JP2002299727A - Magnetic element, tunnel-magnetoresistive effect element, and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic element in which magnetization and a coercive force is freely selectable by reducing the coercive force of a refined ferromagnetic layer. SOLUTION: A second magnetic layer 102 has smaller coercive force than a first magnetic layer 101, so that the magnetization tends to be reversed. When the magnetization of the second magnetic layer 102 is reversed, the magnetization of the first magnetic layer 101, in contact with the second magnetic layer 102, tends to be reversed due to magnetic field leaking from the second magnetic layer 102, and therefore, the coercive force of this magnetic element becomes small. In addition, the coercive force of a tunnel magnetoresistive effect element also becomes small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nonvolatile storage element, and more particularly, to a magnetic element that stores information with a coercive force.

[0002]

2. Description of the Related Art Generally, a ferromagnetic material remains after magnetization generated by an externally applied magnetic field is removed from an external magnetic field. The electric resistance of the ferromagnetic material changes depending on the direction of magnetization. This is called the magnetoresistance effect. The rate of change of the electric resistance value is determined by the magnetoresistance ratio (M
agneto-Resistance Ratio; M
R ratio).

If the magnetoresistance effect is used, a nonvolatile memory that stores information according to the magnetization direction of a ferromagnetic material can be realized. Such a non-volatile memory is a magnetic memory (MRAM; Magnetic Random Ac).
ESS Memory). In recent years, a tunnel magnetoresistive effect (TMR: Tunnel Magneto-Res) having a structure in which a nonmagnetic layer is sandwiched between two ferromagnetic layers.
Giant magnetoresistance effect (Gia)
It has been found that nt Magnet Resistance can be obtained, and is attracting attention. Since the tunnel magnetoresistance effect element has a high magnetoresistance ratio, the MR
Development for practical use of AM and magnetic heads is underway.

This type of MRAM has a tunnel magnetoresistive element in each memory cell. In a tunnel magnetoresistance effect element, the change in electric resistance when a current flows in a direction perpendicular to the film surface is caused by the difference in spin polarizability between the two ferromagnetic layers using the nonmagnetic layer as a tunnel barrier layer. Occurs. If the change in the electric resistance value is detected as a change in the tunnel current, the stored information can be read.

[0005] Recently, mobile devices such as mobile phones and PDAs have been actively developed. As mobile devices become more sophisticated, the need for a large-capacity, high-speed, non-volatile memory as a storage memory is increasing.
In various technical fields, reduction in weight, size, and power consumption are being pursued. To realize these, MRAM
It is desired that two parameters of magnetization and coercive force of a micronized magnetic material can be freely selected. Here, a piece of a magnetic thin film that has been finely processed to realize some function is referred to as a magnetic element.
In the development of magnetic elements, sub-μm devices and even 100 μm
In order to realize nm devices, battles are underway to push the limits of the physical properties of materials.

The basic structure of a tunnel magnetoresistive element is composed of two ferromagnetic layers and a thin non-magnetic layer sandwiched between them. The two ferromagnetic layers have different coercive forces. When the magnetization directions of the two ferromagnetic layers are parallel and in the same direction (hereinafter, referred to as parallel), and when the magnetization directions of the two ferromagnetic layers are parallel and in opposite directions (hereinafter, referred to as anti-parallel), the electric current of the tunnel magnetoresistance effect element is changed. The resistance values are different. The tunnel magnetoresistive element uses this phenomenon to store a binary state of “0” and “1”.

Writing of information to the tunnel magnetoresistive element is performed by changing the magnetization direction of the ferromagnetic layer having the larger coercive force by an external magnetic field. By passing current through the wiring located near the tunnel magnetoresistive element,
A method for generating an external magnetic field to a tunnel magnetoresistive element is known.

As methods for reading information from the tunnel magnetoresistive element, an absolute value detection method and a differential detection method are known. In the absolute value detection method, the determination is made based on the absolute value of the electric resistance value of the tunnel magnetoresistance effect element. In the differential detection method, a weaker external magnetic field is applied at the time of writing to invert only the magnetization of the ferromagnetic layer having a small coercive force. The status is read.

A magnetic element utilizing the tunnel magnetoresistive effect is excellent in radiation resistance because information is stored magnetically, is nonvolatile in principle, can be accessed at high speed, and has no limitation on the number of times of writing. Has many advantages.
Also, with MRAM, high-density recording can be easily realized by diverting existing semiconductor manufacturing technology.
It is expected to replace AM.

[0010]

In memory development, the size of a memory cell as a unit for recording information has been reduced year by year in order to improve the recording density. However, when the magnetic film is miniaturized, its coercive force tends to increase. This is considered to be due to the fact that the proportion of the portion located at the boundary (edge) of the presence or absence of the film is relatively increased when miniaturization is performed. This is because the magnetization direction tends to face the film surface at the end of the film so that the magnetic pole is not emitted to the outside.

As described above, in a film having a component deviated from the axis direction in which the original magnetization is easy, the exchange energy is large, and a large energy is required for magnetization reversal. A large energy for reversing the magnetization means a large coercive force.

In an MRAM, the magnetization of a ferromagnetic layer is reversed by an external magnetic field generated by flowing a current through a wiring near a memory cell. If the coercive force of the memory cell increases, a large current is required for magnetization reversal. If the required current is large, the power consumption is correspondingly large, which is not preferable.

An alloy magnetic thin film of a rare earth metal and a transition metal is particularly excellent in perpendicular anisotropy, and the magnetization is stably oriented in the direction perpendicular to the film surface even when the size is reduced.
It has been considered to be more advantageous than a conventionally proposed ferromagnetic thin film having in-plane magnetic anisotropy such as Co.

However, an alloy magnetic thin film of a rare earth metal and a transition metal has a large original coercive force. Therefore, when a memory cell is miniaturized to a submicron region, a current necessary for writing and reading information becomes in-plane magnetization. There is a problem that the film becomes larger than the film.

A first object of the present invention is to realize a magnetic element in which magnetization and coercive force can be freely selected by reducing the coercive force of a miniaturized ferromagnetic layer.

A second object of the present invention is to reduce the coercive force of the memory cell, thereby reducing the write current required for reversing the magnetization and realizing a low power consumption MRAM.

A third object of the present invention is to provide an MRAM with high cost performance and high productivity.

[0018]

In order to achieve the above object, a magnetic element of the present invention is a magnetic element utilizing a coercive force of a ferromagnetic material, and comprises a first magnetic layer formed on a substrate. ,
And a second magnetic layer having lower magnetic anisotropy than the first magnetic layer and in contact with the first magnetic layer.

Since the second magnetic layer has a lower magnetic anisotropy than the first magnetic layer, it has a smaller coercive force than the first magnetic layer, so that the magnetization is more easily reversed than the first magnetic layer. When the magnetization of the second magnetic layer is reversed, the magnetization of the first magnetic layer is likely to be reversed due to a magnetic field leaking from the second magnetic layer. Therefore, in the magnetic element of the present invention, since the first magnetic layer is inverted with a smaller external magnetic field than when the first magnetic layer exists alone, the coercive force can be reduced in the miniaturized ferromagnetic layer.

According to an embodiment of the present invention, the second magnetic layer is in contact with a periphery of the first magnetic layer.

According to an embodiment of the present invention, the second magnetic layer is in contact with an upper part of the first magnetic layer.

According to an embodiment of the present invention, the main magnetization directions of the first magnetic layer and the second magnetic layer are perpendicular to the film surface.

According to an embodiment of the present invention, the first magnetic layer and the second magnetic layer are an alloy of a rare earth metal and a transition metal.

According to an embodiment of the present invention, said alloy comprises:
It contains at least two of Gd, Tb, Ho, Dy, Fe, Co, and Ni.

According to another embodiment of the present invention, the first
The main magnetization directions of the magnetic layer and the second magnetic layer are horizontal to the film surface.

According to an embodiment of the present invention, the second magnetic layer is a modified product of the first magnetic layer.

According to an embodiment of the present invention, the modified material is a Ga contaminant.

According to another embodiment of the present invention, said modified product is an oxide.

Another magnetic element of the present invention is a magnetic element utilizing the coercive force of a ferromagnetic material, and has a plurality of magnetic layers having different magnetic anisotropies.

The tunnel magnetoresistive element of the present invention has a first magnetic element in which two magnetic layers having different magnetic anisotropies are in contact with each other and a structure in which two magnetic layers having different magnetic anisotropy are in contact with each other. A second magnetic element having a coercive force different from that of the first magnetic element; and a non-magnetic insulating layer sandwiched between the first magnetic element and the second magnetic element.

In a tunnel magnetoresistive element including two magnetic elements and a nonmagnetic insulating layer, if a magnetic element in which magnetic layers having different magnetic anisotropies are in contact with each other is used, a tunnel magnetoresistive element having a small coercive force can be obtained. realizable.

Another tunnel magnetoresistive element of the present invention has a configuration in which a first magnetic element composed of a single magnetic layer and two magnetic layers having different magnetic anisotropies are in contact with each other. A second magnetic element having a different coercive force from the element; and a nonmagnetic insulating layer interposed between the first magnetic element and the second magnetic element.

Still another tunnel magnetoresistance effect element according to the present invention comprises a first magnetic element comprising a plurality of magnetic layers having different magnetic anisotropies and a plurality of magnetic layers having different magnetic anisotropies. A second magnetic element having a different coercive force from the first magnetic element; and a nonmagnetic insulating layer sandwiched between the first magnetic element and the second magnetic element.

Still another tunneling magneto-resistance effect element according to the present invention comprises a first magnetic element composed of a single magnetic layer and a plurality of magnetic layers having different magnetic anisotropies, and is kept in the first magnetic element. A second magnetic element having a different magnetic force; and a nonmagnetic insulating layer sandwiched between the first magnetic element and the second magnetic element.

According to the method of manufacturing a magnetic element of the present invention, a step of forming a first magnetic layer on a substrate, the step of implanting charged particles to modify the first magnetic layer, Forming a second magnetic layer having low magnetic anisotropy.

The coercive force is improved by introducing a process for producing a magnetic element with reduced magnetic anisotropy by irradiating the magnetic layer with an ion beam to implant charged particles and thereby producing a magnetic element with reduced magnetic anisotropy. Can be manufactured.

According to an embodiment of the present invention, the charged particles are driven into a side wall portion of the first magnetic layer.

According to another embodiment of the present invention, the charged particles are implanted into an upper surface portion of the first magnetic layer.

According to an embodiment of the present invention, the entirety of the first magnetic layer is modified by implanting the charged particles.

According to an embodiment of the present invention, the charged particles are made of a rare gas, nitrogen, oxygen or a mixture thereof.

According to another embodiment of the present invention, the charged particles are made of Ga, B, P, As or a mixture thereof.

According to an embodiment of the present invention, the charged particles have an injection energy of 10 to 300 keV.

According to the method of manufacturing a tunnel magnetoresistive element of the present invention, a lower ferromagnetic layer, a non-magnetic insulating layer and an upper ferromagnetic layer are formed on a substrate to form an element, and charged particles are implanted. Modifying at least one of the lower ferromagnetic layer and the upper ferromagnetic layer.

By introducing a process of producing a magnetic element with reduced magnetic anisotropy by irradiating charged particles by irradiating the ferromagnetic layer with an ion beam or the like, a mask manufacturing process is unnecessary and an easy process is adopted. A tunnel magnetoresistive element having reduced coercive force can be manufactured. In addition, it is possible to complete the processing of a key point in a pinpoint manner.

According to an embodiment of the present invention, the charged particles are driven into a side wall portion of the device.

According to another embodiment of the present invention, the charged particles are driven into the upper surface of the device.

According to an embodiment of the present invention, the whole of the upper ferromagnetic layer is modified by implanting the charged particles.

According to an embodiment of the present invention, the charged particles are made of a rare gas, nitrogen, oxygen or a mixture thereof.

According to an embodiment of the present invention, the charged particles are made of Ga, B, P, As or a mixture thereof.

According to an embodiment of the present invention, the charged particles have an injection energy of 10 to 300 keV.

[0051]

Embodiments of the present invention will be described in detail with reference to the drawings.

The magnetic element of the present invention comprises a plurality of magnetic layers having different magnetic anisotropies. As an embodiment of the present invention, a case where two magnetic layers having different magnetic anisotropies are in contact with each other will be exemplified.

The magnetic element of the present embodiment has the domain composed of the first magnetic layer and the second magnetic layer having a lower magnetic anisotropy than the first magnetic layer and having contact with the first magnetic layer. Domain is formed on the substrate. Here, “magnetic element” refers to a film piece formed by finely processing a magnetic thin film in order to realize some function.
The term “domain” refers to a region where a magnetic thin film defined by microfabrication exists.

Since the second magnetic layer has lower magnetic anisotropy than the first magnetic layer, it has a smaller coercive force than the first magnetic layer.
When the magnetic field applied to the magnetic element of the present embodiment from the outside is gradually increased, the magnetization of the second magnetic layer is reversed before the first magnetic layer. When the magnetization of the second magnetic layer is reversed, the magnetization of the first magnetic layer is easily reversed due to a magnetic field leaking from the second magnetic layer. Therefore, the first magnetic layer is
Is reversed by a smaller external magnetic field when it is in contact with the magnetic layer. Therefore, the coercive force can be reduced in the miniaturized ferromagnetic layer, and the magnetic element can be configured by freely selecting the magnetization and the coercive force.

In a tunnel magnetoresistive effect element including a lower ferromagnetic layer, a non-magnetic layer, and an upper ferromagnetic layer, if the magnetic element of the present embodiment is used for the lower or upper ferromagnetic layer, a magnetic memory (MRAM) having a small coercive force is used. ) Can be realized. A magnetic memory having a small coercive force has a low power consumption because an external magnetic field (hereinafter, referred to as a reversal magnetic field) at which magnetization reversal occurs is small.

FIG. 1 is a cross-sectional view of a magnetic element according to an embodiment of the present invention.
It is a perspective view of one form. FIG. 1A shows a cylindrical type, and FIG.
1 (b) shows a rectangular parallelepiped magnetic element, FIG. 1 (c) shows an upper type, and FIG. 1 (d) shows a lower type magnetic element.

Referring to FIGS. 1A and 1B, the first
A second magnetic layer 102 having lower magnetic anisotropy than the first magnetic layer is disposed around the magnetic layer 101. FIG.
Referring to (c) and (d), a second magnetic layer 102 is superimposed on or below the first magnetic layer 101.
In any case, the magnetic element of the present embodiment has a smaller coercive force than the single first magnetic layer 101.

It is desirable that the magnetization directions of the first magnetic layer 101 and the second magnetic layer 102 are substantially the same. Further, the first magnetic layer 101 and the second magnetic layer 102
May be an in-plane magnetization film whose magnetization direction is horizontal to the film surface, or may be a perpendicular magnetization film whose magnetization direction is perpendicular to the film surface.

FIG. 2 is a schematic sectional view showing how the magnetization direction of each magnetic layer of the magnetic element of this embodiment changes. FIG.
2A to 2D show the first and second magnetic layers 101,
The state from the state in which the magnetization directions are aligned to the state in which the magnetization is reversed by application of an external magnetic field and aligned in the opposite direction is shown in time series. In FIG. 2A, the arrow indicates the first
Is a vector representing the magnetization direction of the magnetic layer 101 and the second magnetic layer 102 of FIG.

It is to be noted that this is a simplified model for briefly describing the mechanism of the present invention. Needless to say, the actual magnetization reversal behavior is a microscopic and complicated reaction based on micromagnetics.

The mechanism of the present invention will be described with reference to FIG.

At the time of FIG. 2A, the first magnetic layer 10
The magnetizations of the first and second magnetic layers 102a and 102b are both upward. Here, when the downward external magnetic field applied to the magnetic element is gradually increased, as shown in FIG. 2B, the magnetization directions of the second magnetic layers 102a and 102b having low magnetic anisotropy are inclined. come.

At the time of FIG. 2B, the intensity of the external magnetic field is smaller than the coercive force of the single first magnetic layer 101. The first magnetic layer 101 has a second magnetic layer 102 around it.
In this state, the exchange force is received from the a and 102b, and the magnetization is more likely to be reversed than in the case of a single case. Therefore, FIG.
As shown in (b), the direction of the magnetization of the first magnetic layer 101 is also inclined. However, the inclination of the first magnetic layer 101 is smaller than that of the second magnetic layers 102a and 102b.

At the time of FIG. 2C, the downward external magnetic field is stronger than at the time of FIG. The magnetizations of the second magnetic layers 102a and 102b having low magnetic anisotropy have almost finished reversal. On the other hand, the direction of the magnetization of the first magnetic layer 101 rotates with a slight delay. However, since the coercive force is reduced as compared to the single first magnetic layer 101, the rotation of the magnetization is advanced.

At the time of FIG. 2D, the external magnetic field is stronger than at the time of FIG. 2C. First magnetic layer 10
The magnetization reversal of both the first and second magnetic layers 102a and 102b has been completed. As described above, the first magnetic layer 101
Is reversed by a small external magnetic field, as compared with the case where is used alone.

Therefore, the magnetic element of the present embodiment is
When applied to AM, it is possible to easily lower the coercive force of the memory cell and reduce the write current required for magnetization reversal.

FIG. 3 shows the magnetization curve (a) of the magnetic element of the present embodiment and the magnetization curve (b) of the single first magnetic layer 101.
FIG. The magnetization curve is a graph showing the relationship between the external magnetic field (H) and the magnetization. Arrows in FIG. 3 indicate the direction of progress of magnetization in a portion where the magnetization curve shows hysteresis characteristics. Here, the external magnetic field at the point where the magnetization curve crosses the H axis is defined as the coercive force. The coercive force of the magnetic element of this embodiment is Hc1, and the coercive force of the single first magnetic layer 101 is Hc2.

The coercive force Hc1 and the coercive force Hc2 are Hc1
> Hc2. That is, the magnetization of the magnetic element of the present embodiment is reversed by a weak external magnetic field as compared with the single first magnetic layer 101.

FIG. 4 is a schematic diagram showing a state of magnetization of a magnetic element using a perpendicular magnetization film which is an alloy of a rare earth metal and a transition metal. FIG. 4A shows the magnetization when the transition metal is dominant, and FIG. 4B shows the magnetization when the rare earth metal is dominant.
The thick black arrow indicates the direction of magnetization of the rare earth metal (RE),
A thin arrow indicates the direction of magnetization of the transition metal (TM), and a thick white arrow indicates the direction of magnetization obtained by adding them.

Rare earth metal-transition metal magnetic materials combined with appropriate materials and compositions exhibit ferrimagnetism. Therefore, the magnetization of the rare earth metal and the magnetization of the transition metal are antiparallel. Then, the difference between the main lattice magnetization and the sub lattice magnetization is observed as the entire magnetization.

FIG. 4A shows that the first magnetic layer 401 and the second magnetic layer 402 are both alloys in which a transition metal is predominant.
The magnetic element according to this embodiment includes a first magnetic layer 401 and second magnetic layers 402a and 402b.

In the first magnetic layer 401, the magnetization of the transition metal is larger than that of the rare earth metal, but the difference between them is small. Therefore, the magnetization of the entire first magnetic layer 401 is smaller than the magnetizations of the second magnetic layers 402a and 402b. In the second magnetic layers 402a and 402b, the magnetization of the transition metal is much larger than the magnetization of the rare earth metal. Therefore, the second magnetic layer 4
The magnetizations of the entire layers 02a and 402b are larger than the magnetization of the first magnetic layer 401.

Therefore, the magnetizations of the second magnetic layers 402 a and 402 b having a large magnetization, that is, a low magnetic anisotropy, are reversed by an external magnetic field weaker than that of the first magnetic layer 401.

FIG. 4B shows that the first magnetic layer 403 and the second magnetic layer 404 are both alloys in which rare earth metals are predominant. The magnetic element according to the present embodiment includes the first magnetic layer 403 and the second magnetic layer 403.
Of the magnetic layers 404a and 404b.

In the first magnetic layer 403, the magnetization of the rare earth metal is larger than that of the transition metal, but the difference between them is small. Therefore, the magnetization of the entire first magnetic layer 403 is smaller than the magnetizations of the second magnetic layers 404a and 404b. In the second magnetic layers 404a and 404b, the magnetization of the rare earth metal is much larger than the magnetization of the transition metal. Therefore, the second magnetic layer 4
The magnetizations of the entire layers 04a and 404b are larger than the magnetization of the first magnetic layer 403.

Therefore, the magnetizations of the second magnetic layers 404 a and 404 b having a large magnetization, that is, a low magnetic anisotropy, are inverted by an external magnetic field weaker than that of the first magnetic layer 403.

Therefore, the magnetizations of the second magnetic layers 404 a and 404 b having a large magnetization, that is, low magnetic anisotropy, are reversed by an external magnetic field weaker than that of the first magnetic layer 403.

FIG. 4 shows the relationship between the predominant metal of the first magnetic layer and the second metal.
The case where the predominant metal of the magnetic layer is the same is shown, but if the magnetization of the entire first magnetic layer is larger than the magnetization of the entire second magnetic layer and the direction is the same, either one of them is a rare earth metal. It may be dominant and the other may be transition metal dominant.

Next, a method for manufacturing the magnetic element of this embodiment will be described. There are many methods for manufacturing the magnetic element of the present embodiment. For example, there are a method of modifying the first magnetic layer to obtain a second magnetic layer, and a method of patterning the second magnetic layer by photolithography to form a film.

FIG. 5 is a schematic diagram for explaining a method of manufacturing a magnetic element of the present embodiment in which charged particles are injected into a first magnetic layer and modified to obtain a second magnetic layer.

As shown in FIG. 5A, a first magnetic layer 502 and a protective layer 503 are formed on a substrate 501.

The first magnetic layer 502 is made into an element by a focused ion beam (acceleration voltage: 30 kV) using Ga as an ion source. FIG. 5B shows a state of the processing. When the first magnetic layer 502 is irradiated with the ion beam 504, a modified taper is generated around the element. The modified portion of the first magnetic layer 502 becomes the second magnetic layer 505. FIG. 5C shows a state after the second magnetic layer 505 is generated by the modification.

In the second magnetic layer 505, the magnetic coupling chains in the first magnetic layer 502 are partially cut off by Ga ions, so that the magnetic anisotropy is reduced.

The ions or charged particles used to modify the first magnetic layer 502 are not limited to Ga focused beams. A rare gas such as Ar, a gas such as N ₂ or O ₂ for realizing a reactive process, or Ga, B used as a dopant gas in a semiconductor manufacturing process,
Ions using P, As, and a mixture thereof as a raw material may be used.

The ion or charged particle implantation energy used to modify the first magnetic layer 502 is 1
0 to 300 keV is appropriate. At an energy of 10 keV or less, sufficient reforming does not occur. Also, 300 keV
If the energy exceeds 3, physical damage may be caused to the target object, and the target object may be destroyed.

The injection energy is appropriately selected according to the charged particles, the material, processed shape, processing location, and the like of the first magnetic layer 502 to be modified.

By modifying the first magnetic layer 502, the second
The place where the magnetic layer 505 is formed is not limited to the periphery of the first magnetic layer 502 as shown in FIG.

As shown in FIGS. 1C and 1D,
An embodiment in which the second magnetic layer 505 is formed above or below the first magnetic layer 502 is also conceivable.

FIG. 6B shows a second magnetic layer 505 formed on the first magnetic layer 502. Protective layer 50
By selecting an appropriate thickness as the film thickness of No. 3, the amount of ion implantation into the first magnetic layer 502 is adjusted, and the ion beam 504 is applied to the upper surface of the first magnetic layer 502 as shown in FIG. By irradiation, the thickness of the second magnetic layer 505 can be set to a desired thickness.

If the thickness of the protective layer 503 is further reduced so that the non-magnetic element 506 completely penetrates, FIG.
As described above, the first magnetic layer 502 is entirely reformed.

Note that the manufacturing method for forming the second magnetic layer 505 from the first magnetic layer 502 is not limited to ion beam irradiation such as FIB. For example, the first magnetic layer 502 can be easily modified by naturally oxidizing it in the air.

An example of a manufacturing method for obtaining the second magnetic layer by modifying the first magnetic layer by natural oxidation will be described with reference to FIG.

Referring to FIG. 7, a first magnetic layer 701 is formed on a substrate (not shown). First magnetic layer 70
In 1, the magnetization of the transition metal is larger than the magnetization of the rare earth metal. Since the difference between the two magnetizations is small, the transition metal is dominant. Therefore, the first magnetic layer 701 has large magnetic anisotropy.

When the first magnetic layer 701 is left in the air for a certain period of time, the rare earth metal in the first magnetic layer 701 is easily oxidized and loses magnetization. As a result, the second magnetic anisotropy
Are formed around the first magnetic layer 701. In this example, the second magnetic layer mainly shows the magnetization of the transition metal. Therefore, depending on the type of the transition metal material, the magnetic element has a slight in-plane magnetization component. However, since the magnetization directions of the first magnetic layer and the second magnetic layer are substantially the same, the function of the present invention is not impaired.

The thickness of the second magnetic layer covering the periphery of the first magnetic layer is appropriately selected depending on the combination of materials.

Further, a third layer different from the first magnetic layer and the second magnetic layer may be present at the boundary between the first magnetic layer and the second magnetic layer. The third layer may be composed of a mixture of the materials of the first magnetic layer and the second magnetic layer, or may be composed of a completely different non-magnetic material. In any case, it is desirable that the thickness of the third layer be as small as possible.
It is desirable to be in the range of 0 to 3 nm. If the third layer is too thick, the magnetic coupling force between the first magnetic layer and the second magnetic layer is weakened, and the effect unique to the present invention of reducing the coercive force is reduced.

The magnetic element of this embodiment can be applied to a tunnel magnetoresistance effect element.

FIG. 8 is a perspective view showing an example of a tunnel magnetoresistive element having a configuration in which a nonmagnetic insulating layer is sandwiched between the magnetic elements of this embodiment.

The conventional tunnel magnetoresistive element comprises a lower ferromagnetic layer, a non-magnetic insulating layer and an upper ferromagnetic layer, and both the upper and lower ferromagnetic layers are single layers.

Referring to FIG. 3, the lower ferromagnetic layer of the tunnel magnetoresistive element according to the present embodiment has a first magnetic layer 80.
The first magnetic element 810 includes the first and second magnetic layers 804. The nonmagnetic insulating layer is a tunnel film 80.
2. In addition, the upper ferromagnetic layer is the first magnetic layer 803.
And a second magnetic element 820 including a second magnetic layer 805.

The lower and upper ferromagnetic layers have different coercive forces. The smaller coercive force is the free layer, and the larger coercive force is the pinned layer.

In the present embodiment, the second magnetic layer 804 of the first magnetic element 810 is arranged to cover the periphery of the first magnetic layer 801. The second magnetic layer 805 of the second magnetic element 820 is arranged to cover the periphery of the first magnetic layer 803. Then, the first and second magnetic elements 81
0,820 constitutes a tunnel magnetoresistance effect element.

The tunnel magneto-resistance effect element is electrically connected to a lower sense line 806 and upper sense lines 807a and 807b. In FIG. 8, the upper sense line 807 is divided into 807a and 807b to make the structure easier to see, but it is actually one wiring.

The first magnetic element 8 is connected to the lower sense line 806.
Ten first magnetic layers 801 and second magnetic layers 804 are connected. The second magnetic element 8 is connected to the upper sense line 807.
Twenty first magnetic layers 803 and second magnetic layers 805 are connected. Then, the sense current flows from one sense line to the other sense line through the tunnel magnetoresistive element. FIG. 8 does not show an insulating layer necessary for flowing a sense current.

Since the magnetic element of this embodiment has a small coercive force, information can be easily written by applying an external magnetic field.

The tunnel magnetoresistance effect element has, as constituent elements, an upper ferromagnetic layer and a lower ferromagnetic layer having different coercive forces. These have different coercive forces and different easiness of reversal of magnetization. The one where the magnetization is easily inverted is a soft magnetic material, and the one where the magnetization is hard to be inverted is a hard magnetic material. Since the magnetization of the soft magnetic material is easily inverted, the soft magnetic material functions as a reproducing layer whose magnetization is inverted when information is read.

The hard magnetic material functions as a memory layer for storing information because the magnetization is harder to reverse than the soft magnetic material.

The soft magnetic material and the hard magnetic material are defined by the magnitude relationship of the coercive force between the two ferromagnetic layers, and those having a large coercive force are defined as hard magnetic materials.

When the magnetic element of this embodiment is applied to a tunnel magnetoresistive effect element, it is used for both the upper ferromagnetic layer and the lower ferromagnetic layer as shown in FIG. It is also conceivable to apply to

When the upper ferromagnetic layer is modified by the ion beam, a part of the upper ferromagnetic layer may be modified as described above, or substantially the entire upper ferromagnetic layer may be modified. Is also good.

FIG. 9 is a perspective view of a tunnel magnetoresistive element formed by modifying a part of the upper ferromagnetic layer.

In FIG. 9, the lower ferromagnetic layer is the first magnetic element 830. The non-magnetic insulating layer is a tunnel film 8.
02. Further, the upper ferromagnetic layer is formed of the first magnetic layer 80.
2 and a second magnetic element 840 comprising a second magnetic layer 805
It is. The conductive protective layer 308 prevents ion implantation damage.

The coercive forces of the lower ferromagnetic layer and the upper ferromagnetic layer are different from each other, and the smaller coercive force is a free layer, and the larger coercive force is a pinned layer. Here, it is assumed that the upper ferromagnetic layer is a pinned layer.

As a manufacturing method, after processing for defining an area of a memory cell, the first magnetic layer 803 of the second magnetic element 840 is modified by irradiation with an ion beam, A second magnetic layer 805 is formed on the top of the layer 803.

In the second magnetic layer 805, the magnetic coupling chain in the first magnetic layer 803 is partially cut off by Ga ions, and the magnetic anisotropy is reduced. The coercive force of the second magnetic element 840 serving as a pin layer can be adjusted by selecting the thickness of the conductive protective layer 808.

Since the magnetic element of this embodiment has a small coercive force, the tunnel magnetoresistance effect element shown in FIG. 9 can easily record information by applying an external magnetic field.

FIG. 10 is a perspective view of a tunnel magnetoresistive element formed by modifying the entire upper ferromagnetic layer.

In FIG. 10, the lower ferromagnetic layer is the first magnetic element 830. The non-magnetic insulating layer is a tunnel film 802
It is. The upper ferromagnetic layer is the second magnetic element 850.
In the case of FIG. 10, as in FIG. 9, the upper ferromagnetic layer is a pinned layer.

After the processing for defining the area of the memory cell, the entire upper ferromagnetic layer is reformed by irradiating with an ion beam to generate a second magnetic element 850. The nonmagnetic element 809 is implanted in the second magnetic element 850. By selecting the injection energy at this time, the coercive force of the second magnetic element 850 serving as the pinned layer can be adjusted.

Since the magnetic element of this embodiment has a small coercive force, the tunnel magnetoresistive element of FIG. 10 can easily record information by applying an external magnetic field.

It should be noted that it is relatively easy to introduce a process of manufacturing a magnetic element having reduced magnetic anisotropy by irradiating an ion beam in the manufacturing process of the tunnel magnetoresistive effect element because a mask manufacturing step is unnecessary. It is. In addition, since you can finish important points at a pinpoint,
High productivity in processing to reduce coercive force.

Note that the application range of the magnetic element of this embodiment is not limited to the tunnel magnetoresistance effect element. It goes without saying that the magnetic element of the present embodiment can be widely applied when a magnetic element having a low coercive force is required in a magnetic application product subjected to fine processing.

Next, specific examples of the present invention will be described in detail. (First Embodiment) An example of a magnetic element in which a coercive force is reduced by arranging a second magnetic layer, which is a modification of the first magnetic layer, around the first magnetic layer will be described.

The magnetic film is finely processed by using a FIB (focused ion beam) apparatus, and a 0.3 to 0.7 [μm] square of FIG.
A magnetic element as shown in (c) was prepared. Then, it was verified how the coercive force changed depending on the element size.

At this time, magnetic information measured by a magnetic force microscope (MFM) was used as the coercive force of the magnetic element. In addition, 1c measured by a vibrating magnetometer (VSM)
An m-square perpendicularly anisotropic magnetization single layer film was used as a comparison object. Also,
In the experiment, a ferrimagnetic material in which a transition metal is predominant was used.

Tb ₂₀ Fe was used as the first magnetic layer, and the film thickness was 30 nm. In a Tb-Fe-based perpendicular magnetization film, T
Since the component b has a compensation composition in the vicinity of 25%, Fe, which is a transition metal, becomes dominant below 25%, and Tb, which is a rare earth metal, becomes dominant above 25%.

First, Tb ₂₀ Fe was formed as a first magnetic layer on a substrate. The substrate used here is (1, 0, 0)
Is formed on a 4-inch Si wafer having a crystal orientation of 1 μm and a thermal oxide film of 1 μm. Using a magnetron sputtering method to deposit the Tb ₂₀ Fe, was co-sputtering by Tb target and Fe targets. Since rare earth metals are easily oxidized, an apparatus having a load lock chamber was used. The ultimate pressure of the sputtering chamber was −5 Pa or less.

After forming the first magnetic layer, 45 nm of Si was formed as a protective film by magnetron sputtering.

Next, the substrate was taken out and put into the FIB apparatus. In the FIB apparatus, Ga ions were extracted at an acceleration voltage of 30 kV and a beam current of 11 pA to process a magnetic film into a box-in-box shape, and magnetic films of each size were cut out from the surroundings. The separation distance from the cut magnetic film to the surrounding film was 3 μm.

Next, after removing the substrate from the FIB apparatus, 2 nm of Pt was sputtered to form an antioxidant film on the processed surface.

Next, +1 in the direction perpendicular to the film surface of the substrate
Magnetization was performed by applying a magnetic field of 8 kOe. The substrate after magnetization was introduced into an MFM apparatus, and the magnetization direction of the sample was confirmed.

Table 1 shows that the magnetic field is swept in the minus direction after the magnetization, and then the MFM is performed under zero magnetic field.
5 shows an MFM image at the time of measurement. In Table 1, the case where the magnetization is on the + side is indicated by a white circle, and the case where the magnetization is on the − side is indicated by a black circle.

[0133]

[Table 1]

FIG. 11 is a diagram showing the difference in the MFM image depending on the magnetization direction. FIG. 11A shows a case where the element is magnetized vertically upward to the film surface of the 1 μm square element. FIG.
(B) is a case where a similar element is magnetized vertically and downward. The magnetization direction of the MFM probe was downward.

The MFM is imaged by phase detection using a probe coated with CoCr, and is set so that the whiter the color table, the stronger the repulsive force and the blacker the color table, the stronger the attractive force. Lift scan height is 3
0 nm. The black and white are clearly inverted depending on the magnetization direction of the sample.

The coercive force of the 1 cm square perpendicular anisotropic magnetization single layer film measured by VSM is 12.72 [kOe].
The magnetization was 92.2 emu / cc.

On the other hand, 0.5 [μm] to 0.7
The [μm] square-sized element had a magnetization reversal between the magnetizing magnetic fields of 2 to 3 [kOe]. Also, 0.3 [μm] to 0.4
The [μm] square-sized element had a magnetization reversal between 1 and 2 [kOe].

This indicates that the smaller the element size, the lower the coercive force of the element. This is because the smaller the element size, the larger the area of the Ga ion irradiation portion with respect to the entire area of the element. That is, the second side formed around the first magnetic layer by modifying the side wall of the first magnetic layer.
By arranging the above magnetic layer, the coercive force could be reduced. (Second Embodiment) Another example of a magnetic element in which the coercive force is reduced by disposing a second magnetic layer, which is a modified product of the first magnetic layer, around the first magnetic layer will be described. .

[0139] The magnetic film was modified using FIB, and FIG.
As shown in (b), a second magnetic layer was formed on the first magnetic layer.

Tb ₂₀ Fe was used for the first magnetic layer, and the film thickness was 30 nm. First, as the first magnetic layer, Tb ₂₀
Fe was deposited on the substrate. The substrate used here is (1,
1 μm on a 4-inch Si wafer with a crystal orientation of (0,0)
m thermal oxide film is formed. Using a magnetron sputtering method to deposit the Tb ₂₀ Fe, was co-sputtering by Tb target and Fe targets. Since rare earth metals are easily oxidized, a device with a load lock chamber was used. The ultimate pressure of the sputtering chamber was −5 Pa or less.

After forming the first magnetic layer, 25 nm of Si was formed as a protective film by magnetron sputtering.
The magnetic film thus obtained was processed into an isolated magnetic element by forming a mask by photolithography and ion milling. The element size was 1 μm square. The separation distance from the magnetic element to the surrounding film was 3 μm.

After processing the magnetic element, 2 nm of Pt was sputtered to form an antioxidant film on the processed surface.

Next, the first magnetic layer was modified by a focused ion beam (acceleration voltage: 30 kV) using Ga as an ion source.
Since the protective film Si is thinner than that of the first embodiment, FIG.
When the ion beam 504 is injected into the first magnetic layer as shown in FIG. 6A, a second magnetic layer 505 having reduced anisotropy is formed on the first magnetic layer 502 as shown in FIG. Was done. The amount of Ga ions implanted by a 30 kV focused ion beam is described in J. Org. Electron Micros
According to c 43,322 (1994), it is about 30 nm for a single crystal Si substrate.

Next, in the direction perpendicular to the film surface of the substrate, 25
Magnetization was performed by applying a magnetic field of kOe. Next, the magnetized substrate was introduced into an MFM apparatus, and the magnetization state of the sample was confirmed in the same manner as in the first embodiment.

Table 2 shows the coercive force of the sample according to the second embodiment in which the Si protective film was 25 nm and the coercive force of the comparative sample having the protective film of 45 nm in which the magnetic anisotropy was not reduced by the injection. Shows the results of the measurement. (Third Embodiment) An example of a magnetic element in which a switching field is reduced by forming a second magnetic layer around the first magnetic layer by photolithography will be described.

Here, a ferrimagnetic material composed of a transition metal-dominant rare earth-transition metal was used as a constituent material of the magnetic element.

With reference to FIG. 12, a method for forming the second magnetic layer by photolithography will be described.

First, a first magnetic layer is formed in a pattern on a substrate. FIG. 12A is a view showing a pattern after the patterning is completed, and the first magnetic layer 12 is formed on the substrate 121.
2 are formed. Note that a method of patterning the first magnetic layer 122 includes lift-off and etching.

Next, a second magnetic layer is formed in a pattern shape. FIG. 12B is a view showing a pattern in which the patterning of the second magnetic layer 122 has been completed.
Are formed. Since the second magnetic layer 123 was overlapped after the first magnetic layer 122 was formed, the first magnetic layer 12 was formed at the center of the substrate 121 with reference to FIG.
2 and the second magnetic layer 123 overlap. As a patterning method of the second magnetic layer 123, lift-off, etching, and the like are given. Finally, a portion of the second magnetic layer 123 overlapping the first magnetic layer 122 is removed to form a magnetic element.

Here, the first magnetic layer 122 and the second magnetic layer 12 are formed by forming the second magnetic layer 123 while leaving a mask pattern having the same shape as that of the first magnetic layer 122.
It is also conceivable that 3 do not overlap. But,
In practice, it is not possible to avoid the displacement of the pattern shape, so that a region where the first magnetic layer 122 and the second magnetic layer 123 overlap necessarily occurs. Therefore,
It is said that the second magnetic layer 123 is overlapped on the first magnetic layer 122 with a simple mask shape without performing a complicated operation that leaves a mask pattern having the same shape as the first magnetic layer 122, and there is an overlapping region. When a process is formed on the premise, an unstable position shift region does not occur, and the reliability of processing is improved.

FIG. 12C shows a state in which all patterning has been completed. A second magnetic layer 123 is arranged around the first magnetic layer 122. FIG.
From the state of (b), the second magnetic layer 123 is replaced with the first magnetic layer 1.
The shape shown in FIG. 12C can be obtained by polishing the portion overlapping the portion 22 by a method such as CMP or by specifying the overlapping portion and etching.

Here, an experiment was conducted by the above-described method using a ferrimagnetic material in which a transition metal is predominant. Tb ₂₀ Fe was used for the first magnetic layer, and Tb ₁₈ Fe was used for the second magnetic layer.
Each film thickness was 30 nm using Fe. Tb
Since the Tb component has a compensation composition in the vicinity of 25% in the -Fe-based perpendicular magnetization film, the transition metal, which is a transition metal, is dominant below 25%, and the rare earth metal, which is rare earth metal, is dominant above 25%.

According to the procedure shown in FIG. 12, first, Tb ₂₀ Fe was formed as a first magnetic layer on a substrate. The substrate used here was a 4-inch S with a (1,0,0) crystal orientation.
A 1 μm thermal oxide film is formed on an i-wafer. T
The magnetron sputtering method is used for the film formation of b ₂₀ Fe,
Co-sputtering was performed using the b target and the Fe target. Since rare earth metals are easily oxidized, a device with a load lock chamber was used. The ultimate pressure of the sputtering chamber was −5 Pa or less.

A 30 nm Tb ₂₀ Fe film is formed as a first magnetic layer by magnetron sputtering on a substrate on which a resist mask has been formed by photolithography in advance, and then a 2 nm Pt film is formed as an antioxidant film. Filmed.
The substrate was lifted off by ultrasonic cleaning with acetone to form a pattern.

Next, a resist mask having a pattern shape of the second magnetic layer was formed by photolithography. The substrate on which the mask has been formed is again put into a magnetron sputtering apparatus, and after sufficient degassing, the second magnetic layer Tb ₁₈
Fe was deposited to a thickness of 30 nm, and then Pt was deposited to a thickness of 2 nm as an antioxidant film.

The substrate after these films were formed was lifted off by ultrasonic cleaning of acetone.

Next, the substrate on which the patterning of the second magnetic layer has been completed is again put into a magnetron sputtering apparatus.
This time, a 100 nm SiN film was formed entirely without a mask.

Next, the substrate was put into a CMP apparatus, and a region where the first magnetic layer and the second magnetic layer overlapped was planarized.

Magnetization was performed by applying a magnetic field of 25 kOe in a direction perpendicular to the film surface of the substrate after the planarization. next,
The substrate after the magnetization was introduced into the MFM apparatus, and the magnetization direction of the sample was confirmed.

As a comparative sample, a sample in which the first magnetic layer and the second magnetic layer were Tb ₂₀ Fe was prepared. Then, the magnitude of the magnetic field required to reverse the magnetization direction was compared between the sample of the third embodiment and the comparative sample.

The evaluation was performed by confirming the magnetization direction of the sample using an MFM apparatus and comparing the magnitude of an applied magnetic field required for reversal. As a result of the experiment, it was observed that the magnetization of the sample of the third example was reversed only by applying a smaller magnetic field than that of the comparative sample. Table 2 shows the results. (Fourth Embodiment) Another example of a magnetic element in which a reversal magnetic field is reduced by forming a second magnetic layer around the first magnetic layer by photolithography will be described.

Here, a ferrimagnetic material composed of a rare earth-transition metal in which a rare earth metal is predominant was used as a constituent material of the magnetic element.

Tb ₂₆ Fe was used for the first magnetic layer, and Tb ₂₈ Fe was used for the second magnetic layer. In a Tb-Fe-based perpendicular magnetization film, Tb
Since the component has a compensation composition in the vicinity of 25%, Fe as a transition metal becomes dominant below 25%, and Tb as a rare earth metal becomes dominant above 25%.

According to the procedure shown in FIG. 12, first, Tb ₂₆ Fe as a first magnetic layer was formed on a substrate. The substrate used here was a 4-inch S with a (1,0,0) crystal orientation.
A 1 μm thermal oxide film is formed on an i-wafer. T
The magnetron sputtering method was used to deposit b ₂₆ Fe,
Co-sputtering was performed using the b target and the Fe target. Since rare earth metals are easily oxidized, a device with a load lock chamber was used. The ultimate pressure of the sputtering chamber was −5 Pa or less.

A 30 nm Tb ₂₆ Fe film is formed as a first magnetic layer by magnetron sputtering on a substrate on which a resist mask has been previously formed by photolithography, and then a 2 nm Pt film is formed as an antioxidant film. Filmed.
The substrate was lifted off by ultrasonic cleaning with acetone to form a pattern.

Next, a resist mask having a pattern shape of the second magnetic layer was formed by photolithography. The substrate on which the mask has been formed is again put into a magnetron sputtering apparatus, and after sufficient degassing, the second magnetic layer Tb ₂₈
Fe was deposited to a thickness of 30 nm, and then Pt was deposited to a thickness of 2 nm as an antioxidant film.

The substrate after these films were formed was lifted off by ultrasonic cleaning with acetone.

Next, the substrate on which the patterning of the second magnetic layer has been completed is again put into a magnetron sputtering apparatus.
This time, a 100 nm SiN film was formed entirely without a mask.

Next, the substrate was put into a CMP apparatus, and a region where the first magnetic layer and the second magnetic layer overlapped was planarized.

Magnetization was performed by applying a magnetic field of 25 kOe in a direction perpendicular to the film surface of the substrate after the planarization. next,
The substrate after the magnetization was introduced into the MFM apparatus, and the magnetization direction of the sample was confirmed.

As a comparative sample, a sample in which the first magnetic layer and the second magnetic layer were Tb ₂₆ Fe was prepared. Then, the magnitude of the magnetic field required to reverse the magnetization direction was compared between the sample of the fourth embodiment and the comparative sample.

The evaluation was performed by confirming the magnetization direction of the sample using an MFM apparatus and comparing the magnitude of an applied magnetic field required for reversal. As a result of the experiment, it was observed that the magnetization of the sample of the fourth example was reversed only by applying a magnetic field smaller than that of the comparative sample. Table 2 shows the results. (Fifth Embodiment) Another example of a magnetic element in which the coercive force is reduced by disposing a second magnetic layer, which is a modified product of the first magnetic layer, around the first magnetic layer will be described. . By oxidizing the first magnetic layer, the second magnetic layer is formed on the side wall of the first magnetic layer.
Was formed.

Here, an experiment was conducted using a ferrimagnetic material in which a transition metal is predominant.

Tb ₂₀ Fe was used as the first magnetic layer, and the film thickness was 30 nm. In a Tb-Fe-based perpendicular magnetization film, T
Since the b component has a compensation composition in the vicinity of 25%, Fe, which is a transition metal, becomes dominant below 25%, and Tb, which is a rare earth metal, becomes dominant above 25%.

According to the procedure shown in FIG. 12, first, Tb ₂₀ Fe as a first magnetic layer was formed on a substrate. The substrate used here was a 4-inch S with a (1,0,0) crystal orientation.
A 1 μm thermal oxide film is formed on an i-wafer. T
The magnetron sputtering method is used for the film formation of b ₂₀ Fe,
Co-sputtering was performed using the b target and the Fe target. Since rare earth metals are easily oxidized, a device with a load lock chamber was used. The ultimate pressure of the sputtering chamber was −5 Pa or less.

A 30 nm-thick Tb ₂₀ Fe film was formed as a first magnetic layer by magnetron sputtering on a substrate on which a resist mask was formed by photolithography in advance. next,
The substrate taken out was lifted off by ultrasonic cleaning with acetone to form a pattern.

Next, the substrate on which patterning was completed was left in the air for about one day to oxidize the periphery of the first magnetic layer. Since the oxidized first magnetic layer loses the magnetism of Tb, the transition metal becomes more dominant. Therefore,
A second magnetic layer having a small magnetic anisotropy is substantially formed around the first magnetic layer.

25 kOe perpendicular to the film surface of the substrate
The magnetic field was applied to perform magnetization. Next, the substrate after the magnetization was introduced into the MFM device, and the magnetization direction of the sample was confirmed.

As a comparative sample, immediately after forming the first magnetic layer, 2 nm was formed by magnetron sputtering.
A sample in which Pt was formed as an antioxidant film was prepared. Then, the magnitude of the magnetic field required to reverse the magnetization direction was compared between the sample of the fifth embodiment and the comparative sample.

The evaluation was performed by confirming the magnetization direction of the sample using an MFM apparatus and comparing the magnitude of an applied magnetic field required for reversal. As a result of the experiment, it was observed that the magnetization of the sample of the fifth example was reversed only by applying a magnetic field smaller than that of the comparative sample. Table 2 shows the results. (Sixth Embodiment) Another example of a magnetic element in which the reversal magnetic field is reduced by forming a second magnetic layer around the first magnetic layer by photolithography will be described. An in-plane magnetized film was used as a constituent material of the magnetic element. Fe and Co were used as an example of the in-plane magnetized film.

[0181] Fe was used for the first magnetic layer, and Co was used for the second magnetic layer, and each film thickness was 30 nm.

According to the procedure shown in FIG. 12, first, Fe as the first magnetic layer was formed on a substrate. The substrate used here was a 1-.mu.m thermal oxide film formed on a 4-inch Si wafer having a (1,0,0) crystal orientation. Using a device with a load lock chamber, the ultimate pressure of the sputtering chamber is-
It was 5 Pa or less.

On a substrate on which a resist mask was previously formed by photolithography, 30 nm of Fe was formed as a first magnetic layer by magnetron sputtering, and then 2 nm of Pt was formed as an antioxidant film. .

The substrate thus taken out was lifted off by ultrasonic cleaning with acetone to form a pattern.

Next, a resist mask having a pattern shape of the second magnetic layer was formed by photolithography. The substrate on which the mask has been formed is again put into a magnetron sputtering apparatus, and after sufficient degassing, a second magnetic layer of Co is formed to a thickness of 30 nm, and then Pt is formed as an antioxidant film to a thickness of 2 nm.
A film was formed.

The substrate after these films were formed was lifted off by ultrasonic cleaning of acetone.

Next, the substrate on which the patterning of the second magnetic layer has been completed is again put into a magnetron sputtering apparatus.
This time, a 100 nm SiN film was formed entirely without a mask.

Next, the substrate was put into a CMP apparatus, and a region where the first magnetic layer and the second magnetic layer overlapped was planarized.

Magnetization was performed by applying a magnetic field of 25 kOe in a direction perpendicular to the film surface of the substrate after the planarization. next,
The substrate after the magnetization was introduced into the MFM apparatus, and the magnetization direction of the sample was confirmed.

Further, as a comparative sample, a sample in which the first magnetic layer and the second magnetic layer were Fe was prepared.
Then, with the sample of the sixth embodiment and the sample for comparison,
The magnitude of the magnetic field required to reverse the magnetization direction was compared.

The evaluation was performed by confirming the magnetization direction of the sample using an MFM apparatus and comparing the magnitude of an applied magnetic field required for reversal. As a result of the experiment, it was found that the magnetization reversal of the sample of the present invention was observed with a smaller applied magnetic field than the comparative sample. Table 2 shows the results
Shown in

[0192]

[Table 2]

(Seventh Embodiment) An example of a tunnel magnetoresistance effect element using a magnetic element with reduced coercive force will be described.

The tunnel magneto-resistance effect element has a structure in which a non-magnetic insulating layer is sandwiched between a lower ferromagnetic layer and an upper ferromagnetic layer.
Magnetic elements having reduced coercive force according to the present invention were used as upper and lower ferromagnetic layers.

As shown in FIG. 8, both the upper and lower ferromagnetic layers were formed by a manufacturing method in which the side wall portion was modified by oxidation treatment after processing by ion milling.

Referring to FIG. 13, a method of forming a tunnel magnetoresistive element will be described.

FIG. 13A is a schematic diagram showing a cross-sectional shape of a tunnel junction before processing. A magnetic layer 132 serving as a free layer and a magnetic layer 13 serving as a pinned layer are formed on a substrate 131.
4. Conductive protective layer 135, resist 1 after pattern formation
36 are formed. There is a tunnel film 133 between the magnetic layer 132 and the magnetic layer 134. Here, processing of the element is performed by ion milling, RIE, or the like. In addition, a method is widely used in which after processing, the periphery is buried with an insulating film while leaving the resist 136, and a tunnel junction is completed by lift-off.

FIG. 13 (b) is a comparative example, and is a cross-sectional view of a tunnel junction after processing for forming an element by ion milling with a resist mask formed by photolithography. Referring to FIG. 13B, a tunnel junction is formed in a region where the resist 136 is left. Both sides of the region are filled with an insulating layer 139.

FIG. 13C shows that the side wall portion of the first magnetic layer is oxidized to form the second magnetic layer which is a modified product of the first magnetic layer.
FIG. 3 is a cross-sectional view of a tunnel junction where a magnetic layer is formed.

As can be seen from comparison with FIG. 13B, a magnetic layer 137 modified from the magnetic layer 132 and a magnetic layer 138 modified from the magnetic layer 134 are formed around the tunnel junction. The magnetic layer 137 corresponds to a second magnetic layer when the magnetic layer 132 is a first magnetic layer. Magnetic layer 1
38 denotes a second magnetic layer when the magnetic layer 134 is a first magnetic layer.
Of the magnetic layer.

Next, the steps will be described while specifically describing the materials used in the experiment.

The substrate 131 is a (1, 0, 0) Si wafer having a 1 μm thermal oxide film formed thereon.

The magnetic layers 132, 1 formed on the substrate 131
Table 3 shows the materials and thicknesses of the layer 34, the tunnel film 133, and the conductive protective layer 135. These films were formed by magnetron sputtering. The tunnel film 134 converts Al ₂ O ₃ into Rf.
After film formation by sputtering, oxygen plasma treatment (0.2P
a, Rf5W, 30 sec).

[0204]

[Table 3]

A resist was applied to the sample on which the film formation was completed, and a mask pattern of a tunnel junction was formed by photolithography. Specifically, Tokyo Ohka LOR-P
Forming a resist film of about 1.2 μm thickness using 003;
A pattern was formed by performing contact exposure with halogen light for 6 seconds.

The substrate on which the resist pattern was formed was introduced into an ion milling machine, and processed to form a tunnel element.

Here, a sample on which an insulating layer was formed immediately after the processing was completed was used as a comparative sample. The comparative sample has a cross-sectional shape as shown in FIG.

After the processing is completed, the magnetic layers 137 and 138 are once exposed to the atmosphere to form magnetic layers 137 and 138.
The sample formed in Example 7 was used as a sample of the seventh embodiment.
The sample of the seventh embodiment has a sectional shape as shown in FIG.

Next, the substrate after the completion of the tunnel junction processing was returned to the photolithography step again to form a resist mask for the upper electrode. Next, 50 nm of Al was formed as an upper electrode film using a magnetron sputtering apparatus, thereby completing a tunnel magnetoresistive effect element. The bonding area is 200
μm ² .

Here, the characteristics of the element were measured and evaluated using a magnetoresistance measuring device. The external magnetic field was applied up to 1 kOe, and the current flowing through the element was 1 μA. In addition, four-terminal measurement was performed to remove the influence of the contact resistance due to the probe. The value of the magnetic field Hc was compared between the sample of the seventh embodiment and the comparative sample, where Hc is the magnetic field at which the magnetization reversal occurs. Table 4 shows the results. (Eighth Embodiment) Another example of a tunnel magnetoresistive element using a magnetic element with reduced coercive force will be described.

The tunnel magneto-resistance effect element has a structure in which a non-magnetic insulating layer is sandwiched between a lower ferromagnetic layer and an upper ferromagnetic layer.
Magnetic elements having reduced coercive force according to the present invention were used as upper and lower ferromagnetic layers.

As shown in FIG. 8, both the upper and lower ferromagnetic layers were formed in a manufacturing process in which the side wall was modified with FIB. Here, the layer configuration of the substrate and the magnetic film of the sample used for the experiment and the comparative sample are the same as those of the seventh embodiment.

After the film formation was completed, the sample was finely processed by photolithography to form a lower electrode and the like. Further, a magnetic element composed of a single layer film is formed, and FIG.
In the same manner as in (b), processing for forming a tunnel element with a focused ion beam using Ga as an ion source (acceleration voltage: 30 kV) was performed.

At that time, similarly to FIG. 5B, the peripheral portions of the upper and lower ferromagnetic layers were modified by irradiating a focused ion beam so that the periphery of the device was tapered. In the modified portion, the magnetic anisotropy is reduced because the magnetic coupling chain inside the upper ferromagnetic layer is partially cut off by Ga ions.

The substrate after the completion of the tunnel junction processing was returned to the photolithography step again to form a resist mask for the upper electrode. A 50nm A
1 was formed as an upper electrode film to complete a tunnel magnetoresistive effect element.

Then, the characteristics of the magnetic element were evaluated under the same conditions as in the seventh embodiment. Table 4 shows the results. (Ninth Embodiment) Another example of a tunnel magnetoresistive element using a magnetic element with reduced coercive force will be described.

The tunnel magnetoresistance effect element has a structure in which a nonmagnetic insulating layer is sandwiched between a lower ferromagnetic layer and an upper ferromagnetic layer.
Magnetic elements having reduced coercive force according to the present invention were used as upper and lower ferromagnetic layers.

As shown in FIG. 9, the upper ferromagnetic layer was partially modified by ion beam irradiation. Here, the layer configuration of the substrate and the magnetic film of the sample used for the experiment and the comparative sample are the same as those of the seventh embodiment except for the nonmagnetic conductive layer. The thickness of the nonmagnetic conductive layer was 25 nm of Si to enable partial ion implantation.

[0219] After the film formation was completed, the sample was finely processed by photolithography to form a lower electrode and a tunnel element. Further, a magnetic element composed of a single-layer film is formed, and a process of partially modifying the upper ferromagnetic layer with a focused ion beam (accelerating voltage 30 kV) using Ga as an ion source is performed as in FIG. went.

At this time, as in FIG. 6B, the entire upper surface of the element was irradiated with an ion beam in order to implant Ga ions into the upper ferromagnetic layer. Since the thickness of the conductive protective layer is set so as not to completely prevent the injection of Ga into the upper ferromagnetic layer, the ions partially cut off the magnetic coupling chains inside the upper ferromagnetic layer, and Part of the magnetic layer becomes a low coercive force layer.

The substrate after the completion of the tunnel junction processing was returned to the photolithography step again to form a resist mask for the upper electrode. 50 with magnetron sputtering equipment
nm of Al was formed as an upper electrode film to complete a tunnel magnetoresistive element.

Then, the characteristics of the magnetic element were evaluated under the same conditions as in the seventh embodiment. Table 4 shows the results. (Tenth Embodiment) Another example of a tunnel magnetoresistive element using a magnetic element with reduced coercive force will be described.

The tunnel magneto-resistance effect element has a structure in which a non-magnetic insulating layer is sandwiched between a lower ferromagnetic layer and an upper ferromagnetic layer.
Magnetic elements having reduced coercive force according to the present invention were used as upper and lower ferromagnetic layers.

As shown in FIG. 10, the upper ferromagnetic layer was entirely modified by ion beam irradiation. Here, the layer configuration of the substrate and the magnetic film of the sample used for the experiment and the comparative sample are the same as those of the seventh embodiment except for the nonmagnetic conductive layer. The thickness of the nonmagnetic conductive layer was set to 5 nm in order to enable ion implantation over the entire surface.

After the film formation was completed, the sample was finely processed by photolithography to form a lower electrode and the like. Further, a magnetic element composed of a single layer film is formed, and FIG.
As in (a), the upper ferromagnetic layer was completely reformed with a focused ion beam (acceleration voltage: 30 kV) using Ga as an ion source.

At this time, as in FIG. 6C, the entire upper surface of the element was irradiated with an ion beam in order to implant Ga ions into the upper ferromagnetic layer. Ga is injected over the entire thickness of the upper ferromagnetic layer and partially cuts off the magnetic coupling chain inside the upper ferromagnetic layer, whereby the entire upper ferromagnetic layer is reformed into a low coercivity layer.

The substrate after the completion of the tunnel junction processing was returned to the photolithography step again to form a resist mask for the upper electrode. 50 with magnetron sputtering equipment
nm of Al was formed as an upper electrode film to complete the tunnel magnetoresistive element.

Then, the characteristics of the magnetic element were evaluated under the same conditions as in the seventh embodiment. Table 4 shows the results.

[0229]

[Table 4]

[0230]

According to the present invention, the second magnetic layer comprises the first magnetic layer.
Since the magnetic anisotropy is lower than that of the first magnetic layer, the coercive force is smaller than that of the first magnetic layer, so that the magnetization is more easily reversed than the first magnetic layer. When the magnetization of the second magnetic layer is reversed, the magnetization of the first magnetic layer is likely to be reversed due to a magnetic field leaking from the second magnetic layer. Therefore, the magnetic element of the present invention has the first
Inverts with a smaller external magnetic field than when only one magnetic layer exists, making it possible to reduce the coercive force in a miniaturized ferromagnetic layer and configure the magnetic element by freely selecting the magnetization and coercive force. can do.

According to the present invention, the coercive force can be increased by using a magnetic element in which magnetic layers having different magnetic anisotropies are in contact with each other in a tunnel magnetoresistive effect element including two magnetic elements and a nonmagnetic insulating layer. The tunnel magnetoresistive effect element having a small value can be realized. A magnetic memory having a small coercive force has low power consumption because an external magnetic field in which magnetization reversal occurs is small.

According to the present invention, charged particles are injected by irradiating the ferromagnetic layer with an ion beam or the like.
A tunnel magnetoresistive element with reduced coercive force can be manufactured by an easy process that does not require a mask manufacturing step, by introducing a process for producing a magnetic element with reduced magnetic anisotropy. In addition, it is possible to complete the processing of a key point in a pinpoint manner. Therefore, the productivity of processing for reducing the coercive force is high.

[Brief description of the drawings]

FIG. 1 is a perspective view of four embodiments of a magnetic element according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing how the magnetization direction of each magnetic layer of the magnetic element of the present embodiment changes.

FIG. 3 is a schematic diagram of a magnetization curve (a) of the magnetic element of the present embodiment and a magnetization curve (b) of a single first magnetic layer 101.

FIG. 4 is a schematic diagram showing a state of magnetization of a magnetic element using a perpendicular magnetization film which is an alloy of a rare earth metal and a transition metal.

FIG. 5 is a schematic diagram for explaining a method of manufacturing a magnetic element of the present embodiment in which charged particles are injected into a first magnetic layer and modified to obtain a second magnetic layer.

FIG. 6 is a schematic diagram for explaining a method of manufacturing a magnetic element of the present embodiment in which charged particles are injected into a first magnetic layer and modified to obtain a second magnetic layer.

FIG. 7 is a schematic diagram for explaining an example of a manufacturing method for modifying a first magnetic layer by natural oxidation to obtain a second magnetic layer.

FIG. 8 is a perspective view showing an example of a tunnel magnetoresistive element having a configuration in which a nonmagnetic insulating layer is sandwiched between magnetic elements of the present embodiment.

FIG. 9 is a perspective view of a tunnel magnetoresistive element formed by modifying a part of an upper ferromagnetic layer.

FIG. 10 is a perspective view of a tunnel magnetoresistive element formed by modifying the entire upper ferromagnetic layer.

FIG. 11 is a diagram showing a difference in an MFM image depending on a magnetization direction.

FIG. 12 is a schematic diagram for explaining a method of forming a second magnetic layer by photolithography.

FIG. 13 is a schematic diagram for explaining a method of manufacturing a tunnel magnetoresistance effect element.

[Explanation of symbols]

 101 first magnetic layer 102, 102a, 102b second magnetic layer 401 first magnetic layer 402, 402a, 402b second magnetic layer 501 substrate 502 first magnetic layer 503 protective layer 504 ion beam 505 second Magnetic layer 506 Non-magnetic element 701 First magnetic layer 801 First magnetic layer 802 Tonle film 803 First magnetic layer 804 Second magnetic layer 805 Second magnetic layer 806 Lower sense line 807, 807a, 807b Upper sense Line 808 conductive protective layer 809 non-magnetic element 810, 830 first magnetic element 820, 840, 850 second magnetic element 121 substrate 122 first magnetic layer 123 second magnetic layer 131 substrate 132, 134, 137, 138 magnetic layer 133 tunnel film 135 conductive protective layer 136 resist 139 insulating layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01F 10/32 H01L 43/12 H01L 27/105 G01R 33/06 R 43/12 H01L 27/10 447 F term (Reference) 2G017 AA10 AD55 5E049 AA04 BA06 5F083 FZ10 GA05 GA09 GA28 JA60 PR04 PR22 PR36 PR40

Claims (29)

[Claims] 1. A magnetic element utilizing coercive force of a ferromagnetic material, comprising: a first magnetic layer formed on a substrate; and a first magnetic layer having a lower magnetic anisotropy than the first magnetic layer. And a second magnetic layer in contact with the magnetic layer. 2. The magnetic element according to claim 1, wherein the second magnetic layer is in contact with a periphery of the first magnetic layer. 3. The magnetic element according to claim 1, wherein the second magnetic layer is in contact with an upper part of the first magnetic layer. 4. The main magnetic direction of the first magnetic layer and the second magnetic layer is perpendicular to a film surface.
The magnetic element as described in the above. 5. The magnetic element according to claim 4, wherein the first magnetic layer and the second magnetic layer are an alloy of a rare earth metal and a transition metal. 6. The alloy comprises Gd, Tb, Ho, Dy,
The magnetic element according to claim 5, comprising at least two of Fe, Co, and Ni. 7. The main magnetic direction of the first magnetic layer and the second magnetic layer is horizontal to a film surface.
The magnetic element as described in the above. 8. The magnetic element according to claim 1, wherein the second magnetic layer is a modified product of the first magnetic layer. 9. The magnetic device according to claim 8, wherein the modified material is a Ga contaminant. 10. The method according to claim 8, wherein the reformate is an oxide.
The magnetic element as described in the above. 11. A magnetic element using a coercive force of a ferromagnetic material, wherein the magnetic element has a plurality of magnetic layers having different magnetic anisotropies. 12. A first magnetic element having a configuration in which two magnetic layers having different magnetic anisotropies are in contact with each other, and a configuration in which two magnetic layers having different magnetic anisotropies are in contact with each other. A second magnetic element having a different coercive force from the first magnetic element; and a non-magnetic insulating layer sandwiched between the first magnetic element and the second magnetic element. 13. A structure in which a first magnetic element composed of a single magnetic layer and two magnetic layers having different magnetic anisotropies are in contact with each other, and a second magnetic element having a different coercive force from the first magnetic element. An element, and a tunnel magnetoresistive element having a nonmagnetic insulating layer sandwiched between the first magnetic element and the second magnetic element. 14. A first magnetic element comprising a plurality of magnetic layers having different magnetic anisotropies, and a second magnetic element comprising a plurality of magnetic layers having different magnetic anisotropies and having a different coercive force from the first magnetic element. And a tunnel magnetoresistive element having a nonmagnetic insulating layer sandwiched between the first magnetic element and the second magnetic element. 15. A first magnetic element comprising a single magnetic layer, a second magnetic element comprising a plurality of magnetic layers having different magnetic anisotropies, and having different coercive forces from the first magnetic element; A tunnel magnetoresistive element having a non-magnetic insulating layer sandwiched between a first magnetic element and the second magnetic element. 16. A step of forming a first magnetic layer on a substrate, the step of implanting charged particles to modify the first magnetic layer, the second magnetic layer having a lower magnetic anisotropy than the first magnetic layer. A method for manufacturing a magnetic element, comprising: 17. The method according to claim 16, wherein the charged particles are implanted into a side wall of the first magnetic layer. 18. The method for manufacturing a magnetic element according to claim 16, wherein said charged particles are implanted into an upper surface portion of said first magnetic layer. 19. By driving the charged particles,
17. The method according to claim 16, wherein substantially the entire first magnetic layer is modified. 20. The method according to claim 16, wherein the charged particles are made of a rare gas, nitrogen, oxygen or a mixture thereof. 21. The method according to claim 16, wherein the charged particles are made of Ga, B, P, As, or a mixture thereof. 22. An injection energy of said charged particles is 10 to 10.
22. The method for manufacturing a magnetic element according to claim 20, wherein the voltage is 300 keV. 23. A step of forming an element by forming a lower ferromagnetic layer, a non-magnetic insulating layer and an upper ferromagnetic layer on a substrate; and implanting charged particles into the lower ferromagnetic layer or the upper ferromagnetic layer. A method for manufacturing a tunnel magnetoresistive element, comprising the step of modifying at least one of: 24. The method of manufacturing a tunnel magnetoresistive element according to claim 23, wherein said charged particles are implanted into a side wall portion of said element. 25. The method of manufacturing a tunnel magnetoresistive element according to claim 23, wherein said charged particles are implanted into an upper surface portion of said element. 26. By driving the charged particles,
The method for manufacturing a tunnel magnetoresistive element according to claim 23, wherein substantially the entire upper ferromagnetic layer is modified. 27. The method according to claim 23, wherein the charged particles are made of a rare gas, nitrogen, oxygen, or a mixture thereof. 28. The method according to claim 23, wherein the charged particles are made of Ga, B, P, As or a mixture thereof. 29. The injection energy of the charged particles is 10
The method for manufacturing a tunnel magnetoresistive effect element according to claim 27 or 28, wherein the pressure is -300 keV.