the fourth bias terminal.
7. The integrated AMR sensor of claim 1, wherein an estimated maximum angular error of the integrated AMR sensor due to shape anisotropy is less than 0.04 degrees.
8. The integrated AMR sensor of claim 1, wherein a magnitude of the first tilt angle is equal to a magnitude of the second tilt angle.
9. The integrated AMR sensor of claim 1, wherein:
the first tilt angle has a value of +12 degrees to +18 degrees;
the second tilt angle has a value of-12 degrees to-18 degrees;
each of the first and second resistors has no additional magnetoresistive section other than the first and second magnetoresistive sections; and is
The total resistance of the first magnetoresistive section is balanced with the total resistance of the second magnetoresistive section to cancel angular errors of the integrated AMR sensor due to shape anisotropy.
10. The integrated AMR sensor of claim 1, wherein:
the first resistor includes third magnetoresistive sections each having a third current flow direction oriented at zero degrees with respect to the first reference direction;
the second resistor includes third magnetoresistive sections each having a third current flow direction oriented at zero degrees with respect to the second reference direction;
the first tilt angle has a value of +16 degrees to +24 degrees;
the second tilt angle has a value of 16 degrees to-24 degrees;
each of the first resistor and the second resistor has no additional magnetoresistive section other than the first magnetoresistive section, the second magnetoresistive section, and the third magnetoresistive section; and is
The total resistance of the first magnetoresistive section, the total resistance of the second magnetoresistive section, and the total resistance of the third magnetoresistive section are balanced to cancel angular errors of the integrated AMR sensor due to shape anisotropy.
11. The integrated AMR sensor of claim 1, wherein:
the first resistor includes third magnetoresistive sections each having a third current flow direction oriented at zero degrees with respect to the first reference direction;
the second resistor includes third magnetoresistive sections each having a third current flow direction oriented at zero degrees with respect to the second reference direction;
the first tilt angle has a value of +24 degrees to +36 degrees;
the second tilt angle has a value of 24 degrees to-36 degrees;
each of the first resistor and the second resistor has no additional magnetoresistive section other than the first magnetoresistive section, the second magnetoresistive section, and the third magnetoresistive section; and is
The total resistance of the first magnetoresistive section, the total resistance of the second magnetoresistive section, and the total resistance of the third magnetoresistive section are balanced to cancel angular errors of the integrated AMR sensor due to shape anisotropy.
12. The integrated AMR sensor of claim 1, wherein the first magnetoresistive sections have equal lengths parallel to the first current flow direction and the second magnetoresistive sections have equal lengths parallel to the second current flow direction.
13. The integrated AMR sensor of claim 1, wherein:
the first magnetoresistive sections have a first length parallel to the first current flow direction and a first width laterally perpendicular to the first length, and wherein a ratio of the first length to the first width of each of the first magnetoresistive sections is greater than 10; and is
The second magnetoresistive sections have a second length parallel to the second current flow direction and a second width laterally perpendicular to the second length, and wherein a ratio of the second length to the second width of each of the second magnetoresistive sections is greater than 10.
14. A method, comprising:
assigning a first value of a first tilt angle to a first magnetoresistive segment of a resistor of an integrated AMR sensor and a second value of a second tilt angle to a second magnetoresistive segment, the first tilt angle corresponding to an orientation of the first magnetoresistive segment relative to a reference angle of the resistor and the second tilt angle corresponding to an orientation of the second magnetoresistive segment relative to the reference angle of the resistor;
calculating an estimated maximum angle error due to shape anisotropy for an estimated orientation of a magnetic field of the integrated AMR sensor having the first magnetoresistive section oriented at the first value of the first tilt angle and the second magnetoresistive section oriented at the second value of the second tilt angle;
determining whether the estimated maximum angle error is less than a target value;
if the estimated maximum angle error is less than the target value:
forming the integrated AMR sensor by a process comprising:
forming a first resistor having a first reference direction, the first resistor having: a first magnetoresistive section having a first current flow direction oriented at the first oblique angle relative to the first reference direction; and a second magnetoresistive section having a second current flow direction oriented at the second oblique angle relative to the first reference direction; and
forming a second resistor having a second reference direction perpendicular to the first reference direction, the second resistor having: a first magnetoresistive section having a first current flow direction oriented at the first oblique angle relative to the second reference direction; and a second magnetoresistive section having a second current flow direction oriented at the second oblique angle relative to the second reference direction.
15. The method of claim 14, further comprising: adjusting the first value of the first tilt angle and the second value of the second tilt angle if the estimated maximum angle error is not less than the target value.
16. The method of claim 14, wherein forming the integrated AMR sensor further comprises:
forming a first bias terminal electrically coupled to the first resistor;
forming a sense terminal electrically coupled to the first resistor and the second resistor; and
forming a second bias terminal electrically coupled to the second resistor.
17. The method of claim 14, wherein forming the integrated AMR sensor further comprises:
forming a third resistor having a third reference direction perpendicular to the first reference direction, the third resistor having: a first magnetoresistive section having a first current flow direction oriented at the first oblique angle relative to the third reference direction; and a second magnetoresistive section having a second current flow direction oriented at the second oblique angle relative to the third reference direction; and
forming a fourth resistor having a fourth reference direction perpendicular to the third reference direction, the fourth resistor having: a first magnetoresistive section having a first current flow direction oriented at the first oblique angle relative to the fourth reference direction; and a second magnetoresistive section having a second current flow direction oriented at the second oblique angle relative to the fourth reference direction.
18. The method of claim 17, wherein forming the integrated AMR sensor further comprises:
forming a fifth resistor having a fifth reference direction oriented at 45 degrees relative to the first reference direction, the fifth resistor having: a first magnetoresistive section having a first current flow direction oriented at the first tilt angle relative to the fifth reference direction; and a second magnetoresistive section having a second current flow direction oriented at the second tilt angle relative to the fifth reference direction;
forming a sixth resistor having a sixth reference direction perpendicular to the fifth reference direction, the sixth resistor having: a first magnetoresistive section having a first current flow direction oriented at the first oblique angle relative to the sixth reference direction; and a second magnetoresistive section having a second current flow direction oriented at the second oblique angle relative to the sixth reference direction;
forming a seventh resistor having a seventh reference direction perpendicular to the fifth reference direction, the seventh resistor having: a first magnetoresistive section having a first current flow direction oriented at the first oblique angle relative to the seventh reference direction; and a second magnetoresistive section having a second current flow direction oriented at the second oblique angle relative to the seventh reference direction; and
forming an eighth resistor having an eighth reference direction perpendicular to the seventh reference direction, the eighth resistor having: a first magnetoresistive section having a first current flow direction oriented at the first oblique angle relative to the eighth reference direction; and a second magnetoresistive section having a second current flow direction oriented at the second oblique angle relative to the eighth reference direction.
19. The method of claim 14, wherein forming the integrated AMR sensor further comprises:
a third magnetoresistive section forming the first resistor, the third magnetoresistive section having a third current flow direction oriented at zero degrees with respect to the first reference direction; and
a third magnetoresistive section forming the second resistor, the third magnetoresistive section having a third current flow direction oriented at zero degrees with respect to the second reference direction.
20. The method of claim 10, wherein calculating the estimated maximum angle error is performed by determining a magnetization vector for each magnetoresistive section that minimizes an energy of the magnetoresistive section based on:
a diagonal degaussing matrix of elemental characteristics having the dimensions of the magnetoresistive sections; and
the vector component of the external magnetic field.
Technical Field
The present invention relates to an integrated Anisotropic Magnetoresistive (AMR) sensor.
Background
An Anisotropic Magnetoresistive (AMR) sensor has a magnetoresistive section for detecting an orientation of an external magnetic field. An external magnetic field generates a magnetic moment in the magnetoresistive section. Due to the shape anisotropy of the magneto-resistive sections, the magnetic moments are not parallel to the external magnetic field, which leads to an angular error in the estimation of the orientation of the external magnetic field. The shape anisotropy of the magnetoresistive sections having an elongated shape (e.g., a long, narrow rectangle) is more pronounced, which enables a more efficient layout. For sensors with elongated magneto-resistive sections, the angular error may vary from one orientation of the external magnetic field to another, with an error range above 0.1 degrees. Conversely, magnetoresistive sections with low shape anisotropy values have a low aspect ratio, which leads to the undesirable situation of an increased area and thus increased costs of the AMR sensor. Some AMR sensors use the inflected magnetoresistive regions to average out angular errors over a range of external magnetic field orientations, which narrows the range of angular errors, but undesirably causes the angular error average to become high. Other AMR sensors use a plurality of differently sized and/or oriented continuous magnetoresistive strips to average out the angular error, which also undesirably results in an angle error averaging that is high. The angular errors due to shape anisotropy result in a total error of the AMR sensor.
Disclosure of Invention
A system includes an integrated Anisotropic Magnetoresistive (AMR) sensor and a method for forming an integrated AMR sensor. In one implementation, the described system/method relates to an integrated AMR sensor including a half bridge with two resistors having reference directions perpendicular to each other. In another implementation, the described system/method relates to an integrated AMR sensor including a first wheatstone bridge having four resistors with reference directions in an orthogonal configuration. In another implementation, the described system/method relates to an integrated AMR sensor comprising: a first Wheatstone bridge having four resistors with reference directions in an orthogonal configuration; and a second Wheatstone bridge having four resistors with reference directions in an orthogonal configuration, the second Wheatstone bridge being oriented at 45 degrees with respect to the first Wheatstone bridge.
In each implementation, each resistor includes: a first magnetoresistive section having a first current flow direction oriented at a first tilt angle relative to a reference direction of the resistor; and a second magnetoresistive section having a second current flow direction oriented at a second oblique angle relative to the reference direction. The first and second tilt angles are selected to facilitate cancellation of angular errors due to shape anisotropy of the magnetoresistive segments. In another implementation, the described systems/methods include a method for identifying a tilt angle that cancels an angular error due to shape anisotropy of the magnetoresistive segments.
Drawings
Fig. 1 depicts an example integrated AMR sensor.
FIG. 2 is a top view of an exemplary resistor of the integrated AMR sensor described with reference to FIG. 1 having two Wheatstone bridges.
FIG. 3 is a graph of an estimated maximum angle error for an integrated AMR sensor having a resistor including a first magnetoresistive section and a second magnetoresistive section, each of the first and second magnetoresistive sections having an equal total resistance.
FIG. 4 is a top view of an exemplary resistor of another integrated AMR sensor having two Wheatstone bridges as described with reference to FIG. 1.
FIG. 5 is a graph of an estimated maximum angle error for an integrated AMR sensor having a resistor including a first magnetoresistance section, a second magnetoresistance section, and a third magnetoresistance section, each of the first magnetoresistance section, the second magnetoresistance section, and the third magnetoresistance section having an equal total resistance.
FIG. 6 is a top view of an exemplary resistor of another integrated AMR sensor having two Wheatstone bridges as described with reference to FIG. 1.
FIG. 7 is a graph of an estimated maximum angle error for an integrated AMR sensor having a resistor including a first magnetoresistive section, a second magnetoresistive section, and a third magnetoresistive section.
Fig. 8 is a top view of an exemplary integrated AMR sensor.
Fig. 9 is a flow chart of an example method of forming an integrated AMR sensor.
Detailed Description
The drawings are not drawn to scale. Optionally, some illustrated acts or events are implemented to perform a method in accordance with example embodiments.
Example embodiments include a system comprising an integrated Anisotropic Magnetoresistive (AMR) sensor and a method for forming an integrated AMR sensor. In one implementation, the described system/method involves an integrated AMR sensor that includes a half-bridge having two resistors with reference directions perpendicular to each other. In another implementation, the described system/method involves an integrated AMR sensor including a first wheatstone bridge having four resistors orthogonally configured with reference directions. In another implementation, the described system/method involves an integrated AMR sensor including a first wheatstone bridge having four resistors orthogonally configured with reference directions and a second wheatstone bridge having four resistors orthogonally configured with reference directions, the second wheatstone bridge being oriented at 45 degrees with respect to the first wheatstone bridge.
An integrated AMR sensor can have a half bridge comprising two serially connected resistors with a sensing node between the two resistors. Each resistor has a reference direction that is oriented at a reference angle with respect to a common reference axis of the integrated AMR sensor. The reference directions of the two resistors are perpendicular to each other, so they have an orthogonal configuration.
Another integrated AMR sensor can have a wheatstone bridge comprising four resistors. The four resistors are arranged in two half-bridges, each half-bridge having two series resistors, with a sensing node between the resistors of each half-bridge. Each resistor has a reference direction that is oriented at a reference angle with respect to a common reference axis of the integrated AMR sensor. The reference directions of the resistors in each half-bridge are perpendicular to each other. The reference direction of each resistor is parallel to the reference direction of the resistors in the opposing half-bridge, which results in a quadrature configuration for the wheatstone bridges.
Another integrated AMR sensor can have: a first Wheatstone bridge having four resistors in an orthogonal configuration; and a second Wheatstone bridge having four resistors in an orthogonal configuration, a reference direction of the first Wheatstone bridge being oriented at 45 degrees with respect to the reference direction of the first Wheatstone bridge.
In each of the integrated AMR sensors, each resistor includes at least a first magnetoresistive section and a second magnetoresistive section electrically coupled in series. The first magnetoresistive section has a first current flow direction, which is the direction of current flow through the first magnetoresistive section during operation of the integrated AMR sensor, oriented at a first positive inclination angle with respect to a reference direction of a resistor containing the first magnetoresistive section. The second magnetoresistive section has a second current flow direction oriented at a second negative tilt angle relative to the reference direction of the resistor.
During operation of the integrated AMR sensor, one or more signals are obtained from the sensing nodes. The signal is used to estimate the angle of orientation of the external magnetic field component in the plane of the magneto-resistive section. The tilt angle of the magnetoresistive segments in each resistor is selected to facilitate cancellation of measurement errors due to shape anisotropy when estimating the orientation angle. The magnetoresistive section can have a high aspect ratio, which facilitates achieving an efficient layout and thus reducing the cost of the integrated AMR sensor as compared to another AMR sensor that uses a low aspect ratio magnetoresistive section. In an integrated AMR sensor with only one half bridge, the orientation angle can be estimated to be in the range of about 90 degrees, which is sufficient for some applications. Having only one half-bridge may result in a lower sensor area, and thus lower cost and lower power consumption, compared to other configurations. In the case of an integrated AMR sensor with one wheatstone bridge, the estimated orientation angle may be in the range of about 180 degrees, which is sufficient for other applications. Having one wheatstone bridge allows these applications to be made at the desired cost and power as compared to a dual wheatstone bridge configuration. In an integrated AMR sensor with two wheatstone bridges, the estimated orientation angle can be in the range of 360 degrees.
Examples of specific configurations of integrated AMR sensors are described herein. A method of selecting tilt angles for magnetoresistive segments to counteract measurement errors due to shape anisotropy is described as part of a method of forming an integrated AMR sensor.
In this description, the term "lateral" refers to a direction parallel to the plane of the instantaneous top surface of the integrated AMR sensor. The term "vertical" refers to a direction perpendicular to the plane of the top surface of the integrated AMR sensor. Unless otherwise specified, the terms "angular errors (angular errors and angular errors)" refer to angular errors due to shape anisotropy. In this illustration, resistances that are described as equal are within 5% of each other, which achieves the advantages described herein.
Fig. 1 depicts an example integrated AMR sensor. The
The
The
The
The
The
The
The
The
The
The
During operation of the
In an alternate version of this example, the
FIG. 2 is a top view of an exemplary resistor of the integrated AMR sensor described with reference to FIG. 1 having two Wheatstone bridges. The
In this example, the total resistance of the
FIG. 3 is a graph of estimated maximum angle error due to shape anisotropy for an integrated AMR sensor having a resistor including a first magnetoresistive section and a second magnetoresistive section with no other magnetoresistive sections, each of the first and second magnetoresistive sections having an equal total resistance. The graph of fig. 3 depicts an estimated maximum angle error as a function of tilt angle, wherein the first magnetoresistive section is oriented with a positive tilt angle magnitude relative to a reference direction of a resistor containing the first magnetoresistive section, and wherein the second magnetoresistive section is oriented with a negative tilt angle magnitude relative to the reference direction of the resistor. The tilt angle of +12 to +18 degrees for the first magnetoresistive section and the tilt angle of-12 to-18 degrees for the second magnetoresistive section (such as shown in fig. 2) may be such that the maximum angle error due to shape anisotropy is less than 0.04 degrees for all orientation angles of the external magnetic field. The tilt angle of the first magnetoresistive section closer to +15 degrees and the tilt angle of the second magnetoresistive section closer to-15 degrees may be such that the maximum angle error due to shape anisotropy is less than 0.01 degrees for all orientation angles of the external magnetic field.
FIG. 4 is a top view of an exemplary resistor of another integrated AMR sensor having two Wheatstone bridges as described with reference to FIG. 1. The resistor 404 has a reference direction 406. The reference direction 406 is oriented at a reference angle 408 with respect to a common reference axis 410 of the integrated AMR sensor. The resistor 404 of this example includes a first magnetoresistive section 484, a second magnetoresistive section 486, and a third magnetoresistive section 492 electrically coupled in series, as schematically depicted in fig. 4. Each of the first, second, and third reluctance segments 484, 486, 492 has a length and a width as described with reference to fig. 2. The first, second, and third reluctance sections 484, 486, 492 may have an aspect ratio greater than 10.
In this example, the total resistance of the first magnetoresistive section 484, the total resistance of the second magnetoresistive section 486, and the total resistance of the third magnetoresistive section 492 are balanced to cancel out the angular error due to the shape anisotropy. For example, the total resistance of the first magnetoresistive section 484 may be approximately equal to the total resistance of the second magnetoresistive section 486, and may be approximately equal to the total resistance of the third magnetoresistive section 492. Each of the first magnetoresistive sections 484 has a first current flow direction 488, the first current flow direction 488 being in a direction of current flow through the first magnetoresistive section 484 during operation of the integrated AMR sensor. In this example, each first current flow direction 488 is oriented at +16 degrees to +24 degrees relative to the reference direction 406 of the resistor 404. Each of the second magnetoresistive sections 486 has a second current flow direction 490, the second current flow direction 490 being in a direction of current flow through the second magnetoresistive section 486 during operation of the integrated AMR sensor. In this example, each second current flow direction 490 is oriented at-16 degrees to-24 degrees with respect to the reference direction 406 of the resistor 404. Each of the third magnetoresistive sections 492 has a third current flow direction 494, the third current flow direction 494 being in a direction of current flow through the third magnetoresistive section 492 during operation of the integrated AMR sensor. In this example, each third current flow direction 494 is oriented at 0 degrees relative to the reference direction 406 of the resistor 404. In this example, the two Wheatstone bridges of the integrated AMR sensor each have a similar configuration of magnetoresistive sections. The angular error is further reduced when the first reluctance section 484 is arranged to orient each first current flow direction 488 closer to +20 degrees relative to the reference direction 406 and when the second reluctance section 486 is arranged to orient each second current flow direction 490 closer to-20 degrees relative to the reference direction 406. In this example, each resistor of the two wheatstone bridges of the integrated AMR sensor has a similar magnetoresistive segment configuration. This configuration of magnetoresistive sections in each resistor may cause the angle error due to shape anisotropy to be less than 0.04 degrees for all orientation angles 480 of external magnetic field 482.
FIG. 5 is a graph of estimated maximum angle error due to shape anisotropy for an integrated AMR sensor having a resistor including a first magnetoresistive section, a second magnetoresistive section, and a third magnetoresistive section, and no other magnetoresistive sections, each of the first magnetoresistive section, the second magnetoresistive section, and the third magnetoresistive section having an equal total resistance. The graph of FIG. 5 depicts an estimated maximum angle error as a function of tilt angle, wherein the first magnetoresistive section is oriented at a positive tilt angle magnitude relative to a reference direction of a resistor containing the first magnetoresistive section, and wherein the second magnetoresistive section is oriented at a negative tilt angle magnitude relative to the reference direction of the resistor, and wherein the third magnetoresistive section is oriented at zero degrees relative to the reference direction of the resistor. The tilt angle of the first magnetoresistive section from +16 degrees to +24 degrees and the tilt angle of the second magnetoresistive section from-16 degrees to-24 degrees (such as shown in fig. 4) may be such that the maximum angle error due to shape anisotropy is less than 0.04 degrees for all orientation angles of the external magnetic field. The tilt angle of the first magnetoresistive section closer to +20 degrees and the tilt angle of the second magnetoresistive section closer to-20 degrees may be such that the maximum angle error due to shape anisotropy is less than 0.01 degrees for all orientation angles of the external magnetic field.
FIG. 6 is a top view of an exemplary resistor of another integrated AMR sensor having two Wheatstone bridges as described with reference to FIG. 1.
In this example, the total resistance of the first magneto-
FIG. 7 is a graph of an estimated maximum angle error due to shape anisotropy for an integrated AMR sensor having a resistor including a first magnetoresistance segment, a second magnetoresistance segment, and a third magnetoresistance segment. The total resistance of the first magneto-resistive section is approximately equal to the total resistance of the second magneto-resistive section. The total resistance of the third magneto-resistive section is approximately equal to the sum of the total resistance of the first magneto-resistive section and the total resistance of the second magneto-resistive section. The graph of FIG. 7 depicts an estimated maximum angle error as a function of tilt angle, wherein a first magnetoresistive segment is oriented with a positive tilt angle magnitude relative to a reference direction of a resistor containing the first magnetoresistive segment, and wherein a second magnetoresistive segment is oriented with a negative tilt angle magnitude relative to the reference direction of the resistor, and wherein a third magnetoresistive segment is oriented with zero degrees relative to the reference direction of the resistor. The tilt angle of the first magnetoresistive section of +24 to +36 degrees and the tilt angle of the second magnetoresistive section of-24 to-36 degrees (e.g., shown in fig. 6) may be such that the maximum angle error due to shape anisotropy is less than 0.04 degrees for all orientation angles of the external magnetic field. The tilt angle of the first magnetoresistive section closer to +30 degrees and the tilt angle of the second magnetoresistive section closer to-30 degrees may be such that the maximum angle error due to shape anisotropy is less than 0.01 degrees for all orientation angles of the external magnetic field.
Fig. 8 is a top view of an exemplary integrated AMR sensor. The
Each of
The
Fig. 9 is a flow chart of an example method of forming an integrated AMR sensor. The integrated AMR sensor may have the configuration described with reference to fig. 1. Some of the method steps of forming the
Step 902 includes inputting the dimensions of the magnetoresistive section of the resistor of the integrated AMR sensor. For magnetoresistive segments having a rectangular prism shape, the dimensions may include a length extending in a direction of current flow through the magnetoresistive segment, a width extending laterally perpendicular to the length, and a thickness extending in a perpendicular direction perpendicular to the length and the width. For a magnetoresistive section having an elliptical cylinder shape, dimensions may include a major axis extending in a direction of current flow through the magnetoresistive section, a minor axis extending transversely perpendicular to the length, and a thickness extending in a perpendicular direction perpendicular to the length and width. For magnetoresistive sections having another shape, the dimensions may be selected to calculate the angular error due to shape anisotropy in a subsequent step. The size of the magnetoresistive section of the resistor can be selected to satisfy several criteria, such as providing a sufficient signal of the expected external magnetic field above the noise level of the detection circuit of the integrated AMR sensor; compatible with thin film processes used in manufacturing facilities for fabricating integrated AMR sensors; and is compatible with thin lithographic and etching processes used in manufacturing settings for fabricating integrated AMR sensors. The standard of providing a sufficient signal can be realized by reducing the width of the magnetoresistive section, and the standard compatible with a thin photolithography process and an etching process can be realized by increasing the width.
Step 904 includes assigning a tilt angle to each of the magnetoresistive sections. For each magnetoresistive segment, the tilt angle may describe an angle of a length of the magnetoresistive segment relative to a reference angle of a resistor containing the magnetoresistive segment.
Step 906 includes estimating the angular error due to shape anisotropy in measuring the external magnetic field by an integrated AMR sensor having a magnetoresistive section with dimensions and tilt angles provided by
Wherein:
μois the magnetic permittivity of free space
E is the energy of the magnetoresistive region
M is the magnetization vector of the magnetoresistive sections
[ N ] a diagonal degaussing matrix of elemental characteristics that is the size of the magnetoresistive sections,
h is an external magnetic field, expressed as a vector, and the operator indicates the inner product of the vector, resulting in a scalar; the inner product is sometimes referred to as a "dot product".
In one embodiment of
Estimating the resistance of the magnetoresistive section is a function of the angle θ between the magnetization vector M and the direction of current flow along the length of the magnetoresistive section:
R=R⊥+(R||-R⊥)cos2θ
wherein:
r is the resistance of the magneto-resistive sections,
R⊥is the resistance of the magnetoresistive region when M is perpendicular to the direction of current flow, an
R||Is the resistance of the magneto-resistive section when M is parallel to the direction of current flow.
The resistance of each resistor of the integrated AMR sensor can include a sum of estimated resistances of the magnetoresistive sections in the resistor. In the case of an embodiment of an integrated AMR sensor containing two Wheatstone bridges, as described with reference to FIG. 1, the signal for each Wheatstone bridge can be estimated as the difference between the potentials at the sense terminals of the Wheatstone bridges when a bias is applied to the bias terminals of the Wheatstone bridges. The signals of the wheatstone bridge may be combined, for example, using an arctan function to estimate the orientation of the external magnetic field. The angular error due to the shape anisotropy can be estimated as the difference between the orientation of the external magnetic field and the estimated orientation of the external magnetic field from the integrated AMR sensor. Angular errors due to shape anisotropy are estimated for a plurality of orientations of the external magnetic field that cover a range of orientations expected during operation of the integrated AMR sensor, e.g., from zero degrees to 360 degrees.
Step 908 is a decision step that includes comparing the maximum value of the angular error estimated at
Step 910 includes adjusting a value of a tilt angle of a magnetoresistive section to provide a reduced estimated maximum angle error. In one implementation of
Step 912 includes optionally storing a value for the tilt angle corresponding to an estimated maximum angle error that is less than the target value. The tilt angle value may be stored, for example, in a computer readable medium, such as a Dynamic Random Access Memory (DRAM), a Static Random Access Memory (SRAM), a non-transitory memory (e.g., flash memory), a Ferroelectric Random Access Memory (FRAM), or a Magnetoresistive Random Access Memory (MRAM), a magnetic disk (sometimes referred to as a hard disk or hard drive), a removable magnetic disk (sometimes referred to as a floppy disk), a magnetic tape, or an optically recordable memory medium, such as a compact disk recordable (CD-R) or a recordable digital video disk (DVD-R). Alternatively, the tilt angle value may be stored in non-electronic media, such as printed paper.
After
Step 916 includes fabricating an integrated AMR sensor using the recalled tilt angle value. Forming an integrated AMR sensor by: forming a first resistor having a first reference direction, the first resistor having: a first magnetoresistive section having a first current flow direction oriented at a first tilt angle relative to a first reference direction; and a second magnetoresistive section having a second current flow direction oriented at a second oblique angle relative to the first reference direction; and forming a second resistor having a second reference direction, the second reference direction being perpendicular to the first reference direction, the second resistor having: a first magnetoresistive section having a first current flow direction oriented at a first tilt angle relative to a second reference direction; and a second magnetoresistive section having a second current flow direction oriented at a second oblique angle relative to a second reference direction.
In one implementation of
In another implementation, the recalled tilt angle value may be used in a maskless lithography process (e.g., electron beam lithography) to define an etch mask. In another implementation, the recalled tilt angle value may be used to form the magnetoresistive segments directly through an additive process (e.g., three-dimensional (3D) printing). In this implementation, the tilt angle value may comply with another standard compatible with maskless lithography processes or 3D printing processes.
A plurality of integrated AMR sensors can be formed as part of the implementation of
Example embodiments may be implemented in numerous ways, including as a process, an apparatus, a system, a device, program instructions in a computer readable medium, or a method.
Modifications may be made to the described embodiments, and other embodiments may be within the scope of the claims.
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