Magnetic sensor and manufacturing method thereof

Abstract

To reform a magnetic sensor with a ferromagnetic film having multilayered structure.SOLUTION: A sensor chip 10 of a magnetic sensor 1 comprises: a magneto-sensitive element R1; ferromagnetic films M1, M2 which are provided on an insulating film 32 covering the magneto-sensitive element R1 and form a magnetic gap G1 overlapping the magneto-sensitive element R1: and a passivation film 33 which is provided on the ferromagnetic films M1, M2 in such a manner that the magnetic gap G1 is embedded. Each of the ferromagnetic films M1, M2 includes a lower magnetic film 41 and an upper magnetic film 42, the width of the magnetic gap G1 has a width W2 between the upper magnetic films 42 and a width W1 between the lower magnetic films 41, wherein the width W2 is larger than the width W1, and the lower magnetic film 41 is composed of material having a magnetic permeability higher than that of the material of the upper magnetic films 42. Thus, the magnetic sensor 1 has high detection sensitivity since a magnetic flux is efficiently applied to the magneto-sensitive element.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a magnetic sensor and a manufacturing method thereof, and more particularly to a magnetic sensor having a ferromagnetic film for collecting magnetic flux in a magnetic sensing element and a manufacturing method thereof. [Background technology]

[0002] Patent Document 1 discloses a magnetic sensor having a ferromagnetic film for collecting magnetic flux in a magnetic sensing element. For example, Figure 20 of Patent Document 1 shows an example in which the ferromagnetic film has a two-layer structure. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-219182 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the ferromagnetic film has a multi-layer structure, there is a problem that sufficient detection sensitivity cannot be obtained or the detection sensitivity varies depending on the magnetic material and film formation method used.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS It is therefore an object of the present invention to provide an improved magnetic sensor including a ferromagnetic film having a multi-layer structure, and a method for manufacturing the same. [Means for solving the problem]

[0006] The magnetic sensor according to the present invention comprises a magnetic sensing element having a magnetic sensing direction in a first direction, an insulating film covering the magnetic sensing element, first and second ferromagnetic films spaced apart on the insulating film, and a passivation film provided on the first and second ferromagnetic films to fill a gap between an end of the first ferromagnetic film and an end of the second ferromagnetic film, wherein the magnetic sensing element overlaps with the gap in a planar view, the first and second ferromagnetic films include a lower magnetic film provided on the surface of the insulating film and an upper magnetic film provided on the lower magnetic film, and the gap width in the first direction of the gap between the upper magnetic films is wider than the gap width between the lower magnetic films, and the lower magnetic film is made of a material having a higher magnetic permeability than the upper magnetic film.

[0007] According to the present invention, since the lower magnetic film is made of a material having a higher magnetic permeability than the upper magnetic film, the magnetic flux is efficiently applied to the magnetic sensing element, thereby making it possible to obtain high detection sensitivity.

[0008] In the present invention, the lower magnetic film and the upper magnetic film may be in direct contact with each other without using a film made of another metal material, which reduces the magnetic resistance between the lower magnetic film and the upper magnetic film, thereby making it possible to obtain higher detection sensitivity.

[0009] A method for manufacturing a magnetic sensor according to the present invention includes a first step of covering a magnetic sensing element having a magnetic sensing direction in a first direction with an insulating film, a second step of forming lower magnetic films of first and second ferromagnetic films on the insulating film by a sputtering method, a third step of forming upper magnetic films of the first and second ferromagnetic films on the lower magnetic films of the first and second ferromagnetic films by electrolytic plating, and a fourth step of forming a passivation film on the first and second ferromagnetic films, wherein in the second step, one end of the magnetic sensing element in the first direction overlaps with the lower magnetic film of the first ferromagnetic film in a plan view, The lower magnetic film is formed so that the other end of the magnetic sensing element in the first direction overlaps with the lower magnetic film of the second ferromagnetic film, and the area between one end and the other end of the magnetic sensing element does not overlap with either the lower magnetic film of the first or second ferromagnetic film, and in the third step, the upper magnetic film is formed so that the separation width in the first direction between the end of the upper magnetic film of the first ferromagnetic film and the end of the upper magnetic film of the second ferromagnetic film is wider than the separation width in the first direction between the end of the lower magnetic film of the first ferromagnetic film and the end of the lower magnetic film of the second ferromagnetic film.

[0010] According to the present invention, since the lower magnetic film is formed by sputtering, the positional accuracy with respect to the magnetic sensing element is improved. This makes it possible to reduce the variation in detection sensitivity between products. Moreover, since the upper magnetic film is formed by electrolytic plating, it is possible to obtain a sufficient film thickness in a short time.

[0011] In the third step, electrolytic plating may be performed using the lower magnetic film as a seed layer, which reduces the magnetic resistance between the lower magnetic film and the upper magnetic film since no seed layer made of another metal material is interposed between the lower magnetic film and the upper magnetic film, thereby making it possible to obtain higher detection sensitivity.

[0012] In the fourth step, a passivation film may be formed by sputtering, which prevents the magnetic sensing element from being exposed to high temperatures and thus prevents the characteristics of the magnetic sensing element from deteriorating.

[0013] In the present invention, the lower magnetic film may be made of a material having a higher magnetic permeability than the upper magnetic film, which allows the magnetic flux to be applied to the magnetic sensing element efficiently, thereby making it possible to obtain high detection sensitivity. Effect of the Invention

[0014] In this way, according to the present invention, it is possible to increase the detection sensitivity of the magnetic sensor and reduce the variation in detection sensitivity. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic perspective view for explaining the structure of a magnetic sensor 1 according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic exploded perspective view of the magnetic sensor 1. As shown in FIG. [Diagram 3] FIG. 3 is a schematic plan view of the sensor chip 10. As shown in FIG. [Figure 4] FIG. 4 is a schematic cross-sectional view taken along the line AA shown in FIG. [Diagram 5] FIG. 5 is a schematic cross-sectional view of a sensor chip 10 according to a first modified example. [Figure 6] FIG. 6 is a schematic cross-sectional view of a sensor chip 10 according to a second modified example. [Figure 7] FIG. 7 is a process diagram for explaining the method of manufacturing the sensor chip 10. [Figure 8] FIG. 8 is a process diagram for explaining the method of manufacturing the sensor chip 10. [Figure 9] FIG. 9 is a process diagram for explaining the method of manufacturing the sensor chip 10. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0017] Fig. 1 is a schematic perspective view for explaining the structure of a magnetic sensor 1 according to an embodiment of the present invention, and Fig. 2 is a schematic exploded perspective view of the magnetic sensor 1.

[0018] As shown in FIG. 1 and FIG. 2, the magnetic sensor 1 according to this embodiment includes a sensor chip 10 and external magnetic bodies 21 and 22 that collect magnetic flux to the sensor chip 10. The sensor chip 10 has an element forming surface 11 and a back surface 12 that form a yz plane, side surfaces 13 and 14 that form an xy plane, and side surfaces 15 and 16 that form an xz plane. A magnetic sensing element and ferromagnetic films M1 to M3, which will be described later, are formed on the element forming surface 11 of the sensor chip 10. The external magnetic body 21 is a rod-shaped body with the x direction as the longitudinal direction, and one end of the external magnetic body in the x direction is positioned at approximately the center of the element forming surface 11 in the z direction so as to cover a part of the ferromagnetic film M1. The external magnetic body 22 has a rod-shaped shape with the x direction as the longitudinal direction, covers a part of the ferromagnetic films M2 and M3, and covers the back surface 12 and the side surfaces 13 and 14 of the sensor chip 10.

[0019] FIG. 3 is a schematic plan view of the sensor chip 10. As shown in FIG.

[0020] As shown in Fig. 3, four magnetic sensing elements R1 to R4 and three ferromagnetic films M1 to M3 are formed on the element forming surface 11 of the sensor chip 10. The magnetic sensing elements R1 to R4 are not particularly limited as long as they are elements whose electrical resistance changes depending on the direction of magnetic flux, and for example, MR elements can be used. The fixed magnetization directions of the magnetic sensing elements R1 to R4 are aligned in the same direction (for example, the positive side in the z direction).

[0021] Here, if the parts of the ferromagnetic films M1 to M3 located on one side in the y direction (upper side in FIG. 3) are defined as ferromagnetic films M11, M21, and M31, and the parts located on the other side in the y direction (lower side in FIG. 3) are defined as ferromagnetic films M12, M22, and M32, in a plan view (viewed from the x direction), the magnetic sensing element R1 is arranged at a position overlapping the magnetic gap G1 formed by the ferromagnetic films M11 and M21, the magnetic sensing element R2 is arranged at a position overlapping the magnetic gap G2 formed by the ferromagnetic films M12 and M22, the magnetic sensing element R3 is arranged at a position overlapping the magnetic gap G3 formed by the ferromagnetic films M11 and M31, and the magnetic sensing element R4 is arranged at a position overlapping the magnetic gap G4 formed by the ferromagnetic films M12 and M32. As a result, the magnetic field passing through the magnetic gaps G1 to G4 is applied to the magnetic sensing elements R1 to R4. Here, since the direction of the magnetic field applied to the magnetic sensing elements R1 and R2 and the direction of the magnetic field applied to the magnetic sensing elements R3 and R4 are 180° different from each other, by bridging-connecting the magnetic sensing elements R1 to R4, the direction and strength of the magnetic flux applied via the external magnetic body 21 can be detected.

[0022] 3, the region indicated by reference numeral 21a indicates the region covered by the external magnetic body 21, and the regions indicated by reference numerals 22a and 22b indicate the regions covered by the external magnetic body 22. As shown in FIG 3, the external magnetic body 21 covers the ferromagnetic film M1, and the external magnetic body 22 covers the ferromagnetic films M2 and M3.

[0023] FIG. 4 is a schematic cross-sectional view taken along the line AA shown in FIG.

[0024] 4, the sensor chip 10 has a substrate 30 and an insulating film 31 provided on its surface, and the surface of the insulating film 31 constitutes the element forming surface 11. Magnetic sensing elements R1 to R4 are provided on the element forming surface 11. The magnetic sensing elements R1 to R4 are covered with an insulating film 32, and ferromagnetic films M1 to M3 are provided on the surface of the insulating film 32. The ferromagnetic films M1 to M3 are covered with a passivation film 33.

[0025] The ferromagnetic films M1 to M3 are composed of a lower magnetic film 41 in contact with the insulating film 32 and an upper magnetic film 42 provided on the lower magnetic film 41. The lower magnetic film 41 and the upper magnetic film 42 are made of different magnetic materials. The lower magnetic film 41 has a higher magnetic permeability than the upper magnetic film 42, and the upper magnetic film 42 has a thicker film thickness than the lower magnetic film 41. As an example, a NiFe-based material such as permalloy can be used as the material of the lower magnetic film 41, and a CoFe-based material can be used as the material of the upper magnetic film 42. The lower magnetic film 41 serves to efficiently apply magnetic flux to the magnetosensing elements R1 to R4, and the upper magnetic film 42 serves to reduce the magnetoresistance of the entire ferromagnetic films M1 to M3.

[0026] The end portions of the lower magnetic film 41 in the z direction overlap with the corresponding magnetosensing elements R1 to R4 in a plan view (when viewed from the x direction). In the cross section shown in FIG. 4, one end of the magnetosensing element R1 in the z direction overlaps with the lower magnetic film 41 constituting the ferromagnetic film M1, and the other end of the magnetosensing element R1 in the z direction overlaps with the lower magnetic film 41 constituting the ferromagnetic film M2. Among the magnetosensing element R1, the region that does not overlap with the lower magnetic film 41 overlaps with the magnetic gap G1.

[0027] Here, when the separation width in the z direction of the lower magnetic film 41 constituting the magnetic gaps G1 to G4 is W1, and the separation width in the z direction of the upper magnetic film 42 constituting the magnetic gaps G1 to G4 is W2, W1 < W2. With such a structure, the magnetic flux passing through the magnetic gaps G1 to G4 concentrates on the edges of the lower magnetic film 41 with a high magnetic permeability. Therefore, the magnetic flux can be efficiently applied to the magnetosensing elements R1 to R4, and high detection sensitivity can be obtained. On the contrary, if the lower magnetic film 41 has a lower magnetic permeability than the upper magnetic film 42, the magnetic flux passing through the magnetic gaps G1 to G4 bypasses between the upper magnetic films 42, and the magnetic flux applied to the magnetosensing elements R1 to R4 decreases. In the present embodiment, since a material with a higher magnetic permeability is used for the lower magnetic film 41 than for the upper magnetic film 42, it is possible to suppress a decrease in detection sensitivity due to such a bypass phenomenon.

[0028] Moreover, since the separation widths of the magnetic gaps G1 to G4 formed by the upper magnetic film 42 are expanded to W2, even when the separation width W1 is narrow, it becomes possible to surely embed the magnetic gaps G1 to G4 with the passivation film 33, enhancing the reliability of the product.

[0029] Also, as shown in FIG. 5, the upper edge of the upper magnetic film 42 may be an inclined surface. According to this, since the separation width W2 of the magnetic gaps G1 to G4 formed by the upper magnetic film 42 becomes wider toward the upper side, it becomes easier to embed the passivation film 33 in the magnetic gaps G1 to G4. Further, as shown in FIG. 6, an additional upper magnetic film 43 may be provided on the upper magnetic film 42. In this case, when the separation width in the z direction of the upper magnetic film 43 constituting the magnetic gaps G1 to G4 is W3, by setting W2 < W3, it becomes easier to embed the passivation film 33 in the magnetic gaps G1 to G4. Even in this case, a material having a higher magnetic permeability than the upper magnetic films 42 and 43 is used for the lower magnetic film 41.

[0030] Next, a method for manufacturing the sensor chip 10 will be described.

[0031] FIGS. 7 to 9 are process diagrams for explaining the method for manufacturing the sensor chip 10, and correspond to a cross section along the line A-A shown in FIG. 3.

[0032] First, as shown in FIG. 7, an insulating film 31 is formed on a substrate 30, and then magnetic sensing elements R1 to R4 are formed on the surface of the insulating film 31, and the magnetic sensing elements R1 to R4 are covered with an insulating film 32. Next, a lower magnetic film 41 is formed on the entire surface of the insulating film 32 by a sputtering method. By forming the lower magnetic film 41 by using a sputtering method, it is possible to control the film thickness of the lower magnetic film 41 with high precision. Next, as shown in FIG. 8, a mask 51 is formed on the lower magnetic film 41, and the lower magnetic film 41 in the area not covered by the mask 51 is removed by etching. As a result, the lower magnetic film 41 is separated into the parts constituting the ferromagnetic films M1 to M3. Here, since the mask 51 is formed by patterning using a photolithography method, it is possible to ensure high positional precision with respect to the magnetic sensing elements R1 to R4. Alternatively, the lower magnetic film 41 separated into the parts constituting the ferromagnetic films M1 to M3 may be formed by performing sputtering through a metal mask (not shown). Even in this case, the positional accuracy of the lower magnetic film 41 can be improved by aligning the metal mask with high accuracy.

[0033] Next, after removing the mask 51, a resist 52 is formed as shown in FIG. 9, and in this state, electrolytic plating is performed using the lower magnetic film 41 as a seed layer (power supply body) to form the upper magnetic film 42. Although the positional accuracy of the film formed by electrolytic plating is lower than that of the sputtering method, it is possible to obtain a sufficient film thickness in a short time. Moreover, since the lower magnetic film 41 is used as the seed layer as it is, no film made of other metal material remains between the lower magnetic film 41 and the upper magnetic film 42. In other words, a structure in which the lower magnetic film 41 and the upper magnetic film 42 are in direct contact with each other is obtained, so that it is possible to sufficiently reduce the magnetic resistance between the lower magnetic film 41 and the upper magnetic film 42.

[0034] Then, after removing the resist 52, the passivation film 33 is formed to cover the ferromagnetic films M1 to M3 so as to fill the magnetic gaps G1 to G4, and the sensor chip 10 used in this embodiment is completed. The method for forming the passivation film 33 is preferably a sputtering method. This is because, if the passivation film 33 is formed using a high-temperature process such as a CVD method, the magnetic sensing elements R1 to R4 are exposed to high temperatures and their characteristics may deteriorate. In contrast, if the passivation film 33 is formed using a sputtering method, which is a low-temperature process, the characteristics of the magnetic sensing elements R1 to R4 can be prevented from deteriorating. On the other hand, since the sputtering method has a lower coverage than the CVD method, if the magnetic gaps G1 to G4 are narrow, the magnetic gaps G1 to G4 may not be completely filled with the passivation film 33, and voids may occur. However, in this embodiment, the gap width above the magnetic gaps G1 to G4 is expanded to W2, and the film thickness of the lower magnetic film 41 constituting the gap width W1 is thin, so that even when the sputtering method is used, no voids are generated and the magnetic gaps G1 to G4 can be completely filled with the passivation film 33.

[0035] As described above, according to this embodiment, the lower magnetic film 41 is formed by a sputtering method, and the upper magnetic film 42 is formed by electrolytic plating using the lower magnetic film 41 as a seed layer, making it possible to produce ferromagnetic films M1 to M3 with high positional accuracy and low magnetic resistance in a short period of time.

[0036] Although a preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention, and it goes without saying that these modifications are also included within the scope of the present invention. [Explanation of symbols]

[0037] 1 Magnetic sensor 10 Sensor chip 11 Element formation surface 12 Back side 13~16 Side 21,22 External magnetic material 30 Substrate 31,32 Insulating film 33 Passivation film 41 Lower magnetic film 42,43 Upper magnetic film 51 Mask 52 Resist G1~G4 Magnetic gap M1~M3,M11,M12,M21,M22,M31,M32 Ferromagnetic film R1~R4 Magnetic sensing element

Claims

1. A magnetic sensing element having a magnetic sensing direction in a first direction; An insulating film covering the magnetic sensing element; first and second ferromagnetic films provided on the insulating film and spaced apart from each other; a passivation film provided on the first and second ferromagnetic films so as to fill a gap between an end of the first ferromagnetic film and an end of the second ferromagnetic film; The magnetic sensing element overlaps with the spaced portion in a plan view, the first and second ferromagnetic films include a lower magnetic film provided on a surface of the insulating film and an upper magnetic film provided on the lower magnetic film, the upper magnetic film is thicker than the lower magnetic film, a width of the spaced portion in the first direction between the upper magnetic films is wider than a width of the spaced portion between the lower magnetic films; A magnetic sensor according to claim 1, wherein the lower magnetic film is made of a material having a higher magnetic permeability than the upper magnetic film.

2. 2. The magnetic sensor according to claim 1, wherein the lower magnetic film and the upper magnetic film are in direct contact with each other without an intervening film made of another metal material.

3. A first step of covering a magnetic sensing element having a magnetic sensing direction in a first direction with an insulating film; a second step of forming lower magnetic films of the first and second ferromagnetic films on the insulating film by a sputtering method; a third step of forming upper magnetic films of the first and second ferromagnetic films on the lower magnetic films of the first and second ferromagnetic films by electrolytic plating; a fourth step of forming a passivation film on the first and second ferromagnetic films; in the second step, the lower magnetic film is formed such that, in a plan view, one end of the magnetic sensing element in the first direction overlaps with the lower magnetic film of the first ferromagnetic film, the other end of the magnetic sensing element in the first direction overlaps with the lower magnetic film of the second ferromagnetic film, and a region between the one end and the other end of the magnetic sensing element does not overlap with either of the lower magnetic films of the first and second ferromagnetic films; in the third step, the upper magnetic film is formed such that a separation width in the first direction between an end of the upper magnetic film of the first ferromagnetic film and an end of the upper magnetic film of the second ferromagnetic film is wider than a separation width in the first direction between an end of the lower magnetic film of the first ferromagnetic film and an end of the lower magnetic film of the second ferromagnetic film, and the upper magnetic film is thicker than the lower magnetic film; The method for manufacturing a magnetic sensor is characterized in that the lower magnetic film is made of a material having a higher magnetic permeability than the upper magnetic film.

4. 4. The method for manufacturing a magnetic sensor according to claim 3, wherein in the third step, electrolytic plating is performed using the lower magnetic film as a seed layer.

5. 5. The method for manufacturing a magnetic sensor according to claim 3, wherein in the fourth step, the passivation film is formed by a sputtering method.

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