JP2006100574A - Magnetoresistive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetoresistive device capable of more stably maintaining the magnetizing direction of a pined layer. <P>SOLUTION: The magnetoresistive device 1 contains a magnetoresistive film 3, domain control films 5, 7, electrode films 9, 11, and protective films 13, 15. The protective film protects the electrode film from etching, and has a positive value in a saturation magnetostriction constant and a compression stress of 600 Mpa for giving a tensile stress in a height direction to the magnetoresistive film via the domain control film. As one example, the protective film is composed of aluminum nitride. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnetoresistive element.

  In the field of magnetic recording, thin film magnetic heads using a spin valve film, which is a magnetoresistive effect film, as a reading element have become the mainstream in order to respond to the progress of high density and miniaturization of magnetic disk drive devices.

  Furthermore, among the spin valve films, there is a dual spin valve film whose output is increased by increasing the number of stacked interfaces. The dual spin valve film basically has a configuration in which a nonmagnetic conductive layer, a pinned layer, and an antiferromagnetic layer are symmetrically provided above and below a free layer (see Patent Document 1). ). The pinned layer has a magnetization direction fixed in one direction, and the free layer moves freely in response to a magnetic field applied from the outside. Further, when the magnetization direction of the pinned layer and the magnetization direction of the free layer are the same, the resistance value is minimized, and the resistance value is maximized in the opposite direction. Therefore, an external magnetic field is detected using this resistance change characteristic.

However, in the dual spin-valve film, there appears an individual in which the magnetization direction of the pinned layer on the upper side of the free layer is reversed due to stress at the time of lapping in the manufacturing process, roughness in the upper layer of the stack, and the like.
JP 2004-95587 A

  The present invention has been made in view of the above, and an object of the present invention is to provide a magnetoresistive effect element that can maintain the magnetization direction of the pinned layer more stably.

  In order to solve the above-described problems, the present invention provides a magnetoresistive effect element including at least a central active region having a magnetoresistive effect film and a pair of end passive regions provided on both sides of the central active region. The saturation magnetostriction constant of the pinned layer in the magnetoresistive effect film is a positive value, the end passive region has a compressive stress of 600 MPa to 5000 MPa, and the magnetoresistive effect film has a tensile stress in the height direction. There is a layer that produces

  In the above, preferably, the layer that generates the tensile stress has a compressive stress of 1000 MPa to 5000 MPa.

  Another embodiment of the present invention for solving the same problem includes a magnetoresistive effect including a central active region having at least a magnetoresistive effect film and a pair of end passive regions provided on both sides of the central active region. The saturation magnetostriction constant of the pinned layer in the magnetoresistive film is a positive value, and the end passive region includes aluminum nitride, boron nitride, titanium nitride, silicon nitride, niobium oxide, zirconium oxide, A layer that includes any one of yttrium oxide, hafnium oxide, magnesium oxide, titanium oxide, tantalum oxide, diamond-like carbon, and silicon carbide and that generates tensile stress in the height direction is provided in the magnetoresistive film.

  In the present invention, preferably, the end passive region includes a magnetic domain control film, an electrode film, and a protective film, the layer causing the tensile stress is the protective film, and the protective film is The electrode film is protected from etching.

  Alternatively, the end passive region includes a magnetic domain control film and a protective film, the layer that generates the tensile stress is the protective film, and the protective film protects the magnetic domain control film from etching. You may comprise.

  The magnetoresistive film may be a dual spin valve film.

  According to the present invention, since a tensile stress in the height direction is generated in the magnetoresistive effect film, the magnetization direction of the pinned layer in the magnetoresistive effect film can be stabilized by the inverse magnetostrictive effect. Therefore, it is possible to prevent a phenomenon in which the magnetization direction of the magnetoresistive effect film is reversed, which may be caused by stress at the time of wrapping in the manufacturing process, roughness in the upper layer of the stack, or other causes. Can do.

  The other features of the present invention and the operational effects thereof will be described in more detail with reference to the accompanying drawings.

  Hereinafter, an embodiment in which a magnetoresistive effect element according to the present invention is implemented as a reading element of a thin film magnetic head will be described with reference to the accompanying drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

  FIG. 1 is a schematic diagram showing a configuration outline of a magnetoresistive effect element. The magnetoresistive effect element 1 constitutes a reading element of a CIP (current in plane) type thin film magnetic head, and has a central active region 1a and a pair of end passive regions 1b provided on both sides thereof. The central active region 1 a includes a magnetoresistive effect film 3, and the pair of end passive regions 1 b includes a pair of magnetic domain control films 5 and 7, electrode films 9 and 11, and protective films 13 and 15. Yes.

  The magnetoresistive film 3 is a film that responds to a magnetic field applied from the outside. In the present embodiment, the magnetoresistive film 3 is a dual spin valve film. The dual spin valve film basically includes a free layer 17, a pair of upper and lower nonmagnetic layers 19 and 21, a pair of upper and lower pinned layers 23 and 25, and a pair of upper and lower antiferromagnetic layers 27 and 29. It is out.

  The nonmagnetic layers 19 and 21, the pinned layers 23 and 25, and the antiferromagnetic layers 27 and 29 are arranged symmetrically with respect to the free layer 17. That is, a nonmagnetic layer 19 is provided above the free layer 17, a pinned layer 23 is provided thereon, and an antiferromagnetic layer 27 is provided thereon. A nonmagnetic layer 21 is provided below the free layer 17, a pinned layer 25 is provided below the nonmagnetic layer 21, and an antiferromagnetic layer 29 is provided therebelow.

The pinned layers 23 and 25 have a magnetization direction fixed in one direction and have a positive saturation magnetostriction constant λ _S. The free layer 17 moves freely in response to a magnetic field applied with an external magnetization direction. In the dual spin valve film, the resistance value is minimized when the magnetization direction of the pinned layer and the magnetization direction of the free layer are the same, and is maximized when the magnetization direction is opposite. An external magnetic field is detected using this resistance change characteristic.

  The pair of magnetic domain control films 5 and 7 are provided at both ends of the free layer 17 in the direction orthogonal to the height direction H. In this embodiment, hard magnetic films are used as the magnetic domain control films 5 and 7, and specifically, CoPt, CoPtCr, or the like can be used. However, the present invention is not limited to this, and an antiferromagnetic film or a laminated film of a soft magnetic film and an antiferromagnetic film can also be used as the magnetic domain control film.

  A pair of electrode films 9 and 11 are stacked above the pair of magnetic domain control films 5 and 7. The pair of electrode films 9 and 11 are stacked on the upper surfaces of the pair of magnetic domain control films 5 and 7 and are used to supply a sense current to the magnetoresistive effect film 3.

  Protective films 13 and 15 are stacked above the pair of electrode films 9 and 11. As will be described later, the protective films 13 and 15 are provided to protect the pair of electrode films 9 and 11 from etching performed during the manufacturing process.

  In the present invention, the protective films 13 and 15 are required to be films having a compressive stress of 600 MPa or more and 5000 MPa or less, and preferably 1000 MPa or more and 5000 MPa or less. The significance of such compressive stress will be described later. As a specific example, in this embodiment, the film is made of aluminum nitride and has a compressive stress of 3000 MPa.

  Here, the compressive stress is determined in the following manner. As shown in FIG. 2A, first, a circular disk-shaped substrate 31 made of silicon and having flat upper and lower surfaces is prepared. A thin film 33 made of a material constituting the protective films 13 and 15 is formed on the disk-shaped substrate 31.

  After the film formation, as shown in FIG. 2B, when the disk-shaped substrate 31 is curved so that the surface on the thin film 33 side is recessed, the thin film 33 itself has a tensile stress. That is, the tensile stress of the thin film 33 acts on the disk-shaped substrate 31 as an external force, and the disk-shaped substrate 31 is deformed so that the upper surface thereof contracts, and the state shown in FIG.

  On the other hand, after the film formation, as shown in FIG. 2C, when the disk-shaped substrate 31 is curved so that the surface on the thin film 33 side protrudes, the thin film 33 itself has a compressive stress. . That is, the compressive stress of the thin film 33 acts on the disk-shaped substrate 31 as an external force, and the disk-shaped substrate 31 is deformed so that its upper surface expands, and the state shown in FIG.

Moreover, the value of the stress σ is expressed by the following equation:
σ = (8E _S T _S ² δ / 6 (1-ν _S ) T _f L ² )
Determined by.
Here, the meaning of each symbol in the above equation is
E _S : Young's modulus of the disk-shaped substrate 31 T _S : thickness of the disk-shaped substrate 31 ν _S : Poisson's ratio of the disk-shaped substrate 31 T _f : thickness of the thin film 33 L: diameter of the disk-shaped substrate 31 δ: amount of warpage It is.

The above E _S , T _S , ν _S , T _f , and L are values determined by the substrate and thin film to be used. Further, the warpage amount δ is obtained as a distance to the upper surface of the thin film 33 after the deformation when the upper surface of the disk-shaped substrate 31 before the deformation is the reference surface BF.

Next, a manufacturing process of the thin film magnetic head having the magnetoresistive effect element 1 having such a configuration will be described. First, as shown in FIG. 3, a laminated film 37 constituting the magnetoresistive film 3 is formed on a substrate 35 made of, for example, Al ₂ O ₃ . 3, 4, 6, 7, 8, 9, 11, and 12, the laminated film 37 is illustrated as a single layer in order to prioritize the clarity of the drawing. Actually, it consists of a plurality of layers as shown in FIG. The process diagram corresponds to a section taken along line II-II in FIG.

  Next, as shown in FIGS. 4 and 5, a lift-off resist mask 39 is provided on the upper surface of the laminated film 37. The resist mask 39 is formed by a photolithography process. Then, dry etching such as ion milling is performed from above to etch a portion of the laminated film 37 constituting the magnetoresistive film 3 into a trapezoidal cross section as shown in FIG.

  Next, as shown in FIG. 7, magnetic domain control films 5 and 7, electrode films 9 and 11, and a portion 37 a on both sides of the magnetoresistive effect film 3 removed by etching in the laminated film 37, The protective films 13 and 15 are formed and stacked in that order.

  Next, as shown in FIG. 8, the resist mask 39 is lifted off using a release agent. Subsequently, as shown in FIGS. 9 and 10, a resist mask 41 is provided on the upper surfaces of the magnetoresistive film 3 and the protective films 13 and 15. The resist mask 41 is also formed by a photolithography process.

  Then, dry etching such as ion milling is performed from above, and as shown in FIG. 11, the laminated film 37 remaining outside the magnetic domain control films 5 and 7, the electrode films 9 and 11, and the protective films 13 and 15. The part of is removed.

  Further, by removing the resist mask 41 that is no longer needed, a magnetoresistive element as a reading element of the thin film magnetic head is obtained as shown in FIGS. Thus, the magnetoresistive effect element 1 including the protective films 13 and 15 having the desired compressive stress is configured. Further, as shown in FIG. 14, a part of the protective films 13 and 15 is scraped as indicated by reference numeral 43 by etching performed in the process from the state shown in FIGS. 10 and 11 to FIG. However, the electrode films 9 and 11 below the protective films 13 and 15 are protected without being etched. 14 corresponds to a cross section taken along line III-III in FIG.

  Next, the operation of the magnetoresistive effect element 1 having the above configuration will be described. As shown in FIG. 15, in the dual spin valve film, the magnetization directions P1 and P2 of the pinned layers 23 and 25 above and below the free layer 17 are set in a predetermined direction by the corresponding antiferromagnetic layers 27 and 29. It is fixed. 15 and 16 correspond to a cross section taken along the line II in FIG.

  On the other hand, the magnetization direction F of the free layer 17 is determined in a direction corresponding to the external magnetic field applied at that time. The resistance value of the dual spin valve film is determined by the angle of the magnetization direction F of the free layer 17 with respect to the magnetization directions P1 and P2 of the pinned layers 23 and 25. That is, as shown in FIG. 15A, the resistance value of the dual spin valve film is such that the magnetization direction F of the free layer 17 has a reverse component with respect to the magnetization directions P1 and P2 of the pinned layers 23 and 25. When it has, it becomes large, and as shown in FIG. 15B, it becomes small when it has the same direction component. Therefore, the external magnetic field can be detected by looking at the change in the resistance value.

  By the way, in the dual spin-valve film, the magnetization direction of the pinned layer 23 on the upper side of the free layer 17 as shown in FIG. An individual appears in which only P1 is inverted.

  When such inversion occurs, the resistance of the magnetoresistive film 3 as a whole is almost constant regardless of the direction of magnetization F of the free layer 17. That is, when the magnetization direction F of the free layer 17 is in the direction shown in FIG. 16A, the magnetization direction F and the magnetization direction P1 are in a low resistance relationship, and the magnetization direction F and the magnetization direction P2 are High resistance. On the other hand, when the magnetization direction F of the free layer 17 is in the direction shown in FIG. 16B, the magnetization direction F and the magnetization direction P1 are in a high resistance relationship, and the magnetization direction F and the magnetization direction P2 are It has a low resistance relationship.

  As described above, when only the magnetization direction of one pinned layer is reversed in the dual spin valve film, even if the magnetization direction F of the free layer 17 is changed, the resistance to the upper and lower pinned layers 23 and 25 is increased or decreased. The resistance value of the magnetoresistive film 3 as a whole becomes substantially constant only by reversing the relationship and the increase / decrease relationship. For this reason, an output based on a change in resistance value cannot be obtained, and it may be difficult to capture an external magnetic field.

  Therefore, in the magnetoresistive effect element 1 according to the present exemplary embodiment, the above problem is solved by the following action. As described above, since the protective films 13 and 15 are films having compressive stress, compressive stress is generated in the direction of expanding the film itself. Due to the compressive stress, a tensile stress σ in the height direction H is generated in the magnetoresistive film 3. When the tensile stress σ is generated, the magnetization directions of the pinned layers 23 and 25 in the magnetoresistive effect film 3 are stabilized by the inverse magnetostrictive effect.

  More specifically, as shown in FIG. 1, first, a compressive stress C in a direction orthogonal to the height direction H is generated in the protective films 13 and 15, and this compressive stress C is fixed to the protective films 13 and 15. Is transmitted to the electrode films 9 and 11. As a result, the tensile stress F <b> 1 due to the compressive stress C acts on the electrode films 9 and 11. Further, the tensile stress F2 caused by the tensile stress F1 acts on the magnetic domain control films 5 and 7 fixed to the electrode films 9 and 11. Finally, the pressures of the electrode films 9 and 11 and the magnetic domain control films 5 and 7 to be expanded by the tensile stresses F1 and F2 are transmitted to the magnetoresistive effect film 3, and substantially the magnetoresistive effect film 3 Is a mechanical state in which a tensile stress σ in the height direction H is generated.

  Further, the compressive stress generated in the height direction H in the protective films 13 and 15 is transmitted to the lower electrode films 9 and 11 and the magnetic domain control films 5 and 7 as tensile stress in the height direction H, and the electrode films 9, 11, A tensile stress in the height direction H is also generated in the magnetoresistive film 3 that is in close contact with the magnetic domain control films 5 and 7.

  When the tensile stress σ in the height direction H is generated in the magnetoresistive effect film 3 in this way, the easy axes of magnetization of the pinned layers 23 and 25 in the magnetoresistive effect film 3 are determined so that the magnetoelastic energy Eσ becomes small.

The magnetoelastic energy Eσ is
Eσ = (− 3/2) σλ _S {cos ² θ− (1/3)}
It is represented by
Here, the meaning of each symbol in the above equation is
σ: Stress acting on the magnetoresistive film (the tensile direction is a positive value)
λ _S : Saturation magnetostriction constant θ: The angle formed by the stress (σ) action direction and the easy magnetization axis in the magnetoresistive film.

Since the stress generated in the magnetoresistive film 3 is a tensile stress as described above, σ> 0, and the saturation magnetostriction constants of the pinned layers 23 and 25 are also positive values as described above, and therefore λ _S > 0. . The magnetoelastic energy Eσ is a function of σ, λ _S , θ. If σ and λ _S are positive, the magnetoelastic energy Eσ is the smallest when cos ² θ = 1, that is, θ = 0. Become. Considering that θ is an angle between the stress σ acting on the magnetoresistive effect film 3 and the easy axis of magnetization, the easy axes of the pinned layers 23 and 25 in the magnetoresistive effect film 3 are 3 is induced in the same direction (height direction) as the stress σ acting on the surface 3. Further, since the magnetoelastic energy Eσ decreases as the stress σ increases, the magnetization easy axes of the pinned layers 23 and 25 in the magnetoresistive effect film 3 are induced in the height direction by increasing the stress σ. It will be.

  As described above, in the magnetoresistive effect element 1 according to the present exemplary embodiment, the tensile stress σ in the height direction H is generated in the magnetoresistive effect film 3 by the compressive stress generated in the protective films 13 and 15. By the effect, the magnetization directions of the pinned layers 23 and 25 in the magnetoresistive effect film 3 can be stabilized, that is, the reversal of the magnetization directions of the pinned layers 23 and 25 can be prevented.

  Next, characteristics required for the protective films 13 and 15 including a preferable range of compressive stress will be described. As described above, in the present invention, reversal of the magnetization direction of the pinned layers 23 and 25 is prevented by using films having compressive stress as the protective films 13 and 15. The applicant examined the relationship between the compressive stress and the product yield, and obtained the results shown in Table 1.

  As can be seen from the results in Table 1, the yield improvement effect appears in the range where the compressive stress is 600 MPa or more, and a more preferable range is 1000 MPa or more.

  On the other hand, when the compressive stress exceeds 5000 MPa, the protective films 13 and 15 cannot withstand their own stress and may be peeled off from the upper surfaces of the electrode films 9 and 11 to be stacked. Therefore, the compressive stress of the protective films 13 and 15 needs to be in the range of 600 MPa to 5000 MPa, more preferably 1000 MPa to 5000 MPa.

  Further, as a characteristic required for the protective films 13 and 15, there is a problem of milling rate. The protective films 13 and 15 have a function of protecting the electrode films 9 and 11 from milling in the manufacturing process. As shown in FIG. 10, when removing the excess laminated film 37 around the end passive region 1b by milling, the edge of the resist mask 41 is located on the inner side of the protective films 13 and 15 so that there is no residual removal. It is terminated. For this reason, the protective films 13 and 15 not covered with the resist mask 41 are directly subjected to milling.

  Therefore, in addition to having the necessary compressive stress, the protective films 13 and 15 are required to have a somewhat high milling rate in order to protect the lower electrode films 9 and 11. In this embodiment, aluminum nitride is used as a material having such necessary compressive stress and milling rate, and the protective films 13 and 15 are configured.

  In addition to aluminum nitride, materials having the necessary compressive stress and milling rate include boron nitride, titanium nitride, silicon nitride, niobium oxide, zirconium oxide, yttrium oxide, hafnium oxide, magnesium oxide, titanium oxide, tantalum oxide, diamond Examples thereof include carbon and silicon carbide. Therefore, in the present invention, a protective film can be formed using at least one of these. Moreover, as long as necessary compressive stress and milling rate can be achieved, conventionally used alumina can be added to the protective film.

  Although the contents of the present invention have been specifically described with reference to the preferred embodiments, various modifications can be made by those skilled in the art based on the basic technical idea and teachings of the present invention. It is self-explanatory.

  First, in the above embodiment, the case where the device is implemented as a CIP (current in plane) type element has been described. However, the present invention is not limited to this, and a CPP (current current) as shown in FIG. A perpendicular to plane) type magnetoresistive element 101 may be used. In this case, the electrode films 9 and 11 are disposed on both sides of the magnetoresistive film 3 in the direction perpendicular to the film surface, and the protective films 13 and 15 are disposed on both sides of the magnetoresistive film 3 via the insulating films 14 and 16. It is formed on the upper surface of the magnetic domain control films 5 and 7 provided. By making the protective films 13 and 15 have the above-described characteristics, the same as in the case of the CIP type magnetoresistive effect element is used. The effect is obtained.

  In the present invention, it is only necessary that at least one of the laminations of the end passive regions is provided with a film having the above-described characteristics of compressive stress and milling rate.

  Further, the present invention is not limited to the dual spin valve, and is applied to a magnetoresistive film having a single spin valve, that is, a non-magnetic layer, a pinned layer, and an antiferromagnetic layer assigned to a free layer one by one. You can also. Even in this case, an effect of stabilizing the magnetization direction of the pinned layer can be obtained.

  Moreover, although the example which implemented the magnetoresistive effect element as a reading element of a thin film magnetic head was shown in the said embodiment, this invention is not limited to this aspect. That is, the magnetoresistive element of the present invention can be widely applied to micro devices other than thin film magnetic heads, such as sensors, memories, actuators, and semiconductor devices using thin films.

It is a perspective view which shows the structure of the magnetoresistive effect element which concerns on embodiment of this invention. It is a figure explaining the compressive stress in a protective film. It is a figure which shows one process in the manufacturing process of the magnetoresistive effect element which concerns on embodiment of this invention. FIG. 4 is a diagram showing a step subsequent to FIG. 3. It is a figure which shows the state of FIG. 4 planarly. It is a figure which shows the next process of FIG. It is a figure which shows the next process of FIG. It is a figure which shows the next process of FIG. It is a figure which shows the next process of FIG. It is a figure which shows the state of FIG. 9 planarly. FIG. 10 is a diagram showing a step subsequent to that in FIG. 9. FIG. 12 is a diagram showing a step subsequent to FIG. 11. It is a figure which shows the state of FIG. 12 planarly. It is a figure which shows the cross section which follows the III-III line | wire of FIG. It is a figure explaining the relationship between the appropriate magnetization direction state and resistance in a dual spin valve film. It is a figure explaining the relationship between the improper magnetization direction state in a dual spin-valve film | membrane, and resistance. It is a perspective view which shows the structure of the magnetoresistive effect element which concerns on another embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,101 Magnetoresistance effect element 1a Center active area | region 1b End passive region 3 Magnetoresistance effect film | membrane 5,7 Magnetic domain control film | membrane 9,11 Electrode film | membrane 13,15 Protective film C Compressive stress σ Tensile stress H Height direction

Claims (6)

A magnetoresistive element including at least a central active region having a magnetoresistive effect film and a pair of end passive regions provided on both sides of the central active region,
The saturation magnetostriction constant of the pinned layer in the magnetoresistive film is a positive value,
The end passive region is provided with a layer having a compressive stress of 600 MPa to 5000 MPa and generating a tensile stress in the height direction in the magnetoresistive film.
Magnetoresistive effect element. The magnetoresistive element according to claim 1,
The layer that generates the tensile stress has a compressive stress of 1000 MPa to 5000 MPa.
Magnetoresistive effect element. A magnetoresistive element including at least a central active region having a magnetoresistive effect film and a pair of end passive regions provided on both sides of the central active region,
The saturation magnetostriction constant of the pinned layer in the magnetoresistive film is a positive value,
The end passive region is any one of aluminum nitride, boron nitride, titanium nitride, silicon nitride, niobium oxide, zirconium oxide, yttrium oxide, hafnium oxide, magnesium oxide, titanium oxide, tantalum oxide, diamond-like carbon, and silicon carbide. Including one,
The magnetoresistive film is provided with a layer that generates a tensile stress in the height direction.
Magnetoresistive effect element. The magnetoresistive effect element according to any one of claims 1 to 3,
The end passive region includes a magnetic domain control film, an electrode film, and a protective film,
The layer that generates the tensile stress is the protective film,
The protective film protects the electrode film from etching;
Magnetoresistive effect element. The magnetoresistive effect element according to any one of claims 1 to 3,
The end passive region includes a magnetic domain control film and a protective film,
The layer that generates the tensile stress is the protective film,
The protective film protects the magnetic domain control film from etching;
Magnetoresistive effect element. The magnetoresistive effect element according to any one of claims 1 to 5,
The magnetoresistive film is a dual spin valve film,
Magnetoresistive effect element.

Images