JP2006165059A - Storage element and memory - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a storage memory having satisfactory magnetic characteristic and heat resistance. <P>SOLUTION: The storage medium 3 is configured in such a way that it has a storage layer 17 holding information by a magnetic state of a magnetic body, a magnetized fixed layer 31 is provided via an insulating layer 16 being a tunnel barrier for this storage layer 17, and the storage layer 17 contacts a base layer or an upper protective layer 19 via an oxide layer 18. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention includes a storage layer that stores the magnetization state of a ferromagnetic layer as information, and a magnetization fixed layer whose magnetization direction is fixed, and a storage element that changes the magnetization direction of the storage layer by passing an electric current. The present invention relates to a memory provided with this memory element, and is suitable for application to a nonvolatile memory.

With the rapid spread of information communication devices, especially small personal devices such as portable terminals, the elements such as memory and logic that compose this device are becoming more highly integrated, faster, lower power, etc. There is a demand for higher performance.
In particular, the non-volatile memory has a feature that is essentially advantageous for miniaturization because there is no moving part like a hard disk or an optical disk.

Examples of the nonvolatile memory include a flash memory using a semiconductor and an FRAM (Ferro electric Random Access Memory) using a ferroelectric.
However, the flash memory has a drawback in that it is not suitable for high-speed access because the writing speed is as low as the order of microseconds.
On the other hand, the FRAM has a limited number of rewritable times of 10 ¹² to 10 ^14, and therefore, it is pointed out that the durability is small to completely replace the SRAM and DRAM, and that fine processing of the ferroelectric capacitor is difficult. ing.

A magnetic random access memory (MRAM) that records information by magnetization of a magnetic material is attracting attention as a nonvolatile memory that does not have these drawbacks (see, for example, Non-Patent Document 1).
Since this MRAM stores data by rotating the magnetic moment, the number of rewrites is large.
Also, the access time is very high.

Here, a schematic diagram (perspective view) of a general MRAM is shown in FIG.
A drain region 108, a source region 107, and a gate electrode 101 constituting a selection transistor for selecting each memory cell are formed in a portion separated by the element isolation layer 102 of the semiconductor substrate 110 such as a silicon substrate. Has been.
A word line 105 extending in the front-rear direction in the figure is provided above the gate electrode 101.
The drain region 108 is formed in common to the left and right selection transistors in the drawing, and a wiring 109 is connected to the drain region 108.
A magnetic storage element 103 having a storage layer whose magnetization direction is reversed is disposed between the word line 105 and the bit line 106 disposed above and extending in the horizontal direction in the drawing. The magnetic memory element 103 is composed of, for example, a magnetic tunnel junction element (MTJ element).
Further, the magnetic memory element 103 is electrically connected to the source region 107 via the horizontal bypass line 111 and the vertical contact layer 104.
By applying current to each of the word line 105 and the bit line 106, a current magnetic field is applied to the magnetic memory element 103, thereby reversing the magnetization direction of the memory layer of the magnetic memory element 103 and recording information. be able to.

In order to stably hold recorded information in a magnetic memory such as MRAM, it is necessary that a magnetic layer (storage layer) for recording information has a certain coercive force.
On the other hand, in order to rewrite the recorded information, a certain amount of current must be passed through the address wiring.
However, as the elements constituting the MRAM become finer, the address wiring becomes thinner, so that a sufficient current cannot flow.

Therefore, attention has been paid to a magnetic memory having a configuration using magnetization reversal by spin injection as a configuration capable of reversing magnetization with a smaller current (see, for example, Patent Document 1).
Magnetization reversal by spin injection is to cause magnetization reversal in another magnetic material by injecting spin-polarized electrons that have passed through the magnetic material into another magnetic material.

  For example, when a current is passed through a giant magnetoresistive element (GMR element) or a magnetic tunnel junction element (MTJ element) in a direction perpendicular to the film surface, magnetization of at least a part of the magnetic layer of these elements is performed. Can be reversed.

  Magnetization reversal by spin injection has an advantage that magnetization reversal can be realized with a small current even if the element is miniaturized.

Moreover, the schematic diagram of the magnetic memory of the structure using the magnetization reversal by the spin injection mentioned above is shown in FIG.5 and FIG.6. 5 is a perspective view, and FIG. 6 is a cross-sectional view.
A drain region 58, a source region 57, and a gate electrode 51 constituting a selection transistor for selecting each memory cell are formed in a portion separated by the element isolation layer 52 of the semiconductor substrate 60 such as a silicon substrate. Has been. Of these, the gate electrode 51 also serves as a word line extending in the front-rear direction in FIG.
The drain region 58 is formed in common with the left and right selection transistors in FIG. 5, and a wiring 59 is connected to the drain region 58.
A storage element 53 having a storage layer whose magnetization direction is reversed by spin injection is disposed between the source region 57 and the bit line 56 disposed above and extending in the left-right direction in FIG.
The storage element 53 is configured by, for example, a magnetic tunnel junction element (MTJ element).
In the figure, reference numerals 61 and 62 denote magnetic layers. Of the two magnetic layers 61 and 62, one magnetic layer is a magnetization fixed layer whose magnetization direction is fixed, and the other magnetic layer is a magnetization direction. A changing magnetization free layer, that is, a storage layer is used.
The storage element 53 is connected to the bit line 56 and the source region 57 via the upper and lower contact layers 54, respectively. As a result, a current can be passed through the magnetic memory element 53 to reverse the magnetization direction of the memory layer by spin injection.

In the case of a memory having a configuration using magnetization reversal by spin injection, the device structure can be simplified as compared with the general MRAM shown in FIG. It also has the feature.
Further, by utilizing magnetization reversal by spin injection, there is an advantage that the write current does not increase even when the element is miniaturized as compared with a general MRAM in which magnetization reversal is performed by an external magnetic field.

Nikkei Electronics 2001.1.22 (pages 164-171) JP 2003-17782 A

By the way, the memory element constituting the MRAM is composed of a memory layer made of a magnetic material such as CoFe and CoFeB, a magnetization fixed layer having a ferromagnetic layer made of a magnetic material such as CoFe, and an antiferromagnetic material such as PtMn and IrMn. And an underlayer composed of Ta, Ti, nitrides thereof, Cr, Cu, NiFe, NiFeCr, or the like.
When the magnetization fixed layer has a laminated ferrimagnetic structure in which a plurality of ferromagnetic layers are laminated via a nonmagnetic layer, a nonmagnetic layer mainly composed of a nonmagnetic metal element such as Ru or Rh is provided.

  However, when a memory element is configured using these materials, if the heat of 350 ° C. or more required in the semiconductor process is applied, the resistance change rate and the soft magnetic characteristics of the memory layer are lost, and the memory element Necessary characteristics may be deteriorated.

  In order to solve the above-described problems, in the present invention, even when heat of 350 ° C. or higher is applied, characteristics necessary as a memory element are not impaired, and a memory element having good magnetic characteristics and heat resistance, and A memory having a memory element is provided.

  The storage element of the present invention has a storage layer that holds information according to the magnetization state of a magnetic material, and a magnetization fixed layer is provided to the storage layer via an insulating layer that serves as a tunnel barrier. It is in contact with the underlayer or the upper protective layer through the oxide layer.

  The memory of the present invention includes a storage element having a storage layer that holds information according to the magnetization state of the magnetic material, and two types of wirings that intersect each other, and the storage element stores information according to the magnetization state of the magnetic material. A magnetic pinned layer is provided on the storage layer via an insulating layer serving as a tunnel barrier, and the storage layer is in contact with the underlayer or the upper protective layer via the oxide layer. The storage element is arranged near the intersection of two types of wiring and between the two types of wiring.

According to the above configuration of the memory element of the present invention, the memory layer is in contact with the base layer or the upper protective layer via the oxide layer, so that the memory layer and the base layer or the upper protective layer are interposed. The diffusion of these elements can be suppressed by the oxide layer.
Thereby, deterioration of characteristics due to diffusion of the above-described element when heat is applied to the memory element can be suppressed.

  According to the configuration of the memory of the present invention described above, a memory element having a memory layer that holds information according to the magnetization state of the magnetic material and two kinds of wirings intersecting each other are provided, and the memory element is the memory element of the present invention. The storage element is arranged near the intersection of two types of wiring and between the two types of wiring, thereby suppressing deterioration of the characteristics of the storage element when heat is applied to the storage element Therefore, it is possible to stably record and read information in the memory.

In the memory element of the present invention, the memory layer can be made of CoFeB.
In such a configuration, the amount of saturation magnetization can be reduced and the resistance change rate can be increased by using CoFeB.
And since boron B in CoFeB has the property of easily diffusing when heat is applied, the effect of preventing diffusion by the oxide layer of the present invention is particularly effective.

In the memory element of the present invention, in the fixed magnetization layer, an antiferromagnetic layer is provided on the side opposite to the memory layer, the ferromagnetic layer in contact with the antiferromagnetic layer is a CoFe layer, and the Fe content of the CoFe layer A configuration in which the amount is 10 atomic% or less is also possible.
In such a configuration, since the antiferromagnetic layer is provided on the side opposite to the storage layer, the magnetization direction of the ferromagnetic layer of the magnetization fixed layer is fixed by the antiferromagnetic layer. The ferromagnetic layer in contact with the antiferromagnetic layer of the magnetization fixed layer is a CoFe layer, and the Fe content of the CoFe layer is 10 atomic% or less, so that the ferromagnetic layer is deteriorated even when heat treatment is performed at a high temperature. It becomes difficult to do. Here, if the ferromagnetic layer in contact with the antiferromagnetic layer is, for example, a CoFeB layer, the antiferromagnetic coupling may be smaller than that of the CoFe layer, possibly because of insufficient crystal orientation with the antiferromagnetic layer. The strength is weakened. Therefore, the ferromagnetic layer in contact with the antiferromagnetic layer is preferably a CoFe layer.

In the memory element of the present invention, the ferromagnetic layer in contact with the insulating layer of the magnetization fixed layer may be a CoFeB layer.
In such a configuration, the CoFeB layer has a higher spin polarizability and higher spin injection efficiency than the CoFe layer and the like, so that the amount of current required to reverse the magnetization direction of the storage layer is reduced. It becomes possible.
Further, in the CoFeB layer of the ferromagnetic layer in contact with the insulating layer, when the Fe content is 20 atomic% or more and the B content is 10 to 30 atomic%, the resistance change rate can be increased. In addition, sufficient heat resistance can be ensured.

In the memory element of the present invention, it is also possible to adopt a configuration in which information is recorded on the memory layer by changing the magnetization direction of the memory layer by passing a current in the stacking direction.
In such a configuration, by flowing current in the stacking direction, the magnetization direction of the storage layer changes, and information is recorded on the storage layer. The information can be recorded.

The memory element of the present invention may have a structure in which a plurality of ferromagnetic layers are laminated via a nonmagnetic layer, and the ferromagnetic layer in contact with the nonmagnetic layer is a CoFe layer. Is possible.
In such a configuration, a plurality of ferromagnetic layers are laminated with a nonmagnetic layer, that is, a so-called laminated ferrimagnetic structure, and the ferromagnetic layer in contact with the nonmagnetic layer is a CoFe layer. Thus, sufficient antiferromagnetic coupling can be obtained in the laminated ferrimagnetic structure.

In the memory of the present invention, the storage element has a configuration in which the direction of magnetization of the storage layer is changed by passing a current in the stacking direction, and information is recorded on the storage layer. In addition, a current flowing in the stacking direction may flow through the memory element.
In such a configuration, information can be recorded by spin injection by flowing a current in the stacking direction of the storage element, and information can be recorded by spin injection by flowing a current in the stacking direction of the storage element through two kinds of wirings. Recording can be performed.

According to the above-described present invention, it is possible to suppress the deterioration of the characteristics of the memory element when heat is applied to the memory element. Therefore, it is possible to stably record and read information in the memory. For example, a memory element with little characteristic deterioration can be formed even at a high temperature of 350 ° C. or higher required for a semiconductor process.
As a result, a memory having heat resistance and high reliability can be realized.

  In particular, when a layer that requires a relatively high heat treatment temperature, such as MgO, is used in the film structure of the memory element, the rate of change in resistance is further increased by the heat treatment, and deterioration of magnetic properties is suppressed. be able to.

Prior to the description of specific embodiments of the present invention, an outline of the present invention will be described.
As a result of various investigations on the above-described problem of deterioration of the magnetoresistance change rate due to heat, when heat is applied to the memory element, a material such as Ta used for the underlayer or protective layer is the memory layer. In particular, when CoFeB is used for the memory layer, the diffusion rate of B atoms may degrade the magnetoresistance change rate of the magnetic tunnel junction element (MTJ element) constituting the memory element. all right.

Therefore, in the present invention, the memory element is configured such that the memory layer is in contact with the (lower) underlying layer or the upper protective layer via the oxide layer.
In other words, the memory element according to the present invention basically includes, from the substrate side (lower layer side), the underlayer / antiferromagnetic layer / magnetization fixed layer / tunnel barrier layer (insulating layer) / memory layer / oxide layer / protection. From a laminated film of a layer (cap layer) or a laminated film of an underlayer / oxide layer / memory layer / tunnel barrier layer (insulating layer) / magnetization pinned layer / protective layer (cap layer) Constitute.
The fixed magnetization layer may have a so-called laminated ferrimagnetic structure in which a plurality of ferromagnetic layers are laminated via a nonmagnetic layer.
As the material of the oxide layer, for example, aluminum oxide, magnesium oxide, or other oxides can be used.

In this manner, the storage layer is in contact with the (underlying) underlayer or the upper protective layer via the oxide layer, so that when the heat is applied, the storage layer is changed from the underlayer or the upper layer. The diffusion of elements into the protective layer and the diffusion of elements from the base layer or the upper protective layer into the memory layer can be suppressed by the oxide layer.
Thereby, since deterioration of the magnetoresistance change rate when heat is applied can be suppressed, a memory element having good characteristics and heat resistance can be configured.

As a material of the tunnel barrier layer (insulating layer), an oxide or a nitride can be used.
For example, aluminum oxide, aluminum nitride, magnesium oxide and the like can be mentioned, and an insulating layer mainly composed of these oxides and nitrides is formed.
The aluminum oxide can be formed, for example, by forming a metal Al layer and then oxidizing the Al layer.
The aluminum nitride can be formed, for example, by forming a metal Al layer and then nitriding the Al layer.
Magnesium oxide can be formed by directly depositing an oxide by, for example, RF sputtering.

Moreover, as a material of each other layer which comprises a memory element, the following materials are mentioned, for example.
As materials used for the antiferromagnetic layer, manganese alloys such as iron, nickel, platinum, iridium, and rhodium, cobalt, nickel oxide, and the like can be used.
As a material used for the nonmagnetic layer, ruthenium, copper, chromium, gold, silver or the like can be used. Although the film thickness varies depending on the material, it is used in the range of about 0.4 nm to 2.5 nm.
As a material of the ferromagnetic layer constituting the magnetization fixed layer, a Co—Fe based ferromagnetic material, an amorphous material in which boron B is added to 15 to 30 atomic%, or a ferromagnetic material made of an alloy of Co, Fe, and Ni. Can be used.

Of the ferromagnetic layers constituting the magnetization fixed layer, the ferromagnetic layer in contact with the tunnel barrier layer (insulating layer) is preferably a CoFeB layer. This is because the CoFeB layer has a higher spin polarizability and higher spin injection efficiency than the CoFe layer and the like, so that it is possible to reduce the amount of current required to reverse the magnetization direction of the storage layer. Because.
Furthermore, in this CoFeB layer, the Fe content is 20 atomic% or more and the B content is 10 to 30 atomic%, so that the rate of resistance change can be increased and sufficient heat resistance can be achieved. Can be secured.

  Of the ferromagnetic layers constituting the magnetization fixed layer, in particular, the ferromagnetic layer in contact with the antiferromagnetic layer (eg, PtMn film) is made of Co or Co—Fe ferromagnetic material, and its Fe content is reduced. It should be 0 to 20%. If the Fe content exceeds 20% and becomes too large, it tends to deteriorate due to high-temperature heat treatment.

  In a so-called laminated ferrimagnetic structure in which a plurality of ferromagnetic layers are laminated via a nonmagnetic layer, the ferromagnetic layer in contact with the lower side of the nonmagnetic layer (for example, Ru film) is also a CoFeB / Ru / CoFeB laminated layer. When a laminated ferrimagnetic structure is formed with a film, a sufficient antiferromagnetic coupling cannot be obtained, so a CoFe layer is preferable to a CoFeB layer.

  Therefore, for example, a CoFeB / CoFe laminated film may be used, such as a CoFeB layer on the side in contact with the tunnel barrier layer and a CoFe layer on the side in contact with the nonmagnetic layer of the laminated ferrimagnetic structure. it can.

As the ferromagnetic material used for the memory layer, a ferromagnetic material mainly composed of Co, Fe, and Ni can be used, but a CoFeB material is desirable because the amount of saturation magnetization can be reduced and the rate of resistance change is large. More desirably, the content of boron B is 15 to 30%, and the composition ratio of Co and Fe is preferably Co: Fe = 9: 1 to 5: 5.
Thereby, the amount of saturation magnetization can be reduced and a large resistance change rate can be obtained.

Next, conditions for the storage element to satisfy necessary characteristics will be described.
First, an intermediate layer (hereinafter referred to as a barrier layer) serving as a tunnel barrier of the tunnel magnetic junction element will be described.

In a storage element (of a normal MRAM) that reverses the magnetization direction of the storage layer by a current magnetic field, the resistance value of the barrier layer is preferably in the range of 500Ω to ² kΩμm ² .

Further, in a storage element that reverses the magnetization direction of the storage layer by spin injection, for example, in a tunnel magnetic junction element in which a barrier layer is formed of AlOx, in order to enable magnetization reversal by spin injection, about 3-8. A current density of × 10 ⁶ (A / μm ² ) is required.
Although depending on the reliability such as the pinhole density in the barrier layer, the spin-injection magnetization reversal is possible, and the dielectric breakdown voltage of the relatively low resistance barrier layer is about 1V.
Here, in order to obtain a current density of 3 to 8 × 10 ⁶ (A / μm ² ), assuming that the area of the memory element is 0.06 × 0.167 μm = 0.01 μm ² , The resistance value needs to be smaller than 33.3 to 12.5 (Ωμm ² ).
Note that the smaller the current density required for magnetization reversal, the larger the resistance value of the memory element.
Accordingly, the resistance value of the barrier layer, from the viewpoint of obtaining a current density required for spin injection is preferably at least 30Omegamyuemu ² or less, and more preferably 15Omegamyuemu ² or less.

In addition, when other materials such as MgO are used for the barrier layer instead of AlOx, the required resistance value is determined for the same reason, but the insulation withstand voltage is also obtained when a material such as MgO is used. Since it is almost equivalent to AlOx, it is desirable that the resistance value is 30 Ωμm ² or less.

The other configuration of the memory element can be the same as a conventionally known configuration of the memory element that records information by applying an external magnetic field or spin injection.
The magnetization fixed layer has a configuration in which the magnetization direction is fixed only by the ferromagnetic layer or by using the antiferromagnetic coupling between the antiferromagnetic layer and the ferromagnetic layer.
In addition, the fixed magnetization layer and the storage layer have a structure composed of a single ferromagnetic layer, or a laminated ferrimagnetic structure in which a plurality of ferromagnetic layers are stacked via a nonmagnetic layer.

  As a method for reading information recorded in the memory layer of the memory element, a ferromagnetic layer that flows through the insulating layer is provided by providing a magnetic layer serving as a reference of information via a thin insulating film in the memory layer of the memory element. The recorded information may be read by a tunnel current, or may be read by a magnetoresistive effect.

  Next, embodiments of the present invention will be described.

As an embodiment of the present invention, a schematic configuration diagram (perspective view) of a memory is shown in FIG.
In this memory, a storage element capable of holding information in a magnetized state is arranged near the intersection of two types of address lines (for example, a word line and a bit line) orthogonal to each other.
That is, the drain region 8, the source region 7, and the gate electrode 1 that constitute a selection transistor for selecting each memory cell in a portion separated by the element isolation layer 2 of the semiconductor substrate 10 such as a silicon substrate, Each is formed. Of these, the gate electrode 1 also serves as one address wiring (for example, a word line) extending in the front-rear direction in the figure.
The drain region 8 is formed in common to the left and right selection transistors in the figure, and a wiring 9 is connected to the drain region 8.

The storage element 3 is disposed between the source region 7 and the other address wiring (for example, bit line) 6 disposed above and extending in the left-right direction in the drawing. The storage element 3 has a storage layer composed of a ferromagnetic layer whose magnetization direction is reversed by spin injection.
The storage element 3 is arranged near the intersection of the two types of address lines 1 and 6.
The storage element 3 is connected to the bit line 6 and the source region 7 through upper and lower contact layers 4, respectively.
As a result, a current in the vertical direction (stacking direction of the storage element 3) can be passed through the storage element 3 through the two types of address lines 1 and 6, and the magnetization direction of the storage layer can be reversed by spin injection.

A cross-sectional view of the memory element 3 of the memory according to the present embodiment is shown in FIG.
As shown in FIG. 2, the storage element 3 is provided with a fixed magnetization layer 31 in the lower layer with respect to the storage layer 17 in which the direction of the magnetization M1 is reversed by spin injection.
The antiferromagnetic layer 12 is provided under the magnetization fixed layer 31, and the magnetization direction of the magnetization fixed layer 31 is fixed by the antiferromagnetic layer 12.

  An insulating layer (barrier layer) 16 serving as a tunnel barrier is provided between the storage layer 17 and the magnetization fixed layer 31, and the tunnel magnetic junction element (MTJ) is formed by the storage layer 17, the insulating layer 16, and the magnetization fixed layer 31. Element).

The magnetization fixed layer 31 has a laminated ferrimagnetic structure.
Specifically, the magnetization fixed layer 31 has a configuration in which two ferromagnetic layers 13 and 15 are stacked via a nonmagnetic layer 14 and antiferromagnetically coupled.
Since each of the ferromagnetic layers 13 and 15 of the magnetization fixed layer 31 has a laminated ferrimagnetic structure, the magnetization M13 of the ferromagnetic layer 13 is directed to the right, and the magnetization M15 of the ferromagnetic layer 15 is directed to the left. It has become.
Thereby, the magnetic fluxes leaking from the ferromagnetic layers 13 and 15 of the magnetization fixed layer 31 cancel each other.

  A base layer 11 is formed under the antiferromagnetic layer 12, and a cap layer 19 is formed as the uppermost layer of the memory element 3.

The material of the memory layer 17 is not particularly limited, and an alloy material composed of one or more of iron, nickel, and cobalt can be used. Furthermore, transition metal elements such as Nb and Zr, and light elements such as B can also be contained. In addition, the storage layer 17 may be configured by directly stacking a plurality of films made of different materials, such as a CoFe / NiFe / CoFe stacked film, without using a nonmagnetic layer.
In particular, when the storage layer 17 is a CoFeB layer, the saturation magnetization amount can be reduced and the resistance change rate can be increased. Therefore, the storage layer is preferably a CoFeB layer. More desirably, the content of boron B in CoFeB is 15 to 30%, and the composition ratio of Co and Fe is Co: Fe = 9: 1 to 5: 5.

As the material of the ferromagnetic layers 13 and 15 of the magnetization fixed layer 31, an alloy material composed of one or more of iron, nickel, and cobalt, for example, a CoFe alloy can be used. Furthermore, transition metal elements such as Nb and Zr, and light elements such as B can also be contained.
For example, amorphous (amorphous) CoFeB in which 20 to 30 atomic% of boron B is added to a CoFe alloy can be used.

In particular, by using a CoFeB layer for the ferromagnetic layer 15 in contact with the insulating layer 16 serving as a tunnel barrier of the magnetization fixed layer 31, the spin polarizability can be increased and the spin injection efficiency can be improved. Thereby, the current for reversing the direction of the magnetization M1 of the storage layer 17 can be further reduced.
In particular, when the Fe content of the CoFeB layer is 20 atomic% or more and the B content is 10 to 30%, the rate of resistance change can be increased and the necessary heat resistance can be ensured.

  However, it is not desirable to use a CoFeB layer having a boron B content of 15% or more for the ferromagnetic layer 13 in contact with the antiferromagnetic layer 12, and it is desirable to use a CoFe layer.

  In addition, it is desirable to use a CoFe layer rather than a CoFeB layer for the ferromagnetic layer 13 below the nonmagnetic layer 14 that constitutes the laminated ferrimagnetic pinned layer 31.

  Therefore, for example, the ferromagnetic layer 15 is formed of a CoFeB / CoFe laminated film in which the magnetic layer on the side in contact with the insulating layer 16 serving as a tunnel barrier is a CoFeB layer and the magnetic layer on the nonmagnetic layer 14 side is a CoFe layer. May be configured.

As the material of the nonmagnetic layer 14 constituting the laminated ferrimagnetic pinned layer 31, ruthenium, copper, chromium, gold, silver or the like can be used. Although the film thickness of the nonmagnetic layer 14 varies depending on the material, it is preferably used in the range of approximately 0.4 nm to 2.5 nm.
As a material of the antiferromagnetic layer 12, an alloy of a metal element such as iron, nickel, platinum, iridium and rhodium and manganese, an oxide of cobalt or nickel, or the like can be used.

  In the present embodiment, in particular, the oxide layer 18 is provided between the memory layer 17 and the cap layer (protective layer) 19 of the memory element 3.

  As a material of the oxide layer 18, for example, aluminum oxide (Al—Ox), magnesium oxide (MgO), or other oxides can be used.

  Since the oxide layer 18 is provided between the memory layer 17 and the cap layer (protective layer) 19, the element between the memory layer 17 and the cap layer (protective layer) 19 due to heat is added. Diffusion can be suppressed by the oxide layer 18.

  The memory element 3 of the present embodiment is manufactured by continuously forming the base layer 11 to the cap layer 19 in a vacuum apparatus and then forming the pattern of the memory element 3 by processing such as etching. Can do.

According to the above-described embodiment, since the oxide layer 18 is provided between the storage layer 17 and the cap layer (protective layer) 19 of the storage element 3, the storage layer is formed by applying heat. Diffusion of elements between 17 and the cap layer (protective layer) 19 can be suppressed by the oxide layer 18.
Accordingly, deterioration of characteristics due to diffusion of the above-described element when heat is applied to the storage element 3 can be suppressed, and thus it is possible to stably record and read information in the memory.
Therefore, a memory having heat resistance and high reliability can be realized.

  In particular, when a layer requiring a relatively high heat treatment temperature, such as MgO, is used for the insulating layer 16 of the memory element 3, the resistance change rate is further increased by the heat treatment, and the magnetic characteristics are deteriorated. Can be suppressed.

Next, as another embodiment of the present invention, a cross-sectional view of a memory element constituting a memory is shown in FIG.
The storage element 30 has a configuration in which the layers 12 to 18 between the base layer 11 and the cap layer 19 are stacked upside down with respect to the configuration of the storage element 3 of the previous embodiment shown in FIG. It has become.
That is, the oxide layer 18 is provided between the base layer 11 and the memory layer 17.
Other configurations are the same as those of the memory element 3 shown in FIG.

Further, a memory having a structure similar to that of the memory illustrated in FIG. 1 can be formed using the memory element 30 of this embodiment.
That is, the memory element 30 is arranged near the intersection of two types of address wirings to form a memory, and a current in the vertical direction (stacking direction) is passed through the memory element 30 through the two types of address wirings, and the memory layer is formed by spin injection. The information can be recorded in the memory element 30 by reversing the direction of magnetization of 17.

According to the present embodiment described above, since the oxide layer 18 is provided between the base layer 11 and the memory layer 17 of the memory element 30, the base layer 11 and the memory layer 17 are caused by the application of heat. The oxide layer 18 can suppress the diffusion of elements between the two.
As in the previous embodiment, this makes it possible to suppress deterioration in characteristics due to the diffusion of the above-described elements when heat is applied to the memory element 30, so that information recording and reading can be stably performed in the memory. Can be performed.
Therefore, a memory having heat resistance and high reliability can be realized.

  In particular, when a layer that requires a relatively high heat treatment temperature, such as MgO, is used for the insulating layer 16 of the memory element 30, the resistance change rate is further increased by the heat treatment and the magnetic characteristics are deteriorated. Can be suppressed.

  In each of the above-described embodiments, the description has been made by applying the present invention to a memory that records information by reversing the magnetization direction of the storage layer by spin injection. However, the storage element of each embodiment 3 and 30 can also be used in a memory that records information by reversing the direction of magnetization of the storage layer by means of a current magnetic field. In this case, the heat resistance of the storage element can be similarly improved. Is obtained.

(Example)
Here, in the structure of the memory element of the present invention, the material and film thickness of each layer were specifically selected, and the characteristics were examined.
Actually, as shown in FIGS. 1 and 5, the memory includes a semiconductor circuit for switching in addition to the memory element. Here, for the purpose of examining the magnetoresistance characteristics of the memory layer, the memory is stored. The study was performed using a wafer on which only elements were formed.

(Membrane structure 1: Sample 1)
First, a 300 nm thick thermal oxide film is formed on a 0.575 mm thick silicon substrate, and a Ta (3 nm) / Al (60 nm) laminated film is previously formed thereon as a lower electrode layer. The memory element 3 having the configuration shown in FIG. 2 was formed above.
Specifically, in the memory element 3 having the configuration shown in FIG. 2, the underlayer 11 is a Ta film having a thickness of 3 nm, the antiferromagnetic layer 12 is a PtMn film having a thickness of 30 nm, and the ferromagnetic layer constituting the magnetization fixed layer 31. The layer 13 is a Co ₉₀ Fe ₁₀ film having a film thickness of 2 nm (subscript is atomic%), the nonmagnetic layer 14 constituting the magnetization fixed layer 31 having a laminated ferri structure is the Ru film having a film thickness of 0.8 nm, and the magnetization fixed layer 31 is The ferromagnetic layer 15 to be formed is a CoFeB film having a thickness of 2 nm, the insulating layer 16 to be a tunnel insulating layer is an aluminum oxide film obtained by oxidizing an Al film having a thickness of 0.8 nm, and the storage layer 17 is a CoFeB film having a thickness of 3 nm. Each layer was formed by selecting the physical layer 18 as an aluminum oxide film obtained by oxidizing a 0.6 nm thick Al film and the cap layer 19 as a 5 nm thick Ta film.
That is, the memory element 3 was manufactured with the material and film thickness of each layer as the following configuration (film configuration 1).
Membrane configuration 1:
Ta (3nm) / PtMn (30nm) / Co90Fe10 (2nm) / Ru (0.8nm) / CoFeB (2nm) / Al (0.8nm) -Ox / CoFeB (3nm) / Al (0.6nm) -Ox / Ta (5nm )
In the above film configuration, the composition of PtMn that is not shown in the alloy composition was Pt ₅₀ Mn ₅₀ (atomic%).
Each layer other than the insulating layer 16 and the oxide layer 18 made of an aluminum oxide film was formed using a DC magnetron sputtering method.
As for the insulating layer 16 and the oxide layer 18 made of an aluminum oxide (Al—O _x ) film, a metal Al film was first deposited with a predetermined thickness by a DC sputtering method, and then the metal Al layer was oxidized.
The method for oxidizing the metal Al layer employs a plasma oxidation method using oxygen plasma, the pressure is 1 mTorr, the power is 400 W, the insulating layer 16 is subjected to plasma oxidation for 10 seconds, and the oxide layer 18 is subjected to plasma oxidation for 5 seconds. It was.
After that, it was evacuated again to a high vacuum of 1 × 10 ⁻⁷ to 1 × 10 ⁻⁸ Torr, and the next layer was formed.
Further, after each layer of the memory element 3 is formed, heat treatment is performed at 10 kOe · 300 ° C. and 380 ° C. for 2 hours in a heat treatment furnace in a magnetic field, ordering heat treatment and high-temperature durability heat treatment of the PtMn film of the antiferromagnetic layer 12. Went.

  Next, after masking the word line portion by photolithography, selective etching was performed by Ar plasma on the laminated film other than the word line to form the word line (lower electrode). At this time, except for the word line portion, the substrate was etched to a depth of 5 nm.

  Thereafter, a mask of the pattern of the memory element 3 was formed by an electron beam drawing apparatus, and selective etching was performed on the laminated film to form the memory element 3. Except for the memory element 3 portion, etching was performed up to the Al layer of the lower electrode layer.

As the size of the memory element is reduced, Δ = KuV / kT (Ku is the anisotropic energy, V is the volume of the magnetic material, k is the Boltzmann constant, and T is the temperature) becomes too small. Due to the problem of the thermal fluctuation resistance of the magnetic material, the magnetization direction becomes unstable and the magnetization direction holding characteristic is insufficient. On the other hand, if the size of the memory element is made too large, the above Δ becomes too large, so the spin torque necessary for magnetization reversal becomes large, a larger current density is required, and the area is large. A larger current needs to flow through the memory element.
Therefore, the pattern of the memory element was an elliptical shape having a short axis of 70 nm and a long axis of 170 nm.
The voltage at which the tunnel insulating layer breaks depends on the material and the forming conditions, and depends on the size of the memory element to be measured. However, under the insulating layer forming conditions in the range where the experiment was conducted, the short axis is about 70 nm × the long axis. It was in the range of about 1.0 to 1.2 V for an elliptical storage element of 170 nm.

Next, the portions other than the memory element 3 portion were insulated by sputtering of Al ₂ O ₃ having a thickness of about 100 nm.
Thereafter, a contact on the upper surface of the memory element 3 was formed by lift-off.
Next, an upper electrode layer having a sufficiently low resistance of Cr (20 nm) / Cu (100 nm) / Au (100 nm) is formed, and a bit line and a measurement pad portion to be the upper electrode are formed using photolithography. Thus, a sample of the memory element was manufactured and used as Sample 1.

(Membrane structure 2: Sample 2)
An insulating layer 16 serving as a tunnel barrier layer is formed of a 1.6 nm-thickness MgO (magnesium oxide) film, and the other structure is the same as that of the film structure 1, and the memory element 3 is manufactured as a sample 2 sample. . The MgO film was formed by directly depositing an oxide by RF sputtering using an MgO target.
That is, a memory element was manufactured by setting the material and film thickness of each layer to the following configuration (film configuration 2).
Membrane configuration 2:
Ta (3nm) / PtMn (30nm) / Co90Fe10 (2nm) / Ru (0.8nm) / CoFeB (2nm) / MgO (1.6nm) / CoFeB (3nm) / Al (0.6nm) -Ox / Ta (5nm)

(Membrane structure 3: Sample 3)
The oxide layer 18 was formed of a 0.8 nm-thickness MgO film, and the other configuration was the same as the film configuration 2 to fabricate the memory element 3 as a sample 3 sample. The MgO film was formed by directly depositing an oxide by RF sputtering using an MgO target.
That is, a memory element was manufactured with the material and film thickness of each layer as the following configuration (film configuration 3).
Membrane configuration 3:
Ta (3nm) / PtMn (30nm) / Co90Fe10 (2nm) / Ru (0.8nm) / CoFeB (2nm) / MgO (1.6nm) / CoFeB (3nm) / MgO (0.8nm) / Ta (5nm)

(Membrane structure 4: Sample 4)
The ferromagnetic layer 13 on the antiferromagnetic layer 12 side of the magnetization fixed layer 31 is formed of a Co film having a film thickness of 2.5 nm, and the other configuration is the same as that of the film configuration 1 to fabricate the memory element 3, and sample 4 It was set as the sample of this.
That is, a memory element was fabricated with the material and film thickness of each layer as the following configuration (film configuration 4).
Membrane configuration 4:
Ta (3nm) / PtMn (30nm) / Co (2.5nm) / Ru (0.8nm) / CoFeB (2nm) / Al (0.8nm) -Ox / CoFeB (3nm) / Al (0.6nm) -Ox / Ta ( 5nm)

(Membrane structure 5: Sample 5)
Instead of producing the memory element 3 shown in FIG. 2, the memory element 30 shown in FIG. 3 was produced.
Specifically, in the memory element 30 shown in FIG. 3, the base layer 11 is a Ta film having a thickness of 3 nm, the oxide layer 18 is an aluminum oxide film obtained by oxidizing an Al film having a thickness of 0.6 nm, and the memory layer 17 is formed. A CoFeB film with a thickness of 3 nm, an aluminum oxide film obtained by oxidizing an Al film with a thickness of 0.8 nm as an insulating layer 16 serving as a tunnel insulating layer, and a CoFeB film with a thickness of 2 nm as a ferromagnetic layer 15 constituting the magnetization fixed layer 31 A laminated film with a Co ₉₀ Fe ₁₀ film (subscript is atomic%) with a thickness of 1 nm, a nonmagnetic layer 14 constituting a magnetization fixed layer 31 with a laminated ferri structure, a Ru film with a thickness of 0.8 nm, and a magnetization fixed layer 31 The Co ₉₀ Fe ₁₀ film having a film thickness of 2.5 nm, the PtMn film having a film thickness of 30 nm and the cap layer 19 being a Ta film having a film thickness of 5 nm are selected. Formed. The oxidation conditions of the oxide layer 18 and the insulating layer 16 were the same as the oxidation conditions of the oxide layer 18 and the insulating layer 16 of Sample 1, respectively.
That is, the memory element 30 was manufactured by setting the material and film thickness of each layer to the following configuration (film configuration 5).
Membrane configuration 5:
Ta (3nm) / Al (0.6nm) -Ox / CoFeB (3nm) / Al (0.8nm) -Ox / CoFeB (2nm) / CoFe10 (1nm) / Ru (0.8nm) / Co90Fe10 (2.5nm) / PtMn ( 30nm) / Ta (5nm)

(Membrane structure 6: Sample 6)
A method of reducing the thickness of the metal Al layer forming the insulating layer 16 and the oxide layer 18 serving as a tunnel barrier slightly to 0.5 nm, and oxidizing the metal Al layer of the insulating layer 16 and the oxide layer 18 As described above, a method of filling the chamber with oxygen up to a predetermined pressure and leaving it for a predetermined time was employed, and the other configuration was the same as the film configuration 1, and the memory element 3 was manufactured and used as the sample 6.
That is, a memory element was manufactured with the material and film thickness of each layer as the following configuration (film configuration 6).
Membrane configuration 6:
Ta (3nm) / PtMn (30nm) / Co90Fe10 (2nm) / Ru (0.8nm) / CoFeB (2nm) / Al (0.5nm) -Ox / CoFeB (3nm) / Al (0.5nm) -Ox / Ta (5nm )
The insulating layer 16 was oxidized for 600 seconds with oxygen gas at a pressure of 10 Torr.
The oxide layer 18 was oxidized for 600 seconds with oxygen gas at a pressure of 1 Torr.

(Comparative example)
Samples 1 to 6 described above are the configurations of the present invention, that is, the samples of the examples. On the other hand, as comparative examples, samples of memory elements having configurations other than the configurations of the present invention were produced.

(Membrane structure 7: Sample 7)
The insulating layer 16 is formed in the same manner as the film configuration 1, the storage layer 17 is formed of a 2 nm-thickness Co ₉₀ Fe ₁₀ film (subscript is atomic%), and the cap layer 19 is formed thereon. A memory element was produced. That is, there is no oxide layer 18 in FIG. 2, and a cap layer is formed directly on the memory layer.
That is, a memory element was manufactured with the material and film thickness of each layer as the following configuration (film configuration 7).
Membrane configuration 7:
Ta (3nm) / PtMn (30nm) / Co90Fe10 (2nm) / Ru (0.8nm) / CoFeB (2nm) / Al (0.8nm) -Ox / Co90Fe10 (2nm) / Ta (5nm)
This was used as a sample of the memory element of Sample 7.

(Membrane structure 8: Sample 8)
Up to the memory layer 17 was formed in the same manner as in the film configuration 1, and a memory element was manufactured as a configuration in which the cap layer 19 was formed thereon. That is, there is no oxide layer 18 in FIG. 2, and a cap layer is formed directly on the memory layer.
That is, a memory element was manufactured by setting the material and film thickness of each layer to the following configuration (film configuration 8).
Membrane configuration 8:
Ta (3nm) / PtMn (30nm) / Co90Fe10 (2nm) / Ru (0.8nm) / CoFeB (2nm) / Al (0.8nm) -Ox / CoFeB (3nm) / Ta (5nm)
This was used as a sample of the memory element of Sample 8.

(Membrane structure 9: Sample 9)
The memory element is configured in the same manner as in the film configuration 1 except that the composition of the CoFe film of the ferromagnetic layer 13 on the antiferromagnetic layer 12 side of the magnetization fixed layer 31 is Co ₇₅ Fe ₂₅ (subscript is atomic%). Produced. That is, the Fe content of the ferromagnetic layer 13 on the antiferromagnetic layer 12 side is greater than that of the sample 1.
That is, a memory element was manufactured with the material and film thickness of each layer as the following configuration (film configuration 9).
Membrane configuration 9:
Ta (3nm) / PtMn (30nm) / Co75Fe25 (2nm) / Ru (0.8nm) / CoFeB (2nm) / Al (0.8nm) -Ox / CoFeB (3nm) / Al (0.6nm) -Ox / Ta (5nm )
This was used as a sample of the memory element of Sample 9.

(Membrane structure 10: Sample 10)
A memory element was fabricated with the same configuration as the film configuration 1 except that the ferromagnetic layer 15 on the insulating layer 16 side of the magnetization fixed layer 31 was a Co ₉₀ Fe ₁₀ film.
That is, a memory element was manufactured with the material and film thickness of each layer as the following configuration (film configuration 10).
Membrane configuration 10:
Ta (3nm) / PtMn (30nm) / Co90Fe10 (2nm) / Ru (0.8nm) / Co90Fe10 (2nm) / Al (0.8nm) -Ox / CoFeB (3nm) / Al (0.6nm) -Ox / Ta (5nm )
This was used as a sample of the memory element of Sample 10.

(Membrane structure 11: Sample 11)
Up to the memory layer 17 was formed in the same manner as in the film configuration 6, and a memory element was manufactured as a configuration in which the cap layer 19 was formed thereon. That is, there is no oxide layer 18 in FIG. 2, and a cap layer is formed directly on the memory layer.
That is, a memory element was manufactured by setting the material and film thickness of each layer to the following configuration (film configuration 11).
Membrane configuration 11:
Ta (3nm) / PtMn (30nm) / Co90Fe10 (2nm) / Ru (0.8nm) / CoFeB (2nm) / Al (0.5nm) -Ox / CoFeB (3nm) / Ta (5nm)
This was used as a sample of the memory element of Sample 11.

The characteristics of the memory elements of the above samples were evaluated as follows.
Prior to the measurement, a magnetic field was externally applied to the storage element.

(Measurement of sheet resistance)
The bias voltage applied to the word line terminal and the bit line terminal was adjusted to 10 mV, the magnetization direction of the storage layer was inverted by an external magnetic field, and the sheet resistance value of the entire storage element was measured.

(Measurement of resistance change rate after heat treatment)
In addition, a sample of a memory element that was heat-treated at 300 ° C. for 2 hours and a sample of a memory element that was heat-treated at 380 ° C. for 2 hours were manufactured.
For each sample, the magnetization direction of the memory layer was reversed by an external magnetic field, and the relationship between the resistance and the external magnetic field was examined.
Then, the resistance change rate is calculated from the resistance value (high resistance) in the high resistance state and the resistance value (low resistance) in the low resistance state using the formula (high resistance-low resistance) / low resistance. did.

  As a measurement result, Table 1 shows the area resistance value of the memory element in the low resistance state and the resistance change rate of the memory element after the heat treatment at 300 ° C. and 380 ° C. for each sample. Each measured value in Table 1 is an average value of values obtained by measuring 200 memory elements manufactured on each sample wafer.

  Hereinafter, based on the result of Table 1, the effect by setting it as the memory | storage element of this invention is considered.

First, comparing sample 1 as an example of the present invention with samples 7 and 8 as comparative examples, in sample 1, an oxide layer 18 is provided between a memory layer 17 and a cap layer (protective layer) 19. In contrast, in sample 7 and sample 8, the cap layer is formed directly on the memory layer without providing the oxide layer.
In Sample 1, there is almost no difference in resistance change rate after the heat treatment at 300 ° C. for 2 hours and the heat treatment at 380 ° C. for 2 hours.
On the other hand, in the sample 7 and the sample 8 of the comparative example, the resistance change rate greatly decreases after the heat treatment at 380 ° C. as compared with the heat treatment at 300 ° C.
Further, as a material for the memory layer, sample 7 uses CoFe, and sample 8 uses CoFeB. Sample 8 has a greater decrease in resistance change rate.
That is, when an oxide layer is not provided between the protective layer and the storage layer and a CoFeB material is used for the storage layer, the degree of deterioration at high temperatures is significant.

  Here, the sample 8 was subjected to analysis in the depth direction with the AES (Auger Electron Spectrometer) of the laminated film of each memory element after the heat treatment at 300 ° C. and after the heat treatment at 380 ° C. From this analysis result, boron B in the memory layer diffuses into the protective layer, and Ta used in the protective layer diffuses into the memory layer, and the interface becomes unclear. It can be estimated that the rate of change is greatly degraded.

Therefore, the oxide layer provided between the memory layer and the cap layer (protective layer) is considered to function as a layer that suppresses diffusion.
Further, there is almost no difference in the area resistance value of the memory element between the sample 1 provided with the oxide layer and the sample 7 not provided with the oxide layer.
Therefore, it is considered that the provision of an oxide layer for preventing diffusion hardly causes a parasitic resistance to adversely affect the resistance value of the memory element.

Next, the results of Sample 2 of the example will be described.
In Sample 2, an MgO film is used for the insulating layer 16 serving as a tunnel barrier.
From the measurement results of Sample 2 in Table 1, even when an MgO film is used for the insulating layer 16 serving as a tunnel barrier, the oxide layer 18 is provided between the memory layer 17 and the cap layer 19, so that the memory layer 17 It can be seen that the deterioration of the magnetic properties of the used CoFeB film can be prevented and that the resistance change rate after the heat treatment at 380 ° C. is higher than the resistance change rate after the heat treatment at 300 ° C. The reason why the rate of change in resistance after the heat treatment at 380 ° C. is improved is considered to be because the properties as a tunnel barrier of the MgO film are improved by the high-temperature heat treatment.
Therefore, the structure of the present invention in which an oxide layer for preventing diffusion is effective for a structure that requires a particularly high heat treatment temperature, and is suitable for a structure that uses, for example, an MgO film as an insulating layer of a tunnel barrier. .

Furthermore, in the sample 3 of the example, the MgO film is used not only for the insulating layer 16 but also for the diffusion preventing oxide layer 18.
In the case of Sample 3 as well, as in Sample 2 in which an AlOx film is used for the diffusion preventing oxide layer 18, the deterioration of the resistance change rate at the high temperature heat treatment is suppressed, and the resistance change rate after the high temperature heat treatment is reduced. It has improved.

  Here, with respect to Sample 1 and Sample 4 of the Example and Sample 9 and Sample 10 of the Comparative Example, the magnitude of the magnetization direction fixed magnetic field of the sample after heat treatment at 300 ° C. and 380 ° C. shown in Table 1 respectively. Was measured. The measurement results are shown in Table 2.

Next, Sample 1 and Sample 4 of the example are compared with Sample 9 of the comparative example.
In the ferromagnetic layer 13 on the antiferromagnetic layer 12 side of the magnetization fixed layer 31, the sample 4 uses a Co film, the sample 1 uses a CoFe film having a composition of Co 90 atomic% Fe 10 atomic%, and the sample 9 includes A CoFe film having a composition of Co 75 atomic% Fe 25 atomic% is used.
That is, the Fe content of the ferromagnetic layer 13 increases in the order of sample 4 <sample 1 <sample 9.

As shown in the results of Table 2, in these three samples, as the Fe content of the ferromagnetic layer 13 of the magnetization fixed layer 31 increases, the magnitude of the fixed magnetic field after the high-temperature heat treatment decreases, and the magnetization It can be seen that the stability of the fixed layer 31 deteriorates.
Therefore, the composition of the Co—Fe material used for the ferromagnetic layer 13 on the antiferromagnetic layer 12 side of the magnetization fixed layer 31 is preferably 20 atomic% or less, more preferably 10 atomic% or less.

Next, sample 1 of the example and sample 10 of the comparative example are compared.
In the sample 10, a CoFe film having a composition of Co 90 atomic% Fe 10 atomic% is used for the ferromagnetic layer 15 on the side of the insulating layer 16 serving as a tunnel barrier and the storage layer 17 of the magnetization fixed layer 31. The ferromagnetic layer 15 is also referred to as a reference layer because it serves as a reference for the magnetization direction of the storage layer 17.
As shown in the results of Table 2, the magnetization fixed magnetic field is smaller than that of the sample 1 using the CoFeB film for the ferromagnetic layer (reference layer) 15 at both the heat treatment temperatures of 300 ° C. and 380 ° C. Therefore, the stability of the magnetization fixed layer 31 is inferior.
Accordingly, CoFeB containing B is more preferable than CoFe as the magnetic material used for the insulating layer 16 and the ferromagnetic layer (reference layer) 15 on the storage layer 17 side of the fixed magnetization layer 31.
The composition ratio of the CoFeB film used for the ferromagnetic layer (reference layer) 15 is such that the content of Fe is 20% or more from the viewpoint of increasing the resistance change rate and obtaining necessary heat resistance. The content of is desirably 10 to 30%.

Next, sample 1 of the example and sample 5 of the example are compared.
In the sample 1 of the embodiment, the antiferromagnetic layer 12 and the magnetization fixed layer 31 are arranged on the substrate side. However, in the sample 5, the memory layer 17 is arranged on the substrate side, which is antiferromagnetic as the sample 1. Each layer of the magnetic layer 12 to the storage layer 17 has an upside down structure.
Even in the case of such an upside down structure, by providing the oxide layer 18 between the base layer 11 and the memory layer 17 as in Sample 5, as shown in the results of Table 1, Sample 1 It can be seen that the same effect of improving heat resistance can be obtained.
That is, it can be seen that the effect of the present invention can be obtained even in a so-called Top pin type configuration in which the magnetization fixed layer 31 is disposed above the storage layer 17 as in the sample 5.

Next, sample 6 of the example will be considered.
In this sample 6, the resistance of the insulating layer 16 serving as a tunnel barrier and the oxide layer 18 for preventing diffusion is reduced to a region where the magnetization direction of the memory layer 17 can be reversed by spin injection. is there.
From the results of Sample 6 shown in Table 1, it can be seen that even with a low-resistance memory element of 15 Ωμm ² , the improvement in heat resistance, which is the effect of the present invention, can be seen.

  In such a structure having a low resistance tunnel barrier, the diffusion preventing oxide layer 18 between the memory layer 17 and the protective layer 19 has a lower resistance than the tunnel barrier insulating layer 16. It is desirable to form.

Next, the sample 6 of the example and the sample 11 of the comparative example are compared.
In the sample 6, the oxide layer 18 is provided between the memory layer 17 and the cap layer (protective layer) 19, whereas in the sample 11, the cap layer is formed directly on the memory layer without providing the oxide layer. Is forming. Other configurations are the same.

With respect to Sample 6 and Sample 11, the magnetization reversal current was measured for each of the samples after heat treatment at 300 ° C. for 2 hours.
That is, the measurement temperature was set to room temperature 25 ° C., the amount of current flowing through the memory element was changed, the resistance value of the memory element was measured, and a resistance-current curve was obtained from the measurement result. In addition, the measurement which obtains this resistance-current curve was performed about the electric current of both polarities (plus direction and minus direction).
Here, an example of the resistance-current curve of the sample 11 is shown in FIG.
As shown in FIG. 4, when a certain current or more is applied, the state changes from the high resistance state to the low resistance state or vice versa, and it can be confirmed that the magnetization is reversed.

From the obtained resistance-current curve, a current value at which the resistance value changes was obtained, and this was set as an inversion current value for reversing the direction of magnetization. The inversion current value was obtained for the bipolar current.
In the measurement of the reversal current, the threshold value at which the magnetization direction reverses causes an offset that varies depending on the external magnetic field. In order to eliminate this offset, (1) in the above-described measurement of the rate of change in resistance, the offset magnetic field of the RH loop is obtained in advance from the relationship between the resistance and the external magnetic field, and the inversion is performed while applying the offset magnetic field from the outside. Two methods are conceivable: measuring the current, and (2) measuring the dependence of the reversal current on the external magnetic field while changing the applied magnetic field from the outside. Here, the measurement was performed by employing the method (1).
Further, although it depends on the resistance value of the memory element, it is known that the tunnel insulating layer breaks down at a bias voltage of about 1.0 to 1.2 V. Therefore, the upper limit of the applied current is 0.8 V It was set as the current value which applied.
And the reversal current density was computed from the average value of the reversal current value (absolute value) of both polarity of + and-.

  Table 3 shows the measurement results of the inversion current value and the inversion current density of Sample 6 and Sample 11. Each measured value in Table 3 is an average value of values obtained by measuring 10 memory elements in a sample after heat treatment at 300 ° C. for 2 hours.

From the results of Table 3, it can be seen that magnetization reversal by spin injection is possible in both the sample 6 of the example and the sample 11 of the comparative example.
However, from the measurement results shown in Table 1, in the sample 11 of the comparative example, when the heat treatment temperature was increased to 380 ° C., the resistance change rate was greatly deteriorated, and compared with the sample 6 of the example, the heat resistance was higher. It turns out that the nature is inferior.

As described above, with the structure of the present invention, a memory element and a memory with little deterioration in characteristics can be realized even with a high-temperature heat treatment at 350 ° C. or higher required in a semiconductor process.
In particular, when a material requiring a relatively high heat treatment temperature, such as MgO, is used for the laminated film of the memory element, the resistance change rate can be further improved and the deterioration of the magnetic characteristics can be reduced.

  The present invention is not limited to the above-described embodiment, and various other configurations can be taken without departing from the gist of the present invention.

1 is a schematic configuration diagram (perspective view) of a memory according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the memory element in FIG. 1. It is sectional drawing of the memory element of other embodiment of this invention. 6 is a diagram showing current-resistance characteristics of a memory element of Sample 11. FIG. It is a schematic block diagram (perspective view) of a memory using magnetization reversal by spin injection. FIG. 6 is a cross-sectional view of the memory of FIG. 5. It is the perspective view which showed the structure of the conventional MRAM typically.

Explanation of symbols

  3,30 Memory element, 11 Underlayer, 12 Antiferromagnetic layer, 13,15 Ferromagnetic layer, 14 Nonmagnetic layer, 16 Insulating layer, 17 Memory layer, 18 Oxide layer, 19 Cap layer, 31 Magnetization fixed layer

Claims (10)

It has a storage layer that holds information according to the magnetization state of the magnetic material,
For the storage layer, a magnetization fixed layer is provided via an insulating layer serving as a tunnel barrier,
The memory element, wherein the memory layer is in contact with a base layer or an upper protective layer through an oxide layer.   The memory element according to claim 1, wherein the memory layer is made of CoFeB.   In the magnetization fixed layer, an antiferromagnetic layer is provided on the side opposite to the storage layer, the ferromagnetic layer in contact with the antiferromagnetic layer is a CoFe layer, and the Fe content of the CoFe layer is 10 atoms. The memory element according to claim 1, wherein the storage element is equal to or less than%.   The memory element according to claim 1, wherein in the magnetization fixed layer, the ferromagnetic layer in contact with the insulating layer is a CoFeB layer.   5. The memory element according to claim 4, wherein the CoFeB layer of the ferromagnetic layer in contact with the insulating layer has an Fe content of 20 atomic% or more and a B content of 10 to 30 atomic%.   The memory element according to claim 1, wherein when a current is passed in a stacking direction, a magnetization direction of the memory layer is changed, and information is recorded on the memory layer.   The memory element according to claim 1, wherein the magnetization fixed layer has a structure in which a plurality of ferromagnetic layers are stacked with a nonmagnetic layer interposed therebetween.   The magnetization fixed layer has a structure in which a plurality of ferromagnetic layers are laminated via a nonmagnetic layer, and the ferromagnetic layer in contact with the nonmagnetic layer is a CoFe layer. Item 2. The memory element according to Item 1. A storage element having a storage layer for retaining information by the magnetization state of the magnetic material;
Two types of wiring intersecting each other,
The storage element includes a storage layer that retains information according to the magnetization state of a magnetic material, and a fixed magnetization layer is provided to the storage layer via an insulating layer that serves as a tunnel barrier. The structure is in contact with the underlying layer or the upper protective layer through the physical layer,
A memory characterized in that the storage element is arranged near an intersection of the two types of wiring and between the two types of wiring. The storage element has a configuration in which the direction of magnetization of the storage layer is changed by passing a current in the stacking direction, and information is recorded on the storage layer. The memory according to claim 9, wherein a current in the stacking direction flows in a memory element.

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