JP4951858B2 - memory - Google Patents

Description

The present invention includes a storage layer for storing a magnetization state of a ferromagnetic layer as information consists of a magnetization fixed layer in which the direction of magnetization is fixed, a storage element for changing the direction of the magnetization of the storage layer by applying current The present invention relates to a provided memory 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

  Conventionally, an AlOx layer produced mainly by oxidizing aluminum has been widely used as a material for an insulating layer constituting a tunnel barrier of a magnetic tunnel junction element (MTJ element) constituting an MRAM.

  On the other hand, in recent years, it has been reported that a higher resistance change rate can be obtained when MgO is used instead of AlOx for the tunnel barrier insulating layer (Japanese Journal of Applied Physics, Part 2: Letters-April 15, 2004-Volume 43, Issue 4B, pp. L588-L590). In this report, a Fe ferromagnetic electrode whose crystal plane is oriented in the (100) direction and MgO are epitaxially grown in the (100) direction, and a resistance change rate of 88% is obtained at room temperature. .

  On the other hand, the larger the resistance change rate of the memory element used in the MRAM, the smaller the read error when reading recorded information. Therefore, it is desirable to further increase the resistance change rate of the memory element.

In addition, tunnel barriers using MgO, AlOx, etc. generally depend on the composition of oxides and the formation conditions, but are generally used in the range of 10 to ¹ kΩμm ² , which is a range used as a memory element. And dielectric breakdown at a bias voltage of 1.0 to 1.5V.
Therefore, if the current (reversal current) required for magnetization reversal by spin injection is too large, the tunnel barrier will break down at a bias voltage lower than the bias voltage at which magnetization reversal by spin injection occurs.
Therefore, it is necessary to improve the spin injection efficiency of the memory element and reduce the inversion current so that the tunnel barrier does not break down.

The magnitude of the value of KuV / kBT (Ku is the anisotropy energy, k is the Boltzmann constant, and T is the temperature) determined from the volume V of the magnetic material of the storage layer and the magnetic anisotropy of the storage layer. Is smaller, the magnetization of the storage layer is more easily reversed, so that the reversal current is smaller.
However, when the value of KuV / kBT is too small, it is difficult to define the direction of magnetization due to thermal disturbance due to the influence of thermal fluctuation.
In other words, the smaller the size of the memory element, the smaller the volume V of the magnetic material in the memory layer, so that the reversal current can be reduced. However, if the size of the memory element becomes too small, recording on the memory element is caused by the influence of thermal fluctuation. It becomes difficult to hold.
Further, as the memory element is made smaller, patterning of the memory element by lithography becomes more difficult.

  Therefore, there is a limit to reducing the size of the memory element in order to reduce the inversion current. From this viewpoint, it is necessary to improve the spin injection efficiency of the memory element.

In order to solve the above problem, the present invention provides a memory having a memory element that can reduce the current value required for writing by improving the spin injection efficiency.

The memory of the present invention includes a storage element having a storage layer that holds information according to the magnetization state of a magnetic material, and two kinds of wirings that intersect each other, and the storage element is magnetized via an intermediate layer with respect to the storage layer. A pinned layer is provided, the intermediate layer is made of magnesium oxide, and the ferromagnetic layer in contact with the lower side of the intermediate layer is made of a magnetic material containing CoFeB as a main component. The direction is changed and information is recorded on the storage layer. In the storage element, an antiferromagnetic layer is provided on the opposite side of the storage layer of the magnetization fixed layer. The ferromagnetic layer in contact with the antiferromagnetic layer is a CoFe layer, and the Fe content of the CoFe layer is less than 20 atomic%, and a memory element is disposed near the intersection of two types of wiring and between the two types of wiring. Through two types of wiring A current in the stacking direction flows through the memory element.

According to the configuration of the memory of the present invention described above, the storage element has a storage layer that holds information according to the magnetization state of the magnetic substance, and the magnetization fixed layer is provided to the storage layer via the intermediate layer. By flowing a current in the direction, the magnetization direction of the storage layer changes and information is recorded on the storage layer, so that information can be recorded by spin injection by flowing a current in the stacking direction. .
As the intermediate layer is made of magnesium oxide, a tunnel insulating layer is formed of magnesium oxide as the intermediate layer, and the information recorded in the storage layer (magnetization state of the storage layer) is recorded by the tunnel current flowing through the tunnel insulating layer. Can be read. In addition, the magnetoresistance change rate (MR ratio) can be increased by the tunnel insulating layer made of magnesium oxide.

Further, since the ferromagnetic layer in contact with the lower side of the intermediate layer is made of a magnetic material mainly composed of CoFeB, CoFeB has a higher spin polarizability than a crystalline magnetic material such as CoFe. Efficiency can be increased. This makes it possible to reduce the amount of current required to reverse the magnetization direction of the storage layer.
Moreover, it is considered that the intermediate layer made of magnesium oxide (MgO) is formed on the ferromagnetic layer made of a magnetic material mainly composed of CoFeB, so that the ferromagnetic layer and the intermediate layer are strongly crystallized. . This makes it possible to increase the magnetoresistance change rate (MR ratio) of the memory element as compared with the case where a crystalline magnetic material such as CoFe is used.

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 memory element is arranged near the intersection of two types of wiring and between the two types of wiring, and current in the stacking direction flows through the memory element through these two types of wiring. Information can be recorded by spin injection by passing a current in the stacking direction of the memory element through the wiring.
Further, the amount of current (reversal current, threshold current) necessary for reversing the magnetization direction of the memory layer of the memory element by spin injection can be reduced.
Furthermore, since the magnetoresistive change rate of the memory element is sufficiently large, it is easy to obtain high output by reading the information recorded in the memory layer of the memory element using the magnetoresistive change. Information can be read out.

Further, according to the memory configuration of the present invention, by the storage layer of the magnetization fixed layer has a configuration in which the antiferromagnetic layer is provided on the opposite side, the intensity of the magnetization fixed layer by the antiferromagnetic layer The magnetization direction of the magnetic layer is fixed.

According to the memory configuration of the present invention described above, in the magnetization fixed layer, the ferromagnetic layer in contact with the antiferromagnetic layer is a CoFe layer, and the Fe content of the CoFe layer is less than 20 atomic%. And
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.
Also, by making the Fe content of the CoFe layer less than 20 atomic%, the antiferromagnetic coupling with the antiferromagnetic layer can be made to have a sufficient magnetic field strength. As a result, the magnetoresistive change rate of the memory element can be made sufficiently large.

According to the present invention described above, the amount of current required for recording information can be reduced by improving the spin injection efficiency.
As a result, the power consumption of the entire memory can be reduced.
Therefore, it is possible to realize a memory with low power consumption that has not been conventionally available.

Further, according to the present invention, when the recorded information is read out, it is possible to obtain a high output and easily read out the information.
As a result, in a memory including a memory element, for example, a circuit for reducing power consumption at the time of reading or detecting an output by reducing a current flowing through the memory element when information is read Can be simplified, and read sensitivity can be improved.

Prior to the description of specific embodiments of the present invention, an outline of the present invention will be described.
In the present invention, information is recorded by reversing the magnetization direction of the storage layer of the storage element by the spin injection described above. The memory layer is made of a magnetic material such as a ferromagnetic layer, and holds information by the magnetization state (magnetization direction) of the magnetic material.

  When recording information by reversing the magnetization of the storage layer by spin injection, the efficiency of spin injection, that is, the efficiency of magnetization reversal by current, is generally expressed by the following equation 1 (Journal of Magnetism and Magnetic Materials Volume 159 , Issues 1-2, June 1996, Pages L1-L7).

  As can be seen from this equation, the higher the rate of resistance change and the higher the spin polarizability P, the higher the efficiency of magnetization reversal and the lower the write current.

  As a result of various studies in order to solve the above-described problems, when MgO is used as a material for an insulating layer (barrier layer) serving as a tunnel barrier, a ferromagnetic layer in contact with the MgO barrier layer. It was found that the magnetoresistance change rate (MR ratio) can be improved by using an amorphous magnetic material such as CoFeB as compared with the case of using crystal-oriented Fe reported in the above-mentioned literature.

Therefore, in the present invention, in the storage element having a configuration in which the magnetization fixed layer is provided via the intermediate layer with respect to the storage layer, the intermediate layer is configured by an insulating layer made of MgO (tunnel insulating layer serving as a tunnel barrier), The material of the ferromagnetic layer in contact with the lower side of the intermediate layer is a magnetic material mainly composed of CoFeB.
By configuring the intermediate layer with an insulating layer made of MgO (tunnel insulating layer serving as a tunnel barrier), the magnetoresistance change rate of the memory element can be increased.
Further, by using a magnetic material mainly composed of CoFeB as the material of the ferromagnetic layer in contact with the lower side of the intermediate layer (MgO layer), the magnetoresistance change rate of the memory element can be further increased, and the spin rate The injection efficiency can be increased.
Thereby, by increasing the magnetoresistance change rate of the memory element, it is possible to improve read characteristics and reduce read errors. In addition, it is possible to increase the efficiency of spin injection and reduce the amount of current required to reverse the magnetization direction of the storage layer.

  That is, the memory element according to the present invention basically has a base layer / antiferromagnetic layer / magnetization fixed layer / tunnel insulating layer (MgO layer) / memory layer / protective layer (cap layer) from the substrate side (lower layer side). ) Or a laminated film of an underlayer / memory layer / tunnel insulating layer (MgO layer) / magnetization pinned layer / protective layer (cap layer), and a tunnel insulating layer (MgO) The material of the ferromagnetic layer in contact with the lower side of the layer (the ferromagnetic layer in contact with the lower side of the tunnel insulating layer among the ferromagnetic layers constituting the fixed magnetization layer or the storage layer) is a magnetic material mainly composed of CoFeB And

The magnetization fixed layer has a configuration in which the magnetization direction of the ferromagnetic layer is fixed by using only the ferromagnetic layer or using antiferromagnetic coupling between the antiferromagnetic layer and the ferromagnetic layer.
The fixed magnetization layer may be formed of a single-layered ferromagnetic layer or a plurality of ferromagnetic layers, and may have a so-called laminated ferrimagnetic structure in which a plurality of ferromagnetic layers are laminated via a nonmagnetic layer.

In addition, as a material of each layer which comprises a memory element, the following materials are mentioned, for example.
As the material 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, it is preferable to use Co or a Co—Fe based ferromagnetic material and to make its Fe content 0 to 20%. If the Fe content exceeds 20%, it tends to deteriorate due to high-temperature heat treatment.

However, a CoFeB layer having a boron B content of 15% or more is not suitable for a ferromagnetic layer that is in contact with an antiferromagnetic layer (for example, a PtMn film) and whose magnetization direction is fixed. It is desirable to be. This is because when a CoFeB layer having a boron B content of 15% or more is used as a ferromagnetic layer in contact with the antiferromagnetic layer, a sufficient antiferromagnetic coupling magnetic field cannot be obtained. This is because it becomes impossible to stably fix the orientation of.
The composition of the CoFe layer of the ferromagnetic layer is preferably such that the content of iron Fe is less than 20 atomic%. This is because the antiferromagnetic coupling with the antiferromagnetic layer can be made sufficient magnetic field strength by making the content of iron Fe less than 20 atomic%.

  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 is formed such that a side in contact with an insulating layer serving as a tunnel barrier is a CoFeB layer and a side in contact with a nonmagnetic layer of a laminated ferrimagnetic structure is a CoFe layer. You can also

As a material of the ferromagnetic layer used for the memory layer, a ferromagnetic material mainly composed of Co, Fe, and Ni can be used.
Since the amount of saturation magnetization can be reduced, the rate of change in resistance is large, and excellent soft magnetic properties are obtained, it is desirable to use an amorphous magnetic material having a composition such as CoFeB for the storage layer, and more desirably, boron B The content is preferably 10 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.

  As described above, the tunnel insulating layer (barrier layer) made of MgO is formed using magnesium oxide (MgO) as the material of the intermediate layer.

When the magnetization reversal method using a current magnetic field is used, it is desirable that the sheet resistance value be in the range of 500 to ² kΩμm ^2. However, in order to perform magnetization reversal by spin injection, it is desirable to further reduce the sheet resistance value.
For example, in a memory element having a barrier layer made of AlOx, a current density of about 3 to 8 × 10 ⁶ (A / cm ² ) is required to enable magnetization reversal by spin injection.
Although depending on the reliability such as the pinhole density in the barrier layer, the magnetization reversal by spin injection is possible, and the dielectric breakdown voltage of the relatively low resistance barrier layer is about 1V.
Therefore, assuming that the area of the memory element is 0.06 × 0.167 μm = 0.01 μm ² , in order to obtain a current density of 3 to 8 × 10 ⁶ (A / cm ² ), respectively 33 It is necessary that the sheet resistance value is smaller than 3 to 12.5 (Ωμm ² ).
Note that the smaller the current density required for magnetization reversal, the larger the area resistance value of the memory element.
Accordingly, the sheet resistance 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.

On the other hand, when MgO is used as the material of the barrier layer, the efficiency of spin injection is improved and the current density is 0.5-4 × 10 ⁶ (A / cm ² ). Magnetization reversal is possible even when the sheet resistance value is higher than 30 Ωμm ² .
From the viewpoint of ensuring reliability, it is preferable that a margin exists between the dielectric breakdown voltage and the bias voltage for magnetization reversal. Therefore, even when MgO is used as the barrier layer material, 30 Ωμm ² The following is desirable.

In the memory element of the present invention, the material of the ferromagnetic layer in contact with the lower side of the barrier layer made of MgO is a magnetic material containing CoFeB as a main component.
That is, as a material of this ferromagnetic layer, it has CoFeB and Co, Fe, and B as main components, and further, for example, Ni which is a magnetic element, B, Si, Zr, Nb, Cu, Ta, etc. A nonmagnetic element added is used.
Accordingly, as described above, the efficiency of spin injection of the memory element can be increased, and the magnetoresistance change rate of the memory element can be increased.

More preferably, in the ferromagnetic layer in contact with the lower side of the barrier layer made of MgO, the composition of the ferromagnetic layer is such that the content of B (boron) is in the range of 15 to 30 atomic%.
By setting the content of B (boron) within the above range, the magnetoresistance change rate of the memory element can be sufficiently increased. In addition, deterioration of characteristics of the memory element when heat is applied to the memory element can be suppressed.

On the other hand, in the ferromagnetic layer in contact with the upper side of the barrier layer made of MgO, the range of materials can be widened as compared with the ferromagnetic layer in contact with the lower side of the barrier layer.
That is, the above-described ferromagnetic layer material constituting the magnetization fixed layer and the ferromagnetic layer material constituting the memory layer can be used.

  More preferably, in the ferromagnetic layer in contact with the upper side of the barrier layer made of MgO, in particular, one or more of Co, Fe, and Ni (magnetic element) and boron (B) are mainly used. It is made of a magnetic material as a component, and the boron (B) content is 15 to 30 atomic%. As described above, the ferromagnetic layer in contact with the upper side of the barrier layer is made of a material mainly composed of a magnetic element and boron, and the boron content is within the above range, thereby increasing the magnetoresistance change rate of the memory element. Can do.

  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 memory element 3 is provided with a magnetization fixed layer 19 in the lower layer with respect to the memory layer 17 in which the direction of the magnetization M1 is reversed by spin injection.
An antiferromagnetic layer 12 is provided under the magnetization fixed layer 19, and the magnetization direction of the magnetization fixed layer 19 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 19, and the tunnel magnetic junction element (MTJ) is formed by the storage layer 17, the insulating layer 16, and the magnetization fixed layer 19. Element).

The magnetization fixed layer 19 has a laminated ferrimagnetic structure.
Specifically, the magnetization fixed layer 19 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 fixed magnetization layer 19 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, so that they are opposite to each other. It has become.
Thereby, magnetic fluxes leaking from the ferromagnetic layers 13 and 15 of the magnetization fixed layer 19 cancel each other.
Of the two ferromagnetic layers 13 and 15 of the fixed magnetization layer 19, the ferromagnetic layer 15 on the storage layer 17 side has a direction of magnetization M 15 when reading information recorded in the storage layer 17. In addition, since it becomes a reference for the direction of the magnetization M1 of the storage layer 17, it is also called a reference layer.

  A base layer 11 is formed below the antiferromagnetic layer 12, and a cap layer 18 is formed on 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 a material of the ferromagnetic layers 13 and 15 of the magnetization fixed layer 19, 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 included.
For example, amorphous (amorphous) CoFeB in which 20 to 30 atomic% of boron B is added to a CoFe alloy can be used.
The materials of the ferromagnetic layers 13 and 15 of the fixed magnetization layer 19 are limited as described later in order to improve the characteristics of the memory element 3.

In the memory element 3 of the present embodiment, the insulating layer 16 serving as a tunnel barrier is a magnesium oxide (MgO) layer.
Thereby, the magnetoresistive change rate (MR ratio) of the memory element 3 can be increased as compared with the case where the insulating layer 16 is an aluminum oxide layer.

Further, in the memory element 3 of the present embodiment, a CoFeB layer is used as the ferromagnetic layer (reference layer) 15 in contact with the lower side of the insulating layer 16 serving as a tunnel barrier of the magnetization fixed layer 19.
Thereby, the spin polarizability can be increased and the spin injection efficiency can be improved, so that the current for reversing the direction of the magnetization M1 of the storage layer 17 can be further reduced.
And especially by making B content rate of a CoFeB layer into 10 to 30%, resistance change rate can be enlarged and required 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. More preferably, the Fe content of the CoFe layer is made smaller than 20 atomic%.

  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 constituting the laminated ferrimagnetic pinned layer 19.

  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 19, 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.

  The memory element 3 of the present embodiment is manufactured by continuously forming the base layer 11 to the cap layer 18 in a vacuum apparatus and then forming the pattern of the memory element 3 by processing such as etching. Can do.

According to the configuration of the memory element 3 of the present embodiment described above, the intermediate layer between the memory layer 17 and the magnetization fixed layer 19 is the insulating layer 16, and this insulating layer 16 is a magnesium oxide (MgO) layer. Accordingly, the magnetoresistance change rate (MR ratio) of the memory element 3 can be increased as compared with the case where the insulating layer 16 is an aluminum oxide layer.
Since the rate of change in magnetoresistance of the storage element 3 can be increased, a high output can be obtained when information is read, read errors can be reduced, and information can be easily read.
Thereby, in a memory including the storage element 3, for example, a circuit for detecting power by reducing a current flowing through the storage element 3 when information is read to reduce power consumption at the time of reading or the like It is possible to simplify the configuration of the above and improve the read sensitivity.
Further, since read errors can be reduced, it is possible to increase the number of storage elements 3 and increase the capacity of the memory.

Further, according to the configuration of the memory element 3 of the present embodiment, the use of the CoFeB layer for the ferromagnetic layer 15 in contact with the lower side of the MgO layer of the insulating layer 16 increases the spin polarizability, thereby increasing the spin rate. 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.
That is, the amount of current necessary for recording information in the memory element 3 can be reduced, and power consumption can be reduced in a memory including the memory element 3.
Therefore, it is possible to realize a memory with low power consumption that has not been conventionally available.

In particular, by setting the B content of the ferromagnetic layer (CoFeB layer) 15 to 10 to 30%, the magnetoresistance change rate (MR ratio) of the memory element 3 can be sufficiently increased, and the heat Since the deterioration of the characteristics of the memory element 3 can be suppressed when the is added, information can be recorded and read stably, and the memory element 3 with little characteristic deterioration can be configured even at high temperatures.
As a result, a memory having heat resistance and high reliability can be realized.

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 17 between the base layer 11 and the cap layer 18 are stacked upside down with respect to the configuration of the storage element 3 of the previous embodiment shown in FIG. It has become.
In other words, the memory layer 17 is provided in contact with the insulating layer 16 serving as a tunnel barrier.

  In the memory element 30 of the present embodiment, in particular, the memory layer 17 in contact with the insulating layer 16 serving as a tunnel barrier is formed of a CoFeB layer.

  More preferably, the composition of the CoFeB layer of the memory layer 17 is such that the B content is in the range of 15 to 30 atomic%.

  Other configurations are the same as those of the memory element 3 shown in FIG. That is, a magnesium oxide (MgO) layer is used for the insulating layer 16 serving as a tunnel barrier.

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 configuration of the memory element 30 of the present embodiment described above, the magnetoresistive of the memory element 30 can be obtained by using the insulating layer 16 as a magnesium oxide (MgO) layer as in the memory element 10 of the previous embodiment. Since the rate of change (MR ratio) can be increased, it is possible to obtain a high output when reading information, reduce read errors, and easily read information.
Thereby, in the memory including the memory element 30, it is possible to reduce power consumption at the time of reading, to simplify the configuration of a circuit for detecting an output, and to improve read sensitivity.
In addition, since read errors can be reduced, the number of storage elements 30 can be increased to increase the capacity of the memory.

In addition, according to the configuration of the memory element 30 of the present embodiment, the CoFeB layer is used for the memory layer 17 that is a ferromagnetic layer in contact with the lower side of the insulating layer 16, so that the memory element of the previous embodiment is used. 10, by increasing the spin polarizability and improving the spin injection efficiency, the amount of current necessary for recording information in the memory element 30 can be reduced, and the memory element 30 is provided. In the memory, power consumption can be reduced.
Therefore, it is possible to realize a memory with low power consumption that has not been conventionally available.

In particular, by setting the B content of the memory layer (CoFeB layer) 17 to 10 to 30%, it is possible to sufficiently increase the magnetoresistance change rate (MR ratio) of the memory element 30 and to generate heat. Since the deterioration of the characteristics of the memory element 30 when added can be suppressed, information can be recorded and read stably, and the memory element 30 can be configured with little characteristic deterioration even at high temperatures.
As a result, a memory having heat resistance and high reliability can be realized.

(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 19. The layer 13 is a Co ₉₀ Fe ₁₀ film having a thickness of 2 nm (subscript is atomic%), the nonmagnetic layer 14 constituting the magnetization fixed layer 19 having a laminated ferri structure is the Ru film having a thickness of 0.8 nm, and the magnetization fixed layer 19 is The ferromagnetic layer 15 constituting the Co ₄₈ Fe ₃₂ B ₂₀ film (subscript is atomic%) having a thickness of 2 nm, the insulating layer 16 serving as a tunnel insulating layer being a magnesium oxide (MgO) film having a thickness of 1.6 nm, and a memory layer Each layer was formed by selecting 17 as a Co ₄₈ Fe ₃₂ B ₂₀ film having a thickness of 3 nm (subscript is atomic%) and the cap layer 18 being a Ta film having a thickness of 5 nm.
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 (3 nm) / PtMn (30 nm) / Co ₉₀ Fe ₁₀ (2 nm) / Ru (0.8 nm) / Co ₄₈ Fe ₃₂ B ₂₀ (2 nm) / MgO (1.6 nm) / Co ₄₈ Fe ₃₂ B ₂₀ (3 nm) / 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 made of a magnesium oxide film was formed using a DC magnetron sputtering method.
For the insulating layer 16 made of a magnesium oxide film, an oxide was directly deposited by a predetermined film thickness by RF sputtering using an MgO target.
After each layer of the memory element 3 was formed, heat treatment (magnetic field heat treatment) was performed in a magnetic field heat treatment furnace under predetermined conditions, and regularization heat treatment and high temperature durability heat treatment of the PtMn film of the antiferromagnetic layer 12 were performed.

  Next, after masking the word line portion by photolithography, the word line (lower electrode) was formed by performing selective etching with Ar plasma on the laminated film other than the word line. 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. At this time, the pattern of the memory element 3 was an elliptical shape of 100 nm × 150 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 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 by photolithography. Thus, a sample of the memory element was manufactured and used as Sample 1.

(Membrane structure 2: Sample 2)
A Co ₉₀ Fe ₁₀ film was formed as the memory layer 17, and the other structure was the same as the film structure 1 to fabricate the memory element 3, which was used as the sample 2.
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 (3 nm) / PtMn (30 nm) / Co ₉₀ Fe ₁₀ (2 nm) / Ru (0.8 nm) / Co ₄₈ Fe ₃₂ B ₂₀ (2 nm) / MgO (1.6 nm) / Co ₉₀ Fe ₁₀ (3 nm) / Ta ( 5nm)

(Membrane structure 3: Sample 3)
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 underlying layer 11 is a Ta film with a thickness of 3 nm, the memory layer 17 is a Co ₄₈ Fe ₃₂ B ₂₀ film with a thickness of 3 nm (subscript is atomic%), tunnel The insulating layer 16 serving as an insulating layer is a magnesium oxide film having a thickness of 0.8 nm, and the ferromagnetic layer 15 constituting the magnetization fixed layer 19 is a film of Co ₄₈ Fe ₃₂ B ₂₀ having a thickness of 2 nm (subscript is atomic%). A laminated film with a Co ₉₀ Fe ₁₀ film (subscript is atomic%) having a thickness of 1 nm, a nonmagnetic layer 14 constituting a magnetization fixed layer 19 having a laminated ferri structure, a Ru film having a thickness of 0.8 nm, and a magnetization fixed layer 19 Each layer is formed by selecting a Co ₉₀ Fe ₁₀ film having a film thickness of 2.5 nm as a constituent ferromagnetic layer 13, a PtMn film having a film thickness of 30 nm as an antiferromagnetic layer 12, and a Ta film having a film thickness as 5 nm as a cap layer 18. did.
That is, the memory element 30 was produced by using the material and film thickness of each layer as the following configuration (film configuration 3), and a sample 3 was obtained.
Membrane configuration 3:
Ta (3 nm) / Co ₄₈ Fe ₃₂ B ₂₀ (3 nm) / MgO (0.8 nm) / Co ₄₈ Fe ₃₂ B ₂₀ (2 nm) / Co ₉₀ Fe ₁₀ (1 nm) / Ru (0.8 nm) / Co ₉₀ Fe ₁₀ ( 2.5nm) / PtMn (30nm) / Ta (5nm)

(Membrane structure 4: Sample 4)
A Co ₉₀ Fe ₁₀ film having a film thickness of 2.5 nm is formed as the ferromagnetic layer 15 constituting the magnetization fixed layer 19, and the other elements are formed in the same manner as in the film structure 3. A sample was used.
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 (3 nm) / Co ₄₈ Fe ₃₂ B ₂₀ (3 nm) / MgO (0.8 nm) / Co ₉₀ Fe ₁₀ (2.5 nm) / Ru (0.8 nm) / Co ₉₀ Fe ₁₀ (2.5 nm) / PtMn (30 nm) / Ta (5nm)

(Membrane structure 5: Sample 5)
A Co ₄₂ Fe ₂₈ B ₃₀ film is formed as the ferromagnetic layer (reference layer) 15 and the memory layer 17 of the magnetization fixed layer 19, and the memory element 3 is manufactured in the same manner as the film structure 1 in the other configurations. Five samples were used.
That is, a memory element was manufactured by setting the material and film thickness of each layer to the following configuration (film configuration 5).
Membrane configuration 5:
Ta (3 nm) / PtMn (30 nm) / Co ₉₀ Fe ₁₀ (2 nm) / Ru (0.8 nm) / Co ₄₂ Fe ₂₈ B ₃₀ (2 nm) / MgO (1.6 nm) / Co ₄₂ Fe ₂₈ B ₃₀ (3 nm) / Ta (5nm)

(Membrane structure 6: Sample 6)
A Co ₅₁ Fe ₃₄ B ₁₅ film is formed as the ferromagnetic layer (reference layer) 15 and the memory layer 17 of the magnetization fixed layer 19, and the memory element 3 is manufactured in the same manner as the film structure 1 in the other configurations. Six samples were used.
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 (3 nm) / PtMn (30 nm) / Co ₉₀ Fe ₁₀ (2 nm) / Ru (0.8 nm) / Co ₅₁ Fe ₃₄ B ₁₅ (2 nm) / MgO (1.6 nm) / Co ₅₁ Fe ₃₄ B ₁₅ (3 nm) / Ta (5nm)

(Membrane structure 7: Sample 7)
A Co ₃₂ Fe ₃₂ Ni ₁₆ B ₂₀ film is formed as the ferromagnetic layer (reference layer) 15 and the memory layer 17 of the magnetization fixed layer 19, and the other configuration is the same as that of the film configuration 1 to manufacture the memory element 3. Sample 7 was obtained.
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 (3 nm) / PtMn (30 nm) / Co ₉₀ Fe ₁₀ (2 nm) / Ru (0.8 nm) / Co ₃₂ Fe ₃₂ Ni ₁₆ B ₂₀ (2 nm) / MgO (1.6 nm) / Co ₃₂ Fe ₃₂ Ni ₁₆ B ₂₀ (3nm) / Ta (5nm)

(Membrane structure 8: Sample 8)
A Co ₃₂ Fe ₃₂ Ni ₁₆ B ₂₀ film was formed as the memory layer 17, and the other configuration was the same as the film configuration 1 to fabricate the memory element 3, which was designated as Sample 8.
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 (3 nm) / PtMn (30 nm) / Co ₉₀ Fe ₁₀ (2 nm) / Ru (0.8 nm) / Co ₄₈ Fe ₃₂ B ₂₀ (2 nm) / MgO (1.6 nm) / Co ₃₂ Fe ₃₂ Ni ₁₆ B ₂₀ (3 nm ) / Ta (5nm)

(Membrane structure 9: Sample 9)
A Co film was formed as the ferromagnetic layer 13 constituting the magnetization fixed layer 19, and the other elements were made in the same manner as in the film structure 1 to fabricate the memory element 3 as a sample 9 sample.
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 ) / Co (2nm) / Ru (0.8nm) / Co 48 Fe 32 B 20 (2nm) / MgO (1.6nm) / Co 48 Fe 32 B 20 (3nm) / Ta (5nm )

(Membrane structure 10: Sample 10)
The memory element 3 was fabricated and used as a sample 10 in the same manner as the film configuration 1 except that the thickness of the MgO film of the insulating layer 16 was 0.8 nm.
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 (3 nm) / PtMn (30 nm) / Co ₉₀ Fe ₁₀ (2 nm) / Ru (0.8 nm) / Co ₄₈ Fe ₃₂ B ₂₀ (2 nm) / MgO (0.8 nm) / Co ₄₈ Fe ₃₂ B ₂₀ (3 nm) / Ta (5nm)

(Membrane structure 11: Sample 11)
The ferromagnetic layer (reference layer) 15 was a Co ₉₀ Fe ₁₀ film, and the other configuration was the same as the film configuration 1 to fabricate the memory element 3 as a sample 11.
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 (3 nm) / PtMn (30 nm) / Co ₉₀ Fe ₁₀ (2 nm) / Ru (0.8 nm) / Co ₉₀ Fe ₁₀ (2 nm) / MgO (1.6 nm) / Co ₄₈ Fe ₃₂ B ₂₀ (3 nm) / Ta ( 5nm)

(Membrane structure 12: Sample 12)
The ferromagnetic layer (reference layer) 15 and the memory layer 17 were made of Co ₉₀ Fe ₁₀ films, and other configurations were made in the same manner as the film configuration 1 to fabricate the memory element 3 as a sample 12.
That is, a memory element was manufactured with the material and film thickness of each layer as the following configuration (film configuration 12).
Membrane configuration 12:
Ta (3 nm) / PtMn (30 nm) / Co ₉₀ Fe ₁₀ (2 nm) / Ru (0.8 nm) / Co ₉₀ Fe ₁₀ (2 nm) / MgO (1.6 nm) / Co ₉₀ Fe ₁₀ (3 nm) / Ta (5 nm)

(Membrane structure 13: Sample 13)
The memory layer 17 was a Co ₉₀ Fe ₁₀ film, and the other configuration was the same as the film configuration 3 to fabricate the memory element 30 as a sample 13 sample.
That is, a memory element was manufactured with the material and film thickness of each layer as the following configuration (film configuration 13).
Membrane configuration 13:
Ta (3 nm) / Co ₉₀ Fe ₁₀ (3 nm) / MgO (0.8 nm) / Co ₄₈ Fe ₃₂ B ₂₀ (2 nm) / Co ₉₀ Fe ₁₀ (1 nm) / Ru (0.8 nm) / Co ₉₀ Fe ₁₀ (2.5 nm ) / PtMn (30nm) / Ta (5nm)

(Membrane structure 14: Sample 14)
The storage layer 17 and the magnetization fixed layer 19 of the ferromagnetic layer (reference layer) 15 are Co ₉₀ Fe ₁₀ films, the other configurations are the same as the film configuration 4, and the storage element 30 is manufactured and used as the sample 14. .
That is, a memory element was fabricated with the material and film thickness of each layer as the following configuration (film configuration 14).
Membrane configuration 14:
Ta (3 nm) / Co ₉₀ Fe ₁₀ (3 nm) / MgO (0.8 nm) / Co ₉₀ Fe ₁₀ (2.5 nm) / Ru (0.8 nm) / Co ₉₀ Fe ₁₀ (2.5 nm) / PtMn (30 nm) / Ta ( 5nm)

(Membrane structure 15: Sample 15)
The composition of the ferromagnetic layer (reference layer) 15 of the magnetization fixed layer 19 and the CoFeB film of the storage layer 17 is Co ₃₉ Fe ₂₆ B ₃₅ (subscript is atomic%), and other configurations are the same as the film configuration 1 The memory element 3 was produced and used as the sample 15.
That is, a memory element was manufactured by setting the material and film thickness of each layer to the following configuration (film configuration 15).
Membrane configuration 15:
Ta (3 nm) / PtMn (30 nm) / Co ₉₀ Fe ₁₀ (2 nm) / Ru (0.8 nm) / Co ₃₉ Fe ₂₆ B ₃₅ (2 nm) / MgO (1.6 nm) / Co ₃₉ Fe ₂₆ B ₃₅ (3 nm) / Ta (5nm)

(Membrane structure 16: Sample 16)
The composition of the ferromagnetic layer (reference layer) 15 of the magnetization fixed layer 19 and the CoFeB film of the storage layer 17 is Co ₅₄ Fe ₃₆ B ₁₀ (subscript is atomic%), and other configurations are the same as the film configuration 1 A memory element 3 was produced and used as a sample 16.
That is, a memory element was manufactured with the material and film thickness of each layer as the following configuration (film configuration 16).
Membrane configuration 16:
Ta (3 nm) / PtMn (30 nm) / Co ₉₀ Fe ₁₀ (2 nm) / Ru (0.8 nm) / Co ₅₄ Fe ₃₆ B ₁₀ (2 nm) / MgO (1.6 nm) / Co ₅₄ Fe ₃₆ B ₁₀ (3 nm) / Ta (5nm)

(Membrane structure 17: Sample 17)
The composition of the ferromagnetic layer (reference layer) 15 of the magnetization fixed layer 19 and the CoFeNiB film of the storage layer 17 is Co ₃₆ Fe ₃₆ Ni ₁₈ B ₁₀ (subscript is atomic%), and other configurations are the same as the film configuration 7 Thus, the memory element 3 was manufactured and used as a sample 17.
That is, a memory element was manufactured with the material and film thickness of each layer as the following configuration (film configuration 17).
Membrane configuration 17:
Ta (3 nm) / PtMn (30 nm) / Co ₉₀ Fe ₁₀ (2 nm) / Ru (0.8 nm) / Co ₃₆ Fe ₃₆ Ni ₁₈ B ₁₀ (2 nm) / MgO (1.6 nm) / Co ₃₆ Fe ₃₆ Ni ₁₈ B ₁₀ (3nm) / Ta (5nm)

(Membrane structure 18: Sample 18)
The composition of the ferromagnetic layer (reference layer) 15 of the magnetization fixed layer 19 and the CoFeNiB film of the storage layer 17 is Co ₂₆ Fe ₂₆ Ni ₁₃ B ₃₅ (subscript is atomic%), and other configurations are the same as the film configuration 7 Thus, the memory element 3 was produced and used as a sample 18.
That is, a memory element was manufactured with the material and film thickness of each layer as the following configuration (film configuration 18).
Membrane configuration 18:
Ta (3 nm) / PtMn (30 nm) / Co ₉₀ Fe ₁₀ (2 nm) / Ru (0.8 nm) / Co ₂₆ Fe ₂₆ Ni ₁₃ B ₃₅ (2 nm) / MgO (1.6 nm) / Co ₂₆ Fe ₂₆ Ni ₁₃ B ₃₅ (3nm) / Ta (5nm)

(Membrane structure 19: Sample 19)
The memory element 3 was fabricated by changing the composition of the CoFe film of the ferromagnetic layer 13 of the magnetization fixed layer 19 to Co ₈₀ Fe ₂₀ (subscript is atomic%), and the other configuration was the same as the film configuration 1, and the sample 19 A sample was used.
That is, a memory element was manufactured with the material and film thickness of each layer as the following configuration (film configuration 19).
Membrane configuration 19:
Ta (3 nm) / PtMn (30 nm) / Co ₈₀ Fe ₂₀ (2 nm) / Ru (0.8 nm) / Co ₄₈ Fe ₃₂ B ₂₀ (2 nm) / MgO (1.6 nm) / Co ₄₈ Fe ₃₂ B ₂₀ (3 nm) / Ta (5nm)

(Membrane structure 20: Sample 20)
The tunnel insulating layer 16 was an aluminum oxide film, and the other configuration was the same as that of the film configuration 1, and the memory element 3 was fabricated and used as the sample 20.
That is, a memory element was manufactured by setting the material and film thickness of each layer to the following configuration (film configuration 20).
Ta (3nm) / PtMn (30nm) / Co ₈₀ Fe ₂₀ (2nm) / Ru (0.8nm) / Co ₄₈ Fe ₃₂ B ₂₀ (2nm) / Al (0.5nm) -Ox / Co ₄₈ Fe ₃₂ B ₂₀ (3nm ) / Ta (5nm)
The aluminum oxide film of the tunnel insulating layer 16 is formed by forming a metal Al film with a thickness of 0.5 nm by DC magnetron sputtering and then oxidizing it by exposing it to oxygen at a pressure of 10 Torr for 600 seconds to form an aluminum oxide film. did. After forming the aluminum oxide film, it was again evacuated to a high vacuum of 1 × 10 ⁻⁷ to 1 × 10 ⁻⁸ Torr, and subsequent layers were formed.

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

<Experiment 1>
First, in the configuration of the memory element 3 shown in FIG. 2, the difference in characteristics depending on the material of the ferromagnetic layer (reference layer) 15 constituting the magnetization fixed layer 19 that is in contact with the insulating layer 16 serving as the tunnel barrier is explained. Examined.
Samples 1 and 2 as examples of the present invention and Samples 11 and 12 as comparative examples were prepared by setting the conditions of heat treatment in a magnetic field at 300 ° C. for 2 hours.

And about each of these samples, the area resistance value and the resistance change rate were measured as follows.
The bias voltage applied to the word line terminal and the bit line terminal is adjusted to 10 mV, the direction of magnetization of the storage layer is reversed by an external magnetic field, the area resistance value of the entire storage element is measured, and resistance-external The relationship between magnetic fields was investigated.
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, the area resistance value of the low resistance state of the memory element and the resistance change rate of the memory element of each sample are shown in Table 1. Each measured value in Table 1 is an average value of values obtained by measuring 200 memory elements manufactured on each sample wafer.

In the sample 1 which is an embodiment of the present invention, the CoFeB layer (CoFeB film) is in contact with the lower side and the upper side of the barrier layer made of MgO. In Sample 2 which is an example of the present invention, the CoFeB layer (CoFeB film) is in contact only with the lower side of the MgO barrier layer, and the CoFe layer (CoFe film) is in contact with the upper side of the barrier layer. .
On the other hand, in sample 11 as a comparative example, the CoFe layer (CoFe film) is in contact with the lower side of the barrier layer made of MgO, and the CoFeB film is in contact with the upper side of the barrier layer. In Sample 12 as a comparative example, a crystalline CoFe layer (CoFe film) is in contact with the lower side and the upper side of the barrier layer.

As shown in the results of Table 1, in the samples 1 and 2, the ferromagnetic layer in contact with the lower side of the MgO barrier layer is a CoFeB layer, and the resistances are as high as 155.1% and 135.6%, respectively. The rate of change has been observed.
On the other hand, in the samples 11 and 12 in which the ferromagnetic layer in contact with the lower side of the barrier layer made of MgO is a CoFe layer, only a resistance change rate of about 3% can be obtained. Furthermore, although the formation conditions of the barrier layer made of MgO are the same as those of Sample 1, the sheet resistance value is greatly increased.
For these reasons, in a so-called bottom pin type tunnel junction element in which a magnetization fixed layer is formed under the barrier layer made of magnesium oxide, in order to obtain a high resistance change rate, the CoFeB layer is in contact with the barrier layer. It can be seen that it is necessary to form.

From the results shown in Table 1, the ferromagnetic layer in contact with the barrier layer (memory layer 17 in the memory element 10 in FIG. 1) is either a CoFeB layer as in Sample 1 or a CoFe layer as in Sample 2. , It turns out that either is ok.
That is, at least the ferromagnetic layer in contact with the lower side of the barrier layer made of magnesium oxide may be a CoFeB layer.

Thus, the reason why the rate of change in resistance is improved by forming the CoFeB layer so as to be in contact with the lower side of the barrier layer made of magnesium oxide is not necessarily clear.
Therefore, observation with a transmission electron microscope (TEM) was performed. As a result, it became clear that the MgO layer and the CoFeB layer therebelow were strongly crystallized. On the other hand, the MgO layer is characterized by having a crystal layer even immediately after film formation.
Therefore, perhaps the CoFeB layer, which was amorphous immediately after the film formation, is crystallized by being greatly affected by the crystal orientation of the MgO layer by performing a heat treatment after the film formation, thereby changing the crystal orientation of the MgO layer. It is considered that good orientation can be obtained because crystallization occurs in a self-aligned manner.

<Experiment 2>
Next, in the configuration of the memory element 30 shown in FIG. 3 in which the magnetization fixed layer 19 is formed above the insulating layer (barrier layer) 16 serving as a tunnel barrier, the layer is in contact with the insulating layer (barrier layer) 16. The difference in characteristics depending on the material of the ferromagnetic layer, that is, the material of the memory layer 17 was examined.
Samples 3 and 4 that are examples of the present invention and samples 13 and 14 that are comparative examples were subjected to heat treatment in a magnetic field similar to that in Experiment 1 to prepare samples.
And about each of these samples, the area resistance value and resistance change rate were measured with the measuring method mentioned above.
As a measurement result, the area resistance value of the low resistance state of the memory element and the resistance change rate of the memory element of each sample are shown in Table 2. Each measured value in Table 2 is an average value of values obtained by measuring 200 memory elements manufactured on each sample wafer.

In the sample 3 which is an embodiment of the present invention, the CoFeB layer (CoFeB film) is in contact with the lower side and the upper side of the barrier layer made of MgO. In sample 4 which is an embodiment of the present invention, the CoFeB layer (CoFeB film) is in contact only with the lower side of the MgO barrier layer, and the CoFe layer (CoFe film) is in contact with the upper side of the barrier layer. .
On the other hand, in the sample 13 as a comparative example, the CoFe layer (CoFe film) is in contact with the lower side of the barrier layer made of MgO, and the CoFeB film is in contact with the upper side of the barrier layer. In Sample 14 as a comparative example, a crystalline CoFe layer (CoFe film) is in contact with the lower side and the upper side of the barrier layer.

As shown in the results of Table 2, in the samples 3 and 4 in which the ferromagnetic layer in contact with the lower side of the barrier layer made of MgO is a CoFeB layer, the resistance is high as 135.1% and 65.6%, respectively. The rate of change has been observed.
On the other hand, in the sample 13 and the sample 14 in which the ferromagnetic layer in contact with the lower side of the barrier layer made of MgO is a CoFe layer, only a resistance change rate of about 3% can be obtained. Furthermore, although the formation conditions of the barrier layer made of MgO are the same as those of the sample 3, the sheet resistance value is greatly increased.
For these reasons, even in a so-called top-pin type tunnel junction element in which a magnetization fixed layer is formed on a barrier layer made of magnesium oxide, a CoFeB layer is in contact with the barrier layer in order to obtain a high resistance change rate. It can be seen that it is necessary to form in this way.

  Sample 3 and sample 4 have a barrier layer thickness of 0.8 nm, which is smaller than the barrier layer thickness of sample 1 and sample 2 (1.6 nm). ing.

<Experiment 3>
Next, the range of the composition of CoFeB in which particularly good characteristics were obtained in the CoFeB layer formed in contact with the lower side of the barrier layer in the present invention was examined.
Specifically, for each of Sample 1, Sample 5, Sample 6, Sample 15, and Sample 16, a sample in which the heat treatment conditions in the magnetic field were 260 ° C. · 2 hours, and a sample that was 300 ° C. · 2 hours, Were prepared respectively.
And about each of these samples, the area resistance value and resistance change rate were measured with the measuring method mentioned above.
As a measurement result, the area resistance value of the low resistance state of the memory element and the resistance change rate of the memory element of each sample are shown in Table 3 together with the composition ratio of the CoFeB layer. Each measured value in Table 3 is an average value of values obtained by measuring 200 memory elements fabricated on each sample wafer. In addition, the sheet resistance value does not show a great difference regardless of whether the temperature of the heat treatment in the magnetic field is 260 ° C. or 300 ° C. Is shown.

As shown in the results of Table 3, Sample 1, Sample 5, and Sample 6 each have a sufficiently good resistance change rate.
On the other hand, in the sample 15 having a high B content of 35 atomic%, the resistance change rate is low under the heat treatment conditions of 260 ° C. and 300 ° C., respectively.
Further, Sample 16 having a low B content of 10 atomic% shows a good resistance change rate under the heat treatment condition of 260 ° C., but the resistance change rate greatly decreases under the heat treatment condition of 300 ° C.
Therefore, it is desirable to set the composition of the CoFeB layer in contact with the barrier layer so that the B content is in the range of 15 atomic% to 30 atomic%.

It is not always necessary to make the composition of the CoFeB layer in contact with the upper and lower sides of the barrier layer made of MgO the same as in Sample 1, Sample 5 and Sample 6 of the embodiment of the present invention shown here. I do not care.
That is, the composition of the CoFeB layer in contact with the upper side of the barrier layer made of MgO may be different from the composition of the CoFeB layer in contact with the lower side, and in each CoFeB layer, the B content is in the range of 15 atomic% to 30 atomic%. I just need it.

<Experiment 4>
Next, in the case where CoFeNiB containing Ni in addition to Co, Fe, and B is used for the ferromagnetic layer sandwiching the barrier layer 16 made of MgO, the range of the composition of CoFeNiB in which particularly good characteristics are obtained is investigated. It was.
Specifically, for each of Sample 7, Sample 8, Sample 17, and Sample 18, as in Experiment 3, a sample with a heat treatment condition in a magnetic field of 260 ° C./2 hours and a sample of 300 ° C./2 hours Was made.
And about each of these samples, the area resistance value and resistance change rate were measured with the measuring method mentioned above.
As a measurement result, the area resistance value of the low resistance state of the memory element and the resistance change rate of the memory element of each sample are shown in Table 4 together with the composition ratio (Ni content and B content) of the CoFeNiB layer. In addition, the sheet resistance value does not show a great difference whether the heat treatment in the magnetic field is 260 ° C. or 300 ° C., but in Table 4, the measured value of the sheet resistance value of the sample subjected to the heat treatment in the magnetic field at 300 ° C. for 2 hours. Is shown.

In Sample 7, Sample 17, and Sample 18, as shown in the composition ratio of Table 4, the content of Ni is adjusted to be substantially constant among the ferromagnetic elements of Co, Fe, and Ni. The content of is changed.
As shown in the results of Table 4, among these samples, the resistance change rate of the sample 7 having a B content of 20% is the best, and even when Ni is used for the amorphous magnetic layer, the experiment is performed. Similarly to the result of 3, it is understood that the B content is preferably in the range of 15 atomic% to 30 atomic%.

In Sample 8, the CoFeB layer is in contact with the lower layer of MgO, and the CoFeNiB layer (CoFeNiB film) is in contact with the upper side of the barrier layer. Yes.
Thus, if the B content is within the range of 15 atomic% to 30 atomic%, the composition of the ferromagnetic layer in contact with the lower side of the barrier layer is different from that of the ferromagnetic layer in contact with the upper side of the barrier layer. May be.

Therefore, it is understood that the ferromagnetic layer in contact with the lower side of the barrier layer made of MgO is not limited to the CoFeB layer, and CoFeNiB can be used as the material of the ferromagnetic layer.
Furthermore, known nonmagnetic additives such as B, Si, Zr, Nb, Cu, Ta, etc., which can be inferred from this result, contain any one or more magnetic elements of Co, Fe, and Ni. It is also possible to use a magnetic material to which is added.

  Further, not only in the bottom pin type structure used in Experiment 4, but also in the top pin type structure, similarly, the ferromagnetic layer in contact with the lower side of the barrier layer made of MgO (the storage layer 17 in the storage element 30 in FIG. 3). ) Includes any one or more magnetic elements of Co, Fe, and Ni, and a known nonmagnetic additive such as B, Si, Zr, Nb, Cu, or Ta is added. It is also possible to use a magnetic material.

<Experiment 5>
Next, when the magnetization direction of the fixed magnetization layer is fixed using antiferromagnetic coupling by the antiferromagnetic layer, the ferromagnetic layer on the antiferromagnetic layer side among the ferromagnetic layers constituting the fixed magnetization layer The relationship between the composition and the characteristics of the memory element was examined.
Specifically, samples of Sample 1, Sample 9, and Sample 19 were prepared in the same manner as in Experiment 1, with the heat treatment conditions in the magnetic field being 300 ° C. for 2 hours.
And about each of these samples, while measuring resistance change rate with the measuring method mentioned above, pin magnetic field strength Hpin, ie, the intensity | strength of the magnetic field added with respect to a magnetization fixed layer by an antiferromagnetic layer, was measured.
As a measurement result, the resistance change rate and the pin magnetic field strength Hpin of the memory element of each sample are shown in Table 5 together with the material composition of the ferromagnetic layer 13 on the antiferromagnetic layer 12 side of the magnetization fixed layer 19. .

As shown in the results of Table 5, in sample 1 and sample 9 in which the Fe content of the material composition of the ferromagnetic layer 13 is 10 atomic% or less, sufficient pin magnetic field strength can be obtained even after heat treatment at 300 ° C. for 2 hours. Is obtained.
On the other hand, in the sample 15 in which the Fe content of the ferromagnetic layer 13 is 20 atomic%, the pin magnetic field strength is reduced to 950 (Oe) by the heat treatment at 300 ° C. for 2 hours. Further, the resistance change rate is also lower than those of Sample 1 and Sample 9 due to a cause that seems to be due to a decrease in the pin magnetic field strength.
Therefore, the ferromagnetic layer on the antiferromagnetic layer side of the magnetization fixed layer desirably has an Fe content of less than 20%, and more desirably 10% or less.

<Experiment 6>
Next, the relationship between the barrier layer material and the reversal current was examined.
Sample 10 of Example of the present invention and Sample 20 of Comparative Example were prepared for each sample in the same manner as in Experiment 1 with the condition of heat treatment in a magnetic field being 300 ° C. for 2 hours.
When the area resistance value and the resistance change rate of the sample 10 were measured by the measurement method described above, the film thickness of the barrier layer 16 made of MgO was 0.8 nm (the same film thickness as the sample 3 and the sample 4). The sheet resistance value was about 16 Ωμm ² and the resistance change rate was about 50%. Note that the resistance change rate varies depending on the bias voltage.

Here, FIG. 4 shows a typical measurement result of a resistance-current curve in a memory element that performs magnetization reversal by spin injection.
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.
Further, as shown in FIG. 4, there is an offset in which the absolute value of the reversal current is different between the + side and the-side.

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).
And the electric current value from which resistance value changes was calculated | required from the resistance-current curve, and this was made into the reversal electric current value which reverses the direction of magnetization. The inversion current value was obtained for the bipolar current.
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 6 shows the reversal current values and reversal current densities of Sample 10 and Sample 20 as measurement results. Each measured value in Table 6 is an average value of values obtained by measuring 10 storage elements.

As shown in the results of Table 6, when the sample 10 which is an example of the present invention in which the material of the barrier layer is MgO is compared with the sample 20 which is the comparative example in which the material of the barrier layer is AlOx, spin injection is performed. It can be seen that the reversal current density is approximately halved.
This is presumably because the rate of resistance change is improved by using MgO as the material of the barrier layer, so that the spin injection efficiency is improved and the inversion current density is reduced.

As described above, the material of the ferromagnetic layer in contact with the lower side of the barrier layer made of MgO is the amorphous magnetic material of the present invention, so that compared with the case where a crystalline magnetic material such as CoFe is used. Further, it is possible to realize a memory element with a further increased resistance change rate and with little characteristic deterioration at a high temperature of 300 ° C.
In addition, the efficiency of spin injection can be improved, and the reversal current for performing magnetization reversal by spin injection 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. It is a figure which shows the typical measurement result of a resistance-current curve in the memory element which performs magnetization reversal by spin injection. 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 Cap layer, 19 Magnetization fixed layer

Claims (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,
In the storage element, a fixed magnetization layer is provided with respect to the storage layer via an intermediate layer, the intermediate layer is made of magnesium oxide, and the ferromagnetic layer in contact with the lower side of the intermediate layer is mainly composed of CoFeB. The magnetic layer is made of a magnetic material, and by flowing a current in the stacking direction, the magnetization direction of the storage layer is changed, and information is recorded on the storage layer.
In the storage element, an antiferromagnetic layer is provided on the opposite side of the magnetization fixed layer from the storage layer, and in the magnetization fixed layer, the ferromagnetic layer in contact with the antiferromagnetic layer is a CoFe layer, and Fe content of the CoFe layer is less than 20 atomic%,
The storage element is disposed near the intersection of the two types of wiring and between the two types of wiring,
A memory in which a current in the stacking direction flows in the memory element through the two types of wirings.

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