JP2021071488A - Magnetic sensor - Google Patents

Abstract

To provide a magnetic sensor that suppresses influence of stress and has a magnetic convergence plate and a hall element with less shifts or less variations of magnetic characteristics.SOLUTION: The magnetic sensor includes: a semiconductor substrate with a hall element in a surface; an adhesive layer on a back surface of the semiconductor substrate; and a magnetic convergence plate on the adhesive layer. The magnetic convergence plate is formed by an electric field plating on an underlying conductive layer on a plating substrate prepared separately from the semiconductor substrate, is attached to the back surface of the semiconductor substrate by applying an adhesive as the adhesive layer on a surface of the magnetic convergence plate, and is formed on the back surface of the semiconductor substrate by separating the plating substrate from the underlying conductive layer on the magnetic convergence plate.SELECTED DRAWING: Figure 1

Description

The present invention relates to a magnetic sensor using a Hall element, and more particularly to a magnetic sensor provided with a magnetic focusing plate and detecting a magnetic field in the vertical and horizontal directions.

Hall elements are used in various applications as magnetic sensors because they can detect positions and angles in a non-contact manner.
First, the magnetic detection principle of the Hall element will be described. When a magnetic field perpendicular to the current flowing through a substance is applied, an electric field (Hall voltage) is generated in a direction perpendicular to both the current and the magnetic field. Therefore, in a general Hall element, a current is passed through the surface of a semiconductor substrate (wafer) such as silicon to detect a vertical magnetic field component.

Furthermore, by combining it with a magnetic thin film made of a material with high magnetic permeability and using the magnetic thin film as a magnetic focusing plate that changes the direction of magnetic flux and guides it to the Hall element, not only the vertical magnetic field but also the horizontal direction It is known that a magnetic field can be detected (see, for example, Patent Document 1).

In a magnetic sensor provided with a magnetic convergence plate, for example, a Hall element is formed on a silicon substrate and then a magnetic convergence plate is formed by electroplating on the silicon substrate, or a protective film such as polyimide is formed on the surface of the silicon substrate. , It can be produced by forming a magnetic focusing plate on the protective film by electroplating (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2002-071381 International Publication No. WO07 / 119569

However, when a magnetic converging plate is formed on a silicon substrate on which a Hall element is formed, a large stress is generated because the coefficient of thermal expansion differs greatly between the magnetic material as a metal and the protective film such as a silicon substrate or polyimide. Such stress affects the magnetic characteristics of the magnetic sensor, leading to problems such as a large shift and variation in the magnetic characteristics.
Therefore, an object of the present invention is to provide a magnetic sensor and a method for manufacturing the same, in which the influence of stress is suppressed and the shift and variation of magnetic characteristics are small.

The magnetic sensor of the present invention includes a semiconductor substrate, a pair of Hall elements arranged apart from each other on the surface of the semiconductor substrate via a separation region, and a magnetic convergence plate, and the magnetic convergence plate is the semiconductor substrate. It is provided only on the back surface, and an adhesive layer is provided between the back surface of the semiconductor substrate and the magnetic convergence plate, and the magnetic convergence plate is arranged so as to overlap at least a part of each of the pair of Hall elements in a plan view. It is characterized by being done.

The method for manufacturing a magnetic sensor of the present invention includes a step of forming a hole element on the surface of a semiconductor substrate, a step of forming a base conductive layer on a plating substrate, and an opening for forming a magnetic convergence plate on the base conductive layer. A step of forming a resist having the above, a step of performing electrolytic plating in the state where the resist is formed to form a magnetic convergence plate in the opening, a step of removing the resist, and using the magnetic convergence plate as a mask. The step of etching and removing the underlying conductive layer, the step of applying an adhesive on the magnetic convergence plate, and the magnetic convergence plate formed on the back surface of the semiconductor substrate and the plating substrate are subjected to the adhesive. It is characterized by including a step of laminating and a step of peeling the plating substrate from the underlying conductive layer.

According to the present invention, since the magnetic convergence plate is provided on the back surface of the semiconductor substrate having the Hall element on the front surface, the stress generated by the difference in the thermal expansion coefficient between the semiconductor substrate and the magnetic convergence plate is generated from the back surface side of the semiconductor substrate. This makes it possible to suppress the stress applied to the Hall element provided on the surface side of the semiconductor substrate by the thickness of the semiconductor substrate. Therefore, it is possible to reduce the time-dependent change and variation of the magnetic characteristics of the magnetic sensor.

It is sectional drawing which shows the structure of the magnetic sensor of embodiment of this invention. It is a process sectional view which shows the manufacturing method of the magnetic sensor of embodiment of this invention. It is a process sectional view which shows the manufacturing method of the magnetic sensor of embodiment of this invention. It is a process sectional view which shows the manufacturing method of the magnetic sensor of embodiment of this invention.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view showing the structure of the magnetic sensor according to the embodiment of the present invention.
As shown in FIG. 1, the magnetic sensor of the present embodiment includes a semiconductor substrate 1, a pair of Hall elements 2 provided on the surface of the semiconductor substrate 1 and arranged apart from each other, and a semiconductor substrate including the Hall elements 2. A protective film 3 covering the front surface, an adhesive layer 40 provided on the back surface of the semiconductor substrate 1, a magnetic convergence plate 10 mounted on the back surface of the semiconductor substrate 1 via the adhesive layer 40, and a magnetic convergence plate 10 It is provided with a conductive layer 11 provided on the surface opposite to the adhesive layer 40 of the above.

In the present embodiment, the semiconductor substrate 1 is a P-type semiconductor substrate, and the Hall element 2 has a vertical magnetic field sensing portion having a square or cross-shaped four-fold rotation axis, and surfaces having the same shape at each apex and end thereof. A horizontal Hall element having a vertical magnetic field detection control current input terminal and a vertical magnetic field Hall voltage output terminal in an n-type high-concentration impurity region.

In order to realize a magnetic sensor with small characteristic variation, the positional relationship between the Hall element and the magnetic convergence plate is important, and the magnetic convergence plate 10 overlaps at least a part of each of the pair of Hall elements 2 in a plan view. It is located in.

With this configuration, stress generated by the difference in the coefficient of thermal expansion between the semiconductor substrate 1 and the magnetic convergence plate 10 is applied from the back surface side of the semiconductor substrate 1, so that the stress is provided on the surface of the semiconductor substrate 1 by the thickness of the semiconductor substrate 1. The stress applied to the Hall element 2 is suppressed. As a result, it is possible to obtain a magnetic sensor having a small change and variation in magnetic characteristics with time.

Here, if the thickness of the semiconductor substrate 1 is too large, the distance between the magnetic focusing plate 10 and the Hall element 2 on the surface of the semiconductor substrate 1 becomes long, and sufficient sensitivity of the magnetic sensor cannot be obtained. If the thickness is too small, the semiconductor Since the stress applied to the Hall element 2 on the surface of the substrate 1 becomes large, it is preferably about 100 to 400 μm.

Further, the film thickness of the magnetic focusing plate 10 is preferably about 20 to 50 μm because if it is too small, the sensitivity of the magnetic sensor becomes small, and if it is too large, the influence of stress becomes large.

Next, the method of manufacturing the magnetic sensor shown in FIG. 1 will be described with reference to FIGS. 2 to 4.
2 to 4 are process cross-sectional views showing a manufacturing method of the magnetic sensor of the present embodiment, FIG. 2 is a manufacturing process of a Hall element, FIG. 3 is a manufacturing process of a magnetic focusing plate, and FIG. 4 is a semiconductor substrate. The process of bonding the magnetic converging plate and the magnetic focusing plate is shown.

First, as shown in FIG. 2A, peripheral circuits (not shown) such as the Hall element 2 and its control circuit are formed on the surface of the P-type semiconductor substrate 1 by a normal semiconductor manufacturing process.
Subsequently, as shown in FIG. 2B, the back surface of the semiconductor substrate 1 on which the Hall element 2 and the peripheral circuit are formed is ground to reduce the thickness of the semiconductor substrate 1 to about 100 to 400 μm.

Next, as shown in FIG. 3A, a plating substrate 30 for forming a magnetic convergence plate is prepared separately from the semiconductor substrate 1, and the underlying conductive layer of the magnetic convergence plate 10 is prepared on the plating substrate 30. 11 is formed. Here, the base conductive layer 11 of the magnetic focusing plate 10 serves as an electrode for electrolytic plating. Further, since the plating substrate 30 and the base electrode layer 11 are peeled off in a later process, it is preferable that the adhesion between the two is weak. Therefore, it is preferable to use copper as the base conductive layer 11 and a silicon wafer, acrylic plate, or the like as the plating substrate 30. The thickness of the underlying conductive layer 11 is preferably about 0.3 to 1.0 μm in order to suppress stress.

Then, as shown in FIG. 3B, a resist 20 having an opening (also referred to as an “opening for forming a magnetic convergence plate”) 20a having the shape of the magnetic convergence plate 10 to be formed is formed by photolithography. Here, since the thickness of the resist 20 needs to be larger than the thickness of the magnetic converging plate 10 to be formed, it is desirable to make it about 30 to 60 μm.

Subsequently, as shown in FIG. 3C, a magnetic focusing plate 10 having a thickness of about 20 to 50 μm is formed in the opening 20a of the resist 20 by electrolytic plating. It is desirable that the magnetic focusing plate 10 is made of a soft magnetic material having a low coercive force and a high magnetic permeability such as permalloy or supermalloy.

Then, as shown in FIG. 3D, by removing the resist 20, a magnetic focusing plate 10 having a desired shape can be obtained.
Further, as shown in FIG. 3E, the underlying conductive layer 11 is removed by etching using the magnetic focusing plate 10 as a mask.

In the present embodiment, since the magnetic focusing plate 10 is made of a soft magnetic material having a low coercive force and a high magnetic permeability such as permalloy or supermalloy, the temperature is 800 to 1000 ° C. in a hydrogen atmosphere after plating. It is desirable to perform high temperature annealing treatment. As a result, soft magnetism can be improved and a magnetic focusing plate with good performance can be obtained. On the other hand, in the conventional method of forming a magnetic convergence plate by plating on a conventional semiconductor substrate as described in the background technology, the elements formed on the semiconductor substrate are affected, so such an annealing treatment is performed. I can't. Therefore, according to the present embodiment, it is possible to manufacture a magnetic convergence plate having better performance than the magnetic convergence plate by the conventional manufacturing method.

However, also in this embodiment, when an acrylic plate is used as the plating substrate 30, the annealing treatment cannot be performed. Therefore, when the annealing treatment is required to obtain the desired soft magnetism, the plating substrate 30 is used. Use a silicon wafer.

Next, as shown in FIG. 4A, the adhesive (adhesive layer) 40 is applied onto the magnetic convergence plate 10 produced on the plating substrate 30 by the step shown in FIG. The adhesive 40 needs to have stronger adhesion to the semiconductor substrate 1 than the adhesion between the underlying conductive layer 11 and the plating substrate 30, and for example, an epoxy-based adhesive may be preferably used. it can.

Then, the magnetic convergence plate 10 produced on the plating substrate 30 is attached to the back surface of the semiconductor substrate 1 having the Hall element 2 formed on the front surface, which is produced by the process shown in FIG. 2, with an adhesive 40.

As described above, when the annealing treatment is performed after the formation of the magnetic convergence plate 10, the magnetic convergence plate 10 may be distorted, such as the magnetic convergence plate 10 being warped. However, the semiconductor substrate 1 and the magnetic convergence plate 10 may be distorted. Since the adhesive 40 is used to bond the 10 to the semiconductor substrate 40, the thickness of the adhesive 40 can be adjusted so that the semiconductor substrate 1 and the magnetic focusing plate 10 can be bonded to each other without creating a gap.

Further, when the distortion of the magnetic converging plate 10 caused by the annealing treatment is large, a step of polishing the surface of the magnetic converging plate 10 after the annealing treatment may be added. If polishing is performed after removing the resist 20, the peripheral edge of the magnetic focusing plate 10 may be scraped and tapered, because the magnetic flux is concentrated on the tapered portion and the sensitivity is improved. , No particular problem.

Here, as the plating substrate 30, a silicon wafer having the same shape or shape and the same size as the silicon wafer used as the semiconductor substrate 1 or an acrylic plate having the same shape and the same size is used, and alignment marks are provided on each of them. By simply aligning the semiconductor substrate 1 and the plating substrate 30, the positional variation between the Hall element 2 and the magnetic focusing plate 10 can be reduced, and therefore, a magnetic sensor having a small characteristic variation can be manufactured. Become.

After the adhesive 40 is cured, as shown in FIG. 4B, the plating substrate 30 is peeled off from the underlying conductive layer 11, so that the magnetic focusing plate 10 is formed in a desired region as shown in FIG. Will be done. At this time, as described above, the adhesion between the plating substrate 30 and the base conductive layer 11 is weak, so that the plating substrate 30 can be easily peeled off.

As described above, according to the present embodiment, it is possible to provide a magnetic sensor having a small variation in magnetic characteristics and a small shift due to stress, and a method for manufacturing the same. Further, since the magnetic focusing plate can be formed by photolithography and electroplating, the manufacturing cost can be suppressed.

Although the embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above embodiments and various modifications can be made without departing from the spirit of the present invention.
For example, in the above embodiment, the protective film 3 is formed, but it is not always necessary to provide the protective film 3.
Further, although the above embodiment shows an example in which a P-type semiconductor substrate is used as the semiconductor substrate 1, an N-type semiconductor substrate can also be used.

1 Semiconductor substrate 2 Hall element 3 Protective film 10 Magnetic convergence plate 11 Underlying conductive layer 20 Resist 30 Plating substrate 40 Adhesive (adhesive layer)

Claims (4)

With a semiconductor substrate
A pair of Hall elements arranged apart from each other on the surface of the semiconductor substrate via a separation region,
A magnetic converging plate is provided, and the magnetic converging plate is provided only on the back surface of the semiconductor substrate, and an adhesive layer is provided between the back surface of the semiconductor substrate and the magnetic converging plate.
A magnetic sensor characterized in that the magnetic focusing plate is arranged so as to overlap at least a part of each of the pair of Hall elements in a plan view. The magnetic sensor according to claim 1, further comprising a conductive layer provided on a surface of the magnetic convergence plate opposite to the adhesive layer. The magnetic sensor according to claim 1 or 2, wherein the thickness of the semiconductor substrate is 100 to 400 μm. The magnetic sensor according to any one of claims 1 to 3, wherein the thickness of the magnetic focusing plate is 20 to 50 μm.

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