JP2006032710A - Manufacturing method for magnetic sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a magnetic sensor capable of sufficiently controlling the magnetic anisotropy of a GMR element to an external magnetic field, ensuring the output stability of the magnetic sensor to the external magnetic field, and accurately returning the orientation of the magnetization of a free layer to an initial state even after a ferromagnetic field is applied. <P>SOLUTION: In the manufacturing method for the magnetic sensor 31, a beltlike magnetoresistance effect element 5 is arranged on a substrate, and bias magnet layers 6, 6,... each composed of a magnet film are connected at both ends of the magnetoresistance effect element 5, respectively. The manufacturing method has at least a process A in which a resist is applied on the magnetoresistance effect element 5 and a pattern is formed, a process B in which the resist is made to flow and an inclined resist film is formed, and a process C in which ion beams are projected to the substrate from the oblique direction and the magnetoresistance effect element 5 is milled. In the manufacturing method, side faces 8, 8,... in the beltlike longitudinal direction of the magnetoresistance effect element 5 are machined into tapered shapes. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a magnetic sensor including a spin valve magnetoresistive element.

Conventionally, magnetic sensors using spin-valve type giant magnetoresistive elements (hereinafter also referred to as “GMR elements”) have been proposed and put into practical use.
This GMR element includes a pinned layer whose magnetization direction is pinned in a predetermined direction, and a free layer whose magnetization direction changes corresponding to an external magnetic field. When an external magnetic field is applied, the GMR element A resistance value corresponding to the relative relationship between the magnetization direction and the magnetization direction of the free layer is exhibited.
The magnetic sensor detects the external magnetic field by measuring the resistance value of the GMR element, and measures its strength.

  Since the magnetization direction of the pinned layer of the GMR element is pinned by the pinning layer in the short band direction of the GMR element, the magnetization direction of the free layer is in the initial state where no external magnetic field is applied. It is necessary to align with the longitudinal direction of the GMR element forming an angle of 90 ° with the magnetization direction of the pinned layer. The direction of magnetization of the free layer in this initial state is referred to as the “free layer easy axis direction”.

To make the easy axis direction of the free layer the longitudinal direction of the band of the GMR element, the element pattern of the band-shaped aspect ratio is used to control the magnetic anisotropy of the GMR element and ensure the stability of the magnetic sensor against the external magnetic field. How to do is known.
Alternatively, a method has also been proposed in which a bias magnet layer made of a magnet film is disposed at both ends of the GMR element, and a bias is applied to forcibly control the easy axis direction of the free layer to the belt-like longitudinal direction of the GMR element ( For example, see Patent Document 1). In this method, since the bias magnet layer is magnetized in the free layer easy axis direction and the free layer magnetization is controlled by the magnetization, the stability of the magnetic sensor with respect to the external magnetic field can be improved.
JP 2004-163419 A

  However, only the method of making the GMR element into a strip-like aspect ratio pattern lacks the stability of free layer magnetization with respect to an external magnetic field, and the sensor output value fluctuates when exposed to a relatively weak magnetic field. there were.

  Further, in the method of arranging the magnet layers at both ends of the GMR element, there is a problem that it becomes difficult to restore the free layer magnetization to the original initial state as the external magnetic field increases. FIG. 19 is a plan view schematically showing the magnetization direction of the free layer in the conventional GMR element. As shown in FIG. 19, domain walls (edge curling walls) magnetized by an external magnetic field are formed on both sides of the magnetization of the free layer aligned in the longitudinal direction of the belt. As a result, the magnetization of the free layer becomes difficult to move even if the external magnetic field changes, and the sensitivity of the sensor decreases or the domain wall remains even if the external magnetic field disappears. There is a problem that the magnetization direction of the free layer is aligned in the shifted direction, the output of the magnetic sensor becomes unstable, and the above-described free layer magnetization cannot be restored to the original initial state.

  In view of the above problems of the prior art, the present invention can sufficiently control the magnetic anisotropy of the GMR element with respect to an external magnetic field, ensure the output stability of the magnetic sensor with respect to the external magnetic field, and even after a strong magnetic field is applied. An object of the present invention is to provide a method of manufacturing a magnetic sensor capable of accurately returning the magnetization direction of the free layer to the initial state.

To solve this problem,
The invention according to claim 1 is a method of manufacturing a magnetic sensor in which a band-like magnetoresistive effect element is disposed on a substrate, and a bias magnet layer made of a magnet film is connected to both ends of the magnetoresistive effect element. In step A, a resist is coated on the magnetoresistive effect element to form a pattern, step B is performed to reflow the resist to form an inclined resist film, and an ion beam is obliquely formed with respect to the substrate. And a step C of milling the magnetoresistive effect element, and tapering the side surface in the longitudinal direction of the band of the magnetoresistive effect element.

  The invention according to claim 2 is characterized by comprising, after the step C, a step D of making the magnetoresistive element mill by making the ion beam incident from a direction perpendicular to the substrate. The manufacturing method of the magnetic sensor as described in 1 above.

  According to a third aspect of the present invention, the direction of magnetization in the free layer of the magnetoresistive element when the external magnetic field is not applied is obtained by tapering the side surface in the longitudinal direction of the band of the magnetoresistive element. 3. The method of manufacturing a magnetic sensor according to claim 1, wherein the resistance effect elements are aligned in the longitudinal direction of the belt.

  According to the present invention, since the domain wall is not formed by tapering the side surface in the longitudinal direction of the belt of the GMR element, the magnetic anisotropy of the GMR element with respect to the external magnetic field can be sufficiently controlled, and the magnetization uniformity of the free layer To secure the output stability of the magnetic sensor against an external magnetic field, and to manufacture a magnetic sensor capable of accurately returning the magnetization direction of the free layer to the initial state even after a strong magnetic field is applied. it can.

  Further, according to the method for manufacturing a magnetic sensor of the present invention, the output stability of the magnetic sensor against an external magnetic field can be improved without changing the film structure of the GMR element or the pattern of the magnetic sensor from the conventional one. it can.

  Further, in the method of manufacturing a magnetic sensor according to the present invention, the ion beam is incident on the substrate from an oblique direction to mill the GMR element, so that the material removed by milling is prevented from reattaching to the GMR element. And high-precision processing with improved throughput can be performed.

  Hereinafter, the magnetic sensor manufactured by this invention is demonstrated in detail based on drawing.

[First Embodiment]
FIG. 1 is a schematic plan view of the magnetic sensor according to the first embodiment. The magnetic sensor 1 of this embodiment includes a substrate 2 made of a quartz or silicon wafer having a predetermined thickness, X-axis magnetic sensors 31 and 32 for detecting a magnetic field in the X-axis direction disposed on the substrate 2, and Y A Y-axis magnetic sensor 41, 42 for detecting an axial magnetic field is schematically configured.

  In the magnetic sensor 1 of the present embodiment, the substrate 2 is made of a square quartz or silicon wafer. On the substrate 2, magnetic sensors 31, 32, 41, and 42 are provided along the four sides of the substrate 2 at the center of each side. The magnetic sensors 31, 32, 41, 42 are arranged so that the belt-like longitudinal direction is parallel to the square sides of the substrate 2. In FIG. 1, the direction parallel to the horizontal side of the square of the substrate 2 is defined as the X-axis direction, and the direction parallel to the vertical side is defined as the Y-axis direction. Moreover, the arrow direction drawn on the magnetic sensors 31, 32, 41, and 42 in FIG. 1 represents the direction of magnetization of the pinned layer in each magnetic sensor. Magnetic sensors arranged in parallel with the square vertical side (Y-axis direction) of the substrate 2 are arranged in parallel with the X-axis magnetic sensors 31 and 32 and the horizontal side of the square (X-axis direction). The sensors are Y-axis magnetic sensors 41 and 42.

  2A and 2B are schematic views of the X-axis magnetic sensor 31 according to the first embodiment, where FIG. 2A is a plan view and FIG. 2B is a cross-sectional view taken along line A-A ′. Since the remaining magnetic sensors have the same structure except that the pinning (fixed) direction of the magnetization direction of the pinned layer is different, description thereof will be omitted. The X-axis magnetic sensor 31 (hereinafter referred to as “magnetic sensor”) includes wiring take-out portions 7 and 7 stacked on a substrate 2 (not shown), and underlying films 10, 10. .., And bias magnet layers 6, 6... Stacked on the base films 10, 10..., And a strip-shaped GMR element 5 stacked on the bias magnet layers 6, 6. Has been.

  In the GMR element 5 according to the present embodiment, four narrow strip portions 51, 51... Are arranged with a predetermined interval with the strip longitudinal directions aligned in parallel. Then, the left end portions of the two adjacent upper narrow-width portions 51, 51 are joined to a rectangular first connection portion 52. Further, the right end of the second narrow strip 51 from the top and the right end of the third narrow strip 51 located at the bottom are joined to the rectangular second connecting portion 53, and The left end portion of the third narrow strip portion 51 from the upper stage and the left end portion of the narrow strip portion 51 located at the lowermost step are joined to the rectangular third connecting portion 54. The four narrow strips 51, 51... Are joined together via the first connecting part 52, the second connecting part 53, and the third connecting part 54 so as to form a zigzag folded shape as a whole. The GMR element 5 is formed.

In addition, the right end portions of the narrowest strip portions 51 and 51 at the uppermost and lowermost layers are laminated on one bias magnet layer 6 and 6, respectively. Further, bias magnet layers 6, 6,... Are provided below the first connecting portion 52, the second connecting portion 53, and the third connecting portion 54.
And under the bias magnet layers 6, 6,..., Base films 10, 10,.
Further, the bias magnet layers 6, 6 and the base films 10, 10... Connected to the right end portions of the narrowest strip-shaped portions 51, 51 at the uppermost and lowermost steps are respectively connected to the strip-shaped wiring lead-out portions 7, 7. It is formed on the left end.

  The GMR element 5, the bias magnet layers 6, 6..., The base films 10, 10..., And the wiring take-out portions 7 and 7 are arranged so that each end is connected and forms a zigzag shape as a whole. The GMR element 5 is electrically connected to the wiring extraction portions 7 and 7 through the bias magnet layers 6, 6... And the base films 10, 10. Since the entire structure is electrically connected in series, it can function as a resistance circuit as a whole, and the resistance value of the GMR element 5 is determined by measuring the voltage by applying a current from the outside to the circuit. The strength of the external magnetic field can be calculated from this resistance value.

  Next, the GMR element 5 will be described. FIG. 3 is a schematic cross-sectional view showing the structure of the GMR element 5 according to the first embodiment. The GMR element 5 is a portion of the narrow band portions 51, 51... In FIG. 2, and on the substrate 2, a free layer F, a conductive spacer layer S made of copper (Cu), cobalt-iron ( A pinned layer PD made of a CoFe) alloy, a pinning layer PN made of a platinum-manganese (PtMn) alloy, and a capping layer C made of a metal thin film such as titanium (Ti) or tantalum (Ta) are sequentially laminated.

The free layer F is a layer whose magnetization direction changes according to the direction of the external magnetic field. For example, a cobalt-zirconium-niobium (CoZrNb) amorphous magnetic layer and a nickel-iron layer laminated on the CoZrNb amorphous magnetic layer. It is composed of a (NiFe) magnetic layer and a cobalt-iron (CoFe) layer laminated on the NiFe magnetic layer.
A bias magnetic field is applied to the free layer F by the bias magnet layers 6, 6... In the longitudinal direction of the GMR element 5 in order to maintain the uniaxial anisotropy (the free layer easy axis direction) of the magnetization. ing.
The longitudinal direction of the band of the GMR element 5 is a direction that coincides with the longitudinal direction of the band of the narrow band-like portions 51, 51... In FIG. 2 is a direction coinciding with the short band direction of the narrow band portions 51, 51.

  The CoZrNb amorphous magnetic layer and the NiFe magnetic layer constituting the free layer F are soft ferromagnets, and the CoFe layer formed thereon prevents diffusion of nickel in the NiFe magnetic layer and copper in the spacer layer S To do.

The spacer layer S is a conductive metal thin film made of copper or a copper alloy.
The pinned layer PD is composed of a cobalt-iron (CoFe) magnetic layer. This CoFe magnetic layer is back-coupled to the antiferromagnetic film of the pinning layer PN, which will be described later, in an exchange coupling manner, so that the direction of magnetization is pinned in the short band direction of the GMR element 5 corresponding to the arrow direction shown in FIG. Stopped (fixed).

The pinning layer PN is laminated on the CoFe magnetic layer and is made of an antiferromagnetic film made of a PtMn alloy containing 45 to 55 mol% of platinum. This antiferromagnetic film is formed by a regular heat treatment in a state where a magnetic field is applied in a predetermined direction.
The pinned layer PD and the pinning layer PN are collectively referred to as a pinned layer.

  The capping layer C is a metal thin film made of titanium (Ti), tantalum (Ta) or the like, and is intended to prevent oxidation and protect the pinning layer PN.

FIG. 4 is a schematic perspective view of the GMR element 5 according to the first embodiment. In FIG. 4, the right direction is the short direction, and the depth direction perpendicular thereto is the long direction. The side surface along the short direction is the side surface 9 in the belt-like short direction of the GMR element 5, and the side surface along the longitudinal direction is the side surface 8 in the belt-like longitudinal direction.
In the GMR element 5 according to the present embodiment, the side surface 8 in the belt-like longitudinal direction is tapered so as to form an angle θ with respect to the substrate 2, and has a flared shape. By tapering the band-like longitudinal side surface 8 of the GMR element 5, the magnetization direction in the free layer of the GMR element 5 when no external magnetic field is applied can be aligned with the band-like longitudinal direction of the GMR element 5.

  This angle θ is preferably 50 to 85 °. By setting the angle θ within the above range, the formation of the magnetic domain (domain) changes compared to the case where the angle is 90 °, so that the formation of the domain wall (edge curling wall) shown in FIG. 19 is prevented. The uniformity of the magnetization of the free layer can be improved and the output of the magnetic sensor with respect to the external magnetic field can be stabilized. Furthermore, even after a strong magnetic field is applied, the magnetization direction of the free layer can be accurately returned to the initial strip-like longitudinal direction.

  The bias magnet layers 6, 6... Connected to the GMR element 5 are metal thin films made of a cobalt-platinum-chromium (CoCrPt) alloy magnet film having a high coercive force and a high squareness ratio of about 90 nm. . The bias magnet layers 6, 6... Are magnetized by an external magnetic field after film formation so that the magnetization direction is in the direction along the longitudinal direction of the GMR element 5.

As described above, the magnetization direction of the pinned layer PD is the short band direction of the GMR element 5 corresponding to the arrow direction shown in FIG. 1, and the magnetization direction of the bias magnet layers 6, 6. Therefore, the magnetization direction of the pinned layer PD of the GMR element 5 and the magnetization direction of the bias magnet layers 6, 6... Form an angle of 90 °.
The magnetization direction of the free layer of the GMR element 5 is magnetized in the longitudinal direction of the band of the GMR element 5 by the magnetization of the bias magnet layers 6, 6. Axial direction) can be maintained.

  The magnetic sensor of the present embodiment has a belt-like shape in which the shape of the GMR element 5 is folded, and the bias magnet layers 6, 6... 8, 8... Can be sufficiently controlled to control the magnetic anisotropy of the GMR element with respect to the external magnetic field, improve the uniformity of magnetization of the free layer, and improve the output stability of the magnetic sensor with respect to the external magnetic field. Even after the strong magnetic field is applied, the magnetization direction of the free layer can be accurately returned to the initial state.

  In addition, the magnetic sensor of this embodiment can improve the output stability of the magnetic sensor against an external magnetic field without changing the film structure of the GMR element and the pattern of the magnetic sensor from the conventional one.

Next, a method for manufacturing the magnetic sensor of this embodiment will be described.
FIG. 5 is a flowchart showing the procedure of the method for manufacturing the magnetic sensor according to the first embodiment. 6 to 11 and 14 are schematic cross-sectional views illustrating the method of manufacturing the magnetic sensor according to the first embodiment.

  In the method for manufacturing a magnetic sensor according to this embodiment, first, a substrate 2 made of quartz or a silicon wafer is prepared. An LSI portion for controlling the magnetic sensor can be formed in advance on the substrate 2. In that case, in the previous process (process A), an element such as a transistor and wiring, an insulating film, a contact, etc. are formed by a known method, and a protective film is further formed. An opening is formed.

  Next, as a magnet film formation (step A), as shown in FIG. 6, a base film 10 made of chromium having a thickness of about 40 nm is formed on the upper surface of the substrate 2 made of quartz or a silicon wafer by sputtering. Subsequently, a bias magnet layer 6 made of a cobalt-platinum-chromium (CoCrPt) alloy having a thickness of about 90 nm is formed on the upper surface of the base film 10 by sputtering.

  Next, as a magnet cut (process c), as shown in FIG. 7, a photoresist having an arbitrary thickness is applied to the upper surface of the bias magnet layer 6 by a spin coating method, a dip coating method, or the like. After arranging and exposing a mask having an arbitrary pattern, development processing is performed to remove unnecessary photoresist, and a resist film 11 is formed. Subsequently, the photoresist is heated and reflowed to form a reflowed resist film 11 ′ so that both end portions are curved.

  Next, as shown in FIG. 8, as the magnet milling (process d), the portion of the base film 10 and the bias magnet layer 6 that are not covered with the reflowed resist film 11 ′ are formed by ion milling (arrows in the figure). Simultaneously with the removal, the base film 10 and the bias magnet layer 6 are formed in a predetermined shape. In this step D, the side surfaces of the base film 10 and the bias magnet layer 6 are formed so as to be inclined with respect to the substrate 2 by ion milling according to the curved surface shape of both end portions of the resist film 11 ′ after reflow.

  Next, as shown in FIG. 9, the resist film 11 ′ is removed with a cleaning solution such as acetone or N-methyl-2-pyrrolidone, and the surface of the bias magnet layer 6 is cleaned as a resist removal (process o), as shown in FIG. 11 'is removed.

  Next, as shown in FIG. 10, as GMR film formation (step F), ion beam sputtering, magnetron sputtering, or the like is performed on the upper surface of the substrate 2, the side surface of the base film 10, and the upper surface and side surfaces of the bias magnet layer 6. A GMR element 5 is formed.

  Next, as a magnet array set (process key), a magnet array provided in the external space is arranged at a predetermined position with respect to the bias magnet layer 6, and a magnetic field is applied to the pinned layer of the GMR element 5 in a predetermined direction. To do.

  Next, heat treatment is performed at 280 ° C. for 4 hours in a vacuum while fixing the arrangement of the magnet array and the bias magnet layer 6 as regularizing heat treatment (process k). As a result, the pinning layer of the pinned layer of the GMR element 5 is subjected to a regularized heat treatment, and the pinned layer is pinned (fixed) in the direction of the band-like short direction of the GMR element 5.

  Next, the magnet array is removed from a predetermined position (process step).

  Next, as GMR pattern formation (step A), as shown in FIG. 11, a photoresist having a thickness of 0.3 to 5 μm is applied to the upper surface of the GMR element 5 by spin coating, dip coating, or the like. After a mask having an arbitrary pattern is placed on the surface of the photoresist and exposed, development is performed to remove unnecessary photoresist, and a resist film 20 is formed. The A-A ′ direction in FIGS. 11 and 14 corresponds to the A-A ′ direction in FIG. 12A and is a partial cross-sectional view. By setting the thickness of the resist to be applied within the above range, it is possible to reduce the inclination angle β in the strip-like longitudinal direction of the resist film 20 ′ after the registry flow.

  Subsequently, as a registry flow (step B), the resist film 20 is heated at 120 to 180 ° C. for 1 to 30 minutes to be reflowed, and both end portions of the resist film 20 in the longitudinal and lateral directions form curved surfaces. In this way, an inclined reflowed resist film 20 ′ is formed. By reflowing at a temperature higher than the conventional heating temperature of 100 ° C. and further setting the heating time within the above range, the inclination angle β in the strip-like longitudinal direction of the resist film 20 ′ after reflow can be reduced.

  FIG. 12 is a schematic diagram of the GMR element 5 and the resist film 20 after the GMR pattern formation (step A) and the registry flow (step B) according to the first embodiment, and the resist film 20 ′ after the reflow. (a) is a plan view, (b) is a schematic sectional view of the whole, (c) is a partially enlarged sectional view of the AA ′ section, and (d) is a BB ′ sectional view.

The resist film 20 after the process A has a rectangular parallelepiped shape as indicated by the dotted lines in FIGS. 12C and 12D, and an inclination angle α formed by the resist end surface in the strip-like lateral direction and the longitudinal direction with the upper surface of the GMR element 5. , Β are all 90 °.
The resist film 20 is heated and reflowed. Since reflow is performed on the entire substrate, heating is performed under the same conditions in both the strip-like lateral direction and the longitudinal direction, but the shape of the resist end face after reflowing depends on the resist pattern. In the cross-sectional views of FIGS. 12C and 12D, the shape of the resist film 20 ′ after reflow is indicated by a solid line. As shown in the partially enlarged cross-sectional view of the AA ′ cross section in FIG. 12C, the inclination angle α formed by the end surface in the strip-like short direction of the resist film 20 ′ after reflow with the upper surface of the GMR element 5 is 30˜. On the other hand, as shown in the BB ′ cross-sectional view of FIG. 12D, the inclination angle β formed by the end surface in the strip-like longitudinal direction of the resist film 20 ′ after reflow with the upper surface of the GMR element 5 is as shown in FIG. 50 to 85 ° and larger.

  Next, as GMR milling (step C), an ion beam is incident on the substrate from an oblique direction, and the GMR element 5 is milled, whereby a portion of the GMR element 5 not covered with the reflowed resist film 20 ′ is obtained. At the same time, the side surfaces 8, 8... In the belt-like longitudinal direction of the GMR element 5 are tapered.

  In this step C, the side surfaces 8, 8... Of the GMR element 5 in the longitudinal direction of the GMR element 5 are formed by ion milling according to the curved shape of the both ends in the longitudinal direction and the longitudinal direction of the resist film 20 ′ after reflow. The side surfaces 9, 9... In the short direction are formed to be inclined with respect to the substrate 2 at different taper angles.

As a beam used for ion milling, a gas such as argon, oxygen, or CF ₄ can be used. Among these, argon is preferable. The incident angle of the beam is oblique to the substrate, and the angle is preferably 5 to 30 ° with respect to the normal line of the substrate 2 surface. The milling conditions are preferably performed under a pressure of 0.01 to 0.1 Pa, an acceleration voltage of 0.3 to 0.8 kV, and a milling time of 1 to 3 minutes.

  FIG. 13 is a schematic cross-sectional view showing the relationship between the ion beam incident direction of the GMR milling (step C) and taper processing of the GMR element 5 according to the first embodiment, and FIG. 13A shows the case of vertical milling. BB 'sectional view, (b) is a BB' sectional view when left oblique incidence milling, (c) is a BB 'sectional view when right oblique incidence milling, (d) is vertical A partially enlarged cross-sectional view of the AA ′ cross section when milled, (e) is a partially enlarged cross-sectional view of the AA ′ cross section when left obliquely incident milled, and (f) is a right oblique oblique incident milled. It is a partially expanded sectional view of the AA 'cross section in the case.

  When vertical milling is performed in which the ion beam is incident on the substrate from the vertical direction (90 °) and milled, the cross-section BB ′ in the case of vertical milling in FIG. As shown in the drawing, since the inclination angle β in the strip longitudinal direction of the resist film 20 ′ after reflow is large, the side surfaces 8 and 8 in the strip longitudinal direction of the GMR element 5 are shaped according to the width of the resist film 20 ′. The taper angle θ of the side surfaces 8 and 8 is approximately 90 °.

On the other hand, an oblique incidence milling (left oblique incidence milling) in which an ion beam is incident and milled at an angle of 5 to 30 ° with respect to the normal line of the surface of the substrate 2 from an upper left direction or an upper right direction with respect to the substrate. (Or oblique oblique milling in the right direction), in the longitudinal direction of the band of the GMR element 5, the cross-sectional view taken along the line BB 'in FIG. 13 (b) and obliquely inclined in the right direction in FIG. 13 (c). As shown in the cross-sectional view along the line BB ′ in the case of incident milling, the light is incident from the left and right directions, and finally the taper angle θ of the side surfaces 8 and 8 becomes approximately 50 to 85 °.
In this way, by tapering the side surfaces 8 and 8 of the GMR element 5 in the longitudinal direction of the belt, the direction of magnetization in the free layer of the GMR element 5 when no external magnetic field is applied is changed. Can be aligned in the direction.

  Next, when the GMR element 5 is viewed from the AA ′ cross-sectional view, when vertical milling is performed in which the ion beam is incident on the substrate in a vertical direction (90 °) and milled, the GMR element 5 has a short band shape. In the direction, as shown in the partially enlarged cross-sectional view of the AA ′ cross section in the case of vertical milling in FIG. 13D, the inclination angle α in the short band direction of the resist film 20 ′ after the reflow is a band shape. Despite being smaller than the inclination angle β in the longitudinal direction, depending on the thickness of the resist film 20 ′, the shoulder is scraped, and it is difficult to taper in the belt-like short direction.

  On the other hand, an oblique incidence milling (left oblique incidence milling) in which an ion beam is incident and milled at an angle of 5 to 30 ° with respect to the normal line of the surface of the substrate 2 from an upper left direction or an upper right direction with respect to the substrate. Alternatively, when performing oblique oblique incidence milling in the right direction, in the band-like short direction of the GMR element 5, a partially enlarged sectional view of the AA ′ section in the case of oblique oblique incidence milling in the left direction in FIG. As shown in the partially enlarged cross-sectional view of the AA ′ cross section in the case of f) oblique incidence in the right direction, the light is incident from the left and right directions, and finally the side surface 9 has a taper angle of about 30 to 30 mm. It becomes 80 °.

It should be noted that the side surfaces 8, 8... Of the GMR element 5 in the longitudinal direction of the belt have a taper angle θ in the range of 50 to 85 ° even when oblique incidence milling is performed on the resist film 20 before reflow. It cannot be processed. In the resist film 20 before reflow, the inclination angle β formed by the resist end surface in the longitudinal direction with the upper surface of the GMR element 5 is 90 °, so that the taper angle θ of the side surfaces 8, 8. This is because the angle becomes almost 90 °. That is, after reflowing the resist film 20 and changing the shape to the reflowed resist film 20 ′ whose inclination angle β is in the range of 50 to 85 °, θ is first obtained by performing oblique incident milling. The side surfaces 8, 8... Of the belt-like longitudinal direction of the GMR element 5 having an angle of 50 to 85 ° can be formed.
Further, the side surfaces 9, 9... Of the GMR element 5 in the strip-like direction are also tapered by the registry flow (process B) and the oblique incident milling (process C), and the inclination angle is 30 to 80 °. .

  Further, when the milling is performed by vertical milling, there is a problem that the material shaved by milling is likely to be reattached to the side surfaces 8, 8. In the present invention, when the substrate 2 is rotated during oblique incidence milling and oblique incidence milling is performed from all directions as shown in FIG. 13, this reattachment can be prevented and the processing accuracy can be improved.

  Further, since the GMR element 5 is a metal or a magnetic material, the milling speed is faster than that of the resist film 20 'after reflow. By performing oblique incidence milling, it is possible to taper the side surfaces 8, 8... Of the GMR element 5 in the longitudinal direction of the GMR element 5 faster than the vertical milling, so that the throughput can be improved.

When the angle of inclination between the end face of the resist film 20 ′ after reflow and the upper surface of the GMR element 5 is large, when oblique incidence milling is performed, the side surface of the GMR element 5 in the shadow portion where no ions are irradiated has a ridged shape. Become. Moreover, the material shaved by milling tends to adhere again to this part. As described above, when the oblique incident milling is performed while the substrate 2 is rotated, the reattachment can be removed.
Further, in order to improve the side profile of the GMR element 5, after the oblique incident milling in the process C, a process D in which the ion beam is incident from the vertical direction with respect to the substrate and the GMR element 5 is milled is performed. Good. After the step C, even if the vertical milling in the step D is performed, the side surfaces 8, 8... Of the GMR element 5 in the longitudinal direction of the belt are already tapered. Adhesion does not occur.

  Next, as resist removal (process c), the resist film 20 ′ after reflow is removed with a cleaning solution such as acetone and N-methyl-2-pyrrolidone, the surface of the GMR element 5 is washed, and the resist film 20 ′ after reflow is washed. Remove.

Next, as SiO _x film formation (process step), as shown in FIG. 14, a first protective film 15 made of a silicon oxide film having a thickness of about 150 nm is formed on the upper surface of the GMR element 5 by plasma CVD.

Next, as a SiN film formation (process step), as shown in FIG. 14, a second protective film 16 made of a silicon nitride film having a thickness of about 300 nm is formed on the upper surface of the first protective film 15 by plasma CVD. .
Here, the first protective film 15 and the second protective film 16 may be collectively referred to as a protective film 17. Here, a third protective film made of polyimide resin may be further provided on the first protective film 15 and the second protective film 16.

  Next, as a post-process (process), openings are formed at predetermined locations of the first protective film 15 and the second protective film 16 to form pads, and then the substrate is diced and cut into individual chips. Each chip is sealed with resin.

  The magnetic sensor manufactured by the present invention can sufficiently control the magnetic anisotropy of the GMR element with respect to the external magnetic field, improve the uniformity of magnetization of the free layer, and ensure the output stability of the magnetic sensor with respect to the external magnetic field. Even after the magnetic field is applied, the magnetization direction of the free layer can be accurately returned to the initial state.

  Further, according to the method for manufacturing a magnetic sensor of the present invention, the output stability of the magnetic sensor against an external magnetic field can be improved without changing the film structure of the GMR element or the pattern of the magnetic sensor from the conventional one. it can.

[Second Embodiment]
15A and 15B are schematic views of the magnetic sensor 31 according to the second embodiment, in which FIG. 15A is a plan view and FIG. In the magnetic sensor 31 according to the present embodiment, the bottom surface of the GMR element 5 is slightly smaller than the upper plane of the bias magnet layers 6, 6. Since it is the same as that of 1st Embodiment except having been formed and the level | step difference is provided, those description is abbreviate | omitted. By providing a step between the GMR element 5 and the bias magnet layers 6, 6..., A margin is provided for the positional accuracy when the GMR elements 5 are formed on the bias magnet layers 6, 6. Can do.

[Third Embodiment]
16A and 16B are schematic views of a magnetic sensor 31 according to the third embodiment, in which FIG. 16A is a plan view and FIG. The size of the first connecting part 52, the second connecting part 53, and the third connecting part 54 is made smaller than that in the first embodiment, and the narrow band-like parts 51, 51. Since it is the same as 1st Embodiment except having provided the part 100,100 ..., those description is abbreviate | omitted. By providing the notches 100, 100..., The uniformity of the free layer magnetization can be further improved.

[Fourth Embodiment]
17A and 17B are schematic views of a magnetic sensor 31 according to the fourth embodiment, in which FIG. 17A is a plan view, FIG. 17B is a cross-sectional view along AA ′, and FIG. 17C is a cross-sectional view along BB ′. . The first connecting part 52, the second connecting part 53, the third connecting part 54 and the narrow band-like parts 51, 51... Are provided with notches 100, 100. Since the portion 52, the second connecting portion 53, and the third connecting portion 54 are the same as those in the first embodiment except that they are formed so as to cover the upper surfaces and side surfaces of the bias magnet layers 6, 6,. Those explanations are omitted.

  Hereinafter, the present invention will be described in more detail by way of examples. The present invention is not limited to the following examples.

[Example]
A magnetic sensor having a GMR element with a film thickness of 40 nm was manufactured according to the above-described method for manufacturing a magnetic sensor of the present invention. This magnetic sensor is composed of a strip-shaped GMR element having an aspect ratio of 16, and a bias magnet layer is disposed at both ends thereof, and a taper machining with θ of 75 ° is performed on the side surface in the strip-shaped longitudinal direction of the GMR element. Yes.
After applying an external magnetic field to the obtained magnetic sensor, it was removed, and then an initialization magnetic field of 40 Oe was applied in the free layer easy axis direction (the longitudinal direction of the GMR element), and then the output value of the magnetic sensor was measured. The difference (output fluctuation) (digital count value, no unit) from the output value of the magnetic sensor in the initial state was measured. The smaller the output fluctuation from the initial state, the more accurately the magnetization direction of the free layer is restored to the belt-like longitudinal direction in the initial state.
The relationship between the externally applied magnetic field and the measured output fluctuation from the initial state of the sensor is shown in the graph of FIG.

[Comparative Example 1]
A magnetic sensor having a GMR element with a film thickness of 40 nm was manufactured according to the above-described method for manufacturing a magnetic sensor of the present invention. This magnetic sensor is composed of a strip-shaped GMR element having an aspect ratio of 16.
In the same manner as in the example, the output fluctuation from the initial state of the sensor was measured.
The relationship between the externally applied magnetic field of the sensor of Comparative Example 1 and the output fluctuation from the initial state of the measured sensor is shown in the graph of FIG.

[Comparative Example 2]
A magnetic sensor having a GMR element with a film thickness of 40 nm was manufactured according to the above-described method for manufacturing a magnetic sensor of the present invention. This magnetic sensor is composed of a strip-shaped GMR element having an aspect ratio of 16, and bias magnet layers are arranged at both ends thereof.
In the same manner as in the example, the output fluctuation from the initial state of the sensor was measured.
The relationship between the externally applied magnetic field of the sensor of Comparative Example 2 and the output fluctuation from the initial state of the measured sensor is shown in the graph of FIG.

  From the results shown in FIG. 18, in the sensor having only the band shape of Comparative Example 1 and the sensor having the band shape of Comparative Example 2 and the bias magnet layer, the magnetization direction of the free layer after application of the strong magnetic field is in the initial band longitudinal direction. I found out of the way. On the other hand, in the sensor having the belt-shaped bias magnet layer in the embodiment and tapering the side surface in the longitudinal direction of the belt, the magnetization of the free layer is accurate in the longitudinal direction of the belt in the initial state even after applying the strong magnetic field. I found out that I have returned.

  From the above results, it was confirmed that according to the manufacturing method of the present invention, a magnetic sensor capable of accurately returning the magnetization direction of the free layer to the initial state even after a strong magnetic field was applied was obtained. .

1 is a schematic plan view of a magnetic sensor according to a first embodiment. It is the schematic of the X-axis magnetic sensor which concerns on 1st Embodiment, (a) is a top view, (b) is A-A 'sectional drawing. It is a schematic sectional drawing which shows the structure of the GMR element which concerns on 1st Embodiment. 1 is a schematic perspective view of a GMR element according to a first embodiment. It is a flowchart which shows the procedure of the manufacturing method of the magnetic sensor which concerns on 1st Embodiment. It is a schematic sectional drawing which shows the manufacturing method of the magnetic sensor which concerns on 1st Embodiment. It is a schematic sectional drawing which shows the manufacturing method of the magnetic sensor which concerns on 1st Embodiment. It is a schematic sectional drawing which shows the manufacturing method of the magnetic sensor which concerns on 1st Embodiment. It is a schematic sectional drawing which shows the manufacturing method of the magnetic sensor which concerns on 1st Embodiment. It is a schematic sectional drawing which shows the manufacturing method of the magnetic sensor which concerns on 1st Embodiment. It is a schematic sectional drawing which shows the manufacturing method of the magnetic sensor which concerns on 1st Embodiment. It is the schematic of the GMR element and resist film after GMR pattern formation (process A) and registry flow (process B) which concern on 1st Embodiment, and the resist film after reflow, (a) is a top view, (b) ) Is a schematic sectional view of the whole, (c) is a partially enlarged sectional view of the AA ′ section, and (d) is a BB ′ sectional view. It is a schematic sectional drawing which shows the relationship between the incident direction of the ion beam of GMR milling (process C) which concerns on 1st Embodiment, and the taper process of the GMR element 5, (a) is BB 'at the time of vertical milling Cross-sectional view, (b) is a cross-sectional view taken along line BB ′ when obliquely incident leftward milling, (c) is a cross-sectional view taken along line BB ′ when obliquely incident rightward, and (d) is a case where vertical milling is performed A partially enlarged cross-sectional view of the AA ′ cross section, (e) is a partially enlarged cross-sectional view of the AA ′ cross section in the case of left-direction oblique incident milling, and (f) is an A- in the case of right-direction oblique incident milling. It is a partially expanded sectional view of A 'cross section. It is a schematic sectional drawing which shows the manufacturing method of the magnetic sensor which concerns on 1st Embodiment. It is the schematic of the magnetic sensor which concerns on 2nd Embodiment, (a) is a top view, (b) is A-A 'sectional drawing. It is the schematic of the magnetic sensor which concerns on 3rd Embodiment, (a) is a top view, (b) is A-A 'sectional drawing. It is the schematic of the magnetic sensor which concerns on 4th Embodiment, (a) is a top view, (b) is A-A 'sectional drawing, (c) is B-B' sectional drawing. It is the graph which showed the relationship between the externally applied magnetic field of the magnetic sensor of an Example and the comparative examples 1 and 2, and the output fluctuation from the initial state of the measured sensor. It is the top view which showed typically the direction of magnetization of the free layer in the conventional GMR element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Magnetic sensor, 2 ... Board | substrate, 5 ... Magnetoresistive element (GMR element), 6 ... Bias magnet layer, 8 ... Side surface of a strip | belt-shaped longitudinal direction, 11, 20 ... Resist film, 11 ', 20' ... Reflow resist film, 31 ... Magnetic sensor

Claims (3)

In a method of manufacturing a magnetic sensor in which a strip-like magnetoresistive effect element is disposed on a substrate, and a bias magnet layer made of a magnet film is connected to both ends of the magnetoresistive effect element,
A step of applying a resist on the magnetoresistive element and forming a pattern; and
Reflowing the resist to form an inclined resist film; and
And at least a step C of making an ion beam incident on the substrate from an oblique direction and milling the magnetoresistive element.
A method of manufacturing a magnetic sensor, comprising: tapering a side surface in a longitudinal direction of the belt-like shape of the magnetoresistive effect element.   2. The method of manufacturing a magnetic sensor according to claim 1, further comprising a step D of milling the magnetoresistive element by making the ion beam incident from a direction perpendicular to the substrate after the step C. 3. . The direction of magnetization in the free layer of the magnetoresistive effect element when the external magnetic field is not applied is tapered in the longitudinal direction of the strip of the magnetoresistive effect element by tapering the side surface in the longitudinal direction of the strip of the magnetoresistive effect element. The method for manufacturing a magnetic sensor according to claim 1, wherein the magnetic sensor is aligned.

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