JP2001084532A - Manufacture of magnetoresistance effect element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a method for manufacturing a magnetoresistance effect element capable of forming a ferromagnetic tunnel junction having a resistance value suitable for the size of a practical element in a high yield. SOLUTION: This method for manufacturing a magnetoresistance effect element includes a ferromagnetic single tunnel junction having a structure provided with a dielectric material layer 13 between two ferromagnetic layers 12 and 14 or a ferromagnetic double junction having a structure provided with dielectric layers 13 and 15, between each two layers of three ferromagnetic layers 12, 14 and 16. In this case, this method has a stage for forming a dielectric material film 13a and 15a on the ferromagnetic layers 12 and 14 and a stage for oxidizing or nitriding the dielectric material film by introducing gas containing oxygen or nitrogen or for oxidizing or nitriding 13b and 15b the ferromagnetic material film in plasma by a glow-discharge after introducing the gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a tunnel junction type magnetoresistive element having a laminated structure of ferromagnetic layer / dielectric layer / ferromagnetic layer, and more particularly to a reproducing magnetic head for a high density magnetic disk drive. The present invention relates to a method for manufacturing a magnetoresistive element applied to a magnetic recording element (magnetoresistive memory, MRAM) and a magnetic field sensor.

[0002]

2. Description of the Related Art The magnetoresistance effect is a phenomenon in which the electric resistance changes when a magnetic field is applied to a ferromagnetic material. A magnetoresistive effect element (MR element) using this effect has excellent temperature stability and a wide operating temperature range. Therefore, it is used for a magnetic head or a magnetic sensor. Effect memory, MRAM) and the like. These magnetoresistive elements are required to have high sensitivity to an external magnetic field and a high response speed.

In recent years, a magnetoresistance effect element having a sandwich film in which a dielectric layer is inserted between two ferromagnetic layers and utilizing a tunnel current flowing perpendicularly to the film surface, a so-called ferromagnetic tunnel junction element (tunnel junction) Type magnetoresistive element,
TMR) has been found. A ferromagnetic tunnel junction device exhibits a magnetoresistance ratio of 20% or more (J. Appl.
hys. 79, 4724 (1996)), the possibility of application to magnetic heads and magnetoresistive memories has been increasing.

In this ferromagnetic tunnel junction, a thin Al layer having a thickness of 1.2 to 2.0 mm is formed on a ferromagnetic layer, and the surface thereof is exposed to oxygen plasma to form a dielectric layer made of Al ₂ O _3. It is manufactured by a method of forming a body layer.

However, in this method, Al is very easily oxidized, and the oxidation time is as short as several seconds to several tens of seconds. Therefore, there are many problems in yield, distribution in a wafer, and the like. In this case, there is a problem that if Al remains without being oxidized, the MR change rate is significantly reduced. Further, in order to apply a ferromagnetic tunnel junction device to a device such as a magnetoresistive memory device or a magnetic head, it is necessary that the resistance is small to some extent in practical device dimensions in order to reduce the influence of thermal noise. However, in the above method, a practical low resistance value cannot be obtained unless an Al layer thinner than 1.2 nm is oxidized to form a thin dielectric layer. Further, there is a problem that it is difficult to obtain a sufficient yield for practical use.

As an example of another manufacturing method, see Japanese Patent Application Laid-Open
63254, JP-A-6-244777, JP-A-8-70
148, JP-A-8-70149, JP-A-8-31654
8 and the like are known. In these methods, Al is formed on a ferromagnetic layer and then exposed to the air to convert Al to Al ₂ O ₃ . in this way,
Dust in the air causes pinholes in the dielectric layer,
There is a problem that the dielectric layer is contaminated with carbon oxides, nitrogen oxides and the like, and the yield is reduced.

As another example of the manufacturing method, see Japanese Patent Application Laid-Open
A method described in US Pat.
In this method, after Al is formed on the ferromagnetic layer, pure oxygen is introduced into the chamber to convert Al into Al ₂ O ₃ . According to this method, the dispersion of the resistance value and the magnetoresistance value within the wafer is reduced, but the time required for the oxidation is increased to 10 to 20 minutes. Further, when an MRAM or the like having a resistance value (RPA) of several hundred Ω μm ² and an element area of about 1 μm ² is assumed, it is too small to obtain a resistance value in a wide range according to the element size. .

Further, a ferromagnetic single tunnel junction or a ferromagnetic double tunnel junction via magnetic particles dispersed in a dielectric has been proposed (Phys. Rev. B56 (1)
0), R5747 (1997);
4-2, (1999); Appl. Phys. Let
t. 73 (19), 2829 (1998)). Also in these ferromagnetic tunnel junction elements, a magnetoresistance change rate of 20% or more can be obtained, so that there is a possibility of application to a magnetic head or a magnetoresistance effect memory. In these proposals, the dielectric layer of Al ₂ O ₃ by exposing the surface to an oxygen plasma after forming the Al of Al ₂ O ₃ or a direct sputtering, or on the ferromagnetic layer on the ferromagnetic layer Is used. Therefore, even with these methods, there is a problem that it is difficult to obtain a sufficient yield for practical use due to the variation in the resistance value and the magnetoresistance value within the wafer as in the case described above.

As described above, in order to apply a ferromagnetic tunnel junction device to a device such as a magnetoresistive effect memory or a magnetic head, the resistance value of the practical device is somewhat low in order to reduce the influence of thermal noise. It is necessary to form a ferromagnetic tunnel junction having a resistance value that meets the above requirements with good yield. However, it has been difficult to realize such a conventional tunnel junction forming method.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a magnetoresistive element capable of forming a ferromagnetic tunnel junction having a resistance value suitable for a practical element size with a high yield.

[0011]

According to the present invention, there is provided a method of manufacturing a magneto-resistance effect element, comprising: a ferromagnetic single tunnel junction having a structure in which a dielectric layer is provided between two ferromagnetic layers; In manufacturing a magnetoresistive element including a ferromagnetic double tunnel junction having a structure in which a dielectric layer is provided between each layer of a magnetic layer, a step of forming a dielectric film on the ferromagnetic layer and oxygen or nitrogen Introducing a gas contained therein to oxidize or nitride the dielectric film, or introducing the gas and then performing glow discharge to oxidize or nitride the dielectric film in plasma.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION
A ferromagnetic single tunnel junction having a laminated structure of ferromagnetic layer / dielectric layer / ferromagnetic layer, in which a dielectric layer is provided between the ferromagnetic layers, or a dielectric between three ferromagnetic layers. It includes a ferromagnetic double tunnel junction having a layered structure of ferromagnetic layer / dielectric layer / ferromagnetic layer / dielectric layer / ferromagnetic layer.

The material of the ferromagnetic layer is Fe, Co, N
i or an alloy containing these elements is used. As long as the ferromagnetism is not impaired, Ag, Cu, A
u, Al, Mg, S, Bi, Ta, B, C, O, N, S
Some non-magnetic elements such as i, Pd, Pt, Zr, Ir, W, Mo, and Nb may be contained. The ferromagnetic layer is
In order to adjust the switching magnetic field, a two-layer film (or a multilayer film) including a soft magnetic layer and a hard magnetic layer may be used.

As the material of the dielectric layer, Al, Si, M
g, a rare earth element or an oxide or nitride of an alloy containing these elements is used.

The magnetoresistive element of the present invention can be applied to a magnetoresistive magnetic head, a magnetic recording element, a magnetic field sensor and the like. In this case, it is preferable that the ferromagnetic layer has uniaxial anisotropy. In the case of a ferromagnetic single tunnel junction, it is preferable to design one of the two ferromagnetic layers as a pinned layer. In the case of a ferromagnetic double tunnel junction, two of the three ferromagnetic layers are formed. It is preferable to design as a pin layer.

A ferromagnetic double tunnel junction has two dielectric layers.
Because of the layers, an element having excellent bias dependency can be manufactured, and the resistance value is averaged, thereby further improving the yield. If a mixed layer of a ferromagnetic material and a dielectric material is used as an intermediate ferromagnetic material, the yield is further improved.

When the intermediate ferromagnetic layer of the ferromagnetic double tunnel junction is designed as a hard layer, a ferromagnetic layer sandwiched between two dielectric layers or a mixed layer of a ferromagnetic material and a dielectric material is used. It is preferable to use an alloy in which an element such as Pt, Pd, or Cr is added to a Co or Fe—Co alloy as the ferromagnetic material to be included.

When it is desired to pin the ferromagnetic layer, an anti-ferromagnetic layer may be provided in contact with the ferromagnetic layer to generate an exchange bias magnetic field. Examples of the material of the antiferromagnetic layer include FeMn,
PtMn, PtCrMn, NiMn, IrMn, Ni
O, Fe ₂ O ₃ or the like is used.

In the present invention, the laminated body constituting the ferromagnetic single tunnel junction or the ferromagnetic double tunnel junction may be provided on a substrate via an underlayer, and a protective layer may be provided on the laminated body. You may. Materials for these underlayers and protective layers include Ta, Ti, Pt, Pd, Au, T
It is preferable to use i / Pt, Ta / Pt, Ti / Pd, Ta / Pd, or the like.

Each layer constituting the ferromagnetic tunnel junction included in the magnetoresistive element of the present invention is formed by various sputtering methods, vapor deposition methods, MBE methods and the like. Hereinafter, a case where Al ₂ O ₃ is formed as a dielectric layer by using a sputtering method will be described.

FIGS. 1A to 1C show an example of a method for manufacturing a magnetoresistive element including a ferromagnetic single tunnel junction according to the present invention.
This will be described with reference to FIG. FIGS. 1A to 1C show a first ferromagnetic layer 12, a dielectric layer (tunnel barrier layer) 13, and a second ferromagnetic layer 1 on a substrate 11 using a sputtering apparatus.
4 shows an example of continuously forming a film.

The substrate 11 is placed in a sputtering apparatus, and the initial degree of vacuum is set to 1 × 10 ⁻⁶ Torr or less. The initial vacuum degree is 5 × 10 ⁻⁷ Torr or less, and further 1 × 10 ⁻⁷ Torr.
It is more preferable to set r or less. Thereafter, an inert gas such as Ar is introduced to set a predetermined pressure. First, a first ferromagnetic layer 12 is formed on a substrate 11 by sputtering a ferromagnetic target. Next, an Al ₂ O ₃ target is sputtered. Under the condition of the degree of vacuum as described above, A
By sputtering the l ₂ O ₃ target, an Al ₂ O _x layer 13a having oxygen deficiency is formed (FIG. 1A).

Next, oxygen or a mixed gas of oxygen and a rare gas is introduced into the sputtering apparatus without breaking the vacuum,
The Al ₂ O _x layer 13a is formed with oxygen gas (O ₂ pressure: 10 mTorr).
Above) or by exposure to oxygen plasma (O ₂ pressure: 1 mTorr or more) generated by glow discharge, the Al ₂ O _x is oxidized to be converted into an Al ₂ O ₃ layer 13b having a stoichiometric composition without oxygen deficiency. Thus, the dielectric layer 13 is formed (FIG. 1B). At this time, some Al ₂ O _x may remain,
Al ₂ O _x may be completely oxidized. Even if Al ₂ O _x is not completely oxidized and remains, the MR change rate is not reduced unlike the case where Al remains in the conventional technique, and the resistance value is small. Moreover, when converting the Al ₂ O _x is oxidized Al ₂ O _3, it takes longer oxidation time compared to the case of direct oxidation of Al as in the conventional method, controllability of the very thin Al ₂ O ₃ Can be manufactured well.

Next, after exhausting oxygen, a ferromagnetic target is sputtered to form a second ferromagnetic layer 14 (FIG. 1C). In this manner, the basic structure of the magnetoresistive element including the ferromagnetic single tunnel junction element can be formed.

In the case where the second ferromagnetic layer 14 is a pinned layer, as shown in FIG.
An antiferromagnetic layer 21 is formed on the substrate 4. When the first ferromagnetic layer 12 is used as a pinned layer, as shown in FIG. 2B, an antiferromagnetic layer 22 is formed on the substrate 11 and then the first ferromagnetic layer 12 is formed. , Dielectric layer 13 and second ferromagnetic layer 14
Is formed.

In the method of the present invention, since the dielectric layer is formed without breaking the vacuum as described above, the dielectric layer is not affected by impurities. Also, Al ₂ O _x is oxidized to Al ₂ O ₃
In the case of converting to Al, the oxidation time is longer than in the case of directly oxidizing Al as in the conventional method,
l ₂ O ₃ can be produced with good controllability. In addition, by adjusting the degree of conversion from Al ₂ O _x to Al ₂ O ₃ , the resistance value can be arbitrarily adjusted.

When it is desired to provide a bias-dependent offset, the ferromagnetic layer may be formed, and then oxygen may be introduced to slightly oxidize the ferromagnetic layer. In the present invention, since Al ₂ O _x is formed on the ferromagnetic layer and then only the surface thereof is oxidized, the oxidation of the surface of the underlying ferromagnetic layer is suppressed in this step. Therefore, in the method of the present invention, the bias point can be designed with good controllability. On the other hand, in the conventional method, A
If 1 is excessively oxidized, the oxide film unintentionally grows on the ferromagnetic layer, so that it is difficult to control the bias point.

[0028] In the above oxidizing the Al ₂ O _x Al ₂
Although the case of conversion to O ₃ has been described, a similar method can be applied to oxides such as SiO ₂ and MgO.

Further, for example, after forming AlN _x , nitrogen or a mixed gas of nitrogen and a rare gas is introduced, and if necessary, glow discharge is performed to generate plasma, and AlN _x is converted to AlN by nitriding. By doing so, a dielectric layer may be formed.

Another example of a method of manufacturing a magnetoresistive element including a ferromagnetic double tunnel junction according to the present invention is shown in FIGS.
This will be described with reference to FIG. FIGS. 3A to 3C show the first ferromagnetic layer 1 on a substrate 11 using a sputtering apparatus.
2, first dielectric layer (tunnel barrier layer) 13, second ferromagnetic layer 14, second dielectric layer (tunnel barrier layer) 1
5 shows an example in which the third ferromagnetic layer 16 is continuously formed.

Firstly, in the same manner as FIG. 1 (a) ~ (c) , forming a first ferromagnetic layer 12 on the substrate 11, Al ₂
After forming the O _x layer 13a, the surface side the Al ₂ O ₃ layer 1
3b, a first dielectric layer 13 is formed, and a second ferromagnetic layer 14 is further formed. Next, an Al ₂ O ₃ target is sputtered to form an Al ₂ O _x layer 1 on the second ferromagnetic layer 14.
5a is formed (FIG. 3A). Thereafter, oxygen or a mixed gas of oxygen and a rare gas is introduced into the sputtering apparatus, and A
l ₂ O _x layer 15a of the oxygen gas (O ₂ pressure: 10 mTorr or higher) or oxygen plasma generated by glow discharge (O
₍₂ pressure: 1 mTorr or more) to oxidize Al ₂ O _x and convert it to an Al ₂ O ₃ layer 15b having a stoichiometric composition without oxygen deficiency. Thus, the dielectric layer 15 is formed (FIG. 3).
(B)). At this time, some Al ₂ O _x may remain,
l ₂ O _x may be completely oxidized. Next, after exhausting oxygen, a ferromagnetic target is sputtered to form a second ferromagnetic layer 16 (FIG. 3C).

Also in this case, since the dielectric layer is formed without breaking the vacuum, the dielectric layer is not affected by impurities.
Moreover, when converting the Al ₂ O _x is oxidized Al ₂ O _3, it takes longer oxidation time compared to the case of direct oxidation of Al as in the conventional method, controllability of the very thin Al ₂ O ₃ Can be manufactured well. In addition, by adjusting the degree of conversion from Al ₂ O _x to Al ₂ O ₃ , the resistance value can be arbitrarily adjusted.

The first and third ferromagnetic layers 12, 1
When the pin 6 is a pinned layer, as shown in FIG.
An antiferromagnetic layer 23 is formed between the first ferromagnetic layer 12 and the first ferromagnetic layer 12, and an antiferromagnetic layer 24 is formed on the third ferromagnetic layer 16.

Further, an antiferromagnetic layer may be formed in contact with the second ferromagnetic layer 14 or an antiferromagnetic layer may be interposed between the second ferromagnetic layers 14.

Next, a magnetic recording element (MRAM) and a magnetoresistive head will be described as examples of a device to which the magnetoresistive element of the present invention is applied.

The magnetic recording element may have a structure in which a ferromagnetic tunnel junction element according to the present invention is stacked on a transistor as shown in FIGS. 5 and 6, or a diode and a present invention as shown in FIGS. May be laminated.

Referring to FIGS. 5 and 6, a magnetic recording element having a structure in which a ferromagnetic tunnel junction element is stacked on a transistor will be described. FIG. 5 is an equivalent circuit diagram of the magnetic recording element, and FIG. 6 is a sectional view of the magnetic recording element. As shown in FIG. 6, a transistor 30 including a silicon substrate 1, a gate electrode 31, source and drain regions 32 and 33 is formed. The gate electrode 31 constitutes a read word line (WL1). A write word line (WL2) 41 is formed on the gate electrode 31 via an insulating layer. Drain region 33 of transistor 30
Is connected to a contact metal 42, and further to the contact metal 42, a base layer 43 is connected. A word line (WL2) 41 for writing on the underlayer 43
A tunnel junction type magnetoresistive element (TMR) 10 as shown in FIGS. 1 to 4 is formed at a position corresponding to above. A bit line (BL) is placed on this TMR10.
44 are connected. As shown in the equivalent circuit diagram of FIG. 5, the recording cells including the transistor 30 and the TMR 10 are arranged in a matrix. Transistor 30
The read word line (WL1) composed of the gate electrode 31 of FIG.
1 is arranged in parallel. The bit line (BL) 44 connected to the other end (upper part) of the TMR 10 is connected to the word line (WL1) 31 and the word line (WL).
2) It is arranged orthogonal to 41.

Referring to FIGS. 7 and 8, a magnetic recording element having a structure in which a diode and a ferromagnetic tunnel junction element are stacked will be described. FIG. 7 is an equivalent circuit diagram of the magnetic recording element, and FIG. 8 is a perspective view of the magnetic recording element. As shown in FIG. 7 and FIG. 8, the recording cells composed of a stacked body of the diode 50 and the TMR 10 are arranged in a matrix. The stacked body of the diode 50 and the TMR 10 is formed on the bit line (BL) 61, and one end of the diode 50 and the bit line (BL) 61 are connected. TM
The other end of R10 is connected to a word line (WL) 62 arranged orthogonal to the bit line (BL) 61.

FIG. 9 is a perspective view of a magnetic head assembly equipped with a magnetoresistive head including a tunnel junction type magnetoresistive element according to the present invention. The actuator arm 71 is provided with a hole to be fixed to a fixed shaft in the magnetic disk device, and has a bobbin or the like for holding a drive coil (not shown). A suspension 72 is fixed to one end of the actuator arm 71. At the tip of the suspension 72, a head slider 73 mounted with a magnetoresistive head including the tunnel junction type magnetoresistive elements of the above-described embodiments is mounted. A lead wire 74 for writing and reading signals is wired to the suspension 72, and one end of the lead wire 74 is connected to each electrode of a magnetoresistive head incorporated in the head slider 73. The end is connected to the electrode pad 75.

FIG. 10 is a perspective view showing the internal structure of a magnetic disk drive on which the magnetic head assembly shown in FIG. 9 is mounted. The magnetic disk 101 is mounted on a spindle 102 and is rotated by a motor (not shown) that responds to a control signal from a drive controller (not shown). 9 is fixed to a fixed shaft 103, and supports a suspension 72 and a head slider 73 at the tip thereof. When the magnetic disk 101 rotates, the medium facing surface of the head slider 73 is held in a state of floating above the surface of the magnetic disk 101 by a predetermined amount, and information is recorded and reproduced. At the base end of the actuator arm 71, a voice coil motor 104, which is a type of linear motor, is provided. The voice coil motor 104 includes a drive coil (not shown) wound around a bobbin portion of the actuator arm 71, and a magnetic circuit including a permanent magnet and an opposing yoke which are opposed to each other so as to sandwich the coil. Actuator arm 71 is above and below fixed shaft 103.
It is held by a ball bearing (not shown) provided at a location, and is rotatable and slidable by a voice coil motor 104.

When the tunnel type magneto-resistance effect element according to the present invention is applied to a magneto-resistance effect head, the spins of the adjacent ferromagnetic layers are made substantially orthogonal by film formation or heat treatment in a magnetic field. In this way, a linear response to a magnetic field leaking from the magnetic disk can be obtained, and any head structure can be used.

[0042]

Embodiments of the present invention will be described below.

(Example 1) An example in which a magnetoresistive element having a ferromagnetic single tunnel junction having a structure shown in FIG. 2B using Al ₂ O ₃ as a dielectric layer (tunnel barrier layer) was manufactured. 11 (a)-(c) and FIGS. 12 (a)-
This will be described with reference to FIG.

After placing the Si / SiO ₂ substrate 11 in a sputtering apparatus and setting the initial vacuum degree to 2 × 10 ⁻⁷ Torr,
The pressure was set to 1 × 10 ⁻³ Torr by introducing Ar.
On Si / SiO ₂ substrate 11, continuous ferromagnetic layer 12 of an antiferromagnetic layer 22, a thickness of 3 nm CoFe consisting underlayer 25, a thickness of 17 nm Ir ₂₂ Mn ₇₈ consisting of a thickness of 5 nm Ta Formed. Next, using the following method (A) or (B), a dielectric layer 13 made of Al ₂ O ₃ was formed on the ferromagnetic layer 12 made of CoFe.

(A) An Al ₂ O ₃ target was sputtered in Ar gas to form an Al ₂ O _x film. At this time, Al ₂ O _x
Was changed in the range of 1.5 to 2.5 nm. Then, by introducing pure oxygen into the sputtering apparatus without breaking the vacuum, to oxidize the Al ₂ O _x from the surface side in oxygen gas Al ₂
It was converted to O ₃ to form a dielectric layer 13. At this time, by varying the oxidation time, Al from Al ₂ O _{x 2} O ₃
The degree of conversion to was adjusted.

(B) An Al ₂ O ₃ target was sputtered in Ar gas to form an Al ₂ O _x film. At this time, Al ₂ O _x
Was changed in the range of 1.5 to 2.5 nm. Thereafter, pure oxygen is introduced into the sputtering apparatus without breaking the vacuum, and glow discharge is performed to generate plasma. In the oxygen plasma, Al ₂ O _x is oxidized from the surface side and converted into Al ₂ O ₃ , and the dielectric layer is formed. 13 was formed. At this time, by varying the power and oxidation time during the glow discharge was adjusted conversion degree of the Al ₂ O ₃ from Al ₂ O _x.

By sputtering in Ar gas under the same conditions as described above, a 5 nm thick
Ferromagnetic layer 14 of CoFe and 15 nm thick NiFe, and protective layer 26 of 5 nm thick Ta
Was formed continuously (FIG. 11A).

The above laminated film was processed into a lower wiring shape having a width of 50 μm by using ordinary photolithography technology and ion milling technology (FIG. 11B).

A resist pattern R1 for defining a junction is formed by a usual photolithography technique,
a The protective layer 26 and the CoFe / NiFe ferromagnetic layer 14 were ion-milled. At this time, the bonding area was changed variously (FIG. 11C).

After depositing Al ₂ O ₃ with a thickness of 300 nm by electron beam evaporation while leaving the resist pattern R 1, the resist pattern R 1 and the Al ₂ O ₃ thereon are lifted off, and interlayer insulation is applied to portions other than the junction. A film 27 was formed (FIG. 12A).

After forming a resist pattern R2 covering an area other than the electrode wiring forming area, the surface was cleaned by reverse sputtering (FIG. 12B).

After depositing Al on the entire surface, the resist pattern R2 and the Al thereon were lifted off to form an Al electrode wiring 28 (FIG. 12C). Thereafter, the ferromagnetic layer 12 was introduced into a heat treatment furnace in a magnetic field, and unidirectional anisotropy was introduced into the ferromagnetic layer 12 serving as a pin layer.

Various measurements were performed on the sample A or B on which the dielectric layer was formed by using the above method (A) or (B). These results are shown in FIGS.

FIG. 13 shows the magnetoresistance effect curves of Samples A and B. As shown in FIG.
An MR change rate of 21% is obtained in a small magnetic field e. Similarly, in sample B, an MR change rate of 25% is obtained with a small magnetic field of 25 Oe.

FIG. 14 shows the junction area dependence of the MR ratio and the resistance value (R) for the samples A and B. FIG.
As shown in FIG. 5, it can be seen that the MR change rate hardly depends on the junction area.

FIG. 15 shows the dependence of the resistance value (R) on the oxidation time of Sample A and the dependence of the resistance value (R) on the oxidation time of Sample B using the applied power during plasma oxidation as a parameter. All data are obtained when the bonding area is 200 μm ² . As shown in FIG. 15, the oxidation time and the applied power during plasma oxidation were changed from Al ₂ O _x to Al ₂ O _3.
It can be seen that the resistance value can be adjusted by adjusting the degree of conversion to.

FIG. 16 shows the dependency of the MR ratio and the resistance value (R) on the Al ₂ O _x film thickness (t) of the samples A and B. All are data when the oxidation time or the applied power during plasma oxidation is kept constant. As shown in FIG. 16, when the Al ₂ O _x film thickness is large to some extent, the resistance value and the MR ratio do not change so much. After forming a somewhat thick Al ₂ O _x film, only the surface is oxidized and A
By converting to l ₂ O ₃ , a desired magnetoresistance effect can be obtained, so that the yield of ferromagnetic tunnel junction devices can be improved.

(Example 2) An example in which a magneto-resistance effect element having a ferromagnetic double tunnel junction having the structure shown in FIG. 4 and using Al ₂ O ₃ as a dielectric layer (tunnel barrier layer) is shown in FIG. 17 (a)-(c) and FIGS. 18 (a), (b)
This will be described with reference to FIG.

After placing the Si / SiO ₂ substrate 11 in a sputtering apparatus and setting the initial degree of vacuum to 2 × 10 ⁻⁷ Torr,
The pressure was set to 1 × 10 ⁻³ Torr by introducing Ar.
On a Si / SiO ₂ substrate 11, an underlayer 25 made of Ta with a thickness of 5 nm, an antiferromagnetic layer 22 made of Fe—Mn with a thickness of 20 nm, and a ferromagnetic layer made of NiFe with a thickness of 5 nm and CoFe with a thickness of 3 nm Layer 12 was formed continuously. Next, a dielectric layer 13 made of Al ₂ O ₃ was formed on the ferromagnetic layer 12 using the following method (A2) or (B2).

(A2) An Al ₂ O ₃ target was sputtered in Ar gas to form an Al ₂ O _x film. At this time, Al ₂
The thickness of the O _x was varied in the range of 1.5 to 2.5.
Thereafter, pure oxygen is introduced into the sputtering apparatus without breaking the vacuum, and Al ₂ O _x is oxidized from the surface side in oxygen gas to form Al.
_After conversion to ₂ O ₃ , the dielectric layer 13 was formed. At this time, by varying the oxidation time, Al from Al ₂ O _{x 2} O ₃
The degree of conversion to was adjusted.

(B2) An Al ₂ O ₃ target was sputtered in Ar gas to form an Al ₂ O _x film. At this time, Al ₂
The thickness of the O _x was varied in the range of 1.5 to 2.5.
Thereafter, pure oxygen is introduced into the sputtering apparatus without breaking the vacuum, and glow discharge is performed to generate plasma. In the oxygen plasma, Al ₂ O _x is oxidized from the surface side and converted into Al ₂ O ₃ , and the dielectric layer is formed. 13 was formed. At this time, by changing the power and oxidation time during glow discharge, Al
_The degree of conversion from ₂ O _x to Al ₂ O ₃ was adjusted.

By sputtering in Ar gas under the same conditions as described above, a thickness of 3 nm is formed on the dielectric layer 13.
The ferromagnetic layer 14 of CoFe was formed. Subsequently, the dielectric film 15 was formed by the method (A2) or (B2) in the same manner as described above. Thereafter, the ferromagnetic layer 16 made of 3 nm-thick CoFe and 5 nm-thick NiFe and the antiferromagnetic layer 2 made of 20-nm-thick Fe—Mn are formed by sputtering in Ar gas under the same conditions as described above.
4 and a protective layer 26 made of Ta having a thickness of 5 nm was continuously formed. In this example, each layer is formed through a metal mask to form a lower wiring shape having a width of 1 mm (FIG. 17A).

A resist pattern R1 for defining a junction is formed by ordinary photolithography, and the protective layer 26, the antiferromagnetic layer 24, the ferromagnetic layer 16, and the dielectric layer 1 are formed.
5 and the ferromagnetic layer 14 were ion-milled. At this time, the bonding area was changed variously (FIG. 17B).

After depositing Al ₂ O ₃ with a thickness of 300 nm by electron beam evaporation while leaving the resist pattern R 1, the resist pattern R 1 and Al ₂ O ₃ thereon are lifted off to form an interlayer insulating film 27 ( FIG.
(C)).

After forming a resist pattern R2 covering an area other than the electrode wiring formation area, the surface was cleaned by reverse sputtering (FIG. 18A).

After depositing Al on the entire surface, the resist pattern R2 and the Al thereon were lifted off to form an Al electrode wiring 28 (FIG. 18B). Thereafter, the resultant was introduced into a heat treatment furnace in a magnetic field, and unidirectional anisotropy was introduced into the ferromagnetic layers 12 and 16 serving as pin layers.

Various measurements were performed on the sample A2 or B2 on which a dielectric layer was formed by using the above method (A2) or (B2). These results are shown in FIGS.

FIG. 19 shows the magnetoresistance effect curves of Samples A2 and B2. As shown in FIG. 19, in the sample A2, an MR change rate of 23% is obtained in a small magnetic field of 30 Oe. Similarly, in sample B2, an MR change rate of 27.5% is obtained with a small magnetic field of 35 Oe.

FIG. 20 shows the MR of samples A2 and B2.
4 shows the junction area dependence of the rate of change and the resistance value (R). As shown in FIG. 20, the MR change rate hardly depends on the junction area.

FIG. 21 shows the oxidation time dependence of the resistance value (R) for sample A2 and the resistance value (R) for sample B2.
Is shown with the applied power during plasma oxidation as a parameter. As shown in FIG. 21, the oxidation time and the applied power during plasma oxidation were changed to change Al ₂ O _x to Al ₂ O _3.
It can be seen that the resistance can be adjusted by adjusting the degree of conversion to O ₃ .

FIG. 22 shows the MR of samples A2 and B2.
4 shows the dependence of the rate of change and the resistance value (R) on the Al ₂ O _x film thickness (t). All are data when the oxidation time or the applied power during plasma oxidation is kept constant. As shown in FIG. 22, when the Al ₂ O _x film thickness is somewhat large, the resistance value and the MR change rate do not change so much. After forming a somewhat thick Al ₂ O _x film, a desired magnetoresistance effect can be obtained by oxidizing only the surface and converting it to Al ₂ O ₃ , thereby improving the yield of the ferromagnetic tunnel junction device. it can.

(Example 3) In the same manner as in Examples 1 and 2, 11 types of magnetoresistive elements having a ferromagnetic single tunnel junction or a ferromagnetic double tunnel junction as shown in Table 1 were manufactured. Table 1 shows the laminated structure of each element of Samples 1 to 11. In addition, the sample with an even sample number is subjected to plasma oxidation or plasma nitridation after forming a dielectric layer. In the case of an odd-numbered sample number, after forming a dielectric layer,
Oxidation or nitridation is performed in an O ₂ or N ₂ atmosphere at 30 mTorr.

Table 1 shows the MR change rate and the resistance value of each sample, and the variation of these values in the wafer. Table 1 shows that the variation in the MR change rate and the resistance value within the wafer is relatively small. Therefore,
It is understood that the ferromagnetic tunnel junction device can be manufactured with high yield by using the method of the present invention.

[0074]

[Table 1]

[0075]

As described in detail above, by using the method of the present invention, a high quality dielectric layer can be formed with good controllability, and a tunnel junction type magnetoresistive element can be manufactured with good yield. The present invention can be applied to a resistance effect type head, a magnetic field sensor, a magnetic storage element, and the like.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a method for manufacturing a ferromagnetic single tunnel junction device according to the present invention in the order of steps.

FIG. 2 is a cross-sectional view of a ferromagnetic single tunnel junction device having an antiferromagnetic material according to the present invention.

FIG. 3 is a sectional view showing a method for manufacturing a ferromagnetic double tunnel junction device according to the present invention in the order of steps.

FIG. 4 is a sectional view of a ferromagnetic double tunnel junction device having an antiferromagnetic material according to the present invention.

FIG. 5 is an equivalent circuit diagram illustrating an example of a magnetic recording element (MRAM).

FIG. 6 is a cross-sectional view illustrating an example of a magnetic recording element (MRAM).

FIG. 7 is an equivalent circuit diagram showing another example of the magnetic recording element (MRAM).

FIG. 8 is a perspective view showing another example of the magnetic recording element (MRAM).

FIG. 9 is a perspective view of a magnetic head assembly equipped with a magnetoresistive head including a tunnel junction type magnetoresistive element according to the present invention.

10 is a perspective view showing the internal structure of a magnetic disk drive on which the magnetic head assembly shown in FIG. 9 is mounted.

FIG. 11 is a cross-sectional view illustrating a method of manufacturing the ferromagnetic single tunnel junction device of Example 1 in the order of steps.

FIG. 12 is a cross-sectional view illustrating a method of manufacturing the ferromagnetic single tunnel junction device of Example 1 in the order of steps.

FIG. 13 is a diagram showing magnetoresistance effect curves of samples A and B of Example 1.

FIG. 14 is a diagram showing the dependence of the MR ratio and the resistance value (R) on the junction area for samples A and B of Example 1.

FIG. 15 is a diagram showing the dependence of the resistance value (R) on the oxidation time of the sample A of Example 1 and the dependence of the resistance value (R) on the oxidation time of the sample B using the applied power during plasma oxidation as a parameter.

FIG. 16 is a diagram showing the dependence of MR ratio and resistance value (R) on Al ₂ O _x film thickness (t) for samples A and B of Example 1.

FIG. 17 is a cross-sectional view illustrating a method of manufacturing the ferromagnetic double tunnel junction device of Example 2 in process order.

FIG. 18 is a cross-sectional view illustrating a method of manufacturing the ferromagnetic double tunnel junction device of Example 2 in the order of steps.

FIG. 19 is a view showing the magnetoresistance effect curves of Samples A2 and B2 of Example 2.

FIG. 20 is a diagram showing MR of samples A2 and B2 of Example 2.
The figure which shows the junction area dependence of a rate of change and resistance value (R).

FIG. 21 shows the dependence of the resistance value (R) on the oxidation time of Sample A2 of Example 2 and the resistance value (R) of Sample B2.
FIG. 4 is a diagram showing the oxidation time dependence of the plasma as a parameter with applied power during plasma oxidation.

FIG. 22 shows MR of samples A2 and B2 of Example 2.
Al of change rate and resistance value (R) _TwoO_xDependence on film thickness (t)
FIG.

[Explanation of symbols]

11 ... substrate 12 ... first ferromagnetic layer 13 ... dielectric layer (tunnel barrier layer) 13a ... Al ₂ O _x layer, 13a ... Al ₂ O ₃ layer 14: second ferromagnetic layer 15 ... dielectric layer ( (Tunnel barrier layer) 15a: Al ₂ O _x layer, 15a: Al ₂ O ₃ layer 16: third ferromagnetic layer 21, 22, 23, 24: antiferromagnetic layer 25: underlayer 26: protective layer 27: interlayer Insulating layer 28 ... Electrode wiring 30 ... Transistor 31 ... Gate electrode (read word line) 32,33 ... Source / drain region 41 ... Write word line 42 ... Contact metal 43 ... Under layer 44 ... Bit line 50 ... Diode 61 ... Bit line 62 Word line 71 Actuator arm 72 Suspension 73 Head slider 74 Lead wire 75 Electrode pad 101 Magnetic disk 102: spindle 103: fixed shaft 104: voice coil motor

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Koichiro Inomata 1 Kosuka Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa F-term in the Toshiba R & D Center (reference) 2G017 AA01 AD55 AD59 AD62 AD63 AD65 5D034 BA03 BA15 BA21 DA07

Claims (4)

[Claims] 1. A ferromagnetic single tunnel junction having a structure in which a dielectric layer is provided between two ferromagnetic layers, or a ferromagnetic structure having a structure in which a dielectric layer is provided between respective layers of three ferromagnetic layers. In manufacturing a magnetoresistive element including a magnetic double tunnel junction, a step of forming a dielectric film on a ferromagnetic layer, and a step of oxidizing or nitriding the dielectric film by introducing a gas containing oxygen or nitrogen. And glow discharge after introducing the gas to oxidize or nitride the dielectric film in the plasma. 2. A ferromagnetic double tunnel junction having a structure in which a dielectric layer is provided between each of the three ferromagnetic layers, wherein the ferromagnetic layer sandwiched between the two dielectric layers is a dielectric material. 2. The method for manufacturing a magnetoresistive element according to claim 1, wherein the method is formed of a mixed layer of iron and a ferromagnetic material. 3. The method according to claim 1, wherein the ferromagnetic layer is made of Fe, Co, Ni, or an alloy containing these elements. 4. The method according to claim 1, wherein the dielectric layer is made of Al, Si, Mg, a rare earth element, or a gold oxide or nitride containing these elements. A method for manufacturing a magnetoresistive element.