JP2001094173A - Magnetic sensor, magnetic head and magnetic disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic sensor which can realize MR ratio of at least 30%. SOLUTION: This magnetic sensor has a ferromagnetic tunnel junction unit which includes a first ferromagnetic metal layer and a second ferromagnetic metal layer formed thereon through an insulating barrier layer. At least either of the first and second metal layers is formed of a CoFe alloy containing Fe at a composition ratio of 25 to 51 at.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic sensor, that is, a magnetic sensor that converts a change in a magnetic field into a change in electric resistance, and an apparatus using the magnetic sensor. The present invention particularly relates to a magnetic head equipped with a magnetic sensor as a magnetoresistive transducer, a magnetic disk device equipped with the magnetic head, and a disk array device and an encoder device equipped with a magnetic sensor.

[0002]

2. Description of the Related Art In recent years, a thin film magnetic head capable of coping with a high recording density and miniaturization of a magnetic disk drive has attracted attention, and its high performance has been demanded. In a magnetoresistive element, that is, a reproducing head (MR head) equipped with an MR element as a transducer, an AMR element utilizing an anisotropic magnetoresistance effect and a high speed independent of the moving speed of a magnetic recording medium. Attention has been paid to a GMR element utilizing a giant magnetoresistance effect capable of obtaining an output. Among them,
In particular, a spin valve GMR element has recently been receiving particular attention because it can be manufactured relatively easily and has a higher rate of change in electrical resistance in a low magnetic field than other MR elements.

[0003] As is well known, various ferromagnetic tunnel junction devices capable of obtaining a higher magnetoresistance ratio (so-called MR ratio) than a spin valve device have been proposed. Examples of recently published patent applications are described in, for example, JP-A-10-4227 and JP-A-10-16232.
Japanese Patent Application Laid-Open No. 6-162327 discloses a ferromagnetic tunnel junction device usable as a magnetic sensor or a memory cell in a magnetic random access memory array. The MR head used is disclosed in
No. 90 discloses a ferromagnetic tunnel junction device, a junction memory cellulose and a junction magnetic sensor using the same, respectively. Each of the ferromagnetic tunnel junction devices described in these publications has the same configuration, and includes a lower ferromagnetic layer (lower electrode), a tunnel barrier formed thereon sequentially, and an upper ferromagnetic layer. A ferromagnetic tunnel junction structure including a ferromagnetic layer (upper electrode) is provided. Such a ferromagnetic tunnel junction device having a spin-valve structure is specifically referred to, for example, in FIG. 6 of Japanese Patent Application Laid-Open No. H10-190090, and with reference to the described device, FIG. It has a layer configuration as schematically shown. The illustrated ferromagnetic tunnel junction device includes a lower electrode stack 110, a tunnel barrier 120, and an upper electrode stack 130 on a substrate 109. This device has a 5 nm Ta layer as an electric lead layer 111 + a 10 nm Cu layer (the Cu layer also serves as a seed layer 112) / a 4 nm NiFe layer as a template layer 114 / Magnetic layer 1
10 nm MnFe layer / lower ferromagnetic layer 118
And a lower electrode stack 110 composed of a 6 nm NiFe layer and a 2 nm Co layer. Electric lead layer 1
Reference numeral 11 may be an Au layer, an Al layer, or the like instead of the Ta layer. The tunnel barrier 120 is an aluminum (Al) layer having a thickness of 1.2 nm, which is plasma-oxidized, that is, an alumina (Al ₂ O ₃ ) layer. Upper electrode stack 13
0 is composed of a 20 nm NiFe layer as the upper ferromagnetic layer 132 and a 20 nm Cu layer as the electric lead layer 150. The upper ferromagnetic layer 132 is a NiFe layer or the like, and includes the tunnel barrier 120 and the upper ferromagnetic layer 13.
2, a Co layer may be interposed as in the lower ferromagnetic layer 118. The electrical lead layer 150
Like the electric lead layer 111, Au instead of Cu layer
Layer, an Al layer, or the like.

[0004]

As described above, a conventional ferromagnetic tunnel junction device having a spin valve structure usually has a structure of "... / antiferromagnetic layer (pinned layer) / lower ferromagnetic layer (pinned layer) / Tunnel barrier (insulating barrier layer) / upper ferromagnetic layer (free layer) / ... ". Here, for example, the pinned layer is an IrMn layer and the pinned layer is C
If the layer is an o layer, the Co layer is exchange-coupled with the IrMn layer, and the magnetization direction of the pinned layer is fixed. Therefore, when a magnetic field is externally applied to the element, only the free layer rotates. Then, as described below with reference to mathematical expressions, the tunnel resistance changes depending on the magnetic field.

However, a NiFe layer or C
If the o-layer is used, a sufficiently high magnetoresistance ratio (MR ratio) cannot be achieved as shown by the magnetoresistance effect curve in FIG. In the example shown, only an MR ratio of about 20% can be obtained, and usually the maximum value is about 25%.
However, when such a tunnel junction element is used as a component of the above-described magnetic sensor, particularly, a magnetic head for ultra-high density recording, it is necessary to realize an even larger MR ratio of at least 30%.

It is an object of the present invention to provide a magnetic sensor which can realize an MR ratio of at least 30%. Another object of the present invention is to provide an apparatus using the high-performance magnetic sensor provided by the present invention. The above and other objects of the present invention can be easily understood from the following detailed description.

[0007]

SUMMARY OF THE INVENTION In one aspect, the present invention includes a first ferromagnetic metal layer and a second ferromagnetic metal layer formed thereon via an insulating barrier layer. In a magnetic sensor having a ferromagnetic tunnel junction unit, at least one of the first and second ferromagnetic metal layers has a thickness of 25%.
Provided is a magnetic sensor comprising a CoFe alloy containing Fe at a composition ratio of not less than at% and less than 51 at%.

According to another aspect of the present invention, there is provided a magnetic head including the magnetic sensor of the present invention as a magnetoresistive transducer. According to another aspect of the present invention, there is provided a magnetic disk drive equipped with a magnetic head having the magnetic sensor of the present invention. In another aspect, the present invention provides a disk array device equipped with the magnetic sensor of the present invention.

[0009] In still another aspect, the present invention provides an encoder device equipped with the magnetic sensor of the present invention. The above and other devices provided using the magnetic sensor of the present invention are all high performance.

[0010]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In the following embodiments, the present invention will be described with reference to some limited examples.
Except for the restrictions on e _x alloy, it may subjected to various changes and modifications within the scope of the present invention, it respect to the configuration generally of a magnetic sensor can be applied to that of a conventional magnetic sensor, it is to be understood .

First, for a better understanding of the present invention,
The ferromagnetic tunnel junction employed in the present invention will be described. In a junction having a structure of “metal / insulator / metal”, when a voltage is applied between the metals on both sides, a slight current flows when the insulator is sufficiently thin. Normally, the insulator does not conduct current, but if the insulator is sufficiently thin (several
In several tens of millimeters, a current flows because the electron has a very small probability of being transmitted by the quantum mechanical effect. This current is called “tunnel current”, and a junction having this structure is called “tunnel junction”.

In general, a metal oxide film is used as an insulating barrier for the insulator layer. For example, an oxide film is formed by oxidizing a surface layer of aluminum by natural oxidation, plasma oxidation, thermal oxidation, or the like. In particular, it is advantageous to form an aluminum oxide film (alumina film) by a plasma oxidation method. Further, by adjusting the oxidation conditions, the oxide film can have a depth of several Å to several tens of the aluminum surface layer. Since the formed alumina film is an insulator, it can be used as an insulating barrier layer of a tunnel junction. As a characteristic of such a junction, unlike a normal resistor, a current with respect to an applied voltage has a non-linear property, and thus has been used as a non-linear element.

The structure in which the metal on both sides of the tunnel junction as described above is replaced with ferromagnetic metal is employed in the present invention and is called a ferromagnetic tunnel junction. For ferromagnetic tunnel junctions, tunnel probability (tunnel resistance)
Is known to depend on the magnetization state of the magnetic layers on both sides. That is, the tunnel resistance can be controlled by the magnetic field. Assuming that the relative angle of magnetization is θ, the tunnel resistance R can be expressed by the following equation (1).

R = Rs + 0.5ΔR (1−cos θ) (Equation 1) That is, when the magnetization angles of both magnetic layers are equal (θ
= 0 °), the tunnel resistance is small, and when the magnetizations of both magnetic layers are in opposite directions (θ = 180 °), the tunnel resistance becomes large. This is because electrons inside the ferromagnetic material are polarized. Electrons usually have an upward spin state (up electron) and a downward spin state (down electron), but electrons inside a normal non-magnetic metal have the same number of both electrons. It has no magnetism as a whole. On the other hand, electrons inside the ferromagnetic material have up or down magnetism as a whole because the number of up electrons (Nup) and the number of down electrons (Ndown) are different.

When electrons tunnel, these electrons are known to tunnel while maintaining their spin states. Therefore, if there is a vacancy in the electronic state at the tunnel destination, tunneling is possible, but if there is no vacancy in the electronic state at the tunnel destination, electrons cannot tunnel. The rate of change ΔR of the tunnel resistance is represented by the product of the polarization rate of the electron source and the polarization rate at the tunnel destination.

ΔR / Rs = 2 × P1 × P2 / (1−P1 × P2) (Equation 2) Here, P1 and P2 are polarizabilities of both magnetic layers and are expressed by the following equation (3). P = 2 (Nup−Ndown) / (Nup + Ndown) (Equation 3) The polarizability P depends on the type of ferromagnetic metal.
The polarizability of CoFe used as a ferromagnetic metal in the present invention is 0.46, and theoretically, a magnetoresistance ratio (MR ratio) of or around 54% can be expected. Such a value of the MR ratio is larger than the anisotropic magnetoresistive effect (AMR) or the giant magnetoresistive effect (GMR), so that it can be applied to a magnetic sensor or the like.

FIG. 3 is a sectional view schematically showing a typical example of a magnetic sensor according to the present invention. The illustrated magnetic sensor 1 includes one ferromagnetic tunnel junction unit 2 formed on a silicon oxide film 7 formed by oxidizing the surface of a silicon substrate 6. The tunnel junction unit 2 includes a lower electrode 10, an insulating barrier layer 20, and an upper electrode 30. The lower electrode 10 is formed of a 24 nm thick NiFe layer (first ferromagnetic metal layer) 12 and a 10 nm thick CoFe layer 11. The insulating barrier layer 20 has a thickness of 1.6.
consisting Al-Al ₂ O ₃ layers nm. That is, this layer is an alumina (Al ₂ O ₃ ) layer obtained by plasma-oxidizing an aluminum (Al) layer. The upper electrode 30 is composed of a 10 nm-thick CoFe layer 31 and a 50 nm-thick IrMn layer.
It is composed of a layer 32 and an Al layer 33 having a thickness of 10 nm.

FIG. 4 is a plan view of the magnetic sensor 1 shown in FIG. As shown, orthogonal to the lower electrode 10,
An upper electrode 30 is formed thereabove, and a current source I and a voltage sensor V are connected between the lower electrode 10 and the upper electrode 30. When the magnetic field changes while a constant current is applied to the magnetic sensor 1 by the current source I, the resistance value changes and the voltage developed between the electrodes 10 and 30 changes. This change in voltage can be measured by the voltage sensor V.

The magnetic sensor 1 shown in FIG.
It can be manufactured as follows. First, FIG.
As shown in FIG. 5, a film of NiFe is formed to a thickness of 24 nm on the substrate 6 via a metal mask 41 having a stripe pattern under a magnetic field in the direction of the arrow, and further, CoFe is further formed thereon. Is continuously formed with a film thickness of 10 nm. The two layers thus formed constitute the lower electrode 10 and serve as a first ferromagnetic metal layer whose magnetization freely rotates with respect to a magnetic field. Note that, since CoFe has a higher polarizability than NiFe, it also has a function of increasing the change in ferromagnetic tunnel resistance.

Thereafter, as shown in FIG. 5B, an Al layer 19 is formed with a thickness of 1.6 nm through a mask 42 having a circular pattern. Subsequently, the surface of the Al layer 19 is plasma-oxidized as shown in FIG. Al-
An insulating barrier layer 20 made of Al ₂ O ₃ is obtained. After the formation of the insulating barrier layer 20 is completed, the upper electrode 30 is formed through the mask 43 while applying a magnetic field in the direction of the arrow, as shown in FIG. Here, the magnetic field is applied in a direction orthogonal to the direction of the magnetic field when the lower electrode 10 is formed. The mask 43 has a stripe pattern in a direction orthogonal to the lower electrode 10. In particular,
The upper electrode 30 can be formed by sequentially stacking CoFe to a thickness of 10 nm and IrMn to a thickness of 50 nm. On the formed upper electrode 30, Al having a film thickness of 10 nm is laminated as an antioxidant film.

FIG. 6 is a sectional view schematically showing another typical example of the magnetic sensor according to the present invention. The illustrated magnetic sensor 1 includes one ferromagnetic tunnel junction unit 2 formed on a silicon oxide film 7 formed by oxidizing the surface of a silicon substrate 6. The tunnel junction unit 2 includes a lower electrode 10, an insulating barrier layer 20, and an upper electrode 30.
Consists of The lower electrode 10 includes a 17.1 nm-thick NiFe layer (first ferromagnetic metal layer) 12 and a 3.3-nm thick
nm of the CoFe layer 11. Insulation barrier layer 2
0 consists of Al-Al ₂ O ₃ layer having a thickness of 1.6 nm.
That is, this layer was formed by plasma oxidation of the Al layer.
1 ₂ O ₃ layer. The upper electrode 30 includes a 3.3 nm thick CoFe layer 31 and a 17.1 nm thick NiFe layer 34.
A 45 nm thick FeMn layer 35 and a 8 nm thick T
a layer 36.

In the magnetic sensor according to the present invention, a magnetic resistance change rate (MR ratio) of at least 30% is achieved by using a CoFe alloy containing Fe at a predetermined composition ratio as a magnetic material of the ferromagnetic metal layer. Thus, the use of the magnetic sensor can be broadly expanded, and satisfactory results can be obtained in any use. In the magnetic sensor of the present invention, the first and second ferromagnetic metal layers include:
Preferably, only one of them is at least 25 at% and 51 at%.
It is made of a CoFe alloy containing Fe at a composition ratio of less than at%.

If the first or second ferromagnetic metal layer is made of a metal other than the CoFe alloy as described above, an arbitrary metal is formed as long as the function and effect of the present invention are not adversely affected. Can be used as material. Suitable metals include, but are not limited to, those listed below, Co, NiFe, and the like.

According to another preferred embodiment, both the first and second ferromagnetic metal layers have a content of 25 at% or more and 5 at% or more.
It is made of a CoFe alloy containing Fe at a composition ratio of less than 1 at%. In such a case, the Fe composition ratio of each metal layer may be the same or different. When a ferromagnetic tunnel junction film having a spin-valve structure is used for a magnetic sensor as in the present invention, the antiferromagnetic layer (pin layer) has a force (H) that suppresses the magnetization direction of the ferromagnetic layer (pinned layer). _ua , see FIG. 2) is better. Considering this, it is preferable to form a ferromagnetic tunnel junction film using, for example, a CoFe ₃₁ layer having a large _Hua as the pinned layer and CoFe ₂₆ having a high MR ratio as the free layer. This fact is evident from FIGS. 16 and 15, respectively, described below with reference to FIG. The ferromagnetic tunnel junction film thus obtained can realize a higher MR ratio than a ferromagnetic tunnel junction film using a CoFe ₃₁ layer for both the pinned layer and the free layer. _Hua larger than a ferromagnetic tunnel junction film using a CoFe ₂₆ layer for both layers can be realized.

When a ferromagnetic tunnel junction film having a spin valve structure is used for a magnetic sensor, the smaller the coercive force, the better. For this reason, it is preferable to use, for example, NiFe, which is a soft magnetic material, for the free layer, and to use, for example, CoFe, for example, for the pinned layer. In this case, the MR ratio becomes smaller than that of the ferromagnetic tunnel junction using CoFe for the free layer, and the coercive force becomes smaller. However, when this ferromagnetic tunnel junction is compared with a ferromagnetic tunnel junction film using NiFe for both the free layer and the pinned layer, a larger MR ratio can be realized.

When the magnetic sensor of the present invention is used for an encoder, it is preferably configured such that a plurality of ferromagnetic tunnel junction units are connected in series. When the ferromagnetic tunnel junction unit of the magnetic sensor is configured in this manner, each ferromagnetic tunnel junction element connected in series divides the applied voltage, so that the voltage applied to each ferromagnetic tunnel junction element decreases. . Therefore, a high-performance magnetic sensor having a high magnetoresistance ratio can be obtained. In addition, since the resistance value of the magnetic sensor becomes high, the current flowing through the magnetic sensor decreases, and power consumption can be reduced.

The series connection of the ferromagnetic tunnel junction units can be preferably performed by the following two methods.
The first series connection method includes arranging a plurality of ferromagnetic tunnel junction units side by side on a substrate, and connecting the first ferromagnetic metal layers or the second ferromagnetic metal layers in adjacent ferromagnetic tunnel junction units. This is a method of performing the above-described series connection by integrally forming layers. According to the magnetic sensor according to such a method, the series connection of the ferromagnetic tunnel junction elements is performed simultaneously with the work of forming the upper metal layer and the lower metal layer, so that the production can be performed efficiently. Also, in this magnetic sensor, an extra number of ferromagnetic tunnel junction elements included in the sensor element are prepared, and unnecessary junctions are removed by short-circuiting the upper metal layer and the lower metal layer, thereby reducing the resistance. The value can be adjusted. Thereby, the yield in manufacturing the magnetic sensor can be improved.

FIG. 7 is a sectional view showing a magnetic sensor element in which N ferromagnetic tunnel junction units are arranged in series according to the present invention. In the figure, reference numeral 1 denotes a magnetic sensor, and N ferromagnetic tunnel junction units 2
Are arranged side by side in parallel. Each joining unit 2
It comprises a lower electrode 10, an insulating barrier layer 20, and an upper electrode 30. The lower electrode 10 between two adjacent bonding structures 2
And the upper electrode 30 are integrally formed, and the bonding units 2 are connected in series by the lower electrode 10 and the upper electrode 30, respectively.

According to the magnetic sensor 1, the lower electrode 1
0 and the upper electrode 30 at the same time as the bonding unit 2
Can be connected in series, thereby facilitating the manufacture of the magnetic sensor. Further, the ferromagnetic tunnel junction structure 2 is
In this magnetic sensor 1, the resistance value of one junction structure 2 is R (Ω), and the overall resistance value of the magnetic sensor 1 is N × R (Ω).

In a second series connection method, a plurality of ferromagnetic tunnel junction units are stacked on a substrate to form a multi-stage structure.
The series connection is performed by forming the first ferromagnetic metal layer of the upper tunnel junction unit on the second ferromagnetic metal layer of the lower tunnel junction unit. According to the magnetic sensor according to such a method, a magnetic sensor having a small area can be obtained.

FIG. 8 shows a cross section of a magnetic sensor having a multilayer structure in which N ferromagnetic tunnel junction units are vertically stacked adjacent to each other. In the figure, reference numeral 1
Is a magnetic sensor, and each junction 2 is connected in series by stacking N layers of ferromagnetic tunnel junction units 2 on a substrate 6. One ferromagnetic tunnel junction unit 2 includes a lower electrode 10, an insulating barrier layer 20, and an upper electrode 30, respectively. The respective bonding units are connected in series by forming the lower electrode 10 of the upper bonding unit 2 on the upper electrode 30 of the lower bonding unit 2.

According to the magnetic sensor 1, a current flows in the film thickness direction. Therefore, assuming that the resistance of the single-layer junction unit 2 is R, the overall resistance of the magnetic sensor 1 is N × R.
(Ω). As described above, the magnetic sensor according to the present invention can be advantageously used in various devices by taking advantage of its excellent characteristics.

In one preferred embodiment, the magnetic sensor of the present invention can be utilized in a magnetic head as a magnetoresistive transducer, and therefore, as described in greater detail below, the magnetic sensor of the present invention. A magnetic head provided with a sensor and a magnetic disk device provided with such a magnetic head are provided. Note that the magnetic head and the magnetic disk device described below each show a preferred example in the embodiment of the present invention, and it goes without saying that various configurations other than those shown in the drawings can be adopted.

FIG. 9 is a schematic sectional view for explaining the configuration of a magnetic head provided with the magnetic sensor of the present invention. As shown in the figure, the magnetic head 50 is made of Altic (Al ₂ O ₃ .T).
It is formed on a ceramic substrate 51 such as iC). On the ceramic substrate 51, a lower magnetic shield 52, a non-magnetic insulating film 53, and an upper magnetic shield 54 are formed in this order from the substrate 51. The magnetic sensor 56 of the present invention is disposed in a read gap 55 formed at the front end of the magnetic head 50 by the upper and lower magnetic shields 52 and 54. Further, the upper magnetic shield 5
A magnetic pole 58 is formed on 4 via a non-magnetic insulating film 57. Between the magnetic shield 54 and the magnetic pole 58,
A write gap 59 is formed at the front end of the magnetic head 50, and a write coil pattern 49 is spirally formed in the insulating film 52.

FIG. 10 is a plan view showing the internal structure of a magnetic disk drive equipped with the magnetic head of the present invention. In the figure, in order to facilitate understanding of the magnetic disk device 60 of the present invention, a state in which the upper cover is removed is shown on the left side of the broken line, and a part of the multi-stage magnetic disk assembly 70 is shown on the right side of the broken line. The configuration of the magnetic disk 71 and the arm assembly 72 cooperating therewith is shown.

Referring to FIG. 10, each magnetic disk 71 has a hub 71 driven by a motor (not shown).
a. The arm assembly 72 includes the pivot shaft 7.
2a includes an arm 72b pivotally supported on 2a and a magnetic head 72c provided on a free end of the arm 72b. further,
A coil 72d forming a part of the voice coil motor 73 is wound around the free end of the arm 72b opposite to the free end carrying the magnetic head 72c in parallel with the scanning surface of the arm 72b. Magnets 73a and 73b, which constitute the other part of the voice coil motor 73, are formed above and below the coil 72d. The arm 72 can be freely pivoted around the pivot shaft 72a by exciting the coil 72d. Is possible. The voice coil motor 73 is configured such that the magnetic head 72c carried on the arm 72b is
Servo control is performed so as to follow the upper cylinder or track 71b.

FIG. 11 shows the magnetic disk drive 60 of FIG.
It is a perspective view which shows the internal structure of. Referring to FIG.
The magnetic disk assembly 70 includes a plurality of magnetic disks 71 ₁ , 71 ₂ ,... Commonly held by a rotary hub 71a, and the arm assembly 72 correspondingly comprises a set of a plurality of arms. You can see that there is. Each arm 72b is held on a common turning member 72e which is held so as to be pivotable about a pivot shaft 72a.
It pivots all together with the rotation of 2e. Of course, the rotating member 7
The rotation of 2e occurs in response to the excitation of the voice coil motor 73. The entire magnetic disk drive is housed in a hermetically sealed housing 61.

In the magnetic disk drive 60 of the present invention, the above-described ferromagnetic tunnel junction magnetic sensor of the present invention is used as a read head in the magnetic head 72c, thereby enabling extremely high-density magnetic recording and reproduction. Become. Further, according to another preferred embodiment, the magnetic sensor of the present invention can be used in a disk array device. The disk array device can be basically configured in the same manner as a conventional device. That is, the disks (HDD) on which the magnetic sensor of the present invention is mounted are arranged in an array, and the disks can be connected to each other by connecting means such as a cable.

Further, the magnetic sensor of the present invention has another feature.
One preferred embodiment can be used in an encoder device. Here, the encoder device in which the present invention can be implemented can include various encoder devices known in the art, but preferably, a non-contact type one of which is shown below with reference to FIG. It is an encoder device.

FIG. 12A shows a rotating magnet body 65 used in the encoder device. Rotating magnet 65
Has a diameter D of 10 mm, and the diameter d of a shaft located at the center thereof is 5 mm. On the circumference of the shaft, 16 pairs of N poles 62 and S poles 63 are alternately arranged as shown in the figure. The magnetic sensor 1 is installed such that its center is located at an intermediate position of the rotating magnetized body 65. In the case of the illustrated example, the magnetization period λ is about 1.5 mm.

FIG. 12B shows the magnetic sensor 1 in an enlarged manner. Four rows of sensor elements 22 to 25
Are linearly parallel to the diameter direction of the magnet of the rotating magnet body 65 on the substrate 6 and each sensor element 2
1 are arranged so that the interval of 1 becomes λ / 4. In the illustrated example, the angle between the sensor elements 22 to 25 is about 5.6 degrees,
The center spacing is about 0.37 mm.

FIG. 13 is a plan view showing the manufacturing procedure of the magnetic sensor used in the encoder device of FIG. 12 in order. The magnetic sensor used here has the serial connection structure described above with reference to FIG. Such a magnetic sensor is easy to manufacture because the tunnel junction structure can be formed with only three layers of the lower electrode / insulating barrier layer / upper electrode. Further, each sensor element row is configured by joining six sensor elements 21 in series (joining area: 50 μm × 50 μm).

First, using a mask (not shown), a NiFe film is formed in a stripe shape on the substrate 6 to a film thickness of 17.1 nm, and a CoFe film is continuously formed to a film thickness of 3.3 nm. Thus, the lower electrode 10 is formed. This state is shown in FIG.
It is shown in (A). Next, after replacing the mask, two insulating barrier layers 20 are formed for each lower electrode 10. This insulating barrier layer 20 is formed by forming an Al film having a thickness of 1.3 nm and then subjecting its surface to plasma oxidation.

After the plasma oxidation of Al is completed, the mask is replaced again to form the upper electrode 30 and to form the terminals 26 to 29. This film formation is performed by forming CoFe with a thickness of 3.3 nm, NiFe with a thickness of 17.1 nm, and FeMn with a thickness of 45 nm. Subsequently, a film thickness of 8 n is formed on the upper electrode 30 thus formed.
A Ta film is formed at m. FIG. 13B shows a state in which such a series of film forming steps has been completed.

When a voltage of 3.0 V is applied to the magnetic sensor 1 of the encoder device manufactured as described above using a battery, the voltage applied to each ferromagnetic tunnel junction unit is 0.1.
It becomes 50 V, and the magnetoresistance ratio (MR ratio) becomes 30%. Further, when the rotating magnetized body 65 makes one round, a total of 1
Six output pulses can be obtained.

[0046]

Next, the present invention will be described with reference to examples. It should be understood that the present invention is not limited to the embodiments described below. Using a mask (not shown), a 24 nm-thick film of NiFe is sputtered on a silicon substrate with an oxide film in a stripe shape,
Further, CoFe was continuously formed into a film having a thickness of 10 nm by sputtering. In this example, in order to evaluate the ratio of the composition ratio of Fe in CoFe, as described below with reference to FIG. 14, the composition ratio of Fe was variously changed in the range of 12 to 57 at%. For comparison, the composition ratio of Fe is 0 at.
%, That is, a film composed of only Co was also formed.
During sputtering film formation, a magnetic field was applied in the longitudinal direction of the stripe-shaped NiFe film. The two-layer structure formed as described above becomes a magnetic layer in which magnetization freely rotates with respect to a magnetic field in the magnetic sensor of this example.

Next, after replacing the mask, a film of Al was formed by sputtering to a thickness of 1.6 nm, and the surface was subsequently subjected to plasma oxidation. After the plasma oxidation of Al is completed,
The mask is replaced again, and while applying a magnetic field in a direction perpendicular to the magnetic layer formed previously, the CoF
CoFe having a different composition ratio of Fe in e was formed into a stripe by sputtering with a film thickness of 10 nm, and further, IrMn was formed by sputtering with a film thickness of 50 nm. Further, Al was sputtered to a thickness of 10 nm as an antioxidant film on the IrMn film. Finally, the silicon substrate was placed in a heating furnace and heat-treated at 225 ° C. in a vacuum magnetic field.

[0048] Figure 14 as a function of the magnetoresistance change rate of a magnetic sensor having a spin valve structure fabricated as described above (MR ratio) Fe composition ratio x (the composition ratio of Fe in the CoFe _x, at%) It is a plot. As can be understood from the graph, the MR ratio of the ferromagnetic tunnel junction film using CoFe _x is remarkably large as compared with the tunnel junction film composed of only Co regardless of the magnitude of the Fe composition ratio x. is there. In particular, when the Fe composition ratio x is 26 to 5
When the content is in the range of 7 at%, an excellent MR ratio of 30% or more can be achieved. In particular, when the Fe composition ratio x is 26 at%, a remarkably excellent MR ratio of 42% is actually achieved. be able to.

[0049] Subsequently, the magnetic sensor having various spin valve structure having different composition ratio of Fe in the CoFe _x, was measured the relationship between the magnetoresistance ratio (MR ratio) and applied magnetic field (Oe), The magnetoresistance effect curves plotted in FIGS. 15 to 20 were obtained. Here, the composition ratio of Fe in FIG. 15 is 26 at%, that in FIG. 16 is 31 at%, that in FIG. 17 is 35 at%, that in FIG. 18 is 40 at%, that in FIG. 19 is 51 at%, and that in FIG. is there.

As can be seen from the magnetoresistive effect curves shown in FIGS. 15 to 20, the magnetoresistive effect curves of the bonding films using CoFe _x of x = 26 to 40 at% have very good profiles. 15 to 18),
As the Fe composition ratio increases, the shape is disturbed. For example, using the x = 51 at% of CoFe _x when using (19) and x = 57 at% of CoFe _x (FIG. 20), the applied magnetic field is remarkable form of turbulence in the vicinity of 0 Oe. Such undesirable phenomenon, IrMn layer is pinned layer is considered to have the magnetization direction of the CoFe _x layer is a pinned layer occurs because it is not possible to sufficiently secure.

The following are conceivable causes of insufficient fixing of the magnetization direction. Ir which is a pin layer
When the underlying crystal structure of the Mn layer is fcc, the crystal structure becomes a γ structure, and a force for fixing the magnetization direction of the pinned layer appears. Here, when the CoFe _x layer is used as the pinned layer, the composition ratio x of Fe in the CoFe _x layer is 51 at.
% Or the more, the crystal structure of the CoFe _x layer b
Since cc structure becomes dominant, as the crystal structure (the above IrMn layer deposited on the CoFe _x layer, originally γ
Should be a structure) and the force fixing the magnetization direction is reduced.

Further, generally speaking, the profile of the magnetoresistance effect curve of the bonding film has a problem that the MR ratio does not reach the level targeted by the present invention.
It is desirable that the profile is close to the profile of the magnetoresistance effect curve as described above with reference to FIG. In summing up the facts described above, when manufacturing the magnetic sensor having the spin valve structure of the present invention, CoFe _x
Is preferably in a range of 26 at% or more and less than 51 at%.

As apparent from the above detailed description, the present invention resides in a magnetic sensor, a magnetic head, and a magnetic disk drive. The magnetic sensor according to the present invention is as described in the claims, but also includes the following magnetic sensors. 1. The magnetic sensor according to claim 1, wherein a plurality of ferromagnetic tunnel junction units are connected in series.

2. A plurality of ferromagnetic tunnel junction units are arranged side by side on the substrate, and in the adjacent ferromagnetic tunnel junction units, the first ferromagnetic metal layers or the second ferromagnetic metal layers are integrally formed. 2. The magnetic sensor according to claim 1, wherein the series connection is performed by the connection. 3. A plurality of ferromagnetic tunnel junction units are stacked on the substrate and formed in multiple stages, and in the vertically adjacent ferromagnetic tunnel junction units, the second ferromagnetic metal layer of the lower tunnel junction unit is formed. 2. The magnetic sensor according to claim 1, wherein the series connection is performed by forming a first ferromagnetic metal layer of an upper-stage tunnel junction unit on the upper side.

[0055]

As described above, according to the present invention, a high-performance magnetic sensor having a magnetoresistance ratio (MR ratio) of at least 30% can be provided. Further, according to the present invention, various excellent devices can be provided by using a high-performance magnetic sensor. As a typical device, for example, a magnetic head equipped with a magnetic sensor as a magnetoresistive transducer and a magnetic disk device equipped with the magnetic head, a disk array device equipped with a magnetic sensor, an encoder device equipped with a magnetic sensor, In particular, a contactless encoder device can be mentioned.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a magnetic sensor having a conventional ferromagnetic tunnel junction.

FIG. 2 is a graph showing the magnetoresistance ratio (MR) of the magnetic sensor of FIG. 1;
(Ratio) as a function of coercivity H (Oe).

FIG. 3 is a schematic sectional view showing a preferred example of a magnetic sensor having a ferromagnetic tunnel junction structure according to the present invention.

FIG. 4 is a plan view of a ferromagnetic tunnel junction structure of the magnetic sensor of FIG. 3;

FIG. 5 is a cross-sectional view showing a manufacturing procedure of the magnetic sensor of FIG. 3 in order.

FIG. 6 is a schematic sectional view showing another preferred example of a magnetic sensor having a ferromagnetic tunnel junction structure according to the present invention.

FIG. 7 is a schematic sectional view showing the structure of a sensor element according to the present invention in which N ferromagnetic tunnel junction structures are arranged in series.

FIG. 8 is a schematic cross-sectional view showing the structure of a sensor element in which an N-layer ferromagnetic tunnel junction structure is stacked in multiple stages according to the present invention.

FIG. 9 is a schematic cross-sectional view illustrating a configuration of a magnetic head including a magnetic sensor according to the present invention.

FIG. 10 is a plan view illustrating the configuration of a magnetic disk drive provided with the magnetic sensor of FIG. 9 according to the present invention.

FIG. 11 is a perspective view illustrating the internal structure of the magnetic disk drive of FIG. 10;

FIG. 12 is a plan view illustrating a configuration of a contactless encoder device including a magnetic sensor according to the present invention.

FIG. 13 is a plan view sequentially showing a manufacturing procedure of a magnetic sensor used in the encoder device of FIG. 12;

FIG. 14 shows the MR ratio of the magnetic sensor having a spin-valve structure manufactured in the example, wherein the MR ratio is Fe composition ratio x (F of CoFe _x
5 is a graph plotted as a function of composition ratio of e (at%).

FIG. 15 is a magnetic sensor having a spin valve structure,
The composition ratio of Fe in the CoFe _x constituting the ferromagnetic metal layer is a magneto-resistance effect curves plotted the MR ratio as a function of applied magnetic field but is 26 atomic%.

FIG. 16 shows a magnetic sensor having a spin valve structure.
The composition ratio of Fe in the CoFe _x constituting the ferromagnetic metal layer is a magneto-resistance effect curves plotted the MR ratio as a function of applied magnetic field although a 31 at%.

FIG. 17 shows a magnetic sensor having a spin valve structure.
The composition ratio of Fe in the CoFe _x constituting the ferromagnetic metal layer is a magneto-resistance effect curves plotted the MR ratio as a function of applied magnetic field although a 35 at%.

FIG. 18 is a magnetic sensor having a spin valve structure,
The composition ratio of Fe in the CoFe _x constituting the ferromagnetic metal layer is a magneto-resistance effect curves plotted the MR ratio as a function of applied magnetic field although a 40 at%.

FIG. 19 shows a magnetic sensor having a spin valve structure.
The composition ratio of Fe in the CoFe _x constituting the ferromagnetic metal layer is a magneto-resistance effect curves plotted the MR ratio as a function of applied magnetic field although a 51 at%.

FIG. 20 is a magnetic sensor having a spin valve structure,
The composition ratio of Fe in the CoFe _x constituting the ferromagnetic metal layer is a magneto-resistance effect curves plotted the MR ratio as a function of applied magnetic field although a 57 at%.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Magnetic sensor 2 ... Ferromagnetic tunnel junction unit 6 ... Substrate 10 ... Lower electrode 11 ... 1st ferromagnetic layer 20 ... Insulation barrier layer 30 ... Upper electrode 31 ... 2nd ferromagnetic layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 43/10 G01R 33/06 R (72) Inventor Kazuo Kobayashi 4-chome, Kamikodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa No. 1 Fujitsu Limited F term (reference) 2G017 AD55 AD63 AD65 5D034 BA02 BA08 BA15 5E049 AA04 AA07 AA09 AA10 AC00 AC05 BA12 BA16

Claims (7)

[Claims] 1. A magnetic sensor comprising a ferromagnetic tunnel junction unit including a first ferromagnetic metal layer and a second ferromagnetic metal layer formed thereon with an insulating barrier layer interposed therebetween, wherein: At least one of the first and second ferromagnetic metal layers is
F at a composition ratio of 25 at% or more and less than 51 at%.
A magnetic sensor comprising a CoFe alloy containing e. 2. The method according to claim 1, wherein only one of the first and second ferromagnetic metal layers is made of a CoFe alloy containing Fe at a composition ratio of 25 at% or more and less than 51 at%. The magnetic sensor as described. 3. A method according to claim 1, wherein the first and second ferromagnetic metal layers are both made of a CoFe alloy containing Fe at a composition ratio of 25 at% or more and less than 51 at%. The magnetic sensor according to claim 1, wherein the composition ratio may be the same or different. 4. A magnetic head comprising the magnetic sensor according to claim 1 as a magnetoresistive transducer. 5. A magnetic disk drive equipped with a magnetic head provided with the magnetic sensor according to claim 1. Description: 6. A disk array device equipped with the magnetic sensor according to claim 1. 7. An encoder device comprising the magnetic sensor according to claim 1. Description: