JP2003188439A - Magneto-resistive effect element, method of manufacturing the same, and magnetic memory device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve low power consumption when a magnetic memory device is configured by enabling, for a free layer provided in a magneto-resistive effect element, the control of rotary magnetic field without technical difficulty and limitation to reduction in thickness of the free layer. <P>SOLUTION: The magneto-resistive effect element is formed by laminating at least a ferromagnetic free layer 12, a non-magnetic layer 13 and a ferromagnetic fixed layer (not illustrated). In this magneto-resistive effect element, a value of the rotary magnetic field at the free layer 12 can be controlled by the growth of the free layer 12 up to the thickness enough to attain the continuation thereof, the formation of a mixed layer region 12b, which has extremely reduced or perfectly eliminated magnetism, to a part of the free layer 12, and substantial reduction in thickness of the free layer 12 to show its function as much as the thickness of the mixed layer region 12b. <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 method of manufacturing the same, and a magnetic memory device configured as a memory device that stores information 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 layer and the other as the free layer, the magnetization direction in the free layer can correspond to the voltage signal through the tunnel magnetoresistive effect. It becomes possible to take out as a signal.

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, for example, low power consumption is strongly desired. In MRAM,
Information is written by a current, but at that time, it is necessary to flow a sufficient current to generate a magnetic field exceeding Hc (h) described above. Although this current value depends on the constituent material and structure of the memory element, it is generally said to be about several mA, which is a barrier to lower power consumption.
In addition, since a large current is required, disconnection due to electromigration of wiring may occur when miniaturization is advanced.

As one method for realizing low power consumption, it is possible to reduce Hc (h) peculiar to a material, for example. Hc (h) is determined by Hc (0), asteroid shape, h value, etc., but reducing Hc (0) and Hc (h) are qualitatively consistent. Therefore, the reduction of Hc (0) will be described below. Hc (0) is approximately Hc (0) =
It is given by Hc (Film) + a * Ms * t / W. Hc
(Film) is Hc of the film itself before fine processing. The second term on the right side is the effect due to the demagnetizing field, a is a proportional constant, Ms is the saturation magnetization of the free layer, t is the thickness of the free layer, and W is the length of the free layer in the direction of the hard axis. In the case of an element having a size in the sub μm class, the demagnetizing field term becomes dominant because W becomes small. Therefore, as is clear from this equation, it can be easily estimated that thinning the free layer is one of the effective methods for reducing Hc (0).

[0010]

However, although making the free layer thin is effective for reducing Hc (0) and thus Hc (h), it is difficult to solve the technical problems as described below. With limits. For example, in order to reduce the power consumption of the MRAM, the thickness t of the free layer is set to 1 to 2.
It is considered necessary to reduce the thickness to about nm. However, it is not easy to uniformly grow such a thin free layer over the entire surface of the wafer substrate. This is because when the wettability between the material for forming the free layer and the material for forming the layer directly below the free layer is poor, for example, as shown in FIG.
At the initial stage of growth, the free layer grows like an island,
This is because a uniform layer may not be formed with a thickness of about 2 nm. Therefore, the free layer may not be a continuous film if it is simply thinned. Also,
In addition, there are many problems in the manufacturing method that hinder the thinning of the free layer, such as difficulty in controlling the growth rate.

In view of the above conventional circumstances, the present invention makes it possible to suppress the reversal magnetic field without the technical difficulty or limitation of thinning the free layer, thereby reducing the power consumption. It is an object of the present invention to provide a magnetoresistive effect element, a method for manufacturing the same, and a magnetic memory device that can realize the following.

[0012]

A magnetoresistive effect element according to the present invention has been devised in order to achieve the above object, and at least a ferromagnetic free layer, a nonmagnetic nonmagnetic layer and a ferromagnetic material. In the magnetoresistive effect element in which the fixed layer is laminated, a mixed layer region of a ferromagnetic substance and a nonmagnetic substance is formed in the vicinity of the interface of the free layer that is not on the nonmagnetic layer side. It is a thing.

Also, in the method of manufacturing a magnetoresistive effect element according to the present invention, a ferromagnetic material forming the free layer and a nonmagnetic material that easily forms a solid solution are adjacent to each other on the side of the free layer which is not the nonmagnetic layer side. Film is formed by exposing the free layer to a predetermined atmosphere after forming the free layer, or by implanting different atoms or ions into the free layer after forming the free layer. A mixed layer region of a ferromagnetic material and a non-magnetic substance is formed in the vicinity of the interface of the layer which is not on the non-magnetic layer side.

The magnetic memory device according to the present invention further comprises a magnetoresistive effect element in which at least a ferromagnetic free layer, a nonmagnetic nonmagnetic layer, and a ferromagnetic fixed layer are laminated, and the free layer. In a magnetic memory device configured to record information by utilizing the change in the magnetization direction of the magnetic layer, a mixed layer region of a ferromagnetic substance and a nonmagnetic substance is formed in the vicinity of the interface of the free layer that is not on the nonmagnetic layer side. It is characterized by being formed.

According to the magnetoresistive effect element having the above configuration, the magnetoresistive effect element configured by the manufacturing method according to the above procedure, or the magnetic memory device having the above configuration, the saturation magnetic moment of the mixed layer region is used as the material for forming the free layer. If it is made smaller than the ferromagnetic material or made non-magnetic, the thickness that functions as a free layer is substantially reduced by the mixed layer region. Therefore, even if a free layer having a thickness sufficient for continuity is formed, the magnitude of the reversal magnetic field in the free layer is suppressed as compared with the case where the entire thickness is made only of a ferromagnetic material. It will be.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetoresistive effect element, a method of manufacturing the same, 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 which constitutes 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 such a configuration, in the MRAM, the T
With respect to 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,
Information is written by changing the magnetization direction of the free layer in the TMR element 1 using the combined current magnetic field. Information is read from the TMR element 1 by selecting the TMR element 1 using a field effect transistor and extracting the magnetization direction of the free layer in the TMR 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 is composed of a three-layer structure of ferromagnetic material / insulator / ferromagnetic material, and the magnetization direction of one ferromagnetic material layer is a fixed layer (or fixed reference layer) 11 and the other is a free layer 1.
Used as 2. Then, the word line 2 and the bit line 3
Information is written (recorded) by changing the magnetization direction of the free layer 12 by the combined current magnetic field generated by the free layer 1 through the tunnel MR effect.
The magnetization direction in 2 corresponds to the voltage signal. These two ferromagnetic layers, that is, the nonmagnetic layer 13 made of an insulator sandwiched between the fixed layer 11 and the free layer 12 is made of, for example, Al oxide and has a function as a tunnel barrier layer. The other layers such as the underlayer 14 and the protective layer 15 are generally made of a material having no magnetism.

By the way, the TMR element 1 having such a configuration
As described above, by thinning the free layer 12, the switching field can be reduced and power consumption can be suppressed. That is, if the free layer 12 can be grown uniformly with an extremely thin thickness of about 1 to 2 nm, it is considered to be effective in reducing power consumption. Figure 4 (a)
It is explanatory drawing which shows a mode when the metallic magnetic material 12a carries out ideal layered growth. However, when the metallic magnetic material 12a having a thickness of about 1 to 2 nm is actually grown on the nonmagnetic layer 13 made of, for example, Al oxide, the surface free energy of the Al oxide is that of a general transition metal magnetic material. Since it is smaller than the above, the metal magnetic material 12a is likely to have an island shape. FIG. 4B is an explanatory diagram showing a state in which the metallic magnetic material 12a has an island shape. Thus, simply the free layer 12
It is not easy to uniformly grow the metallic magnetic material 12a over the entire surface of the non-magnetic layer 13 only by thinning the thickness, and as a result, the continuity of the free layer 12 may be impaired.

Therefore, in the TMR element 1 described in this embodiment, the free layer 12 is constructed as described below. FIG. 5 is an explanatory diagram showing a configuration example of the main part of the TMR element. As shown in FIG. 5A, in the TMR element 1 of this embodiment, in order to achieve both film continuity and thinness, a ferromagnetic material is provided near the interface of the free layer 12 that is not on the nonmagnetic layer 13 side. A mixed layer region 12b with a non-magnetic substance is formed. In the case of a so-called bottom type TMR element 1 in which the free layer 12 is located on the upper surface side of the non-magnetic layer 13 as shown in the figure, the mixed layer region 1 is formed near the interface of the free layer 12 on the protective layer 15 side.
2b will be formed. However, a so-called top type T in which the fixed layer 11 is located on the upper surface side of the non-magnetic layer 13
In the MR element, the mixed layer region 12b is formed near the interface of the free layer 12 on the underlayer 14 side.

[Manufacturing Method of Magnetoresistive Effect Element] Next, a manufacturing method of the TMR element 1 having the above configuration will be described. Here, the case of manufacturing the bottom type TMR element 1 is taken as an example, and the procedure for forming the mixed layer region 12b is mainly described.

First, a first example of the method of manufacturing the TMR element 1 will be described. In the first example, the mixed layer region 12b in the free layer 12 is formed by selecting the material of the protective layer 15. Specifically, for example, by using a magnetron sputtering apparatus in which the back pressure is exhausted to an ultrahigh vacuum region, a metal magnetic material 12a, which is a constituent material of the free layer 12, is formed on the nonmagnetic layer 13 made of Al oxide or the like. To do. As the metallic magnetic material 12a, for example, a Ni (nickel) -Fe (iron) -based alloy, specifically, a Ni ₈₁ Fe ₁₉ alloy (hereinafter, simply referred to as "NiF
e ”). However,
The film formation at this time is performed so that the NiFe film grows to a thickness sufficient to secure its continuity. For that purpose, for example, the designed film thickness of the NiFe film may be set to 3 nm or more.

After that, the free layer 1 is formed on the NiFe film.
A protective layer 15 that covers 2 is formed. However, as the constituent material of the protective layer 15, a non-magnetic substance that easily forms a solid solution with NiFe is selected. That is, a nonmagnetic substance that easily forms a solid solution with the NiFe film is formed adjacently on the NiFe film. Specifically, NiFe
It is conceivable to form Ta (tantalum), which is a dissimilar metal, with a thickness of, for example, about 5 nm.

When a Ta film is formed adjacent to the NiFe film, spontaneous diffusion of Ta occurs in the NiFe. Then, in the NiFe, NiFe reacts with Ta to form a solid solution. As a result, a mixed layer region 12b of NiFe, which is a ferromagnetic substance, and Ta, which is a nonmagnetic substance, is formed near the interface on the protective layer 15 side.

At this time, it may be possible to perform heat treatment such as annealing after the Ta film is formed. When heat treatment is performed, NiF
The diffusion of Ta with respect to the inside of e is promoted, and as a result, it is possible to further ensure the formation of the mixed layer region 12b and increase the film thickness.

The mixed layer region 12 thus formed
Since b is formed by mixing NiFe and Ta, its saturation magnetization becomes smaller than that of NiFe alone. Therefore, even if the NiFe film is grown to a thickness sufficient to be continuous, the saturation magnetization of the NiFe itself is exerted only in the portion obtained by subtracting the thickness of the mixed layer region 12b. That is, the thickness that functions as the free layer 12 is substantially reduced by the mixed layer region 12b. From this, even if the design film thickness of the NiFe film formed as the free layer 12 is 3 nm or more, the value obtained by subtracting the thickness of the mixed layer region 12b from the total thickness of the NiFe film is 3n.
When the thickness is m or less (the thickness that is difficult to secure the continuity of the film in the past), the effective thickness of the free layer 12 is reduced while securing the continuity of the film, and as a result, the free layer 12 is free. It can be said that the switching magnetic field of the layer 12 can be suppressed.

Mixed layer region 12b for realizing this
May eventually become a magnetic material, but it is very important for suppressing the switching magnetic field that the saturation magnetization of the mixed layer region 12b does not become larger than the original saturation magnetization of the free layer 12. . Further, from the viewpoint of suppressing the reversal magnetic field, it is desirable that the mixed layer region 12b be a non-magnetic material. This point can be appropriately set by selecting the material of the protective layer 15 with respect to the free layer 12, such as stacking Ta on the NiFe film.

In the above-mentioned first example, NiFe is used as the free layer 12, and a dissimilar metal layer (protective layer 1) that covers the NiFe is used.
Although the case where Ta is used as 5) is taken as an example, the material of each layer is not limited to these. For example, as the free layer 12, a NiFe alloy, a CoFe alloy, or a NiFeCo alloy having a composition different from Ni ₈₁ Fe ₁₉ may be used. Alternatively, an alloy obtained by adding an element different from these to an alloy containing one or more of Ni, Fe, and Co (cobalt) may be used. This can be freely selected in consideration of tunnel magnetic resistance, reversal magnetic field, heat resistance and the like. Further, as the dissimilar metal layer, in addition to Ta, Ru (ruthenium), Cu, Pt (platinum), Au (gold), Ag (silver), Pd (palladium),
Any of Al, Cr (chromium), Ti (titanium), Rh (rhodium), W (tungsten), Ir (iridium), etc. may be used, or an alloy containing one or more of these may be used.

Next, a second example of the method of manufacturing the TMR element 1 will be described. In the second example, after forming the free layer 12, the mixed layer region 12b is formed by exposing the free layer 12 to a predetermined atmosphere. Specifically, in order to form the mixed layer region 12b which is non-magnetic or whose magnetic property is significantly weakened, the adjacent free metal layer as in the first example is not used, and the free layer 12 after film formation is kept constant in a predetermined atmosphere. Expose for hours. The predetermined atmosphere may be, for example, the atmosphere, water vapor, or a predetermined gas. Other than this point, it is the same as the normal case. Therefore, in the second example, the mixed layer region 12
The non-magnetic substance forming b is not a metal material as in the case of the first example, but H (hydrogen) and O forming a predetermined atmosphere.
(Oxygen), N (nitrogen), Cl (chlorine), S (sulfur), C
(Carbon), F (fluorine), etc., or one or more compounds.

The mixed layer region 12 thus formed
b is also H, which forms a predetermined atmosphere with a ferromagnetic material such as NiFe
Since it is mixed with a non-magnetic substance such as, the saturation magnetization becomes smaller than the saturation magnetization of the ferromagnetic substance alone.
Therefore, the thickness that functions as the free layer 12 is substantially reduced by the mixed layer region 12b, and thus the free layer 1
Even if the designed film thickness of the ferromagnetic material formed as No. 2 is 3 nm or more, the mixed layer region 12b is
If the value obtained by subtracting the thickness of 3 is 3 nm or less, the effective thickness of the free layer 12 is reduced while securing the continuity of the film, and as a result, the reversal field of the free layer 12 is reduced. It can be said that suppression is possible.

In the second example described above, the mixed layer region 12b is formed by exposing the free layer 12 to a predetermined atmosphere, but the mixed layer region 12b is formed.
The non-magnetic substance that forms the layer may be contained in the oxide layer or the like adjacent to the free layer 12. That is, the mixed layer region 12b may be a compound layer with an oxide layer or the like. However, also in this case, it is assumed that the saturation magnetization of the mixed layer region 12b is not higher than the original saturation magnetization of the ferromagnetic material forming the free layer 12.

Next, a third example of the method of manufacturing the TMR element 1 will be described. In the third example, after the formation of the free layer 12, the mixed layer region 12b is formed by implanting different atoms or ions into the free layer 12. Specifically, on the surface of the free layer 12 after film formation, Ga
By implanting (gallium) ions or the like, the magnetism on the surface is lost or significantly reduced. In addition,
Since the driving process itself is well known, its description is omitted here.

The mixed layer region 12 thus formed
Since b is also a mixture of a ferromagnetic substance such as NiFe and a non-magnetic substance such as Ga ions, its saturation magnetization is smaller than that of the ferromagnetic substance alone. Therefore,
Since the thickness functioning as the free layer 12 is substantially reduced by the mixed layer region 12b, even if the designed film thickness of the ferromagnetic material formed as the free layer 12 is 3 nm or more, the ferromagnetic material If the value obtained by subtracting the thickness of the mixed layer region 12b from the total thickness is 3 nm or less, the effective thickness of the free layer 12 is reduced while securing the continuity of the film. As a result, it can be said that the switching field of the free layer 12 can be suppressed.

Although the mixed layer region 12b can be formed by any of the above-mentioned first to third examples,
It goes without saying that it is effective to use these in combination as appropriate.

[Characteristics of Magnetoresistive Element] Next, characteristics of the TMR element 1 manufactured as described above will be described. 6 to 8 show the non-magnetic layer 13 made of Al oxide.
Magnetic properties of the free layer 12 were investigated when a NiFe film was grown as the free layer 12 with various design thicknesses and a Ta film was stacked as the dissimilar metal layer with a thickness of about 5 nm. It is explanatory drawing which shows a result.

FIG. 6 shows the value of the saturation magnetic moment per unit area (hereinafter, simply referred to as "saturation magnetic moment") measured by a vibrating sample magnetometer (VSM) with respect to the designed film thickness of NiFe which is a ferromagnetic material. Is shown. Since the saturation magnetic moment is determined by the volume of the magnetic substance and the saturation magnetization peculiar to the material, it should theoretically be proportional to the film thickness. However, according to the measurement results shown in the figure, the following two points behave outside the theoretical prediction. The first point is that when the design film thickness is about 3 nm or more, the saturation magnetic moment is well approximated by a straight line with respect to the design film thickness. It is that. The second point is that a straight line approximated on the thick film side of 3 nm or more does not pass the origin and takes a positive x intercept value.

Of these, the first point is further clarified by FIG. FIG. 7 is the saturation magnetic moment shown in FIG. 6 divided by the design film thickness. According to the illustrated example, it can be seen that, when the NiFe design film thickness is 3 nm or more, the saturation magnetization is substantially constant, but below that, the saturation magnetization is reduced.

The cause of the abnormality of the first point is as follows.
The discontinuous film formation as described with reference to FIG. That is, since the continuous film is not formed when the design film thickness of NiFe is 3 nm or less, it does not show the saturation magnetization that NiFe originally should have, and it is considered that the saturation magnetic moment is also reduced accordingly. The state of the cross section of this discontinuous film formation is shown in FIG. When such a magnetic layer is formed, NiFe is extremely thin locally,
Alternatively, the probability that there is a nonexistent portion becomes very high, and the tunnel magnetoresistive effect necessary for the operation as the TMR element 1 may be reduced, which is extremely unpractical in practice.

The cause of the abnormality of the second point is that even if the design film thickness is sufficiently thick, the adjacent layer (for example, the protective layer 1)
It is considered that a region called so-called dead layer in which magnetism is remarkably reduced or completely eliminated, that is, the mixed layer region 12b is formed between (5) and (5).
(See (a)). When a value obtained by subtracting the thickness of the mixed layer region 12b from the design film thickness is called an effective film thickness, this effective film thickness effectively affects the free layer 12, that is, the demagnetizing field. It corresponds to the thickness of the magnetic layer.
The thickness of this dead layer corresponds to the x-intercept of the approximate straight line on the thick film side in FIG. 6, and its specific value is manufactured by the manufacturing method (for example, the first example) described above. In the case of TMR element 1, it was 0.78 nm.

Now, FIG. 8 shows the value of the saturation magnetic moment shown in FIG. 6 divided by the effective film thickness and plotted against the effective film thickness. According to this figure, it can be seen that the NiFe magnetism is sufficiently exhibited up to an effective film thickness of 2.22 nm (= 3-0.78 nm).

From the above, it can be said that the following is verified for the TMR element 1 described in the present embodiment. That is, in order to manufacture NiFe of 2 nm for the purpose of suppressing the demagnetizing field, the designed film thickness is not set to 2 nm, but, for example, 3 n is used as described above.
It can be seen that it is effective to make the design film thickness thicker than the desired thickness such as m and to bring the effective film thickness close to 2 nm by forming the mixed layer region 12b with the adjacent layer. Moreover, the TMR element 1 using NiFe having an effective film thickness of 2.22 nm due to the existence of the mixed layer region 12b exhibits a tunnel magnetic resistance equivalent to that when NiFe having an effective film thickness larger than this is used. It can also be seen that there is no practical problem in terms of read signal.

Therefore, according to the TMR element 1 of the present embodiment, it is possible to reduce the effective thickness of the free layer 12 while maintaining the continuity of the free layer 12. It is possible to suppress the reversal magnetic field without being accompanied, and thus it is also possible to realize low power consumption when configuring the MRAM.

Here, the effective film thickness is 2.22 nm.
However, this is not the lower limit of the effective film thickness, and the combination of the free layer 12 and the protective layer 15 (or the underlayer 14) which is a dissimilar metal layer and the condition of the annealing treatment are not limited to the above. By optimizing
A thinner effective film thickness is also possible.

In this embodiment, the TMR element has been described as an example of the magnetoresistive effect element.
It goes without saying that even if the non-magnetic layer between the free layer and the fixed layer is of the GMR type composed of Cu or the like, the same applies.

[0047]

As described above, in the present invention, in order to achieve both the continuity and the thinness of the film, the free layer is first grown to a sufficient thickness to be continuous, and the free layer is By forming a mixed layer region in a part, the effective free layer thickness is reduced. Therefore, according to the present invention, it is possible to suppress the switching magnetic field in the free layer without any technical difficulty or limit to thinning, and thus it is possible to reduce the power consumption of the magnetic memory device.

[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 an explanatory view showing a film formation state of a metal magnetic material,
(A) is a diagram showing a state in the case of ideal layered growth,
(B) is a figure which shows a mode that it became an island shape.

5A and 5B are explanatory views showing a configuration example of a main part of a TMR element to which the present invention is applied, FIG. 5A is a side sectional view showing the film configuration, and FIG. 5B is a film configuration as a comparative example. FIG.

FIG. 6 is an explanatory diagram showing a specific example of the measurement result of the saturation magnetic moment per unit area of the designed film thickness of NiFe which is a ferromagnetic material.

FIG. 7 is an explanatory diagram showing a specific example of the result of dividing the measurement result of the saturation magnetic moment shown in FIG. 6 by the design film thickness of the free layer.

FIG. 8 is an explanatory diagram in which the measurement result of the saturation magnetic moment shown in FIG. 6 is divided by the effective film thickness of the free layer and plotted against the effective film thickness.

FIG. 9 is an asteroid diagram showing an example of a magnetic field response of a memory element forming an MRAM.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... TMR element, 11 ... Fixed layer, 12 ... Free layer, 12a
... metallic magnetic material, 12b ... mixed layer region, 13 ... non-magnetic layer, 14 ... underlayer, 15 ... protective layer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuhiro Oba             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation F term (reference) 5F083 FZ10 GA05 JA60 PR36

Claims (13)

[Claims] 1. A magnetoresistive effect element comprising at least a ferromagnetic free layer, a nonmagnetic nonmagnetic layer, and a ferromagnetic pinned layer, wherein the free layer is near an interface that is not on the nonmagnetic layer side. A magnetoresistive effect element, wherein a mixed layer region of a ferromagnetic material and a non-magnetic material is formed. 2. The magnetoresistive effect element according to claim 1, wherein the mixed layer region has a saturation magnetization smaller than a saturation magnetization of the ferromagnetic material itself forming the mixed layer region. 3. The magnetoresistive effect element according to claim 1, wherein the mixed layer region is non-magnetic. 4. The magnetoresistive effect element according to claim 1, wherein the non-magnetic substance forming the mixed layer region is made of a metal material. 5. The magnetoresistive effect element according to claim 4, wherein the metal material is made of a material for forming a non-magnetic protective layer laminated after the growth of the free layer. 6. The magnetoresistive effect element according to claim 4, wherein the metal material comprises a material for forming a non-magnetic underlayer laminated before the growth of the free layer. 7. The non-magnetic material forming the mixed layer region is made of one or more compounds selected from hydrogen, oxygen, nitrogen, chlorine, sulfur, carbon and fluorine. The magnetoresistive effect element according to claim 1. 8. The magnetoresistive effect element according to claim 1, wherein a value obtained by subtracting the thickness of the mixed layer region from the thickness of the free layer is 3 nm or less. 9. A method of manufacturing a magnetoresistive element comprising at least a ferromagnetic free layer, a non-magnetic non-magnetic layer and a ferromagnetic pinned layer, wherein the non-magnetic layer of the free layer. On the side that is not the side, a ferromagnetic material that forms the free layer and a non-magnetic substance that easily forms a solid solution are formed adjacent to each other, and the ferromagnetic material and the ferromagnetic material are formed near the interface of the free layer that is not the non-magnetic layer side. A method of manufacturing a magnetoresistive effect element, which comprises forming a mixed layer region with a non-magnetic substance. 10. The method of manufacturing a magnetoresistive element according to claim 9, wherein a heat treatment is performed after forming a nonmagnetic material adjacent to the free layer. 11. A method of manufacturing a magnetoresistive effect element comprising at least a ferromagnetic free layer, a non-magnetic non-magnetic layer and a ferromagnetic fixed layer, which are laminated after the free layer is formed. A method of manufacturing a magnetoresistive element, characterized in that the free layer is exposed to a predetermined atmosphere, and a mixed layer region of a ferromagnetic material and a nonmagnetic material is formed in the vicinity of an interface of the free layer that is not on the nonmagnetic layer side. . 12. A method of manufacturing a magnetoresistive effect element, comprising at least a ferromagnetic free layer, a non-magnetic non-magnetic layer and a ferromagnetic pinned layer, which are formed after the free layer is formed. A magnetoresistive device characterized in that a mixed layer region of a ferromagnetic substance and a nonmagnetic substance is formed in the vicinity of an interface of the free layer, which is not on the nonmagnetic layer side, by implanting different atoms or ions into the free layer. Method for manufacturing effect element. 13. A magnetoresistive element comprising at least a ferromagnetic free layer, a non-magnetic non-magnetic layer and a ferromagnetic pinned layer, wherein the change in the magnetization direction of the free layer is utilized. In the magnetic memory device configured to record information, the free layer has a mixed layer region of a ferromagnetic substance and a nonmagnetic substance formed in the vicinity of an interface which is not on the nonmagnetic layer side. Characteristic magnetic memory device.