JP2019021840A - Magnetic sensor - Google Patents

Abstract

To stabilize characteristics of a magnetic sensor by mitigating stress generated between an insulating layer and a magnetic layer.SOLUTION: A magnetic sensor includes a magnetoresistive element, an insulating layer 12, and a magnetic layer 13. The insulating layer 12 covers the magnetoresistive element. The magnetic layer 13 is located on the insulating layer 12 and covers at least part of the magnetoresistive element as viewed from a direction perpendicular to the insulating layer 12. A portion at least in contact with the magnetic layer 13 in the insulating layer 12 contains a resin.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a magnetic sensor.

  As a prior document disclosing the configuration of the magnetic sensor, there is JP 2013-44641 A (Patent Document 1). The magnetic sensor described in Patent Document 1 includes a sensor circuit unit. The sensor circuit unit includes a first series circuit and a second series circuit. In the first series circuit, the first magnetoresistive element and the third magnetoresistive element are connected in series. In the second series circuit, the second magnetoresistive element and the fourth magnetoresistive element are connected in series. The sensor circuit unit is configured by a bridge circuit in which a first series circuit and a second series circuit are connected in parallel.

  The surfaces of the first magnetoresistive element, the second magnetoresistive element, the third magnetoresistive element, and the fourth magnetoresistive element are covered with an insulating layer. On each surface of the third magnetoresistive element and the fourth magnetoresistive element, a magnetic layer made of a magnetic material is formed with an insulating layer interposed therebetween.

JP 2013-44641 A

  Depending on the difference between the thermal expansion coefficient of the insulating layer and the thermal expansion coefficient of the magnetic layer, stress may be generated between the insulating layer and the magnetic layer. When this stress is applied to the magnetoresistive element, the magnetic characteristics of the magnetic sensor change due to magnetostriction of the magnetoresistive element. Further, the stress value applied to the magnetoresistive element is changed due to the temperature change around the magnetic sensor, so that the temperature characteristics of the magnetic sensor are deteriorated and the reliability of the magnetic sensor is lowered. Furthermore, when a crack occurs in the insulating layer due to the stress generated between the insulating layer and the magnetic layer, the durability of the magnetic sensor decreases.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a magnetic sensor having stable characteristics by relaxing stress generated between an insulating layer and a magnetic layer. .

  The magnetic sensor based on this invention is provided with a magnetoresistive element, an insulating layer, and a magnetic body layer. The insulating layer covers the magnetoresistive element. The magnetic layer is located on the insulating layer and covers at least a part of the magnetoresistive element when viewed from the direction orthogonal to the insulating layer. At least a portion in contact with the magnetic layer in the insulating layer contains a resin.

  In one embodiment of the present invention, the insulating layer includes a first layer made of an inorganic material and a second layer located on the first layer and containing a resin. Between the magnetoresistive element and the magnetic layer, the first layer is in contact with the magnetoresistive element and covers the magnetoresistive element, and the second layer is in contact with the magnetic layer.

In one embodiment of the present invention, the resin is a polyimide resin or an epoxy resin.
In one embodiment of the present invention, the inorganic substance contains silicon.

  According to the present invention, the stress generated between the insulating layer and the magnetic layer can be relieved to stabilize the characteristics of the magnetic sensor.

It is a top view which shows the structure of the magnetic sensor which concerns on Embodiment 1 of this invention. It is sectional drawing which looked at the magnetic sensor of FIG. 1 from the II-II line arrow direction. It is sectional drawing which shows the structure of the magnetic sensor which concerns on Embodiment 2 of this invention. It is sectional drawing which shows the structure of the magnetic sensor which concerns on the modification of Embodiment 2 of this invention. It is sectional drawing which shows the structure of the magnetic sensor which concerns on a comparative example. In the magnetic sensor which concerns on a comparative example, it is a graph which shows the change of the magnetic characteristic of a magnetic sensor by the magnitude | size of the stress loaded on a magnetoresistive element. It is a graph which shows the dispersion | variation in the magnetic sensitivity of a magnetic sensor when the stress value applied to a magnetoresistive element changes with the surrounding temperature changes of a magnetic sensor. In the magnetic sensor which concerns on a comparative example, it is a fragmentary sectional view which shows the state which the crack generate | occur | produced in the insulating layer by the stress which generate | occur | produced between the insulating layer and the magnetic body layer.

  Hereinafter, magnetic sensors according to embodiments of the present invention will be described with reference to the drawings. In the following description of the embodiments, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a plan view showing the configuration of the magnetic sensor according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view of the magnetic sensor of FIG. 1 as viewed from the direction of arrows II-II. As shown in FIGS. 1 and 2, the magnetic sensor 1 according to the first embodiment of the present invention includes a magnetoresistive element, an insulating layer 12, and a magnetic layer 13. In the present embodiment, the magnetic sensor 1 includes a first magnetoresistive element R1, a second magnetoresistive element R2, a third magnetoresistive element R3, and a fourth magnetoresistive element R4 as magnetoresistive elements.

  The magnetoresistive element is formed on the surface of the substrate 4 extending along the X direction and the Y direction orthogonal to each other. As a material constituting the substrate 4, silicon, glass, sapphire, or the like can be used.

  In the present embodiment, the magnetoresistive element is an AMR (Anisotropic Magneto Resistance) element, but is not limited to an AMR element, and may be a GMR (Giant Magneto Resistance) element or a TMR (Tunnel Magneto Resistance) element.

  Each of the first magnetoresistive element R1, the second magnetoresistive element R2, the third magnetoresistive element R3, and the fourth magnetoresistive element R4 has a meander shape in which long strip-shaped patterns and short strip-shaped patterns are alternately connected. Is formed. The shape of the magnetoresistive element is not limited to the meander shape.

  In each of the first magnetoresistive element R1 and the second magnetoresistive element R2, a long strip pattern extends along the X direction. Each of the first magnetoresistive element R1 and the second magnetoresistive element R2 has the smallest resistance value when a magnetic field in the Y direction is applied.

  In each of the third magnetoresistive element R3 and the fourth magnetoresistive element R4, a long strip pattern extends in the Y direction. Each of the third magnetoresistive element R3 and the fourth magnetoresistive element R4 has the smallest resistance value when a magnetic field in the X direction is applied.

  In the present embodiment, the magnetoresistive element is made of permalloy (NiFe). However, the constituent material of the magnetoresistive element is not limited to NiFe, and may be a soft magnetic material such as NiFeCo or FeCo.

  In this embodiment, a permalloy film is formed on a silicon substrate, and a meandering magnetoresistive element is formed using a fine processing technique such as a photolithography technique.

  For example, a film made of permalloy is formed on the entire surface of the substrate 4 by electron beam evaporation while the substrate 4 is heated to 100 ° C. The thickness of the permalloy film is, for example, 30 nm. After a positive photoresist is formed on the permalloy film, the photoresist is exposed using a mask aligner, which is an exposure apparatus, and then developed. Thereafter, the permalloy film is patterned by wet etching. The line width of the patterned permalloy film is, for example, 10 μm.

  A wire bond pad is formed on the substrate 4. The magnetic sensor 1 includes a ground terminal 8, a drive voltage terminal 9, a first output terminal 10, and a second output terminal 11 that are pads for wire bonding. The pad for wire bonding is formed by, for example, a lift-off method.

  As shown in FIG. 1, the first magnetoresistive element R1 is located at the lower left of the substrate 4, the second magnetoresistive element R2 is located at the upper right of the substrate 4, and the third magnetoresistive element R3 is located at the upper left of the substrate 4. The fourth magnetoresistive element R4 is located at the lower right of the substrate 4.

  The first magnetoresistive element R1, the second magnetoresistive element R2, the third magnetoresistive element R3, and the fourth magnetoresistive element R4 are connected to each other by a full bridge to form a bridge circuit 5.

  Specifically, the first magnetoresistive element R1 and the third magnetoresistive element R3 are connected in series at the first connection point P1, and the first series circuit 6 is configured. The second magnetoresistive element R2 and the fourth magnetoresistive element R4 are connected in series at the second connection point P2, and the second series circuit 7 is configured. The end of the first series circuit 6 on the first magnetoresistive element R1 side and the end of the fourth series magnetoresistive element R4 of the second series circuit 7 are connected to each other at a third connection point P3. The end of the third magnetoresistive element R3 of the first series circuit 6 and the end of the second series circuit 7 on the second magnetoresistive element R2 side are connected to each other at a fourth connection point P4.

  Thereby, the 1st series circuit 6 and the 2nd series circuit 7 are connected in parallel, and the bridge circuit 5 is comprised. The magnetic sensor 1 is not limited to the configuration including the full bridge circuit, and may include a half bridge circuit.

  The third connection point P3 is connected to a ground terminal 8 connected to an external ground (GND). The fourth connection point P4 is connected to a drive voltage terminal 9 to which a drive voltage (Vdd) is supplied. As a result, the drive voltage (Vdd) can be applied to the bridge circuit 5.

  The first connection point P1 is connected to the first output terminal 10 for taking out the output voltage V1. The second connection point P2 is connected to the second output terminal 11 for taking out the output voltage V2. Each of the first output terminal 10 and the second output terminal 11 is connected to an input terminal of a differential amplifier (not shown). The differential amplifier amplifies the potential difference (V1-V2) between the output voltage V1 and the output voltage V2 and outputs the amplified signal as a detection signal Vout.

  The insulating layer 12 covers the magnetoresistive element. The insulating layer 12 has an opening so that the wire bond pad is exposed. The insulating layer 12 is formed above the entire surface of the substrate 4 except for the opening. As a material constituting the insulating layer 12, polyimide resin or epoxy resin can be used. As the epoxy resin, for example, a permanent photoresist (SU-8) can be used.

  In the present embodiment, when forming the insulating layer 12, first, a photosensitive polyimide resin is applied on the substrate 4 on which the magnetoresistive element is formed. The thickness of the polyimide layer is, for example, 3 μm. Thereafter, the laminate on which the polyimide layer is formed is put in an oven having a temperature of 80 ° C. and maintained for 10 minutes, and prebaked. After the polyimide layer is exposed using a mask aligner, it is placed in an oven having a temperature of 120 ° C. and maintained for 6 minutes to perform PEB (Post exposure bake). Next, the polyimide layer is developed to provide an opening, and then placed in an oven having a temperature of 200 ° C. and maintained for 60 minutes to be cured. Thereby, the insulating layer 12 provided with the opening is formed.

  The magnetic layer 13 is located on the insulating layer 12. In the present embodiment, the magnetic layer 13 is formed so as to cover each of the third magnetoresistive element R3 and the fourth magnetoresistive element R4. When viewed from a direction orthogonal to the insulating layer 12, the magnetic layer 13 in a portion covering the third magnetoresistive element R3 has a rectangular shape. When viewed from the direction orthogonal to the insulating layer 12, the magnetic layer 13 in a portion covering the fourth magnetoresistive element R4 has a rectangular shape. The formation position of the magnetic layer 13 is not limited to the above, and it is sufficient that it covers at least a part of the magnetoresistive element when viewed from the direction orthogonal to the insulating layer 12.

  In the present embodiment, the magnetic layer 13 is made of permalloy (NiFe). However, the constituent material of the magnetic layer 13 is not limited to NiFe, and any material including a soft magnetic material such as NiFeCo or FeCo may be used.

  The magnetic layer 13 may be formed of, for example, a metal layer or a ceramic layer formed by vapor deposition, sputtering, plating, or the like, and is a resin layer formed by applying a resin containing magnetic powder. There may be.

  In the present embodiment, the magnetic layer 13 made of permalloy is formed on the insulating layer 12 by electrolytic plating. First, a power feeding layer made of Ti having a thickness of 300 nm is formed on the insulating layer 12 by electron beam evaporation. A film resist is formed on the power feeding layer, and an opening is formed at a position corresponding to the formation position of the insulating layer 12 in the film resist using a photolithography technique. Electroplating is performed using the power feeding layer, and after removing the film resist, the power feeding layer is removed by etching, whereby the patterned magnetic layer 13 is formed. The thickness of the magnetic layer 13 is, for example, 10 μm.

  In order to increase the magnetic flux collection effect, it is preferable that the magnetic layer 13 has a large magnetic permeability and the magnetic layer 13 is thick. Since each of the third magnetoresistive element R3 and the fourth magnetoresistive element R4 is covered with the magnetic layer 13, the magnetic flux passes through the magnetic layer 13, so that the third magnetoresistive element R3 and the fourth magnetoresistive element Application of a detection magnetic field to each of the elements R4 can be suppressed.

  In the magnetic sensor 1 according to the present embodiment, since the insulating layer 12 is made of resin, the stress generated between the insulating layer 12 and the magnetic layer 13 can be relieved. As a result, the characteristics of the magnetic sensor 1 can be stabilized. Specifically, it is possible to stabilize the magnetic characteristics of the magnetic sensor 1 by suppressing stress from being applied to the magnetoresistive element. Further, it is possible to suppress the stress value applied to the magnetoresistive element from changing due to the temperature change around the magnetic sensor 1, stabilize the temperature characteristics of the magnetic sensor 1, and improve the reliability of the magnetic sensor 1. . Furthermore, it is possible to prevent cracks from being generated in the insulating layer 12 and to reduce the durability of the magnetic sensor 1.

(Embodiment 2)
Hereinafter, a magnetic sensor according to Embodiment 2 of the present invention will be described with reference to the drawings. The magnetic sensor according to the second embodiment of the present invention is different from the magnetic sensor 1 according to the first embodiment only in the configuration of the insulating layer. Therefore, the description of the same configuration as the magnetic sensor 1 according to the first embodiment will not be repeated.

  FIG. 3 is a cross-sectional view showing the configuration of the magnetic sensor according to the second embodiment of the present invention. In FIG. 3, the same cross-sectional view as FIG. 2 is shown.

  As shown in FIG. 3, in the magnetic sensor 1a according to the second embodiment of the present invention, the insulating layer 12 includes a first layer 12a made of an inorganic material, and a second layer that is located on the first layer 12a and contains a resin. 12b. Between the magnetoresistive element and the magnetic layer 13, the first layer 12 a is in contact with the magnetoresistive element and covers the magnetoresistive element, and the second layer 12 b is in contact with the magnetic layer 13.

The inorganic material constituting the first layer 12a contains silicon. As the inorganic material constituting the first layer 12a, SiO ₂ or SiN can be used. The first layer 12a may be composed of a laminated structure SiN is provided on the SiO _2.

  The second layer 12b is formed on the surface of the first layer 12a and covers the entire surface of the first layer 12a. As a material constituting the second layer 12b, polyimide resin or epoxy resin can be used.

  In the magnetic sensor 1a according to this embodiment, since the insulating layer 12 includes the first layer 12a made of an inorganic material and the second layer 12b containing a resin, the first layer 12a stabilizes the magnetoresistive element. Thus, the stress generated between the insulating layer 12 and the magnetic layer 13 can be relaxed by the second layer 12b. As a result, the characteristics of the magnetic sensor 1a can be stabilized.

  The second layer 12b does not necessarily cover the entire surface of the first layer 12a. FIG. 4 is a cross-sectional view showing a configuration of a magnetic sensor according to a modification of the second embodiment of the present invention. In FIG. 4, the same cross-sectional view as FIG. 2 is shown.

  As shown in FIG. 4, in the magnetic sensor 1 b according to the modification of the second embodiment of the present invention, the second layer 12 b is formed only at a position directly below the magnetic layer 13. Thus, the second layer 12b may be provided only in the portion in contact with the magnetic layer 13.

  In addition, at least a portion in contact with the magnetic layer 13 in the insulating layer 12 only needs to contain a resin. For example, a portion of the insulating layer 12 not in contact with the magnetic layer 13 is made of only an inorganic material and is magnetic. The portion in contact with the body layer 13 may be composed of a mixture of an inorganic material and a resin.

(Experimental example)
Hereinafter, experimental examples performed using the magnetic sensor according to the comparative example in which the insulating layer is formed of only an inorganic material and the magnetic sensor according to the example will be described.

  FIG. 5 is a cross-sectional view showing a configuration of a magnetic sensor according to a comparative example. Note that FIG. 5 shows the same cross-sectional view as FIG. Note that the magnetic sensor according to the comparative example is different from the magnetic sensor 1 according to the first embodiment only in the configuration of the insulating layer, and therefore the description of the same configuration as the magnetic sensor 1 according to the first embodiment will not be repeated.

As shown in FIG. 5, in the magnetic sensor 1z according to the comparative example, the insulating layer 92 covers the magnetoresistive element. The magnetic layer 13 is located on the insulating layer 92. The insulating layer 92 is made of an inorganic material such as SiO ₂ .

  FIG. 6 is a graph showing changes in the magnetic characteristics of the magnetic sensor according to the magnitude of stress applied to the magnetoresistive element in the magnetic sensor according to the comparative example. In FIG. 6, data when the stress applied to the magnetoresistive element is large is indicated by a solid line, and data when the stress applied to the magnetoresistive element is small is indicated by a dotted line. In FIG. 6, the vertical axis represents the output voltage (Vout) of the magnetic sensor, and the horizontal axis represents the magnetic field strength (H).

  As shown in FIG. 6, in the magnetic sensor 1 z according to the comparative example, when the stress applied to the magnetoresistive element is large, the magnetic sensor 1 z of the magnetic sensor 1 z is compared with when the stress applied to the magnetoresistive element is small. The output voltage is low. Thus, in the magnetic sensor 1z according to the comparative example, the output value varies depending on the stress value applied to the magnetoresistive element, so that the magnetic characteristics of the magnetic sensor 1z are not stabilized and the reliability is lowered.

  FIG. 7 is a graph showing variations in magnetic sensitivity of the magnetic sensor when the ambient temperature of the magnetic sensor changes. In FIG. 7, the vertical axis represents magnetic sensitivity (Hon), and the horizontal axis represents the sample name.

  Comparative Example 1 is a magnetic sensor having the structure shown in FIG. 6, and Comparative Example 2 is a magnetic sensor that differs from the structure shown in FIG. 6 only in that no magnetic layer is provided. Example 1 is a magnetic sensor having the structure shown in FIG. 2, and Example 2 is a magnetic sensor having the structure shown in FIG.

  As shown in FIG. 7, the magnetic sensitivity of the magnetic sensor according to Comparative Example 2 in which the magnetic layer 13 is not provided is compared with the magnetic sensitivity of each of the magnetic sensors according to Comparative Example 1, Example 1, and Example 2. It was extremely low. The variation in magnetic sensitivity of the magnetic sensor according to Comparative Example 1 was larger than the variation in magnetic sensitivity of each of the magnetic sensors according to Example 1 and Example 2.

  From this result, since the portion of the insulating layer 12 that is in contact with the magnetic layer 13 contains resin, it is possible to suppress a change in the stress value applied to the magnetoresistive element due to a temperature change around the magnetic sensor. Thus, it was confirmed that the temperature characteristics of the magnetic sensor can be stabilized and the reliability of the magnetic sensor can be improved.

  FIG. 8 is a partial cross-sectional view showing a state in which a crack is generated in the insulating layer due to the stress generated between the insulating layer and the magnetic layer in the magnetic sensor according to the comparative example. In FIG. 8, the same cross-sectional view as FIG. 5 is shown.

  As shown in FIG. 8, in the magnetic sensor 1 z according to the comparative example, the stress generated between the insulating layer 92 and the magnetic layer 13 causes cracks from the insulating layer 92 at a position immediately below the edge of the magnetic layer 13. C was generated. Thus, when the crack C occurs in the insulating layer 92, the durability of the magnetic sensor 1z is lowered. If the crack C reaches the magnetoresistive element, the output of the magnetic sensor 1z becomes unstable and the reliability decreases.

  According to this experimental example, it was confirmed that relaxing the stress generated between the insulating layer 12 and the magnetic layer 13 is important in stabilizing the characteristics of the magnetic sensor.

  In the description of the above-described embodiment, configurations that can be combined may be combined with each other.

  It should be thought that embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1, 1a, 1b, 1z magnetic sensor, 4 substrate, 5 bridge circuit, 6 first series circuit, 7 second series circuit, 8 ground terminal, 9 drive voltage terminal, 10 first output terminal, 11 second output terminal, 12, 92 Insulating layer, 12a 1st layer, 12b 2nd layer, 13 Magnetic layer, C crack, P1 1st connection point, P2 2nd connection point, P3 3rd connection point, P4 4th connection point, R1 1st 1 magnetoresistive element, R2 2nd magnetoresistive element, R3 3rd magnetoresistive element, R4 4th magnetoresistive element, V1, V2 output voltage, Vout detection signal.

Claims (4)

A magnetoresistive element;
An insulating layer covering the magnetoresistive element;
A magnetic layer located on the insulating layer and covering at least a part of the magnetoresistive element when viewed from a direction perpendicular to the insulating layer;
A magnetic sensor in which at least a portion in contact with the magnetic layer in the insulating layer includes a resin. The insulating layer includes a first layer made of an inorganic material, and a second layer located on the first layer and containing a resin,
The first layer is in contact with the magnetoresistive element and covers the magnetoresistive element, and the second layer is in contact with the magnetic layer between the magnetoresistive element and the magnetic layer. The magnetic sensor described in 1.   The magnetic sensor according to claim 1, wherein the resin is a polyimide resin or an epoxy resin.   The magnetic sensor according to claim 2, wherein the inorganic substance includes silicon.

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