JP7795776B2 - Magnetic sensor and method for manufacturing the same - Google Patents

Description

The present invention relates to a magnetic sensor and a method for manufacturing a magnetic sensor.

Conventional magnetic sensors that utilize the magnetoresistance effect include MR sensors (magnetoresistive sensors) that utilize the TMR effect of tunneling magnetoresistance (TMR) elements. In these magnetic sensors, the element for detecting magnetic fields has a magnetic detection layer with a variable magnetization direction, a barrier layer containing a non-magnetic material and located on one surface of the magnetic detection layer, and a reference layer with a fixed magnetization direction and located on the surface of the barrier layer opposite the magnetic detection layer (see, for example, Patent Document 1).

Furthermore, to improve magnetic flux collection efficiency and enhance magnetic field detection sensitivity, magnetic sensors equipped with magnetic flux concentrators near the element are widely used. For example, as shown in Figure 5, a magnetic sensor equipped with magnetic flux concentrators has an interlayer insulating film provided to cover the entire side and top surfaces of the element to insulate the element formed on a substrate such as a silicon wafer, and a pair of magnetic flux concentrators provided on a protective layer to sandwich the element (see, for example, Patent Document 2).

Japanese Patent Application Laid-Open No. 2021-52050 JP 2018-194534 A

In conventional magnetic sensors with magnetic concentrators, such as those shown in Figure 5 and Patent Document 2, the positional relationship between the element and the magnetic concentrator must be controlled with high precision in order to increase the magnetic field detection sensitivity. However, because each layer of the element and the magnetic concentrator are deposited separately, variations in the accuracy of masks, patterning, etc. during the manufacturing process can cause the position of the magnetic concentrator to shift relative to the element, posing a problem in that the magnetic field detection sensitivity cannot be improved as expected.

The present invention was developed in response to these issues, and aims to provide a magnetic sensor and a method for manufacturing a magnetic sensor that can improve magnetic field detection sensitivity.

To achieve the above object, the magnetic sensor of the present invention is characterized by having a sensor section including a magnetic detection layer whose magnetization direction is variable, a barrier layer containing a non-magnetic material and arranged on one surface of the magnetic detection layer, and a reference layer whose magnetization direction is fixed and arranged on the surface of the barrier layer opposite the magnetic detection layer, and a magnetic converging layer made of the same material as the magnetic detection layer and arranged to the side of the magnetic detection layer with a gap between it and the side of the magnetic detection layer.

The method for manufacturing a magnetic sensor according to the present invention is a method for manufacturing a magnetic sensor according to the present invention, and is characterized in that after depositing the layers that constitute the magnetic detection layer and the magnetic converging layer, a groove is formed that penetrates the layer in the thickness direction, thereby dividing the layer into the magnetic detection layer and the magnetic converging layer.

The magnetic sensor manufacturing method according to the present invention can suitably manufacture the magnetic sensor according to the present invention. The magnetic sensor manufacturing method according to the present invention can form a magnetic detection layer and a magnetic converging layer by dividing a deposited layer by forming a groove that penetrates the layer in the thickness direction. Because the magnetic detection layer and the magnetic converging layer can be formed simultaneously by simply forming the groove, the positional accuracy of the magnetic converging layer relative to the magnetic detection layer can be improved. Furthermore, the width of the groove can easily adjust the distance between the magnetic detection layer and the magnetic converging layer. In this way, the magnetic sensor and magnetic sensor manufacturing method according to the present invention can improve the positional accuracy of the magnetic converging layer relative to the sensor section including the magnetic detection layer, thereby improving the magnetic field detection sensitivity.

In the magnetic sensor and magnetic sensor manufacturing method according to the present invention, the surfaces of the magnetic detection layer and magnetic convergence layer are located on the same plane. Therefore, for example, when processing the sensor portion by etching or other processes, processing accuracy can be improved by monitoring the position of the surface of the magnetic convergence layer. In particular, when etching the sensor portion through the barrier layer to the surface of the magnetic detection layer, etching can be stopped at the same height as the surface of the magnetic convergence layer, allowing for high-precision processing even when the barrier layer is very thin, at just a few nanometers thick.

In the magnetic sensor and method for manufacturing a magnetic sensor according to the present invention, the magnetic detection layer, reference layer, and magnetic flux concentrating layer preferably contain a ferromagnetic material. The barrier layer preferably comprises an insulating non-magnetic material. In the magnetic sensor and method for manufacturing a magnetic sensor according to the present invention, other layers may be provided on the surface of the sensor section facing the magnetic detection layer and the surface facing the reference layer. Other layers may also be inserted between the magnetic detection layer and the barrier layer, and between the barrier layer and the reference layer. In the method for manufacturing a magnetic sensor according to the present invention, the barrier layer and the reference layer may be formed before forming the groove separating the magnetic detection layer and the magnetic flux concentrating layer, or the barrier layer and the reference layer may be formed after the groove is formed. In addition, the magnetic sensor according to the present invention may be any type of sensor section, such as a TMR sensor, an AMR sensor, a GMR sensor, an MI sensor, or a fluxgate sensor.

In the magnetic sensor according to the present invention, the magnetic concentrating layers preferably consist of a pair and are arranged so as to sandwich the magnetic sensing layer from the sides. In the method for manufacturing the magnetic sensor according to the present invention, the grooves are preferably formed on both sides of the magnetic sensing layer, and a pair of magnetic concentrating layers are preferably formed so as to sandwich the magnetic sensing layer from the sides. In these cases, the magnetic collection efficiency can be further increased, further improving the magnetic field detection sensitivity. Furthermore, during manufacturing, the layers can be efficiently arranged on a substrate such as a silicon wafer, thereby improving manufacturing efficiency.

In the magnetic sensor according to the present invention, the magnetic detection layer is preferably electrically insulated from the magnetic converging layer. In the method for manufacturing a magnetic sensor according to the present invention, an insulating film is preferably provided in the groove formed between the magnetic detection layer and the magnetic converging layer. In these cases, noise can be blocked, improving magnetic field detection sensitivity.

The magnetic sensor according to the present invention preferably has a substrate on one surface of which the sensor section and the magnetic converging layer are formed, and the sensor section is preferably formed on the substrate with the magnetic detection layer facing the substrate. In the method for manufacturing the magnetic sensor according to the present invention, it is preferable to form the magnetic detection layer and the magnetic converging layer on one surface of the substrate, and then form the barrier layer and the reference layer on the surface of the magnetic detection layer opposite the substrate. In these cases, it is easy to form the magnetic converging layer.

The magnetic sensor according to the present invention may include a magnetic concentrator plate disposed parallel to the surface of the magnetic concentrator layer, spaced apart from the magnetic concentrator layer, along the stacking direction from the magnetic detection layer toward the reference layer, and located inside the area projected in the stacking direction of the magnetic concentrator layer. The method for manufacturing a magnetic sensor according to the present invention may also include forming a magnetic concentrator plate parallel to the surface of the magnetic concentrator layer, spaced apart from the magnetic concentrator layer, along the stacking direction from the magnetic detection layer toward the reference layer, and located inside the area projected in the stacking direction of the magnetic concentrator layer. In these cases, the magnetic concentrator plate can further increase the magnetic collection efficiency and further improve the magnetic field detection sensitivity.

The present invention provides a magnetic sensor and a method for manufacturing a magnetic sensor that can improve magnetic field detection sensitivity.

1A is a plan view of a magnetic sensor according to an embodiment of the present invention, seen through an insulating film, and FIG. 1B is a cross-sectional view thereof. 1A and 1B are a plan view and a cross-sectional view showing a modified example of the magnetic sensor according to the embodiment of the present invention, respectively, seen through an insulating film. 1A shows a design pattern of a magnetic detection layer of a comparative example, and FIG. 1B shows design patterns of a magnetic detection layer and a magnetic flux concentrator layer of a magnetic sensor and a method of manufacturing the magnetic sensor according to an embodiment of the present invention. 3A shows the magnetoresistance curve of the comparative example shown in FIG. 3A, and FIG. 3B shows the magnetoresistance curve of the magnetic sensor according to the embodiment of the present invention shown in FIG. 3B. 1A is a plan view of a conventional magnetic sensor seen through an interlayer insulating film, and FIG. 1B is a cross-sectional view thereof.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
1 to 4 show a magnetic sensor and a method for manufacturing the magnetic sensor according to an embodiment of the present invention.
As shown in FIG. 1, the magnetic sensor 10 includes a substrate 11, a sensor portion 12, a magnetic flux concentrating layer 13, and an insulating film 14.

The substrate 11 is made of a commercially available silicon wafer. The sensor section 12 is provided on one surface of the substrate 11 and includes a magnetic sensing layer 21, a barrier layer 22, and a reference layer 23. The magnetic sensing layer 21 is made of a ferromagnetic material and is formed on the substrate 11. The magnetic sensing layer 21 is configured so that its magnetization direction can change in a direction parallel to the surface of the layer in response to the influence of external magnetic flux. The magnetic sensing layer 21 is made of a soft magnetic material such as CoFeSiB, FeCuNbSiB, or NiFe, and has a thickness of approximately 10 to 200 nm.

The barrier layer 22 is made of an insulating non-magnetic material and is formed on the surface of the magnetic detection layer 21 opposite the substrate 11. The barrier layer 22 is made of, for example, MgO, Mg-Al-O, AlOx, etc., and has a thickness of approximately 1 nm to 10 nm. The reference layer 23 is made of a ferromagnetic material and is formed on the surface of the barrier layer 22 opposite the magnetic detection layer 21. The magnetization direction of the reference layer 23 is fixed parallel to the surface of the layer. The reference layer 23 is made of, for example, CoFeB, and has a thickness of approximately 2 nm to 10 nm.

The sensor unit 12 may have each layer stacked so that the reference layer 23 faces the substrate 11. The magnetic detection layer 21 and reference layer 23 may each be composed of multiple layers, for example, multiple magnetic layers with an insertion layer sandwiched between them. In this case, it is preferable that the magnetic layers are magnetostatically coupled with each other via the insertion layer. The insertion layer is preferably made of, for example, Ru, Ta, TaB, or the like, and has a thickness of 2 nm or more. The sensor unit 12 may also have other layers inserted between the magnetic detection layer 21 and the barrier layer 22, and between the barrier layer 22 and the reference layer 23.

The magnetic converging layer 13 is made of the same ferromagnetic material as the magnetic sensing layer 21 and has the same thickness as the magnetic sensing layer 21. The magnetic converging layer 13 is formed on the substrate 11 on the side of the magnetic sensing layer 21 with a gap between it and the side of the magnetic sensing layer 21. The magnetic converging layer 13 is arranged with a groove 15 between it and the magnetic sensing layer 21. In the specific example shown in Figure 1, the magnetic converging layer 13 consists of a pair and is arranged to sandwich the magnetic sensing layer 21 from the sides of the magnetic sensing layer 21.

The insulating film 14 is provided on the surfaces of the substrate 11, sensor unit 12, and magnetic convergence layer 13 so as to cover the sensor unit 12 and magnetic convergence layer 13. The insulating film 14 is formed so that its surface is flat. The insulating film 14 also extends between the magnetic detection layer 21 and magnetic convergence layer 13, electrically insulating them. The insulating film 14 may be made of any material that can insulate the sensor unit 12, such as silicon oxide, silicon nitride, or aluminum oxide.

In the specific example shown in FIG. 1, the surfaces of the barrier layer 22 and the reference layer 23 are the same size and are smaller than the surface of the magnetic detection layer 21. The barrier layer 22 and the reference layer 23 are arranged in pairs, parallel to each other and spaced a predetermined distance apart on one magnetic detection layer 21. The pair of barrier layers 22 and reference layers 23 are aligned perpendicular to the magnetic detection layer 21 and the pair of magnetic concentrating layers 13.

The magnetic sensor 10 may also have other layers between the reference layer 23 and the insulating film 14 of the sensor section 12. In the specific example shown in FIG. 1, the magnetic sensor 10 is made up of a TMR sensor, but it is not limited to a TMR sensor and may also be made up of, for example, an AMR sensor, a GMR sensor, an MI sensor, or a fluxgate sensor.

The magnetic sensor 10 is preferably manufactured by a method for manufacturing a magnetic sensor according to an embodiment of the present invention. In this method, layers constituting the magnetic sensing layer 21 and the magnetic converging layer 13 are first deposited on one surface of the substrate 11. Then, a groove 15 is formed through the layer in the thickness direction to the substrate 11, dividing the layer into the magnetic sensing layer 21 and the magnetic converging layer 13. A barrier layer 22 and a reference layer 23 are then deposited on the magnetic sensing layer 21, i.e., on the surface of the magnetic sensing layer 21 opposite the substrate 11. In this manner, the sensor section 12 and the magnetic converging layer 13 are formed. The groove 15, which divides the magnetic sensing layer 21 and the magnetic converging layer 13, may be formed by any processing method, such as etching. Alternatively, the barrier layer 22 and the reference layer 23 may be deposited on the portion that will become the magnetic sensing layer 21 before the groove 15 is formed, and then the groove 15 is formed to divide the layer into the magnetic sensing layer 21 and the magnetic converging layer 13.

After forming the sensor section 12 and magnetic converging layer 13, an insulating film 14 is formed on the surfaces of the substrate 11, sensor section 12, and magnetic converging layer 13 so as to cover the sensor section 12 and magnetic converging layer 13. At this time, the insulating film 14 is also formed in the groove 15 formed between the magnetic detection layer 21 and magnetic converging layer 13. In this manner, the magnetic sensor 10 can be manufactured. Note that the method for forming each layer may be any method that allows for film formation, such as sputtering or vapor deposition.

The method for manufacturing a magnetic sensor according to an embodiment of the present invention allows the magnetic sensing layer 21 and magnetic converging layer 13 to be formed simultaneously simply by forming the groove 15, thereby improving the positional accuracy of the magnetic converging layer 13 relative to the magnetic sensing layer 21. Furthermore, the spacing between the magnetic sensing layer 21 and the magnetic converging layer 13 can be easily adjusted by adjusting the width of the groove 15. In this way, the magnetic sensor 10 and method for manufacturing a magnetic sensor according to an embodiment of the present invention can improve the positional accuracy of the magnetic converging layer 13 relative to the sensor section 12, which includes the magnetic sensing layer 21, and thereby improve the sensitivity of detecting magnetic fields.

In the magnetic sensor 10 and magnetic sensor manufacturing method according to the present invention, the surfaces of the magnetic detection layer 21 and magnetic convergence layer 13 are located on the same plane. Therefore, for example, when processing the sensor unit 12 by etching or other processes, the processing accuracy can be improved by monitoring the position of the surface of the magnetic convergence layer 13. In particular, when etching the sensor unit 12 through the barrier layer 22 to the surface of the magnetic detection layer 21, etching can be stopped at the same height as the surface of the magnetic convergence layer 13, allowing for high-precision processing even when the barrier layer 22 is very thin, at only a few nanometers thick.

In the magnetic sensor 10 and magnetic sensor manufacturing method according to the embodiment of the present invention, a pair of magnetic concentrating layers 13 are arranged on either side of the magnetic sensing layer 21, sandwiching the magnetic sensing layer 21. This increases the magnetic flux collection efficiency and further improves the magnetic field detection sensitivity. Furthermore, during manufacturing, the sensor can be efficiently placed on a substrate 11 such as a silicon wafer, thereby improving manufacturing efficiency.

In addition, in the magnetic sensor 10 and magnetic sensor manufacturing method according to the embodiment of the present invention, an insulating film 14 is also formed in the groove 15 between the magnetic detection layer 21 and the magnetic converging layer 13, electrically insulating the magnetic detection layer 21 and the magnetic converging layer 13, thereby blocking noise and improving magnetic field detection sensitivity.

As shown in FIG. 2, the magnetic sensor 10 may also have a magnetic concentrator plate 31 disposed parallel to the surface of the magnetic concentrator layer 13, with a gap between it and the magnetic concentrator layer 13, on the surface of the insulating film 14 opposite the magnetic concentrator layer 13. The magnetic concentrator plate 31 is provided within the range of the magnetic concentrator layer 13 projected in the stacking direction from the magnetic detection layer 21 toward the reference layer 23. In this case, the magnetic concentrator plate 31 can further increase the magnetic collection efficiency and further improve the magnetic field detection sensitivity.

The magnetic sensor 10 shown in Figure 1 was manufactured, and its magnetoresistance curve was measured. In the manufactured magnetic sensor 10, the magnetic sensing layer 21 and magnetic converging layer 13 were made of CoFeSiB amorphous with a thickness of 140 nm, the barrier layer 22 was made of MgO with a thickness of 2 nm, and the reference layer 23 was made of CoFeB with a thickness of 3 nm. The insulating film 14 had a thickness of 200 nm from the surface of the magnetic sensing layer 21 and magnetic converging layer 13. The distance between the magnetic sensing layer 21 and magnetic converging layer 13 was 5000 nm. As a comparative example, a sensor without a magnetic converging layer 13 was also manufactured. The design patterns of the magnetic sensing layer 21 of the manufactured comparative example and the magnetic sensing layer 21 and magnetic converging layer 13 of the magnetic sensor 10 are shown in Figures 3(a) and (b), respectively.

The magnetoresistance curves of the comparative example and magnetic sensor 10 are shown in Figures 4(a) and (b), respectively. Comparing Figures 4(a) and (b), it is confirmed that the magnetoresistance curve of magnetic sensor 10 in Figure 4(b) has a smaller anisotropy magnetic field Hk than that of the comparative example in Figure 4(a). From this result, it can be said that the magnetic concentrating layer 13 reduces magnetic anisotropy and significantly increases the magnetic field detection sensitivity.

Furthermore, in the magnetic sensor 10, when the sensor portion 12 and other components are etched, the magnetic concentrating layer 13 is also etched at the same time, making it possible to detect the etching endpoint using a large signal from a wide area. To detect the etching endpoint, plasma spectroscopy or secondary ion mass spectrometry, for example, can be used. For example, the magnetic sensor 10 with the design pattern of FIG. 3(b) has an opening area 141 times larger during etching than the comparative example with the design pattern of FIG. 3(a), making it possible to accurately detect the etching endpoint and improve the etching processing accuracy.

REFERENCE SIGNS LIST 10 magnetic sensor 11 substrate 12 sensor section 21 magnetic detection layer 22 barrier layer 23 reference layer 13 magnetic converging layer 14 insulating film 15 groove

31 Magnetic concentrator

Claims (5)

a sensor unit including a magnetic detection layer whose magnetization direction is variable, a barrier layer containing a non-magnetic material and disposed on one surface side of the magnetic detection layer, and a reference layer whose magnetization direction is fixed and disposed on the surface side of the barrier layer opposite to the magnetic detection layer;
a magnetic concentrator layer made of the same material as the magnetic sensing layer and disposed laterally of the magnetic sensing layer with a gap between the magnetic concentrator layer and the side surface of the magnetic sensing layer ;
a magnetic concentrator plate disposed parallel to a surface of the magnetic concentrator layer along a stacking direction from the magnetic detection layer toward the reference layer, with a gap between the magnetic concentrator plate and the magnetic concentrator layer, and provided inside a range obtained by projecting the magnetic concentrator layer in the stacking direction;
A magnetic sensor comprising: The magnetic sensor of claim 1, characterized in that the magnetic concentrating layers consist of a pair and are arranged to sandwich the magnetic sensing layer from the sides. A magnetic sensor as described in claim 1 or 2, characterized in that the magnetic detection layer is electrically insulated from the magnetic concentrating layer. a substrate on one surface of which the sensor unit and the magnetic concentrating layer are formed;
The magnetic sensor according to claim 1 , wherein the sensor section is formed on the substrate so that the magnetic detection layer faces the substrate. A method for manufacturing the magnetic sensor according to any one of claims 1 to 4 , comprising the steps of:
a method for manufacturing a magnetic sensor, comprising: forming a layer constituting the magnetic detection layer and the magnetic convergence layer; and then forming a groove penetrating the layer in a thickness direction to divide the layer into the magnetic detection layer and the magnetic convergence layer.