JP2003168833A - Magnetoresistive effect element and its producing system, and magnetic memory - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a magnetoresistive effect memory element in which good characteristics can be attained even in a multilayer film structure. <P>SOLUTION: In the magnetoresistive effect memory element of multilayer film structure comprising two ferromagnetic layers 24 and 26 and a nonmagnetic layer sandwiched between, at least one of the ferromagnetic layers 24 and 26 is composed of an aggregate of crystal grains 31 and grain boundaries 32. The grain boundary 32 is imparted with properties bonding to a diffusion substance, so that the diffusion substance bonds to the grain boundary 32 preferentially even if the diffusion substance is diffused from layers adjacent to the ferromagnetic layers 24 and 26. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

The present invention relates to a so-called MR (Ma
The present invention relates to a magnetoresistive effect element that produces a gnetoResistive effect, a manufacturing apparatus thereof, and a magnetic memory device configured as a memory device for storing information by using the magnetoresistive effect element.

[0002]

2. Description of the Related Art In recent years, with the rapid spread of information communication devices, especially small personal devices such as portable terminal devices, devices such as memory and logic are highly integrated, have high speed, and have low power consumption. There is a demand for even higher performance, such as higher performance. In particular, increasing the density and capacity of non-volatile memory is a complementary technology that replaces hard disk devices and optical disk devices, which are inherently difficult to miniaturize due to the presence of moving parts (such as head seek mechanism and disk rotation mechanism). It is becoming more and more important.

The nonvolatile memory includes a flash memory using a semiconductor and a FeRAM (FeRAM using a ferroelectric substance).
rro electric Random Access Memory) etc. are widely known. However, the flash memory has an information writing speed of the order of microseconds, and the DRAM (Dynamic Ra
ndom Access Memory) and SRAM (Static Random Acce
It has the drawback of being slower than volatile memory such as ss Memory). It has been pointed out that the FeRAM has a small number of rewritable times. Therefore, MRAM (Magnetic Random Access Memory) is attracting attention as a non-volatile memory that does not have these drawbacks.
Called a magnetic memory device. MRAM is a giant magnetoresistive effect (Giant Magnetoresistive; GMR) type or a tunnel magnetoresistive effect (Tunnel Magnetoresistive;
Information is recorded using a TMR type memory element.
In particular, the improvement of the properties of TMR materials in recent years has attracted attention (for example, “Naji et al. ISSCC200
1 ").

Here, the operating principle of the MRAM will be briefly described. The MRAM has magnetoresistive effect type storage elements (cells) arranged in a matrix, and has a conductor line (word line) and a read line which traverses these element groups vertically and horizontally for recording information in a specific storage element. It has a (bit line), and is configured to selectively write information only to the element located in the intersection region.
In other words, writing to the memory element is performed by controlling the magnetization direction of the magnetic substance in each memory element by using the combined current magnetic field generated by applying the current to both the word line and the bit line. In general, either "0" or "1" information is stored according to the magnetization direction. On the other hand, reading of information from a storage element is performed by selecting the storage element using an element such as a transistor and extracting the magnetization direction of the magnetic substance in the storage element as a voltage signal through the magnetoresistive effect. The film structure of the memory element is a three-layer structure of ferromagnetic material / non-magnetic material / ferromagnetic material, that is, a ferromagnetic tunnel junction (Magnetic T
A structure called unnel junction (MTJ) has been proposed. Therefore, by using the magnetization direction of one of the ferromagnets as the fixed reference layer (pinned layer) and the other as the storage layer (free layer), the magnetization direction in the storage layer corresponds to the voltage signal through the tunnel magnetoresistive effect. Therefore, extraction as a voltage signal as described above can be realized.

Next, the selection of the storage element at the time of writing will be described in more detail. In general, when a magnetic field in the direction of the easy axis of a ferromagnetic material is applied in the direction opposite to the magnetization direction, the magnetization direction may be reversed to the direction of the applied magnetic field at a certain critical value ± Hsw (hereinafter referred to as “reversal magnetic field”). Are known. The value of this reversal magnetic field can theoretically be obtained from the minimum energy condition. Furthermore, it is known that when a magnetic field is applied not only to the easy axis of magnetization but also to the hard axis of magnetization, the absolute value of this reversal magnetic field decreases. This can also be obtained from the minimum energy condition. That is, assuming that the magnetic field applied in the direction of the hard axis is Hx, the reversal magnetic field Hy at this time is:
The relationship of Hx ^(2/3) + Hy ^(2/3) = Hc ^(2/3) is established. Hc is the anisotropic magnetic field of the storage layer. This curve is called an asteroid curve because it forms an asteroid (star) on the Hx-Hy plane as shown in FIG.

The selection of the memory element is easy to explain using this asteroid. Generally, an MR having a configuration in which the magnetic field generated from the word line is substantially aligned with the easy axis direction of magnetization.
In AM, information is recorded by reversing the magnetization by the magnetic field generated from the word line. However, since there are a plurality of storage elements located equidistant from the word line, when a current that causes a magnetic field not less than the reversal magnetic field is applied to the word line,
The same recording will be performed for all the storage elements located at the same distance. However, at this time, when a current is passed through the bit line that crosses the storage element to be selected to generate a magnetic field in the hard axis direction, the reversal magnetic field in the storage element to be selected is lowered. Therefore, assuming that the reversal magnetic field at this time is Hc (h) and the reversal magnetic field when the bit line magnetic field is “0” is Hc (0), the word line magnetic field H is Hc (h) <H <Hc (0). If set so that
It becomes possible to selectively record information only on the storage element desired to be selected. This is a method of selecting a storage element when recording information in the MRAM.

The MRAM having such a structure is non-volatile, and has the following characteristics in addition to the fact that non-destructive reading and random access are possible. That is, since the structure is simple, high integration is easy, and the number of rewritable times is large because information is recorded by rotation of the magnetic moment in the magnetoresistive storage element (for example, 10 ¹⁶ times or more). . Furthermore, the access time is expected to be very fast, and it has already been confirmed that it can operate in the nanosecond range (for example, 5 ns or less). In addition, MOS (Metal Oxid
e Semiconductor) is formed only in the wiring process after fabrication, so process compatibility is good. In particular, it is superior to flash memory in terms of the number of rewritable times, random access, and high-speed operation, and Fe in terms of process consistency.
Outperforms RAM. Furthermore, it has a high degree of integration similar to DRAM and S
Since it is expected that the high speed of RAM can be achieved at the same time, it has the potential of becoming a mainstream memory device.

On the other hand, some technical problems have been pointed out for the MRAM. Specifically, it is strongly desired to reduce power consumption and increase the S / N ratio. On the other hand, for example, the reduction of power consumption is solved mainly by improving the magnetic characteristics of the storage layer, and the increase of the S / N ratio is solved by increasing the MR effect (tunnel MR effect in the case of MTJ). Are believed to be possible. From these facts, the characteristics that the material forming the memory layer of the MRAM should have must be such that the switching field can be suppressed low and a high MR effect can be generated. As such materials, various compositions of Co (cobalt) -Fe (iron) binary alloy, Ni (nickel) -F
e binary alloys, Co-Ni-Fe ternary alloys, etc. have been proposed.

[0009]

However, in reality, only the characteristics in the state where the memory layer is a material single film (a single layer film having no multilayer film structure as a magnetoresistive effect element) is a technique for MRAM. It is not easy to try to solve specific problems. This means that even if the storage layer in the state of a single film of material shows good characteristics, when it is laminated together with other layers to form a magnetoresistive effect element, the storage layer in the multilayer film structure is This is because it does not always show good characteristics.

Specifically, considering the MTJ structure, for example, when the non-magnetic material sandwiched by the ferromagnetic materials is composed of an oxide barrier layer, diffusion of oxygen from the oxide barrier layer can reach the storage layer. There is a possibility that the magnetic characteristics of the storage layer may be changed. Further, in the magnetoresistive effect element using the metal nonmagnetic layer, the nonmagnetic layer material may diffuse. Furthermore, not only the non-magnetic material layer sandwiched between ferromagnetic materials such as an oxide barrier layer and a metal non-magnetic layer,
Diffusion from a layer (eg, a protective layer) on the opposite side of the storage layer adjacent to the storage layer may also change the magnetic characteristics of the storage layer. That is, in the multi-layered film structure, the characteristics of the memory layer may change due to the diffusion material from the adjacent layer.

Further, the environment at the time of manufacturing the multilayer film structure such as the growth temperature does not necessarily optimize the magnetic characteristics of the storage layer. For example, when a fixed reference layer that employs an antiferromagnetic material is used, even if the antiferromagnetic material requires ordered annealing at high temperature, the heat treatment deteriorates the magnetic characteristics of the storage layer. should not be done.
For this reason, it is desirable that the ferromagnetic material forming the storage layer be such that its magnetic characteristics can be flexibly adjusted by some means in various manufacturing environments.

Therefore, in view of the above conventional circumstances, the present invention provides a magnetoresistive effect element having good characteristics even in a multi-layered structure and realizing high performance, a manufacturing apparatus therefor, and a magnetic memory. The purpose is to provide a device.

[0013]

The present invention has been devised to achieve the above object, and has a multilayer film structure including two ferromagnetic layers and a non-magnetic layer sandwiched therebetween. In the magnetoresistive effect element, at least one of the ferromagnetic layers is composed of an aggregate of crystal grains and crystal grain boundaries, and the crystal grain boundaries are ferromagnetic layer to which the crystal grain boundaries belong. It has a binding property with a diffusion material from the adjacent layer of.

According to the magnetoresistive effect element having the above-mentioned structure, in addition to the ferromagnetic layer being composed of an aggregate of crystal grains and crystal grain boundaries, the crystal grain boundaries have a binding property with the diffusing substance. Therefore, the diffusion of the diffusion material from the adjacent layer (for example, the non-magnetic layer or the layer adjacent to the non-magnetic layer on the opposite side) preferentially progresses at the grain boundary portion, and at the other crystal grain portion, the original magnetic The property remains retained. In addition, the magnetic characteristics of the ferromagnetic material layer composed of aggregates of crystal grains and crystal grain boundaries are:
It depends not only on various heat treatment temperatures but also on its composition and particle size. Therefore, even when the environment such as the temperature at the time of manufacturing the magnetoresistive effect element is specified in advance, the magnetic characteristics of the ferromagnetic layer can be controlled by controlling the composition and particle size of the ferromagnetic layer. Can be adjusted.

The manufacturing apparatus of the present invention is a manufacturing apparatus for manufacturing a magnetoresistive effect element having a multilayer film structure including two ferromagnetic layers and a non-magnetic layer sandwiched therebetween. And a magnetic material including at least one of the ferromagnetic layers, the magnetic material including at least one of cobalt, iron, and nickel. Is formed by adding one or more different kinds of elements to each other, the at least one ferromagnetic layer is composed of an aggregate of crystal grains and crystal grain boundaries, and the crystal grain boundaries are formed by the different elements. It is characterized in that

According to the apparatus for manufacturing a magnetoresistive effect element having the above-mentioned structure, the ferromagnetic layer is composed of an aggregate of crystal grains and crystal grain boundaries, and the crystal grain boundaries are formed by an element different from the magnetic material. Therefore, in the magnetoresistive effect element thus manufactured, the diffusion of the diffusion material from the layer adjacent to the ferromagnetic layer preferentially proceeds at the grain boundary depending on the kind of the different element. However, the original magnetic characteristics may be maintained in the other crystal grain portions. Even if the environment such as the temperature at the time of manufacturing the magnetoresistive effect element is specified in advance, the magnetic properties of the ferromagnetic layer can be controlled by controlling the composition and particle size of the ferromagnetic layer. It is also possible to adjust.

Further, the present invention has been devised to achieve the above object, and has a magnetoresistive effect of a multilayer film structure including two ferromagnetic layers and a nonmagnetic layer sandwiched therebetween. In a magnetic memory device comprising an element and configured to record information by utilizing a change in the magnetization direction of the ferromagnetic layer, at least one of the ferromagnetic layers has a crystal grain and a crystal grain. It is composed of an aggregate of boundaries, and the crystal grain boundary has a binding property with a diffusion substance from a layer adjacent to the ferromagnetic layer to which the crystal grain boundary belongs.

According to the magnetic memory device having the above structure, in addition to the fact that the ferromagnetic material layer in the magnetoresistive element for recording information is composed of aggregates of crystal grains and crystal grain boundaries,
The crystal grain boundaries have a binding property with the diffusing substance. Therefore, the diffusion of the diffusing material from the adjacent layer preferentially progresses at the crystal grain boundaries, so that even when the magnetoresistive effect element has a multilayer film structure, the characteristic change in the ferromagnetic layer can be suppressed. Even if the environment such as the temperature at the time of manufacturing the magnetoresistive effect element is specified in advance, the magnetic properties of the ferromagnetic layer can be controlled by controlling the composition and particle size of the ferromagnetic layer. Can be adjusted. Therefore,
Since good characteristics can be obtained for the magnetoresistive effect element,
It becomes possible to realize low power consumption and increase of S / N ratio when information is recorded on the magnetoresistive effect element.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetoresistive effect element, a manufacturing apparatus therefor, and a magnetic memory device according to the present invention will be described below with reference to the drawings. Here, a TMR type spin valve element (hereinafter simply referred to as “TMR element”) as a magnetoresistive effect element and an MRAM having a TMR element as a magnetic memory device will be described as examples.

[Outline of Magnetic Memory Device] First, a schematic configuration of the entire magnetic memory device according to the present invention will be described. FIG. 1 is a schematic diagram showing a basic configuration example of an MRAM. The MRAM includes a plurality of TMR elements 1 arranged in a matrix. In addition, these TM
A word line 2 and a bit line 3 intersecting each other are provided so as to correspond to the rows and columns in which the R elements 1 are arranged, respectively.
It is provided so as to traverse each group of TMR elements vertically and horizontally. Each TMR element 1 is arranged so as to be sandwiched between the word line 2 and the bit line 3 from above and below and to be located in the intersection region of these. Note that the word line 2 and the bit line 3 are well-known methods in which a conductive substance such as Al (aluminum), Cu (copper), or an alloy thereof is chemically or physically deposited and then selectively etched. Shall be formed using.

FIG. 2 shows a single TMR constituting the MRAM.
It is a schematic diagram which shows an example of the cross-sectional structure of an element part. In each of the TMR element portions, a field effect transistor including a gate electrode 5, a source region 6 and a drain region 7 is arranged on a semiconductor substrate 4, and a word line 2, a TMR element 1 and a bit line 3 are provided above the field effect transistor. Are arranged in order. As is clear from this, the TMR element 1
Are arranged so as to be sandwiched by the word line 2 and the bit line 3 from above and below at the intersection of the word line 2 and the bit line 3. The TMR element 1 has a bypass line 8
Is connected to the field effect transistor via.

With this configuration, the MRAM has a T
With respect to the storage layer of the MR element 1, a current is applied to both the word line 2 and the bit line 3 to generate a combined current magnetic field, and the combined current magnetic field is used to change the magnetization direction of the storage layer. Write information. Also,
To read information from the TMR element 1, the TMR element 1 is selected using a field effect transistor, and the TMR element 1 is selected.
This is performed by extracting the magnetization direction of the information storage layer in the element 1 as a voltage signal.

[Structure of Magnetoresistive Effect Element] Next, the structure of the TMR element 1 itself used in such an MRAM will be described. The TMR element 1 has a film structure of MTJ structure. FIG. 3 is a schematic diagram showing a basic configuration example of the MTJ structure. The MTJ structure has a three-layer structure of ferromagnetic material / insulator / ferromagnetic material, and the magnetization direction of one ferromagnetic material layer is a fixed reference layer (pinned layer) 11 and the other is a storage layer (free layer). Used as 12. Information is written (recorded) by changing the magnetization direction of the storage layer 12 by the combined current magnetic field generated by the word line 2 and the bit line 3, and the magnetization of the storage layer 12 is tunneled through the tunnel MR effect. Correspondence between direction and voltage signal. The two ferromagnetic layers, that is, the insulating layer sandwiched between the fixed reference layer 11 and the storage layer 12 is made of, for example, an oxide of Al (aluminum) and has a function as the tunnel barrier layer 13. The other layers such as the base layer 14 and the protective layer 15 are generally made of a material having no magnetism.

FIG. 4 is a schematic view for explaining the TMR element having the MTJ structure more specifically. As the TMR element 1, for example, a Ta (tantalum) film 2 to be a base layer 14 is formed on a substrate (for example, a bypass line) 21 which is a film formation target.
2 and a PtMn (platinum-manganese) film 2 serving as an antiferromagnetic layer
3, a CoFeB (cobalt-iron-boron) film 24 serving as the fixed layer, an Al—Ox (aluminum oxide) film 25 serving as the tunnel barrier layer 13, a CoFeB film 26 serving as the memory layer 12, and a Ta serving as the protective layer 15. There is a multilayer film structure in which the film 27 and the film 27 are sequentially stacked. Of these, P
The tMn film 23 and the CoFeB film 24 are laminated on each other to form the fixed reference layer 11.

By the way, the TMR element 1 described here
Is characterized by the structure of the CoFeB film 24 that constitutes the fixed reference layer 11 and the CoFeB film 26 that is the memory layer 12. FIG. 5 is a schematic diagram showing an outline of the film structure.

The CoFeB films 24 and 26 are formed by adding B (boron), which is an element of a different type from these magnetic materials, to magnetic materials such as Co and Fe, which are general ferromagnetic materials. However, this results in fine crystal grains 3
1 and a crystal grain boundary 32 are aggregated. It should be noted that the term "fine" as used herein means that the average grain size when the crystal grains 31 are approximated to a spherical shape is 2 for the reason described later.
It is about 100 nm.

More specifically, the CoFeB films 24 and 26
In, the composition of the crystal grain 31 is different from the composition of the crystal grain boundary 32, and B is precipitated in the crystal grain boundary 32. That is, by adding B, the B mainly forms the crystal grain boundaries 32, and thereby a structure composed of an aggregate of the fine crystal grains 31 and the crystal grain boundaries 32 is formed.
B forming the crystal grain boundary 32 generally has a higher bondability with O (oxygen) than Co, Fe, or the like. Therefore, it can be said that the crystal grain boundary 32 has a bondability with O.

In the CoFeB films 24 and 26, the spin polarizability exhibited by the materials (mainly Co and Fe) forming the fine crystal grains 31 as B mainly forms the crystal grain boundaries 32, The spin polarizability is higher than that of the material (mainly B) forming the crystal grain boundary 32. In general, electrons have a rotation (spin) and become a unit of a very small magnet. The directions of the magnets (spins) of electrons in a solid are usually two directions, upward and downward. Therefore, the conduction band of metal is divided into two bands, an electron band having an upward spin (upward spin band) and an electron band having a downward spin (downward spin band). Since the shapes of the upward spin band and the downward spin band are different in a ferromagnet, the number of electrons existing at the Fermi level is different between the electrons having the upward spin and the electrons having the downward spin. The difference in the number of these two electrons is called spin polarizability. It is known that this spin polarizability has a great influence on the MR effect, and the tunnel MR effect increases as the spin polarizability of the ferromagnetic material forming the tunnel junction increases.

[Manufacture of Magnetoresistive Effect Element] Next, a manufacturing procedure of the TMR element 1 having the above-described structure and a manufacturing apparatus used for the same will be described. As a manufacturing apparatus of the TMR element 1, for example, a magnetron sputtering apparatus whose back pressure is exhausted to an ultrahigh vacuum region is used. Then, the Ta film 22 and Pt are formed on the Si (silicon) substrate 21 whose surface is thermally oxidized.
The Mn film 23, the CoFeB film 24, and the Al film are sequentially stacked. After that, the Al film is plasma-oxidized in pure oxygen to obtain a uniform Al-Ox film 25. The thickness of Al at this time may be 1 nm. After the Al—Ox film 25 is obtained, the CoFeB film 26 and the Ta film 27 are sequentially formed again using, for example, a magnetron sputtering device. Finally, heat treatment for ordered alloying of the PtMn film 23 is performed.
It is carried out in a magnetic field, for example, at 280 ° C. for 1 hour.

In such a manufacturing procedure, CoFeB
When forming the films 24 and 26, B, which is an element of a different type from these magnetic materials, is added to magnetic materials such as Co and Fe, and the films are formed. However, at this time, the target, the sputter rate, etc. are set so that the addition ratio of B is 15% or more with respect to the magnetic material containing Co and Fe at a ratio of CoxFe1-x (0.45 <x <0.95). Have been adjusted. Specifically, Co
The design composition of the FeB films 24 and 26 is, for example, (Co90Fe
10) 80B20 (atomic%), and Co
It can be considered to form the FeB films 24 and 26. As a result, the CoFeB films 24 and 26 are composed of an aggregate of fine crystal grains 31 and crystal grain boundaries 32, and the crystal grain boundaries 32 are mainly formed of B. This is also confirmed by observing the CoFeB film 26 after film formation with a transmission electron microscope (TEM).

[Characteristics of Magnetoresistive Element] Next, characteristics of the TMR element 1 manufactured as described above will be described. FIG. 6 is an explanatory diagram showing the measurement results of the TMR effect. As shown in the figure, when the TMR effect of the TMR element 1 having the above-mentioned configuration was measured, it showed a high magnetoresistance change rate of 55% at room temperature and a bias voltage of 5 mV. On the other hand, for example, Co75Fe25 (atomic%)
In the conventional CoFe system as described above, the magnetoresistance change rate is about 45% at most. Therefore, in the TMR element 1 in the present embodiment, a value exceeding this is obtained.

The reason why a high magnetoresistive change rate is obtained in the TMR element 1 of this embodiment is considered as described below. FIG. 7 is a conceptual diagram for explaining the reason why a high magnetoresistance change rate is obtained.

In general, it is the two ferromagnetic layers sandwiching the tunnel barrier layer 13, that is, the fixed reference layer 11 and the memory layer 12, that play an important role in realizing the TMR effect, and particularly the tunnel barrier layer 13. The spin polarizability of each of the ferromagnetic layers 11 and 12 near the interface with is important. However, in reality, as shown in FIG. 7B, the Al—Ox film 2 that is the tunnel barrier layer 13 passes through this interface.
O (oxygen) is diffused from 5 and a layer 33 of a ferromagnetic oxide is formed near the interface.
Since the polarizability is generally lowered by oxidation, the TMR effect of the conventional one is caused based on this reduced spin polarizability.

On the other hand, in the TMR element 1 of the present embodiment, both the CoFeB film 24 that constitutes the fixed reference layer 11 and the CoFeB film 26 that is the memory layer 12 are aggregates of fine crystal grains 31 and crystal grain boundaries 32. It has a body structure. Moreover, B having a bondability with O is precipitated in the crystal grain boundary 32. Therefore, as shown in FIG. 7A, the Al—Ox film 2 which is the tunnel barrier layer 13 is formed.
O diffused from 5 is preferentially combined with the crystal grain boundary 32 in which B is precipitated, and is contained in the material forming the crystal grain boundary 32 more than in the material forming the crystal grain 31. . That is, it is considered that the crystal grain boundaries 32 are preferentially oxidized and the oxidation into the crystal grains 31 is suppressed.

As described above, in the TMR element 1 of the present embodiment, the TMR element 1 is provided with the regions in which the oxygen diffusion from the Al—Ox film 25 adjacent to the CoFeB films 24 and 26 occurs preferentially. It is considered that a region where the spin polarizability of the interface, which is important for the effect, is not reduced (inside the crystal grain 31) remains, and therefore a high TMR effect can be realized. Such high TMR effect is
AM has a high signal-to-noise ratio and high S / N.
A ratio can be realized.

Furthermore, there are other advantages of having a structure composed of an aggregate of fine crystal grains 31 and crystal grain boundaries 32. Generally, when the TMR element is used in the MRAM, reducing the switching magnetic field of the storage layer in the TMR element is one of the major problems. This is because the reversal magnetic field determines the magnitude of the recording current, and the magnitude of the recording current leads to the magnitude of power consumption. Normally, the reversal magnetic field of the storage layer is determined by the anisotropic magnetic field and the demagnetizing field of the film. However, the CoFeB film 26, which is the memory layer 12, has the crystal grains 3
When the structure has an aggregate of 1 and crystal grain boundaries 32, the crystal magnetic anisotropies of the crystal grains 31 cancel each other out because the orientations of the crystal grains 31 are substantially random, and become substantially zero. That is, the component of the reversal magnetic field due to the anisotropy of the film is zero. Therefore, according to the TMR element 1 of the present embodiment, it is possible to contribute to the reduction of the switching magnetic field.

By the way, the magnetic anisotropy of a film depends on its heat treatment temperature. Therefore, even in the CoFeB film 26, if it is heated to the heat treatment temperature (for example, 280 ° C.) or higher, crystal grain growth may proceed and desired characteristics may not be obtained. However, the crystal grain growth can be controlled by the composition of the film and the like, and by selecting a composition that has the optimum characteristics at the temperature to which the film is exposed in the actual device process, a high TMR effect and a low anisotropic magnetic field can be obtained. It can be realized. That is, even if the manufacturing environment such as the heat treatment temperature is defined in advance, the magnetic characteristics of the storage layer 12 can be controlled by controlling the composition, grain size, etc. of the ferromagnetic material forming the storage layer 12. It is also possible to adjust.

In this embodiment, the Al-Ox film 25 is used.
The CoFeB films 24 and 26 sandwiching the tunnel barrier layer, that is, the two ferromagnetic layers sandwiching the tunnel barrier layer 13 will be described by taking as an example the case where they each have a structure composed of an assembly of fine crystal grains 31 and crystal grain boundaries 32. However, only one of the ferromagnetic layers may have such a structure.
That is, even when only one of the ferromagnetic layers is composed of the aggregate of the crystal grains 31 and the crystal grain boundaries 32, A
Since the influence of oxygen diffusion from the l-Ox film 25 can be suppressed, good soft magnetic characteristics can be obtained. Therefore, the structure including the aggregate of the crystal grains 31 and the crystal grain boundaries 32 may be applied to at least one of the two ferromagnetic layers.

Further, in this embodiment, the Al--Ox film 25 is used.
The case where B precipitated in the crystal grain boundary 32 is preferentially bonded to the O that diffuses from the crystal grain boundary 32 has been described as an example. However, the crystal grain boundary 32 binds to the diffusion material from the adjacent layer. If it has, the diffusing substance is not particularly limited. Therefore, the diffusion material may be from a layer other than the Al—Ox film 25 (for example, the Ta layer 27). However, it is desirable that the crystal grains 31 and the crystal grain boundaries 32 have different compositions and thus have different affinity for diffusion of various elements. This is because if there is a difference, the material forming the crystal grain boundary 32 contains a larger amount of the diffusing substance than the material forming the crystal grain 31.
This is because the spin polarizability indicated by the material forming 1 is higher than the spin polarizability indicated by the material forming the crystal grain boundary 32. That is, it is possible to ensure the realization of good soft magnetic characteristics.

In order to obtain such good soft magnetic characteristics, it is a standard that the size of the crystal grains 31 is not more than the width of the domain wall. The width of the domain wall depends on the constituent material, but is generally about 100 nm. Therefore, the upper limit of the size of the crystal grains 31 is preferably about 100 nm (the average grain size when approximated to a spherical shape). On the other hand, the lower limit of the size of the crystal grain 31 may be such that it does not become an amorphous state, and it is preferable that the lower limit is about 2 nm which is the superparamagnetic limit.

Further, in this embodiment, the CoFeB film 2 is used.
Design composition of 4,26 is (Co90Fe10) 80B20
However, in view of the essence of the invention, the composition is not limited to this. For example, a base Co-Fe system may be prepared from various compositions of Ni-Fe, Co-Ni,
It is also effective to use a binary alloy or a ternary alloy such as a Co-Ni-Fe system, but especially CoxFe1-x (0.
By setting 45 <x <0.95), a high TMR effect can be expected. On the other hand, it is desirable to add B to such a base magnetic material considering that the diffusion material from the Al—Ox film 25 is O. In addition to this, Si, C ( Carbon), Hf (hafnium), T
Addition of a, N (nitrogen), Cu, Nb (niobium), etc. is also effective. That is, it is sufficient that one or more different elements including B are added. Therefore, the addition ratio of the different element is not limited to the ratio of 20% B alone as described in the present embodiment. However, in order to surely form the structure composed of the aggregate of the crystal grains 31 and the crystal grain boundaries 32 and to make the crystal grain boundaries 32 have the bondability with the diffusing substance, one or more different kinds of all elements It is desirable that the addition ratio of is 15% or more.

Furthermore, the film structure of the TMR element 1 is not limited to the illustrated one. For example, the fixed reference layer 11 is laminated earlier (lower) than the memory layer 12, not the so-called bottom type TMR element 1, but the memory layer is laminated earlier (lower) than the fixed reference layer. The same applies to so-called top-type TMR elements. Also, TMR
It goes without saying that not only the element but also the non-magnetic material layer between the storage layer and the fixed reference layer may be of the GMR type composed of Cu or the like.

[0043]

As described above, according to the present invention, the ferromagnetic layer in the magnetoresistive effect element is composed of fine crystal grains and crystal grain boundaries, and the crystal grain boundaries have a binding property with a diffusing substance. Since the effect of diffusion from the adjacent layer to the ferromagnetic layer is suppressed even in the multilayer film structure, good characteristics can be obtained, and as a result, a high MR effect can be realized. it can. Further, it can contribute to the reduction of the switching magnetic field by suppressing the magnetic anisotropy. Therefore, when a magnetic memory device is constructed using the magnetoresistive effect element, it is possible to improve the performance of the magnetic memory device through low power consumption and a high S / N ratio.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a basic configuration example of an MRAM.

FIG. 2 is a schematic diagram showing a configuration example of a single TMR element portion that constitutes an MRAM.

FIG. 3 is a schematic diagram showing a basic configuration example of an MTJ structure.

FIG. 4 is a schematic diagram for more specifically explaining a TMR element having an MTJ structure.

FIG. 5 is a schematic diagram showing an outline of a film structure of a ferromagnetic layer in a TMR element to which the present invention is applied.

FIG. 6 is an explanatory diagram showing measurement results of TMR effect.

7A and 7B are conceptual diagrams for explaining the reason why a high magnetoresistance change rate is obtained, where FIG. 7A is a diagram showing an example of a film structure in the present invention, and FIG. 7B is an example of a conventional film structure. It is a figure.

FIG. 8 is an asteroid diagram showing an example of a magnetic field response of a memory element forming an MRAM.

[Explanation of symbols]

1 ... TMR element, 11 ... Fixed reference layer, 12 ... Storage layer, 1
3 ... Tunnel barrier layer, 14 ... Underlayer, 15 ... Protective layer, 2
1 ... Substrate, 22 ... Ta film, 23 ... PtMn film, 24 ... C
oFeB film, 25 ... Al-Ox film, 26 ... CoFeB film
Film, 27 ... Ta film, 31 ... Crystal grain, 32 ... Crystal grain boundary

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01F 10/32 H01L 43/12 H01L 27/105 27/10 447 43/12 G01R 33/06 R (72) Inventor Kazuhiro Oba 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation (72) Inventor Tetsuya Mizuguchi 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation (72) Inventor Tetsuya Yamamoto 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation (72) Inventor Hiroshi Kano 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation F-term (reference) 2G017 AA01 AD55 AD65 5D034 BA03 BA15 DA07 5E049 AA01 AA04 AA07 BA06 CB02 5F083 FZ10 JA38 JA39

Claims (13)

[Claims] 1. A magnetoresistive effect element having a multi-layer structure including two ferromagnetic layers and a non-magnetic layer sandwiched between the ferromagnetic layers, wherein at least one of the ferromagnetic layers has crystal grains and It is composed of an aggregate of crystal grain boundaries, wherein the crystal grain boundaries are those having a binding property with a diffusion material from an adjacent layer of a ferromagnetic material layer to which the crystal grain boundaries belong. Magnetoresistive element. 2. The magnetoresistive effect element according to claim 1, wherein the composition of the crystal grains is different from the composition of the crystal grain boundaries. 3. The magnetoresistive effect element according to claim 2, wherein the diffusing substance is contained more in the material forming the crystal grain boundaries than in the material forming the crystal grains. 4. The magnetoresistive element according to claim 2, wherein the spin polarizability of the material forming the crystal grains is higher than the spin polarizability of the material forming the crystal grain boundaries. 5. The magnetoresistive effect element according to claim 1, wherein the crystal grains have an average grain size of 100 nm or less when the crystal grains are approximated to a spherical shape. 6. The magnetoresistive effect element according to claim 5, wherein the crystal grains have an average grain size of 2 nm or more when the crystal grains are approximated to a spherical shape. 7. The ferromagnetic layer composed of the crystal grains and an aggregate of the crystal grain boundaries comprises a magnetic material containing at least one of cobalt, iron and nickel, and one or more different elements added to the magnetic material. The magnetoresistive effect element according to claim 1, characterized in that 8. The magnetoresistive effect element according to claim 7, wherein boron is contained as the different element. 9. The ferromagnetic layer composed of an aggregate of the crystal grains and the crystal grain boundaries is CoxFe1-x (0.45 <
9. The magnetoresistive effect element according to claim 8, wherein the magnetic material containing cobalt and iron in a ratio of x <0.95) has one or more different elements containing boron added thereto. 10. The magnetoresistive effect element according to claim 9, wherein a total addition ratio of the one or more different elements is 15% or more. 11. The nonmagnetic layer is a tunnel barrier layer made of an insulator, and the nonmagnetic layer and two ferromagnetic layers sandwiching the nonmagnetic layer form a ferromagnetic tunnel junction. The magnetoresistive effect element according to claim 1. 12. A manufacturing apparatus for manufacturing a magnetoresistive effect element having a multilayer film structure, which comprises two ferromagnetic layers and a non-magnetic layer sandwiched therebetween, wherein the ferromagnetic layers are The film forming means includes a film forming means for forming a film, and the film forming means forms at least one of the ferromagnetic layers into a magnetic material containing at least one of cobalt, iron and nickel. Is added to form a film, the at least one ferromagnetic layer is made of an aggregate of crystal grains and crystal grain boundaries, and the crystal grain boundaries are formed by the different elements. An apparatus for manufacturing a magnetoresistive effect element, comprising: 13. A magnetoresistive element having a multilayer film structure including two ferromagnetic layers and a non-magnetic layer sandwiched between the ferromagnetic layers, and utilizing a change in the magnetization direction of the ferromagnetic layers. In the magnetic memory device configured to record information by using at least one of the ferromagnetic material layers, the ferromagnetic material layer includes an aggregate of crystal grains and crystal grain boundaries, and the crystal grain boundaries are the crystal grains. A magnetic memory device characterized by having a binding property with a diffusion material from a layer adjacent to a ferromagnetic layer to which a grain boundary belongs.