JP2002289941A - Magnetoresistive effect element and magnetic storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tunnel junction-type magnetic element which operates in a small switching magnetic field, with a minute cell size, for less variations and drop in magnetoresistive change coefficient. SOLUTION: The magnetoresistive effect element comprises one or more lamination of magnetoresistive element parts comprising a first magnetic lamination film, a second magnetic laminated film, and a non-magnetic layer held between the first and second magnetic laminated films. The first magnetic lamination film which is a storage layer comprises 3-layer magnetic laminated film with ferromagnetic layers laminated on both upper and lower surfaces with other non-magnetic layer in between. The second magnetic laminated film which is a reference layer and fixes a magnetizing direction comprises a ferromagnetic layer, or a magnetic lamination film in which the ferromagnetic layer and an antiferromagnetic layer are laminated. A magnetic layer contacting the non-magnetic layer contains a ferromagnetic material as a component element. The ferromagnetic layer constituting the first magnetic laminated film is composed of a continuous film of uneven thickness, a film comprising an island-like growth region, or fine particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording and reproducing technique using a ferromagnetic material, and more particularly to a magnetoresistive effect element magnetic element used for a magnetic sensor or a reproducing magnetic head of a high-density magnetic disk drive, and The present invention relates to a magnetic storage device using the same.

[0002]

2. Description of the Related Art Some conventional magnetoresistive elements using a ferromagnetic thin film are used for a magnetic head, a magnetic sensor and the like. In recent years, a magnetic random access memory (hereinafter, referred to as MRAM: MRAM) having a magnetoresistive element formed on a semiconductor substrate has been developed.
magnetic random access memory) has been proposed, and is receiving attention as a next-generation semiconductor memory device having both high-speed operation, large capacity, and non-volatility.

Here, the magnetoresistive effect element is a phenomenon in which when a magnetic field is applied to a ferromagnetic material, the electric resistance changes in accordance with the direction of magnetization of the ferromagnetic material. This direction of magnetization is used for writing information. By using the magnitude of the corresponding electric resistance for reading information, the device is operated as a storage element.

In recent years, the tunnel magnetoresistance effect (hereinafter referred to as the TMR effect) in a sandwich-structured ferromagnetic tunnel junction in which one insulating layer is inserted between two ferromagnetic layers.
ngMagneto-Resistance effect) has attracted attention, and the rate of change of magnetoresistance (hereinafter, MR ratio: Magneto-Resista)
As a result, a value of 20% or more was obtained (J. Appl. Phys. 79 , p. 4724 (1996)).

[0005] In view of this, research and development for using a tunnel junction type magnetic element utilizing the TMR effect (hereinafter, referred to as a TMR element) in an MRAM has been advanced, and for example, recent literature (Appl. Phys. Lett. 77, p. 283 (2000))
It has been reported that the MR ratio of the TMR effect at room temperature reaches 49.7%.

In a TMR element used in an MRAM, the direction of magnetization of one of the two ferromagnetic layers is fixed so as not to change under the influence of an external magnetic field, and this is fixed to a reference layer (or a fixed layer of magnetization). ), And the direction of the other magnetization is easily changed under the influence of an external magnetic field, and this is used as a storage layer.

The storage layer and the reference layer are arranged in parallel via an insulating layer forming a tunnel barrier layer, and the direction of magnetization of the storage layer is changed by the external magnetic field with respect to the direction of magnetization of the fixed reference layer. The information is stored in association with “0” and “1” of the binary information so as to be parallel or antiparallel.

Writing of storage information is performed by passing a current through a write wiring provided near the TMR element and inverting the direction of magnetization of the storage layer with a magnetic field generated at this time. In addition, reading of stored information is performed by T
This is performed by detecting a change in resistance of the MR element.

Therefore, the reference layer is required to have a material or a laminated structure capable of increasing the MR ratio of the TMR element because magnetization reversal by an external magnetic field is difficult, while the storage layer is required to have an external magnetic field. Magnetization reversal by TM
It is required to have a material or a laminated structure capable of increasing the MR ratio of the R element.

In order to fix the direction of magnetization of the reference layer,
Although it is effective to use a hard magnetic material having a large coercive force, in addition to this, the tunnel junction is provided by providing an antiferromagnetic layer so as to be in contact with the ferromagnetic layer and fixing the direction of magnetization. The method of fixing the magnetization direction of the ferromagnetic layer while taking advantage of the material characteristics of the ferromagnetic layer that increases the MR ratio of the ferromagnetic layer is widely used.

On the other hand, a method of using a soft magnetic material having a small coercive force or a method of reducing the coercive force by making the layer thinner has been considered for the storage layer configured to easily change the direction of magnetization.

However, when the TMR element is used as a memory cell,
In order to highly integrate the MRAM, it is necessary to reduce the size of the TMR element. Therefore, the ferromagnetic layer included in the TMR element also needs to be reduced. In general, the coercive force increases as the width of the ferromagnetic layer (the length in the plane of the ferromagnetic layer in the direction perpendicular to the axis of easy magnetization) decreases.

The magnitude of the coercive force is a measure of the magnitude of the switching magnetic field required to reverse the magnetization.
Reduction of the MR element means an increase in the switching magnetic field.
For this reason, when writing information, a large current needs to flow through the write wiring, and the power consumption of the MRAM using the TMR element as a memory cell increases. Therefore, in the TMR element for the MRAM, the reduction of the coercive force of the ferromagnetic layer serving as the storage layer is an important issue in promoting the high integration of the MRAM.

In a fine ferromagnetic layer included as a storage layer in a memory cell (TMR element) of a highly integrated MRAM,
The main reasons for the increase in coercive force are (1) that the shape anisotropy is strong, (2) that the demagnetizing field generated by the stray magnetic field prevents the rotation of magnetization, and (3) that the proportion of the edge domain increases. And the like.

Here, the edge domain means that, for example, when the width of the short axis is from several microns to submicron, a magnetic structure different from the central part of the magnetic material is caused by a demagnetizing magnetic field. (See, for example, J. Appl. Phys. 81 , p. 5471 (1997)).

In a memory cell of a highly integrated MRAM,
Since the size of the edge domain generated at the end of the minute ferromagnetic layer forming the storage layer is substantially equal to the cell size, the ratio of the area occupied by the edge domain increases as the cell size decreases. For this reason, it has a great influence on the pattern change of the magnetic structure (magnetic domain structure) accompanying the magnetization reversal,
The magnetization reversal process is complicated. Therefore, the coercive force increases, and the switching magnetic field increases.

In order to solve the above-mentioned problem of increasing the coercive force,
Generally, a method of reducing the thickness of the ferromagnetic layer is used.
The purpose of this method is to reduce the shape anisotropy energy, and it is possible to suppress the increase in coercive force by reducing the thickness to the limit of functioning as a ferromagnetic material.

In addition, there has been proposed a device in which a multilayer film having a nonmagnetic layer interposed between two ferromagnetic layers is used as a storage layer, and these ferromagnetic layers are antiferromagnetically coupled to each other ( Japanese Patent Application No. 9-25162, Japanese Patent Application No. 11-263741, U.S. Patent No. 5,953,
248).

In this case, the two ferromagnetic layers have different magnetic moments or thicknesses, and their magnetizations are in opposite directions due to antiferromagnetic coupling. For this reason, the magnetizations cancel each other, and the entire storage layer effectively operates as a ferromagnetic material having a small magnetization in the easy axis direction, which is equivalent to a reduction in the thickness of the ferromagnetic layer. be able to.

When a magnetic field is applied in the opposite direction to the small magnetization in the easy axis direction in the storage layer, the magnetization of each ferromagnetic layer is inverted while maintaining the antiferromagnetic coupling. At this time, the influence of the demagnetizing field is reduced because the magnetic field lines are closed, and the switching magnetic field of the storage layer is determined by the coercive force of each ferromagnetic layer, so that the magnetization can be reversed with a small switching magnetic field.

On the other hand, a method of fixing an edge domain to prevent a change in a complicated magnetic domain structure has been proposed (US Pat.
748,524, JP-A-2000-100153). If the edge domain is fixed, it is possible to control the change of the complex magnetic domain structure in the magnetization reversal, but this method cannot substantially reduce the value of the switching magnetic field. Further, it is necessary to add another structure to fix the edge domain, which is not suitable for high density.

[0022]

As described above, in the conventional TMR element, in order to reduce the switching magnetic field of the fine storage layer forming the memory cell, a method of reducing the thickness of the storage layer, a method of reducing the strength of the storage layer, and the like. A method of effectively reducing the thickness using magnetic coupling, a method of controlling the magnetic domain structure, and the like have been studied. However, (1) simply reducing the thickness of the storage layer,
Depending on the material and the film forming conditions, the storage layer becomes fine particles or islands and does not function as a ferromagnetic material. Therefore, there is a limit to thinning the storage layer. Since the magnetic domain structure changes depending on the shape, cell size, and aspect ratio of the cell, the magnitude of the coercive force changes. (3) If the lower limit of the thickness is reduced equivalently by using antiferromagnetic coupling, the coercive force increases due to the influence of the edge domain, and (4) the width. 0.1 μm
Assuming the following cell sizes, there have been many problems such as the necessity of a technique for further reducing the switching magnetic field.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a TMR element which operates with a small switching magnetic field even if the cell size is reduced, has small variations, and has a small decrease in MR ratio. With the goal.

[0024]

A magnetoresistive element according to the present invention comprises a first magnetic layer and a first magnetic layer laminated on the first magnetic layer.
A second magnetic layer laminated with the first magnetic layer via the first nonmagnetic layer and magnetically coupled to the first magnetic layer; and a second magnetic layer formed of the nonmagnetic layer A second nonmagnetic layer laminated with the second magnetic layer on a surface opposite to a surface in contact with the second magnetic layer;
A third magnetic layer laminated with a second magnetic layer via a second nonmagnetic layer, wherein the first or second magnetic layer is a continuous film having an uneven thickness, an island region, Alternatively, a plurality of fine particles are provided.

Preferably, the thickness of the thinnest portion of the continuous film having a non-uniform thickness is 1 nm or less, and the thickness of the thickest portion is at least 20% greater than the thickness of the thinnest portion. It is characterized by. Further, an average thickness of the island-shaped region or the fine particles is 0.3 nm or more and 3 nm or less.

Preferably, the first or second magnetic layer comprises:
Exhibiting superparamagnetism, and having the first and second magnetic layers
The ratio of the residual magnetization to the saturation magnetization of the nonmagnetic layer of
The ratio of the residual magnetization to the saturation magnetization of the first or second magnetic layer is larger than that of the first or second magnetic layer.

Further, the magnetoresistance effect element of the present invention has a first
A non-magnetic layer formed on the first magnetic layer;
And a second magnetic layer provided with a continuous film having a non-uniform thickness, the second magnetic layer being stacked with the first magnetic layer via the non-magnetic layer.

Further, in the magnetoresistance effect element according to the present invention, the second nonmagnetic layer is a conductive layer (GMR element) or a dielectric (TMR element). Also the first
And the second magnetic layer is ferromagnetically or antiferromagnetically coupled via the first nonmagnetic layer.

Preferably, the material of the magnetic layer is cobalt,
Iron, and an alloy of a ferromagnetic metal containing any one of nickel, or a compound of the ferromagnetic metal, or a solid solution of the ferromagnetic metal and a non-metal, the material of the first non-magnetic layer,
A metal containing any one of Ru, Ir, Cu, Au, and Ag, or an alloy thereof.

Further, the magnetoresistive element of the present invention is characterized in that it comprises a fourth magnetic layer laminated on the third magnetic layer via a third nonmagnetic layer. The first and second magnetic layers are magnetization free layers in which the direction of magnetization changes according to a predetermined external magnetic field, and the third magnetic layer has a state in which the external magnetic field is zero under the external magnetic field. The present invention is characterized in that the pinned layer is a pinned layer that substantially holds the magnetization direction.

The magnetoresistance effect element of the present invention can be suitably used as a component of a magnetic storage device.

[0032]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, the magnetic characteristics of the magnetic multilayer film included in the TMR element according to the first embodiment of the present invention and the simulation results will be described with reference to FIG.

In the magnetic laminated film of the TMR element shown in FIG. 1, fine magnetic layers 101 and 103 (including island-shaped growth) are formed via a nonmagnetic layer 102. Non-magnetic layer 10
2 a magnetic layer 10 composed of fine particles and the like laminated on both upper and lower surfaces
2, 103 are ferromagnetically coupled to each other. Such a magnetic laminated film exhibits ferromagnetism as a whole.

The change in the magnetic properties when the magnetization is reversed by applying a magnetic field in the opposite direction to the magnetic laminated film will be described. Generally, the magnetization of fine particles made of a ferromagnetic material is easily inverted. However, since the direction of magnetization of the aggregate of fine particles fluctuates in a weak magnetic field due to the effects of thermal fluctuations, etc., the remanent magnetization becomes almost zero, and the superparamagnetic magnetic properties that the magnetization does not saturate unless a large magnetic field is applied Is shown.

However, if weak ferromagnetic coupling is added between these fine particles, each of the fine particles undergoes magnetization reversal while feeling the ferromagnetic coupling force that tends to be in the same direction of magnetization while having the characteristic of easy magnetization reversal. Therefore, the magnetization is reversed with a small switching magnetic field as a whole.

At this time, as the size of the fine particles is smaller,
Also, the weaker the bonding force between the fine particles, the smaller the value of the reversal magnetic field. Even if the magnetic coupling is not only ferromagnetic but also partially or entirely antiferromagnetic, the same applies if a force that directs the magnetization in almost the same direction acts as a whole. This produces an effect of reducing the switching magnetic field.

The reason why the switching magnetic field is reduced in the magnetic laminated film including the fine ferromagnetic layer shown in FIG. 1 is as described above. In such a magnetic laminated film, since the respective magnetic fine particles are separated from each other, it is possible to obtain a memory cell which is hardly affected by the shape and size of the cell and has a small variation in the switching magnetic field.

A ferromagnetically coupled via a non-magnetic layer,
In a memory cell having three magnetic laminated films composed of ferromagnetic layers, when the ferromagnetic layers on the upper and lower surfaces are continuous films, when one ferromagnetic layer is in the form of fine particles, and when the ferromagnetic layers on both surfaces are FIG. 2 shows the results of obtaining the coercive force by simulation for each of the fine particles.

Here, as a simulation model, the width of the memory cell is 100 nm and the length of the memory cell is 40 nm.
It was assumed that the thickness was 0 nm and the thickness of the magnetic layer was 1 nm. Also,
For convenience of simulation, it is assumed that the bottom surface of the fine particles is a square with a side length of 40 nm, the height is 1 nm, and the height between the fine particles is 20 nm.

From the results of the simulation shown in FIG.
When the upper and lower magnetic layers are in the form of fine particles, the value of the coercive force Hc is 1 compared to the case where the upper and lower magnetic layers are continuous films.
/ 4.

The case where isolated fine particles are disposed on the upper and lower surfaces of the non-magnetic layer has been described above. It was clarified from the comparison with the experiment that almost the same effect was obtained even when the magnetic coupling was weak.

Specifically, when the magnetic layer is formed of a continuous film having a non-uniform thickness, the thickness of the thinnest portion is 1 nm or less, and the thickness of the thickest portion is smaller than that of the thinnest portion. 2
When the thickness is larger than 0%, almost the same effect can be obtained. However, when the thickness of the thin portion is more than 1 nm, the value of the coercive force is almost different from that in the case where the magnetic layer is a continuous film having a uniform thickness. It became clear that there was no longer.

When the magnetic layer is grown in the form of fine particles or islands, if the average height of the fine particles or islands is formed to be 0.3 nm or more and 3 nm or less, substantially the same protection as in the simulation can be obtained. It became clear that the effect of reducing the magnetic force was obtained.

These magnetic layers have superparamagnetic components whose residual magnetization is close to zero in the magnetization hysteresis curve evaluated for a single layer and whose magnetization is not saturated unless a large magnetic field is applied. Further, the residual magnetization M with respect to the saturation magnetization Ms
The ratio Mr / Ms of r is larger than 0 but smaller than 1, and has the disadvantage that the squareness of the hysteresis curve is poor and the switching magnetic field is large.

However, even in a single-layer ferromagnetic layer exhibiting superparamagnetic characteristics, this magnetic layer is formed on both the upper and lower surfaces of the non-magnetic layer, and these magnetic layers are ferromagnetically coupled via the non-magnetic layer. With such a three-layer magnetic laminated film, Mr / Ms approaches 1, and the value of the switching magnetic field can be reduced.

The magnetic material usable as the magnetic layer of the present invention is an alloy or compound containing any one of Co, Fe and Ni, or a solid solution of these metals and nonmetals. Materials that can be used as the nonmagnetic layer interposed between the magnetic layers of the layers include Ru, Ir, Cu, Au, and Ag.
And the like.

Next, a double junction type TMR element according to a second embodiment will be described with reference to FIG. FIG. 3 is a schematic process sectional view showing a manufacturing process of the double junction TMR element.

As shown in FIG. 3A, a lower wiring electrode W 304, a buffer layer Ta 305, and a lower reference layer Co _{5 are formed} on a semiconductor substrate by using a high vacuum sputtering method (not shown). Fe ₅ 306 and an insulating layer Al ₂ O ₃ 307 as a lower tunnel barrier layer are sequentially deposited.

The multilayer film shown in FIG.
Since everything from 304 to the uppermost layer of Al ₂ O ₃ 307 is sequentially deposited on the metal layer, it can be formed as a multilayer film having excellent flatness.

Next, as shown in FIG.
On the l ₂ O ₃ 307, a three-layer magnetic laminated film is laminated as a storage layer. First, a thickness of 1.2 nm is calculated from the film formation rate.
Ni ₃ Co ₃ Fe ₄ 301 is deposited so that
The non-magnetic layer Ru 302 is deposited so as to have a thickness of 1.4 nm calculated from the film forming rate, and further, Ni ₃ Co ₃ Fe ₄ 30 is formed so as to have a thickness of 1.2 nm calculated from the film forming rate.
3 is deposited.

At this time, Ni ₃ Co ₃ Fe ₄ 301 is deposited on the insulating layer Al ₂ O ₃ 307 forming the tunnel barrier layer. In this case, when the metal layer is deposited on the insulating layer, Since the bonding force of the metal atoms to the insulating layer is weak, the metal layer initially grows in an island shape, and as the deposition proceeds, the islands fuse with each other to increase the film thickness.

[0052] Therefore, as shown in FIG. _{3 (b), Ni 3 Co} 3 Fe 4 3 deposited on the insulating layer Al ₂ O ₃ 307
01 becomes non-uniform. At this time, Ni ₃ Co ₃ Fe ₄ 30 is controlled by controlling the substrate temperature and gas pressure of the sputtering apparatus.
The non-uniformity of Ni ₃ Co ₃ Fe ₄ 301 is controlled such that the film thickness of the thinnest portion is 1 nm or less and the film thickness of the thickest portion is 20% or more larger than the film thickness of the thinnest portion. be able to.

Next, the non-magnetic layer Ru 302 and the Ni ₃ Co ₃ Fe ₄ 303 deposited on the Ni ₃ Co ₃ Fe ₄ 301
Are sequentially deposited on the metal layer, so that the flatness is restored. If the surface of Ni ₃ Co ₃ Fe ₄ 303 does not show the flatness required for the next step, a normal flattening step may be introduced.

Next, as shown in FIG. 3C, an insulating layer Al ₂ O ₃ 307 serving as an upper tunnel barrier layer, an upper reference layer Co ₅ Fe ₅ 309, and an upper protective layer W 310 are deposited. As shown in FIG. 4D, in order to process W 304 as a lower wiring electrode, a mask pattern is formed by using a photoresist (not shown), and ion milling is performed using the mask as a mask. Pattern formation (not shown) for defining the shape of the part and ion milling are performed to form a TMR element part.

Next, as shown in FIG. 4E, after an interlayer insulating film SiO ₂ 311 is deposited by using a reactive sputtering method, a connection hole with the upper protective layer W 310 and an upper portion connected thereto are formed. A wiring electrode 312 is formed in a pattern, and TM
Complete the R element.

The TMR element manufactured as described above has
0nm × 600nm rectangle, 0.1V bias voltage
, An MR ratio of 40% and a switching magnetic field of 2.
It showed a characteristic of 4 kA / m, and as shown in FIG. 5A, the squareness ratio of the magnetization hysteresis characteristic was extremely good.

On the other hand, in the manufacturing process of the TMR element shown in FIGS. 3 and 4, except that the three-layer magnetic laminated film serving as the storage layer is replaced with a single-layer Ni ₃ Co ₃ Fe ₄ having a thickness of 1.2 nm. In a TMR element manufactured by substantially the same process, FIG.
As shown in (b), it is clear that the squareness ratio of the magnetization hysteresis characteristic deteriorates, the remanent magnetization is close to zero, and a superparamagnetic magnetic characteristic in which the magnetization is not saturated unless a large magnetic field is applied is exhibited. Was.

Further, Ni ₃ Co ₃ Fe ₄ contained in the _three magnetic laminated films forming the storage layer has a uniform thickness.
In particular, in the sample deposited by controlling the substrate temperature and the gas pressure of the sputtering apparatus, the MR ratio at a bias voltage of 0.1 V is 40% in a memory cell of 200 nm × 600 nm, while the switching magnetic field is 9.6 kA. / M, a good TMR element could not be obtained.

From the above results, according to the present invention, in a TMR element using a laminated structure in which Ni ₃ Co ₃ Fe ₄ having a non-uniform thickness is magnetically coupled via a nonmagnetic layer as a storage layer, as in the present invention, It was found that the squareness ratio of the magnetization hysteresis characteristics was very good, and at the same time, the switching magnetic field was significantly reduced. The TMR according to the second embodiment
Since the element is suitably used structurally, for example, as a magnetic sensor, it does not necessarily need to be formed on a semiconductor substrate, but can be formed on, for example, a glass substrate.

Next, a dual spin valve type TMR element for an MRAM according to a third embodiment will be described with reference to FIG. FIG. 6 is a schematic process sectional view showing a manufacturing process of the dual spin-valve TMR element of the present invention. Here, the dual spin-valve TMR element has a spin-valve structure that firmly fixes the magnetization of the reference layer by laminating a ferromagnetic layer serving as a reference layer in contact with the antiferromagnetic layer. It is a double junction type TMR element provided.

As described above, when the ferromagnetic layer serving as the reference layer is laminated in contact with the antiferromagnetic layer, the magnetization direction of the ferromagnetic layer in the reference layer is extremely firmly fixed, and the highly integrated M
As a TMR element for RAM, the probability of malfunction due to a leakage magnetic field can be reduced to zero.

Since the dual spin-valve TMR element of the present invention is formed on a part of a semiconductor integrated circuit, it is formed on a lower wiring electrode on an insulating film covering the surface of a semiconductor substrate. The lower wiring electrode is connected to a selection transistor formed on the main surface of the semiconductor substrate via a plug penetrating the insulating film.

First, as shown in FIG. 6A, a lower wiring electrode / buffer layer Ta 604 is formed on a semiconductor substrate (not shown) on which an interlayer insulating film and a plug have been formed by using a high vacuum sputtering method. And the lower antiferromagnetic layer Pt
Mn 605 and a lower reference layer Co ₇ Fe ₃ 606 are sequentially deposited.

Next, in order to form a lower tunnel barrier layer, after depositing Al with a thickness of 0.8 nm, this Al is oxidized in an ozone atmosphere to form an insulating layer AlO _x 607 (1) as a tunnel barrier layer. .Ltoreq.x.ltoreq.1.5).

Next, as shown in FIG.
_A substantially three-layer magnetic laminated film is formed as a storage layer on x607 as follows. First, a fine particle layer (or an island-shaped growth layer, the same applies hereinafter) Co ₉ Fe 601a is deposited so as to have a thickness of 0.5 nm as calculated from the film formation rate, and then a thickness of 1 as calculated from the film formation rate. Ni ₄ Fe ₆ 601b is deposited to a thickness of 0.0 nm. Next, the nonmagnetic layer Cu is adjusted to have a thickness of 1.5 nm in terms of the deposition rate.
After depositing 602, Ni ₃ Co ₃ Fe ₄ 603 is further deposited so as to have a thickness of 1.2 nm calculated from the film forming rate.

Here, Co ₉ Fe 601a is deposited as a fine particle layer (or island-like growth layer), and Ni ₄ Fe ₆ 601
b is deposited as a continuous film having a non-uniform thickness so as to fill the gap between the fine particle layers. Co ₉ Fe 601a and N
i ₄ Fe ₆ 601b is combined to form a ferromagnetic layer having a non-uniform thickness, and forms a substantially three-layer magnetic laminated film together with Ni ₃ Co ₃ Fe ₄ 603 formed via the non-magnetic layer Cu 602. Form.

Next, as shown in FIG. 6 (c), Ni ₃ C
In order to form an upper tunnel barrier layer on the surface of o ₃ Fe ₄ 603, 0.8 nm of Al is deposited,
By oxidizing 1 in an ozone atmosphere, AlO _x 608 (1 ≦ x ≦ 1.5) to be a tunnel barrier layer is formed. Further, Co ₇ Fe ₃ 609 as an upper reference layer,
Upper antiferromagnetic layer PtMn 610 and upper protective layer W 611
Is deposited.

Next, as shown in FIG. 7D, in order to process Ta 604, which is the material of the lower wiring electrode portion, as a lower wiring electrode, a mask pattern is formed by using a photoresist (not shown) and the mask is formed. After the lower wiring electrode portion is formed by ion milling, patterning and ion milling for defining the shape of the TMR element portion are further performed to form a dual spin valve type TMR element portion shown in FIG. 7D. .

Next, as shown in FIG. 7 (e), after depositing an SiO ₂ interlayer insulating film 808 by using the reactive sputtering method, 300 ° C. is applied while applying a magnetic field of 500 kA / m in a vacuum. Anneal for 2 hours. By this step, the magnetization of the reference layer is fixed and the dual spin valve type TMR
It functions as an element. Finally, the upper protective layer W6
11 and an upper wiring electrode (M
A RAM bit line 806 is provided to complete the device. Note that Ta 604 is used as the lower wiring electrode 805 of the MRAM.

In the MRAM thus completed,
The dual spin valve type TMR element of the memory section is 100
nm × 300 nm rectangle, MR ratio 25% at 0.5 V bias voltage, switching field 3.2
It exhibited a characteristic of kAm ^-1 , and it became possible to reduce the current value 10 mA of the wiring conventionally required for magnetization reversal to 1 mA. In the third embodiment, in addition to PtMn, PhMn, IrM
n, PrPhMn and PtCrMn can be used.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In the fourth embodiment, an MRA using a dual spin-valve TMR element as a memory cell
The structure of M will be specifically described.

In the MRAM shown in FIG. 8, an N ⁺ source / drain region 802 of a MOS transistor formed on a main surface of a P-type silicon substrate 801 and an N ^+
+ The gate electrode 803 of the MOS transistor formed on the N-type channel between the source / drain regions;
A conductive plug 804 connected to one of the drain regions 802 is provided.

The dual spin valve type TMR element shown in FIG. 7E surrounded by a broken line has a lower wiring electrode 805 connected to one of the source / drain regions 802 via a conductive plug 804, and an upper wiring electrode. It is connected to a bit line 806 formed along the plane of the drawing. MRAM
The word line 807 is formed between the gate electrode 803 and the lower wiring electrode 805 in a direction perpendicular to the plane of the drawing. Note that a space between these components is filled with an interlayer insulating film 808.

The operation of the MRAM is as follows. Writing of storage data to the TMR element which is a main part of the memory cell is performed by using a bit line 806 and a word line 807 which are orthogonal to each other.
Is carried out by passing a current of about 1 mA into

That is, when a current is applied to the bit line 806 and the word line 807 selected by the address decoder, an external magnetic field generated by the current is applied to the selected T at the intersection.
In addition to the MR element, the switching field of the TMR element exceeds the magnitude of the switching magnetic field. However, for the TMR element at the intersection of the other unselected word lines and the selected bit line, the selected bit line Since only a magnetic field due to the current 806 is applied, the magnetization reversal of the TMR element does not occur.

For reading the stored data, the MOS transistor formed on the P-type silicon substrate 801 is used to select the TMR element in which the stored data is written,
This can be performed by reading a resistance value corresponding to the direction of magnetization of the R element. Dual spin valve type TMR
The MRAM using the element as a memory cell can be increased in density. In addition, since the magnetization of the reference layer of the TMR element is fixed firmly by using an antiferromagnetic layer, there is no possibility of malfunction and non-volatile operation. It is possible to provide a storage device which has no restriction on the number of times of rewriting.

Next, a fifth embodiment of the present invention will be described with reference to FIG. In the fifth embodiment, TMR
The structure of the magnetic laminated film used as the storage layer and the reference layer (the pinned layer of magnetization) of the device will be described in general terms,
The magnetization fixed layer suitable for the M memory cell will be described in detail.

As described above, in the TMR element of the present invention, the magnetic laminated film forming the storage layer and the magnetic laminated film forming the fixed layer of magnetization are formed via the insulating layer forming the tunnel barrier layer. . FIG. 9 is a schematic view showing the configuration of these magnetic laminated films, focusing on the features of the storage layer and the pinned layer of magnetization of the present invention.

The magnetic laminated film forming the storage layer is formed by laminating the ferromagnetic layers 1 and 3 via the non-magnetic layer 2 as shown in FIG. In addition, the storage layer may be formed using only one soft magnetic material whose magnetization direction easily rotates. At this time, the direction of magnetization is a direction along the plane of the magnetic laminated film, and a storage layer with a small switching magnetic field is realized by optimizing the thickness and material of each layer.

However, if the magnetic laminated film forming the storage layer is formed as a flat laminated film (or a single-layer flat film),
As shown in the plan view of FIG. 9B, an edge domain 5 is generated at the end of a normal magnetic domain (domain) 4.

Usually, the planar shape of the storage layer makes the direction of the axis of easy magnetization longer with respect to the width in order to reduce the influence of the demagnetizing field. Is hindered.

Therefore, in the storage layer of the present invention, in particular, FIG.
As shown in (c), the ferromagnetic layer 1 is interposed via the non-magnetic layer 2a.
When laminating the ferromagnetic layers 1a and 3a, the thickness of the ferromagnetic layers 1a and 3a or any one of them is made non-uniform, so that FIG.
As shown in (1), only a single domain 6 exists in the plane to avoid generation of an edge domain.

As described above, a magnetic layer having a continuous film having a non-uniform thickness is used as a magnetization free layer in which the direction of magnetization changes according to a predetermined external magnetic field. Can also be used for a magnetization fixed layer that maintains the direction of magnetization at zero magnetic field.

The effect of making the ferromagnetic layer non-uniform is not necessarily achieved only by the film thickness. For example, by making the composition of the ferromagnetic layer non-uniform, the generation of edge domains can be avoided. . In addition, as described above, by forming the ferromagnetic layers 1a, 3a, or one of them, in the form of fine particles or islands, generation of edge domains can be avoided. At this time, the domains in the plane operate cooperatively so that the single domain in each particle or each island forms a single domain in the entire plane.

At this time, the magnetic film in the form of fine particles may be, for example, one in which fine particles of ferromagnetic material are dispersed in a matrix made of a non-magnetic material, or may be such that the island-shaped growth portion is covered with another magnetic layer. Is also good.

Next, the magnetic laminated film forming the pinned layer of magnetization is:
As shown in FIG. 1E, the ferromagnetic layer 1 made of a hard magnetic material is adjacent to one of the insulating layers 11 forming a tunnel barrier layer.
By forming 2, it can function as a fixing layer. However, in this configuration, the degree of magnetization fixation is not always sufficient, which leads to a malfunction of the TMR element.

Also, as indicated by the dashed line in FIG. 1E, the leakage magnetic field from the ferromagnetic layer 12 shifts the center value of the switching magnetic field of the storage layer 10 adjacent to the other of the insulating layer 11. Similarly, a malfunction of the TMR element is caused.

In particular, since the TMR element for the MRAM is highly integrated, the probability of a malfunction must be zero.
Therefore, the MRAM described in the third and fourth embodiments
As shown in FIG. 9 (f), in a TMR element for use, a ferromagnetic layer 12 and an antiferromagnetic layer 13 are laminated to form a spin-valve-type pinned layer of magnetization, thereby strengthening the pinning of magnetization.

However, the effect of the leakage magnetic field of the ferromagnetic layer 12 cannot be removed by the pinned layer of the spin valve type magnetization shown in FIG. 9F. Therefore, in the MRAM according to the fifth embodiment, As shown in FIG. 9G, adjacent to one side of the insulating layer 11 forming the tunnel barrier layer, the non-magnetic layer 13 interposes antiferromagnetically so that the directions of magnetization are opposite to each other. A magnetic laminated film composed of the coupled ferromagnetic layers 12 and 14 is formed, and this is used as a pinned layer of magnetization of the TMR element for MRAM.

In the pinned layer of magnetization shown in FIG. 9G, an extremely strong antiferromagnetic coupling can be obtained by selecting the thickness t of the nonmagnetic layer 13, so that the pinning of magnetization can be strengthened. . Also, the ferromagnetic layers 12, which are antiferromagnetically coupled to each other,
Since a closed magnetic circuit is formed between the storage layers 14, the effect of the leakage magnetic field on the storage layer 10 formed adjacent to the other of the insulating layer 11 forming the tunnel barrier layer can be eliminated. 9 (f) and FIG.
The magnetic laminated film combining (g) is the most suitable.

In the magnetic laminated film shown in FIG.
If the thickness t of the nonmagnetic layer and the material and thickness of the ferromagnetic layers 12 and 14 are selected, the storage layer shown in FIG.
It is also possible to suppress the generation of the edge domain 5 shown in (b) and reduce the value of the switching magnetic field.

As described above, a laminated structure in which the first magnetic laminated film serving as the storage layer and the second magnetic laminated film serving as the magnetization fixed layer are formed on both sides of the insulating layer serving as the tunnel barrier layer via the insulating layer The TMR element including the section has been described. In order to facilitate rotation of the direction of magnetization in the first magnetic laminated film, the first magnetic laminated film has a three-layer structure in which first and second ferromagnetic layers are laminated via a non-magnetic layer. It was extremely effective to make the second ferromagnetic layer or any one of them non-uniform.

As described above, the first magnetic laminated film having a three-layer structure useful as the storage layer is not necessarily applied to the TMR element. First and second via the non-magnetic layer
A magnetic element in which the first magnetic laminated film is a storage layer and the second magnetic laminated film is a pinned layer of magnetization. First of structure
Can be used as a storage layer.

As such a magnetic element, for example, TMR
Giant Magneto-Resistive Effect (GMR) having a structure in which a tunnel barrier layer (insulating layer) in the element is replaced with a non-magnetic metal layer (eg, Cu)
Element) is known. In the GMR element, electron scattering depending on the direction of magnetization (spin) occurs at the interface between the nonmagnetic metal layer and the magnetic multilayer film.

That is, as the direction of magnetization of the first magnetic laminated film is rotated with respect to the second magnetic laminated film having the fixed magnetization direction, the magnetoresistance at the interface with the nonmagnetic metal layer is increased. I do. This increase in magnetoresistance occurs in the direction along the plane of the magnetic laminated film and in the direction perpendicular to the plane. GMR
For the element, the first magnetic laminated film serving as the storage layer and the second magnetic laminated film serving as the magnetization fixed layer described in each of the above embodiments can be suitably used.

The present invention is not limited to the above embodiment. For example, in the first and second embodiments, a double junction type TMR element has been described as an example, but the present invention is not necessarily limited to a double junction type TMR element. The same effect is obtained for the single junction type TMR element. In this case, the three-layer magnetic laminated structure and the wiring or protection metal layer in the first and second embodiments are
They will be stacked adjacently.

In the first and second embodiments,
Although the storage layer is described as a three-layer magnetic laminated structure in which a nonmagnetic layer is interposed between two ferromagnetic layers, fine particles of a ferromagnetic material can be weakly and ferromagnetically coupled. If so, it is not necessary to use a non-magnetic layer.
Alternatively, it may have a two-layer structure of a ferromagnetic layer having a particulate or island-shaped growth region and a non-ferromagnetic layer. Even when a non-magnetic layer is used, the present invention includes a state in which ferromagnetic fine particles exist as a solid solution in the non-magnetic metal. In addition, various modifications can be made without departing from the spirit of the present invention.

[0098]

As described above, according to the TMR element of the present invention, two ferromagnetic layers each having a fine-grained or island-shaped growth region or having an uneven thickness are connected to each other via a non-magnetic layer. By using a laminated structure that is ferromagnetically coupled as a storage layer, the switching magnetic field can be reduced without lowering the MR ratio.

The TMR element provided with this storage layer not only exhibits excellent performance as a storage element, but also has a small variation, can be manufactured with good yield, and is inexpensive, and thus has excellent productivity. In addition, T provided with this storage layer
Since the structure of the MR element is suitable for miniaturization, the degree of integration of an MRAM in which the MR element is integrated as a memory cell can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a configuration of a storage layer of a TMR element according to a first embodiment.

FIG. 2 is a diagram showing a simulation result of coercive force for three types of magnetic laminated films.

FIG. 3 shows a double tunnel junction type T according to a second embodiment.
Sectional drawing which shows the manufacturing method of an MR element.

FIG. 4 shows a double tunnel junction type T according to a second embodiment.
Sectional drawing which shows the continuation of the manufacturing method of an MR element.

FIG. 5 shows a double tunnel junction type T according to a second embodiment.
FIG. 7 is a diagram comparing a magnetization hysteresis curve of an MR element with a conventional TMR element.

FIG. 6 is a process sectional view showing a method for manufacturing a dual tunnel junction type TMR element having a dual spin valve structure according to a third embodiment.

FIG. 7 is a process cross-sectional view showing a continuation of the method of manufacturing the dual tunnel junction type TMR element having the dual spin valve structure according to the third embodiment.

FIG. 8 illustrates an M using the TMR element according to the fourth embodiment.
FIG. 2 illustrates a configuration of a RAM.

FIG. 9 is a diagram illustrating a configuration of a storage layer and a pinned layer of magnetization according to a fifth embodiment.

[Explanation of symbols]

1, 3, 1a, 3a, 12, 14 ... ferromagnetic layer 2, 2a, 15 ... nonmagnetic layer 4, 6 ... domain 5 ... edge domain 10 ... storage layer 11 ... tunnel barrier layer 13 ... antiferromagnetic layer 101, 103 ... ferromagnetic layers 102 ... non-magnetic layer _{301,303 ... Ni 3 Co 3 Fe 4} 302 ... Ru 304,310 ... W 305 ... Ta 306,309 ... Co 5 Fe 5 307,308 ... Al 2 O 3 311 ... interlayer insulating film 312 ... upper wiring electrode _{601a ... Co 9 Fe 601b ... Ni} 4 Fe 6 602 ... Cu 603 ... Ni 3 Co 3 Fe 4 604 ... Ta 605,610 ... PtMn 606,609 ... Co 7 Fe 3 607,608 ... AlO _x 611 ... W 801 ... silicon substrate 802 ... N ⁺ source / drain regions 803 ... gate electrode 804 ... plug 805 ... lower wiring electrode 806 ... bit Line 807 ... word line 808 ... interlayer insulating film

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01F 10/08 G01R 33/06 R H01L 27/105 H01L 27/10 447 (72) Inventor Yoshiaki Saito Kanagawa In-house Toshiba Research and Development Center, Komukai Toshiba-cho, Kawasaki-shi, Kanagawa Prefecture (72) Inventor Masayuki Sunai In Toshiba Research and Development Center, Komukai Toshiba-cho, Kochi-ku, Kawasaki-shi, Kanagawa Prefecture (72) Inventor Shigeki Takahashi 1 Toshiba R & D Center, Komukai Toshiba-ku, Kawasaki City, Kanagawa Prefecture (72) Inventor Kentaro Nakajima 1 Toshiba Komukai Toshiba-cho, Saiwai-ku, Kawasaki City, Kanagawa Prefecture R & D Center Toshiba Corporation F term (reference) 2G017 AA01 AB07 AD55 AD65 5D034 BA03 BA05 BA15 CA08 5E049 BA12 BA16 5F083 FZ10 GA05 GA09 GA11 GA27 GA30 JA39 JA60 PR04 PR12 PR22 PR38

Claims (14)

[Claims] A first magnetic layer; a first non-magnetic layer laminated on the first magnetic layer; and a first magnetic layer laminated on the first non-magnetic layer via the first non-magnetic layer. A second magnetic layer magnetically coupled to the first magnetic layer; and a second magnetic layer laminated with the second magnetic layer on a surface of the second magnetic layer opposite to a surface in contact with the nonmagnetic layer. And a third magnetic layer laminated with the second magnetic layer with the second nonmagnetic layer interposed therebetween, wherein the first or second magnetic layer has a non-thickness. Uniform continuous membrane,
A magnetoresistive element comprising an island region or a plurality of fine particles. 2. The film thickness of the thinnest portion of the continuous film having a non-uniform thickness is 1 nm or less, and the film thickness of the thickest portion is 20% or more larger than the film thickness of the thinnest portion. The magnetoresistive element according to claim 1, wherein: 3. The magnetoresistive element according to claim 1, wherein the average thickness of the island region or the fine particles is not less than 0.3 nm and not more than 3 nm. 4. The method according to claim 1, wherein the first or second magnetic layer has superparamagnetism.
Item 7. The magnetoresistive element according to item 1. 5. The ratio of the residual magnetization to the saturation magnetization indicated by the first and second magnetic layers and the first nonmagnetic layer is determined by the ratio of the residual magnetization to the saturation magnetization indicated by the first or second magnetic layer. The magnetoresistive element according to claim 1, wherein the ratio is larger than the ratio. 6. A first magnetic layer, a non-magnetic layer formed on the first magnetic layer, and a non-magnetic layer interposed between the first magnetic layer and a non-uniform thickness. And a second magnetic layer having a continuous film. 7. The magnetoresistive element according to claim 1, wherein the second nonmagnetic layer is a conductive layer. 8. The magnetoresistance effect element according to claim 1, wherein the second nonmagnetic layer is a dielectric. 9. The method according to claim 1, wherein the first and second magnetic layers include the first magnetic layer.
9. The magnetoresistive element according to claim 1, wherein ferromagnetic coupling or antiferromagnetic coupling is performed via the nonmagnetic layer. 10. The material of the magnetic layer is made of cobalt, iron,
And an alloy of a ferromagnetic metal containing any one of nickel and
The magnetoresistance effect element according to any one of claims 1 to 9, wherein the magnetoresistance effect element is a compound of the ferromagnetic metal or a solid solution of the ferromagnetic metal and a nonmetal. 11. The material of the first nonmagnetic layer is Ru,
The magnetoresistive element according to any one of claims 1 to 10, wherein the element is a metal containing any one of Ir, Cu, Au, and Ag, or an alloy thereof. 12. The semiconductor device according to claim 1, further comprising: a fourth magnetic layer laminated on the third magnetic layer via a third nonmagnetic layer. The magnetoresistive effect element as described in the above. 13. The first and second magnetic layers are magnetization free layers in which the direction of magnetization changes according to a predetermined external magnetic field, and the third magnetic layer has an external magnetic field under the external magnetic field. 13. The pinned layer according to claim 1, wherein the pinned layer substantially holds the magnetization direction in a zero state.
Item 7. The magnetoresistive element according to item 1. 14. The method according to claim 1, wherein
A magnetic storage device comprising a plurality of magnetoresistive elements described in the section.