JP3472207B2 - Method of manufacturing magnetoresistive element - Google Patents

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 effect element including a laminated structure of a ferromagnetic layer / dielectric layer / ferromagnetic layer, and more particularly to a reproducing magnetic head for a high density magnetic disk device. , A magnetic recording element (magnetoresistive effect memory, MRAM), and a method of manufacturing a magnetoresistive effect element applied to a magnetic field sensor.

[0002]

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

Recently, a so-called ferromagnetic tunnel junction element (tunnel junction) 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 Type magnetoresistive effect element,
TMR) has been found. The ferromagnetic tunnel junction element exhibits a magnetoresistance change rate of 20% or more (J. Appl. P.
hys. 79, 4724 (1996)), the possibility of application to magnetic heads and magnetoresistive memory has increased.

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 then the surface thereof is exposed to oxygen plasma to form a dielectric layer made of Al ₂ O _3. It is produced by a method of forming a body layer.

However, in this method, Al is extremely easily oxidized, and the oxidation time is short at several seconds to several tens seconds, so that there are many problems in terms of yield and distribution in the wafer. In this case, if Al remains without being oxidized, there is a problem that the MR change rate is significantly reduced. Further, in order to apply the ferromagnetic tunnel junction element to a device such as a magnetoresistive effect memory element or a magnetic head, it is necessary that the resistance value is low to some extent in practical element 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. Therefore, variations in the resistance value and the magnetoresistive value within the wafer occur. Further, there is a problem that it becomes more remarkable and it is difficult to obtain a sufficient yield for practical use.

As another example of the manufacturing method, Japanese Patent Laid-Open No.
63254, JP-A-6-244477, and JP-A-8-70.
148, JP-A-8-70149, and JP-A-8-31654.
The method described in 8 etc. is known. These methods are methods of forming Al on the ferromagnetic layer and then exposing it to the atmosphere to convert Al into Al ₂ O ₃ . in this way,
Pinholes may occur in the dielectric layer due to dust in the atmosphere,
There is a problem that the dielectric layer is contaminated with carbon oxides, nitrogen oxides, etc. and the yield is reduced.

As another example of the manufacturing method, Japanese Unexamined Patent Publication No. Hei 11
The method described in -54814 etc. is known.
This method is a method of converting Al into Al ₂ O ₃ by introducing pure oxygen into the chamber after forming an Al film on the ferromagnetic layer. According to this method, the variation in the resistance value and the magnetic resistance value in the wafer is reduced, but the time required for oxidation is increased to 10 to 20 minutes. Further, when assuming an MRAM or the like having a resistance value (RPA) of several hundred Ωμm ² and an element area of about 1 μm ^2, it is too small to obtain a resistance value in a wide range according to the element size. .

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); Journal of Applied Magnetics, 23,
4-2, (1999); Appl. Phys. Let
t. 73 (19), 2829 (1998)). Even in these ferromagnetic tunnel junction devices, the rate of change in magnetoresistance of 20% or more can be obtained, and thus 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 variations in the resistance value and the magnetic resistance value within the wafer as in the case described above.

As described above, when the ferromagnetic tunnel junction element is applied to a device such as a magnetoresistive effect memory or a magnetic head, the resistance value is low to some extent in the practical element size in order to reduce the influence of thermal noise. It is necessary to form a ferromagnetic tunnel junction having a resistance value that satisfies However, it was difficult to realize it by the conventional tunnel junction forming method.

[0010]

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

[0011]

A method of manufacturing a magnetoresistive effect element according to the present invention comprises a ferromagnetic single tunnel junction having a structure in which a dielectric layer is provided between two ferromagnetic layers, or a three-layer strong tunnel junction. In manufacturing a magnetoresistive effect element including a ferromagnetic double tunnel junction having a structure in which a dielectric layer is provided between the magnetic layers, a step of forming a dielectric film on the ferromagnetic layer by sputtering , After forming the film by sputtering,
Without breaking the vacuum of the location, or by introducing a gas containing oxygen or nitrogen to oxidize or nitride the dielectric film, before in a plasma by glow discharge after the introduction of the gas
And a step of oxidizing or nitriding the dielectric film.

[0012]

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

Materials for the ferromagnetic layer include Fe, Co and N.
i or an alloy containing these elements is used. In the ferromagnetic layer, Ag, Cu, A
u, Al, Mg, S, Bi, Ta, B, C, O, N, S
A small amount of non-magnetic element such as i, Pd, Pt, Zr, Ir, W, Mo and Nb may be contained. The ferromagnetic layer is
A two-layer film (or a multilayer film) including a soft magnetic layer and a hard magnetic layer may be used to adjust the switching magnetic field.

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

The magnetoresistive effect element of the present invention can be applied to a magnetoresistive effect type 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. Further, in the case of a ferromagnetic single tunnel junction, it is preferable to design one of the two ferromagnetic layers as a pin layer, and in the case of a ferromagnetic double tunnel junction, two layers of the three ferromagnetic layers are used. It is preferably designed as a pin layer.

The ferromagnetic double tunnel junction has two dielectric layers.
Since the layer is provided, an element having excellent bias dependency can be manufactured, and the resistance value is averaged to further improve the yield.

When the intermediate ferromagnetic layer of the ferromagnetic double tunnel junction is designed as a hard layer, Co or Fe-- is used as the ferromagnetic material that constitutes the ferromagnetic layer sandwiched by the two dielectric layers. It is preferable to use an alloy obtained by adding an element such as Pt, Pd, or Cr to a Co alloy.

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

In the present invention, the laminated body forming the ferromagnetic single tunnel junction or the ferromagnetic double tunnel junction may be provided on the substrate via an underlayer, and a protective layer may be provided on the laminated body. May be. The materials for these underlayer and protective layer are Ta, Ti, Pt, Pd, Au, and 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 effect element of the present invention is formed by various sputtering methods, vapor deposition methods, MBE methods and the like. In the following, a case of forming Al ₂ O ₃ as a dielectric layer by using the sputtering method will be described.

An example of a method for manufacturing a magnetoresistive effect element including a ferromagnetic single tunnel junction according to the present invention is shown in FIGS.
Will be described with reference to. 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 by using a sputtering apparatus.
4 shows an example in which 4 is continuously formed.

The substrate 11 is put into a sputtering apparatus, and the initial degree of vacuum is set to 1 × 10 ^-6 Torr or less. Initial vacuum is 5 × 10 ^-7 Torr or less, and further 1 × 10 ^-7 Torr
It is more preferable to set r or less. After that, an inert gas such as Ar is introduced to set a predetermined pressure. First, a ferromagnetic target is sputtered to form the first ferromagnetic layer 12 on the substrate 11. Next, an Al ₂ O ₃ target is sputtered. Under the above vacuum conditions, A
The Al ₂ O _x layer 13a having oxygen deficiency is formed by sputtering the l ₂ O ₃ target (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 filled with oxygen gas (O ₂ pressure: 10 mTorr).
Or above) or exposed to oxygen plasma (O ₂ pressure: 1 mTorr or more) generated by glow discharge to oxidize Al ₂ O _x and convert it into an Al ₂ O ₃ layer 13b having a stoichiometric composition without oxygen deficiency. In this way, 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 ratio is not reduced unlike the case where Al is left 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 It can be made well.

After exhausting oxygen, a ferromagnetic target is sputtered to form the second ferromagnetic layer 14 (FIG. 1 (c)). Thus, the basic structure of the magnetoresistive effect element including the ferromagnetic single tunnel junction element can be formed.

When the second ferromagnetic layer 14 is a pinned layer, the second ferromagnetic layer 1 is formed as shown in FIG. 2 (a).
An antiferromagnetic layer 21 is formed on the film 4. Further, when the first ferromagnetic layer 12 is used as the pinned layer, as shown in FIG. 2B, the antiferromagnetic layer 22 is formed on the substrate 11 and then the first ferromagnetic layer 12 is formed. , The dielectric layer 13 and the second ferromagnetic layer 14
To form a film.

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 form Al ₂ O ₃
When converting to Al, the oxidation time is longer than that in the case where Al is directly oxidized as in the conventional method, and therefore, it is very thin.
l ₂ O ₃ can be produced with good controllability. Moreover, the resistance value can be arbitrarily adjusted by adjusting the degree of conversion from Al ₂ O _x to Al ₂ O ₃ .

If a bias-dependent offset is desired, oxygen may be introduced to slightly oxidize the ferromagnetic layer after forming the ferromagnetic layer. In the present invention, since Al ₂ O _x is formed on the ferromagnetic layer and then only its surface is oxidized, oxidation of the underlying ferromagnetic layer surface 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 l is excessively oxidized, the oxide film grows on the ferromagnetic layer unintentionally, and it becomes difficult to control the bias point.

In the above, Al ₂ O _x is oxidized to form Al ₂ O _x.
Although the case of converting into O ₃ has been described, the same method can be applied to oxides such as SiO ₂ and MgO.

Further, for example, after forming a film of 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 nitrided and converted to AlN. You may form a dielectric layer by doing.

Another example of the method of manufacturing the magnetoresistive effect element including the ferromagnetic double tunnel junction of the present invention is shown in FIGS.
This will be described with reference to (c). 3A to 3C show the first ferromagnetic layer 1 on the substrate 11 by using the 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 thereof is Al ₂ O ₃ layer 1
3b is converted to form the first dielectric layer 13, and then the second ferromagnetic layer 14 is 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). After that, oxygen or a mixed gas of oxygen and a rare gas is introduced into the sputtering apparatus, and A
Oxygen plasma (O ₂ pressure: 10 mTorr or more) or oxygen plasma (O ₂ ) generated by glow discharge is applied to the l ₂ O _x layer 15a.
₂ pressure: 1 mTorr or more) to oxidize Al ₂ O _x and convert it into an Al ₂ O ₃ layer 15b having a stoichiometric composition without oxygen deficiency. In this way, the dielectric layer 15 is formed (FIG. 3).
(B)). At this time, some Al ₂ O _x may remain, and A
The l ₂ O _x may be completely oxidized. Next, after exhausting oxygen, a ferromagnetic target is sputtered to form the 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 It can be made well. Moreover, the resistance value can be arbitrarily adjusted by adjusting the degree of conversion from Al ₂ O _x to Al ₂ O ₃ .

The first and third ferromagnetic layers 12, 1
When 6 is used as the 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.

The antiferromagnetic layer may be formed in contact with the second ferromagnetic layer 14, or the antiferromagnetic layer may be sandwiched between the second ferromagnetic layers 14.

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

The magnetic recording element may have a structure in which the ferromagnetic tunnel junction element according to the present invention is laminated on the transistor as shown in FIGS. 5 and 6, or the diode and the present invention as shown in FIGS. 7 and 8. It may have a structure in which the ferromagnetic tunnel junction element according to the present invention is laminated.

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

A magnetic recording element having a structure in which a diode and a ferromagnetic tunnel junction element are laminated will be described with reference to FIGS. 7 and 8. 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 made of a laminated 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
A word line (WL) 62 arranged orthogonal to the bit line (BL) 61 is connected to the other end of R10.

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

FIG. 10 is a perspective view showing the internal structure of a magnetic disk device equipped with the magnetic head assembly shown in FIG. The magnetic disk 101 is mounted on a spindle 102 and rotated by a motor (not shown) in response to a control signal from a drive device controller (not shown). The actuator arm 71 in FIG. 9 is fixed to the fixed shaft 103, and supports the suspension 72 and the 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 being levitated from the surface of the magnetic disk 101 by a predetermined amount, and information is recorded / reproduced. A voice coil motor 104, which is a type of linear motor, is provided at the base end of the actuator arm 71. The voice coil motor 104 is composed of a drive coil (not shown) wound around a bobbin of the actuator arm 71, and a magnetic circuit including a permanent magnet and an opposing yoke that are arranged so as to face each other so as to sandwich the coil. The actuator arm 71 is located above and below the fixed shaft 103.
It is held by a ball bearing (not shown) provided at a place, and can be freely rotated and slid by the voice coil motor 104.

When the tunneling magnetoresistive effect element according to the present invention is applied to a magnetoresistive effect head, spins of adjacent ferromagnetic layers are made substantially orthogonal by film formation in a magnetic field or heat treatment in a magnetic field. By doing so, a linear response to the leakage magnetic field from the magnetic disk can be obtained, and any head structure can be used.

[0042]

EXAMPLES Examples of the present invention will be described below.

Example 1 An example of manufacturing a magnetoresistive effect element having a ferromagnetic single tunnel junction having the structure shown in FIG. 2B, in which Al ₂ O ₃ is used as a dielectric layer (tunnel barrier layer). 11 (a)-(c) and FIG. 12 (a)-
This will be described with reference to (c).

After placing the Si / SiO ₂ substrate 11 in the 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 the Si / SiO ₂ substrate 11, an underlayer 25 made of Ta having a thickness of 5 nm, an antiferromagnetic layer 22 made of Ir ₂₂ Mn _{78 having} a thickness of 17 nm, and a ferromagnetic layer 12 made of CoFe having a thickness of 3 nm are continuously formed. Formed. Next, the dielectric layer 13 made of Al ₂ O ₃ was formed on the ferromagnetic layer 12 made of CoFe by using the following method (A) or (B).

(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 varied 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 and the dielectric layer 13 was formed. At this time, by changing the oxidation time, Al ₂ O _x can be changed to Al ₂ O ₃
Adjusted the degree of conversion to.

(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 varied in the range of 1.5 to 2.5 nm. After that, pure oxygen was introduced into the sputtering apparatus without breaking the vacuum, glow discharge was performed to generate plasma, and Al ₂ O _x was oxidized from the surface side in oxygen plasma to be converted to Al ₂ O ₃ and the dielectric layer 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 above, a thickness of 5 nm is formed on the dielectric layer 13.
Ferromagnetic layer 14 made of CoFe and 15 nm thick NiFe, and a protective layer 26 made of 5 nm thick Ta.
Were continuously formed (FIG. 11A).

Using the ordinary photolithography technique and ion milling technique, the above laminated film was processed into a lower wiring shape having a width of 50 μm (FIG. 11B).

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

Al ₂ O ₃ having a thickness of 300 nm is deposited by electron beam evaporation while leaving the resist pattern R1. Then, the resist pattern R1 and Al ₂ O ₃ on the resist pattern R1 are lifted off, and interlayer insulation is performed on a portion other than the joint portion. A film 27 was formed (FIG. 12 (a)).

After forming a resist pattern R2 covering the area other than the area where the electrode wiring is formed, the surface is reverse-sputtered and cleaned (FIG. 12B).

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

Various measurements were carried out on samples A and B having a dielectric layer formed thereon by the method (A) or (B). These results are shown in FIGS.

FIG. 13 shows the magnetoresistive effect curves of Samples A and B. As shown in FIG. 13, in sample A, 23O
An MR change rate of 21% is obtained in a small magnetic field of e. Similarly, in sample B, a MR change rate of 25% is obtained with a small magnetic field of 25 Oe.

FIG. 14 shows the dependence of the MR change rate and the resistance value (R) on the junction area of Samples A and B. 14
It can be seen that the MR change rate hardly depends on the junction area, as shown in FIG.

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. Both are data when the bonding area is 200 μm ² . As shown in FIG. 15, by changing the oxidation time or the power applied during plasma oxidation, Al ₂ O _x can be changed 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 dependence of the MR change rate and the resistance value (R) on the Al ₂ O _x film thickness (t) of Samples A and B. Both are data when the oxidation time or the applied power during plasma oxidation is constant. As shown in FIG. 16, if the Al ₂ O _x film thickness is thick to some extent, the resistance value and the MR change rate do not change so much. After forming a thick Al ₂ O _x film to some extent, only the surface is oxidized to
Since the desired magnetoresistive effect can be obtained by converting to l ₂ O ₃ , the yield of the ferromagnetic tunnel junction device can be improved.

Example 2 An example in which a magnetoresistive element having a ferromagnetic double tunnel junction having the structure shown in FIG. 4 in which Al ₂ O ₃ is used as a dielectric layer (tunnel barrier layer) was manufactured is shown in FIG. 17 (a)-(c) and FIGS. 18 (a), (b)
Will be described with reference to.

After inserting the Si / SiO ₂ substrate 11 into the 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 the Si / SiO ₂ substrate 11, an underlayer 25 made of Ta having a thickness of 5 nm, an antiferromagnetic layer 22 made of Fe—Mn having a thickness of 20 nm, a ferromagnetic layer made of NiFe having a thickness of 5 nm and CoFe having a thickness of 3 nm. Layer 12 was continuously formed. Next, the dielectric layer 13 made of Al ₂ O ₃ was formed on the ferromagnetic layer 12 by 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.
After that, pure oxygen was introduced into the sputtering apparatus without breaking the vacuum, and Al ₂ O _x was oxidized from the surface side in oxygen gas to form Al.
_It was converted to ₂ O ₃ to form the dielectric layer 13. At this time, by changing the oxidation time, Al ₂ O _x can be changed to Al ₂ O ₃
Adjusted the degree of conversion to.

(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.
After that, pure oxygen was introduced into the sputtering apparatus without breaking the vacuum, glow discharge was performed to generate plasma, and Al ₂ O _x was oxidized from the surface side in oxygen plasma to be converted to Al ₂ O ₃ and the dielectric layer 13 was formed. At this time, by changing the power and the oxidation time during glow discharge, Al
_The degree of conversion of ₂ O _x to Al ₂ O ₃ was adjusted.

By sputtering in Ar gas under the same conditions as above, a thickness of 3 nm is formed on the dielectric layer 13.
The ferromagnetic layer 14 made of CoFe was formed. Subsequently, the dielectric film 15 was formed by the method (A2) or (B2) in the same manner as above. Then, by sputtering in Ar gas under the same conditions as described above, the ferromagnetic layer 16 made of CoFe having a thickness of 3 nm and NiFe having a thickness of 5 nm and the antiferromagnetic layer 2 made of Fe—Mn having a thickness of 20 nm are used.
4 and a protective layer 26 made of Ta and 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 having a width of 1 mm (FIG. 17A).

A resist pattern R1 for defining the junction is formed by a normal photolithography technique, 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 variously changed (FIG. 17B).

Al ₂ O ₃ having a thickness of 300 nm is deposited by electron beam evaporation while leaving the resist pattern R1 and then the resist pattern R1 and Al ₂ O ₃ on the resist pattern R1 are lifted off to form an interlayer insulating film 27 ( FIG. 17
(C)).

After forming the resist pattern R2 covering the area other than the area where the electrode wiring is formed, the surface is reverse-sputtered and cleaned (FIG. 18A).

After Al was deposited on the entire surface, the resist pattern R2 and Al on the resist pattern R2 were lifted off to form an Al electrode wiring 28 (FIG. 18B). Then, it was introduced into a heat treatment furnace in a magnetic field, and unidirectional anisotropy was introduced into the ferromagnetic layers 12 and 16 to be pinned layers.

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

FIG. 19 shows the magnetoresistive effect curves of Samples A2 and B2. As shown in FIG. 19, in sample A2, an MR change rate of 23% was 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 MR of samples A2 and B2.
The junction area dependence of a rate of change and a resistance value (R) is shown. As shown in FIG. 20, it can be seen that 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.
The oxidation time dependence of is shown by the applied power at the time of plasma oxidation as a parameter. As shown in FIG. 21, by changing the applied power during the oxidation time and plasma oxidation Al ₂ O _x of Al ₂
It is understood that the resistance value can be adjusted by adjusting the degree of conversion into O ₃ .

FIG. 22 shows MR for samples A2 and B2.
The Al ₂ O _x film thickness (t) dependence of the rate of change and the resistance value (R) is shown. Both are data when the oxidation time or the applied power during plasma oxidation is constant. As shown in FIG. 22, if the Al ₂ O _x film thickness is thick to some extent, the resistance value and MR change rate do not change so much. The desired magnetoresistive effect can be obtained by forming an Al ₂ O _x film with a certain thickness and then oxidizing only the surface to convert it to Al ₂ O ₃ , thus improving the yield of the ferromagnetic tunnel junction device. it can.

Example 3 By the same method as in Examples 1 and 2, 11 kinds of magnetoresistive effect elements having a ferromagnetic single tunnel junction or a ferromagnetic double tunnel junction were manufactured. Table 1 shows the laminated structure of each element of Samples 1 to 11. In the case of even sample numbers, plasma oxidation or plasma nitridation was performed after the dielectric layer was formed. If the sample number is odd, after forming the dielectric layer,
Oxidizing or nitriding in an O ₂ or N ₂ atmosphere of 30 mTorr.

Table 1 shows the MR change rate and resistance value of each sample, and the variation of these values within the wafer. From Table 1, it can be seen that the variation in the MR change rate and the resistance value within the wafer is relatively small. Therefore,
It can be seen that the method of the present invention can be used to manufacture a ferromagnetic tunnel junction device with high yield.

[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, a tunnel junction type magnetoresistive effect element can be manufactured with high yield, and It can be applied to a resistance effect type head, a magnetic field sensor, a magnetic memory element, and the like.

[Brief description of drawings]

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

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

3A to 3C are sectional views showing a method of manufacturing a ferromagnetic double tunnel junction element 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 showing an example of a magnetic recording element (MRAM).

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

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

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

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

10 is a perspective view showing the internal structure of a magnetic disk device equipped with the magnetic head assembly shown in FIG.

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

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

13 is a diagram showing magnetoresistive effect curves of Samples A and B of Example 1. FIG.

FIG. 14 is a diagram showing the junction area dependence of the MR change rate and the resistance value (R) 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 Sample A and the dependence of the resistance value (R) on the oxidation time of Sample B of Example 1 as parameters of the applied power during plasma oxidation.

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

FIG. 17 is a cross-sectional view showing the method of manufacturing the ferromagnetic double tunnel junction element of Example 2 in the order of steps.

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

19 is a diagram showing magnetoresistance effect curves of samples A2 and B2 of Example 2. FIG.

FIG. 20: MR for 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 oxidation time dependence of the resistance value (R) of the sample A2 of Example 2 and the resistance value (R) of the sample B2.
FIG. 7 is a diagram showing the dependence of the oxidation time on the oxidation time as a parameter of the applied power during plasma oxidation.

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

[Explanation of reference numerals] 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 ... Base 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 1 2 ... The spindle 103 ... fixed shaft 104 ... voice coil motor

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP 2000-3507 (JP, A) JP 2000-113428 (JP, A) JP 11-177161 (JP, A) (58) Fields investigated ( Int.Cl. ⁷ , DB name) G11B 5/39 G01R 33/09 H01L 43/08 H01L 43/12

Claims (3)

(57) [Claims] 1. A ferromagnetic single tunnel junction having a structure in which a dielectric layer is provided between two ferromagnetic layers, or a strong structure having a dielectric layer between each of three ferromagnetic layers. in producing the magnetoresistive effect element including a magnetic double tunnel junction, comprising the steps of sputtering a dielectric film on the ferromagnetic layer, after the dielectric film is sputtered true sputtering apparatus
Without breaking the sky, or by introducing a gas containing oxygen or nitrogen to oxidize or nitride the dielectric film, to oxidize or nitride the dielectric film in a plasma by glow discharge after the introduction of the gas And a step of manufacturing the magnetoresistive effect element. Wherein according to said ferromagnetic layer is equal to or made of an alloy containing Fe, Co, Ni or these elements
Item 1. A method of manufacturing a magnetoresistive effect element according to Item 1 . 3. The magnetoresistive element according to claim 1, wherein the dielectric layer is made of an oxide or a nitride of Al, Si, Mg, a rare earth element or an alloy containing these elements. Production method.