JP2007073638A - Memory element and memory - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a memory element which has a large change in resistance and reduces read-out errors. <P>SOLUTION: The memory element 3 includes a memory layer 17 which holds information by the magnetized state of a magnetic material. With respect to the memory layer 17, a magnetization-fixed layer 31 is formed via an intermediate layer 16. The intermediate layer 16 is formed of a magnesium oxide, and the memory layer 17 or at least one layer out of ferromagnetic layers 17, 13, and 15 which constitute the magnetization-fixed layer 31 is mainly formed of at least one kind selected among Co and Fe, while at the same time containing 5 to 20 atomic% of at least one kind selected among V, Cr, and Nb. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a storage element comprising a storage layer for storing the magnetization state of a ferromagnetic layer as information, a magnetization fixed layer whose magnetization direction is fixed, and a memory including the storage element, and is applied to a nonvolatile memory. And suitable.

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. Performance improvement is required.
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.

  As a candidate for a non-volatile memory, a magnetic random access memory (MRAM) that records information by magnetization of a magnetic material has attracted attention and is under development (for example, see Non-Patent Document 1).

In the MRAM, current is supplied to two types of address lines (word lines and bit lines) that are substantially orthogonal to each other, and the magnetization of the magnetic layer of the magnetic memory element at the intersection of the address lines is caused by a current magnetic field generated from each address line. Inverted information is recorded.
Since this MRAM stores data by rotating the magnetic moment, the number of rewrites is large.
Also, the access time is very high.

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, it is necessary to pass a certain amount of current through the address wiring.

In addition, a memory that uses magnetization reversal by spin injection has attracted attention as a configuration that allows magnetization reversal 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 without increasing current even if the element is miniaturized.

6 and 7 are schematic diagrams of a memory having a configuration using the above-described magnetization reversal by spin injection. 6 is a perspective view, and FIG. 7 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. Among 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 to the left and right selection transistors in FIG. 6, 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 memory element 53 to reverse the magnetization direction of the memory layer by spin injection.

Such a memory using a magnetization reversal by spin injection has a feature that the device structure can be simplified as compared with the general MRAM shown in FIG.
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.

  In the case of an MRAM, a write wiring (word line or bit line) is provided separately from a memory element, and information is written (recorded) by a current magnetic field generated by passing a current through the write wiring. Therefore, a sufficient amount of current required for writing can be passed through the write wiring.

On the other hand, in a memory configured to use magnetization reversal by spin injection, it is necessary to reverse the magnetization direction of the storage layer by performing spin injection with a current flowing through the storage element.
Since the current is directly supplied to the memory element and information is written (recorded) as described above, the memory cell is configured by connecting the memory element to a selection transistor in order to select a memory cell to be written. In this case, the current flowing through the memory element is limited to the magnitude of the current that can flow through the selection transistor (the saturation current of the selection transistor).
Therefore, it is necessary to perform writing with a current lower than the saturation current of the selection transistor, and it is necessary to improve the efficiency of spin injection and reduce the current flowing through the memory element.

Also, in order to increase the read signal, it is necessary to secure a large rate of change in magnetoresistance. To that end, a memory element having a tunnel insulating layer (tunnel barrier layer) as an intermediate layer in contact with both sides of the memory layer is required. The configuration is effective.
When the tunnel insulating layer is used as the intermediate layer as described above, the amount of current flowing through the memory element is limited in order to prevent the tunnel insulating layer from being broken down. From this viewpoint, it is necessary to suppress the current during spin injection.

  Therefore, in a memory element configured to reverse the magnetization direction of the memory layer by spin injection, it is necessary to improve the spin injection efficiency and reduce the required current.

Further, in the conventional MRAM, AlO _X in which aluminum is mainly oxidized has been widely used as a material for the tunnel insulating layer of the memory element. However, it is known that a high magnetoresistance change rate (MR ratio) can be obtained by changing the material used for the insulating layer from AlO _X to MgO.
For example, an MR ratio of 88% is obtained at room temperature by using an Fe ferromagnetic layer whose crystal plane is oriented in the (100) direction and an MgO insulating layer epitaxially grown in the (100) direction. (Refer nonpatent literature 2).

Nikkei Electronics 2001.1.22 (pages 164-171) Japanese Journal of Applied Physics, Part 2: Letters April 15, 2004 Volume 43, Issue 4B, p.L588-L590 JP 2003-17782 A

  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 order to solve the above-described problem, the present invention provides a memory element that has a large resistance change rate and can reduce read errors, and a memory having the memory element.

  The memory element of the present invention has a memory layer that holds information according to the magnetization state of a magnetic material, and a magnetization pinned layer is provided via the intermediate layer with respect to the memory layer, and the intermediate layer is made of magnesium oxide. At least one of the ferromagnetic layers constituting the layer or the magnetization fixed layer is composed mainly of at least one selected from Co and Fe, and at least one selected from V, Cr and Nb is 5 atom% or more and 20 atoms. % Or less.

  The memory according to the present invention includes a memory element having a memory layer that holds information according to the magnetization state of a magnetic material, and two kinds of wirings that intersect each other, and the memory element has the configuration of the memory element according to the present invention. A storage element is arranged near the intersection of the types of wirings and between the two types of wirings.

  According to the configuration of the memory element of the present invention described above, the intermediate layer is composed of magnesium oxide, and at least one of the ferromagnetic layers constituting the memory layer or the magnetization fixed layer is composed mainly of at least one selected from Co and Fe. The resistance change rate can be increased by containing at least one selected from V, Cr, and Nb in an amount of 5 atomic% to 20 atomic%.

  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. With this configuration, the resistance change rate can be increased.

According to the above-described present invention, since a high MR ratio can be obtained, a sufficient operation margin of the memory element can be obtained, and the memory element can be operated without error.
Therefore, a highly reliable memory that operates stably can be realized.

First, an outline of the present invention will be described prior to description of specific embodiments of the present invention.
In the present invention, information is recorded by reversing the direction of magnetization of the storage layer of the storage element by means of a current magnetic field or the above-described spin injection. 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.

  By constructing a magnetic tunnel junction (MTJ) element using a tunnel insulating layer as a nonmagnetic intermediate layer between the storage layer and the magnetization fixed layer, a giant magnetoresistive effect (GMR) is achieved using the nonmagnetic conductive layer. Compared with the case where the element is configured, the magnetoresistance change rate (MR ratio) can be increased, and the read signal intensity can be increased.

  In particular, by using magnesium oxide (MgO) as the material of the tunnel insulating layer, the magnetoresistance change rate (MR ratio) can be made larger than when aluminum oxide is used. Therefore, the read signal intensity can be increased by using magnesium oxide as the material of the tunnel insulating layer which is an intermediate layer.

Therefore, in the present invention, the intermediate layer between the storage layer and the magnetization fixed layer has a configuration (tunnel insulating layer) made of magnesium oxide.
Thereby, the MR ratio (TMR ratio) can be increased, and the read signal intensity can be increased.

  It is more desirable for the tunnel insulating layer made of a magnesium oxide (MgO) film to maintain crystal orientation in the (100) direction because the MgO film is crystallized.

  In addition, as a result of various studies, it is possible to increase the magnetoresistance change rate by limiting the material of at least one of the ferromagnetic layers constituting the storage layer or the magnetization fixed layer and further defining the composition of this layer. I found out that In addition, it has been found that in a storage element that records information by spin injection, the spin injection efficiency is improved and the current density required to reverse the magnetization direction of the storage layer is reduced.

Therefore, in the present invention, at least one of the ferromagnetic layers constituting the storage layer or the magnetization fixed layer is composed mainly of at least one selected from Co and Fe and selected from V, Cr and Nb. It is set as the structure containing 5 atomic% or more and 20 atomic% or less. Among these, at least one kind selected from Co and Fe as the main components includes Co alone, Fe alone, and Co—Fe alloy.
Thereby, the magnetoresistance change rate (MR ratio) can be increased. Further, in a memory element that records information by spin injection, the spin injection efficiency can be improved and the current density required for reversing the magnetization direction of the memory layer can be reduced.

  Hereinafter, the reason why a high MR ratio can be obtained by incorporating at least one selected from V, Cr, and Nb into the ferromagnetic layer will be described.

V, Cr, and Nb are close in ion radius to elements such as Co and Fe used in the ferromagnetic layer in contact with the tunnel insulating layer, and even if Fe or Co in the crystal lattice is replaced with V, Cr, or Nb. A sufficiently oriented magnetic material is obtained.
V, Cr, and Nb have a slightly larger ionic radius than Fe and Co, and increase the lattice constant of the crystal by adding V, Cr, and Nb to a magnetic material composed of Fe and Co. Can do.

The lattice constant of MgO constituting the tunnel insulating layer is larger than the lattice constant of Fe or Co, and a lattice mismatch occurs between the ferromagnetic layer in contact with the tunnel insulating layer.
Therefore, the addition of V, Cr, Nb having an ionic radius larger than that of Fe or Co to the ferromagnetic layer increases the lattice constant of the ferromagnetic layer, and the difference in lattice constant from MgO constituting the tunnel insulating layer. Can be reduced and lattice mismatch can be reduced.

Hereinafter, reduction of lattice mismatch between the ferromagnetic layer and the tunnel insulating layer will be specifically described based on the first principle calculation.
The first-principles calculation is a calculation method that can determine the lattice constant, magnetization, and electronic state using only the atomic number of each atom as a parameter.
In particular, a method called Coherent Potential Approximation (CPA) can be used in the calculation of a material in which each atom such as an alloy forms a lattice at random.
As one of the electronic state calculation methods using this CPA, there is a calculation method called a KKR-CPA method (Korringa-Kohn-Rostoker Coherent Potential Approximation). As one of the KKR-CPA method programs, a program called “MACHIKANEYAMAMA2000” (H & M.Akai, Korringa-Kohn-Rostoker Coherent Potential Approximation Package (H.Akai, Osaka University) , 2000)).

As a result of the calculation based on the first principle calculation, the lattice mismatch between the ferromagnetic material made of Fe and the intermediate layer made of MgO having no oxygen defects was about 3%.
Therefore, when the lattice mismatch between the ferromagnetic material in which 20% of V having a slightly larger ion radius is added to Fe and the intermediate layer made of MgO without oxygen defects is calculated based on the first principle calculation, the lattice mismatch is calculated as 2. It was reduced to 3%.
If MgO has about 1% lattice defects and the lattice constant is reduced, the lattice mismatch between the ferromagnetic material and the intermediate layer when Fe is added to 20% is reduced to 1.5%. To do.
By reducing this lattice mismatch, the crystallinity of MgO is improved and the breakdown voltage is also increased.
Similarly, Cr and Nb having an ionic radius larger than that of Fe and Co can also reduce the lattice mismatch with the intermediate layer made of MgO by adding Cr and Nb to the ferromagnetic layer made of Co and Fe. Obtained. Table 1 shows the ionic radius of each element.

  In addition, since transition metal elements such as Cr, V, and Nb have fewer electrons in 3d orbitals than Co and Fe, saturation magnetization can be lowered, and the concentration and mixing ratio of these transition metals can be adjusted. Thus, a crystal-oriented magnetic material having a desired magnetization reversal efficiency can be obtained.

  When transition metal elements such as Cr, V, and Nb are added to Fe and Co, the state of electrons contributing to electrical conduction such as p-orbital electrons and s-orbital electrons at the Fermi level of the metal elements changes. The electric conduction characteristics such as the MR ratio can be directly adjusted.

  Next, a case where a configuration in which at least one selected from V, Cr, and Nb is contained in a ferromagnetic layer is applied to a memory element that records information by spin injection will be described.

The basic operation of reversing the magnetization direction of the magnetic layer by spin injection is perpendicular to the film surface of a memory element composed of a giant magnetoresistive element (GMR element) or a tunnel magnetoresistive element (MTJ element). In such a direction, a current exceeding a certain threshold is passed. At this time, the polarity (direction) of the current depends on the direction of magnetization to be reversed.
When a current having an absolute value smaller than this threshold is passed, magnetization reversal does not occur.

  When the magnetization direction of the magnetic layer is reversed by spin injection, the threshold value Ic of the necessary current is phenomenologically expressed by the following formula 1 (for example, Applied Physics Letter Volume 78, Number 23 4 June). 2001, etc.).

The present invention utilizes the fact that the threshold value of the current can be arbitrarily set by controlling so as to lower the saturation magnetization M _s of the magnetic layer, as represented by the expression (1). .
Then, a storage element having a magnetic layer (storage layer) capable of holding information depending on the magnetization state and a magnetization fixed layer in which the magnetization direction is fixed is configured.

The threshold value of the current that changes the magnetization state of the storage layer is actually a substantially elliptical giant magnetoresistive element (GMR element) having a storage layer thickness of 2 nm and a planar pattern of 120 to 130 nm × 100 nm, for example. , The positive threshold value + Ic = + 0.6 mA, the negative threshold value −Ic = −0.2 mA, and the current density at that time is about 6 × 10 ⁶ A · cm ² . These almost agree with the above formula (1) (see Rooftop et al., Journal of Japan Society of Applied Magnetics, Vol.28, No.2, p.149, 2004).

On the other hand, a normal MRAM that performs magnetization reversal by a current magnetic field requires a write current of several mA or more.
On the other hand, when the magnetization reversal is performed by spin injection, the threshold value of the write current becomes sufficiently small as described above, which is effective for reducing the power consumption of the integrated circuit.
Further, since the wiring for generating a magnetic field (105 in FIG. 8) required for a normal MRAM is not necessary, the degree of integration is also advantageous compared to a normal MRAM.

However, as described above, in a memory configured to use magnetization reversal by spin injection, it is necessary to reverse the magnetization direction of the storage layer by performing spin injection with a current flowing through the storage element.
Since the current is directly supplied to the memory element and information is written (recorded) as described above, the memory cell is configured by connecting the memory element to a selection transistor in order to select a memory cell to be written. In this case, the current flowing through the memory element is limited to the magnitude of the current that can flow through the selection transistor (the saturation current of the selection transistor).
Therefore, it is necessary to perform writing with a current lower than the saturation current of the selection transistor, and it is necessary to improve the efficiency of spin injection and reduce the current flowing through the memory element.

In addition, a tunnel insulating layer using MgO, AlO _X, or the like is generally used in a range of 10 to 1 kΩμm ² , which is a range used as a memory element, although it depends on an oxide composition and formation conditions. Therefore, dielectric breakdown occurs 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 value of KuV / k _B T (Ku is the anisotropy energy, k _B is the Boltzmann constant, and T is the temperature) determined from the volume V of the magnetic material of the memory layer and the magnetic anisotropy of the memory layer. The smaller the thickness is, the more easily the magnetization of the storage layer is reversed, so that the reversal current is small.
However, when the value of KuV / k _B T is too small, the magnetization is thermally disturbed due to the influence of thermal fluctuation, and it becomes difficult to define the magnetization direction.
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.

Since the efficiency of spin injection generally depends on the MR ratio, the larger the MR ratio, the higher the spin injection efficiency and the lower the magnetization reversal current density.
Therefore, by configuring the intermediate layer between the storage layer and the magnetization fixed layer of magnesium oxide, the MR ratio (TMR ratio) can be increased, and the write threshold current due to spin injection can be reduced. Information can be written (recorded) with a small current.

Furthermore, the MR ratio can be increased by containing at least one selected from V, Cr, and Nb in the ferromagnetic layer constituting the storage layer or the magnetization fixed layer, so that the spin injection efficiency is further improved. be able to.
As a result, the write threshold current due to spin injection can be reduced, and information can be written (recorded) with a smaller current.
In addition, the saturation magnetization of the ferromagnetic layer can be reduced by containing at least one selected from V, Cr, and Nb in the ferromagnetic layer, and this action also reduces the write threshold current due to spin injection. can do.

Here, the first-principles calculation was performed by the KKR-CPA method using "MACHIKANEYAMAMA2000" about the ferromagnetic material which added V or Cr with respect to Fe or CoFe.
First, the content of added V or Cr (ratio to the ferromagnetic material) was set to 5 atom%, 10 atom%, and 20 atom%, and the saturation magnetization was obtained by first principle calculation. FIG. 4 shows the relationship between Fe, CoFe (content 0%) not added and the saturation magnetization.

FIG. 4 shows that the saturation magnetic moment is greatly reduced as the amount of V or Cr added is increased.
Thereby, the magnetization reversal current Ic can be reduced by the decrease of the saturation magnetization Ms from the equation (1), and thus the magnetization reversal efficiency by spin injection can be improved.

At the Fermi level, up-spin s-orbital electrons and p-orbital electrons have a relatively high transmission probability (see Physical Review B, volume 63, 054416, 8 January 2001).
Here, electronic density of state (DOS) based on first-principles calculation was determined for CoFe and ferromagnetic materials obtained by adding V or Cr to CoFe.
The calculation results are shown in FIGS. 5A to 5C. FIG. 5A shows the calculation results for Co70Fe30 (subscript is atomic%), FIG. 5B is the calculation result for Co63Fe27V10 (subscript is atomic%), and FIG. 5C is the calculation result for Co63Fe27Cr10 (subscript is atomic%). Table 2 shows the density of electronic states of up-spin or down-spin s-orbital electrons, p-orbital electrons, and d-orbital electrons calculated by the first principle calculation.

  As can be seen from the comparison between FIG. 5A and FIG. 5B and FIG. 5C and Table 2, when V or Cr is added, the up-spin s-orbital electrons and p having a relatively high transmission probability as described above. The electronic state density of orbital electrons increases. As a result, the resistance change rate increases.

  4 and 5 show the case where V or Cr is added to Co and Fe, but the same result can be obtained when Nb is added to Co and Fe.

The addition amount of V, Cr, and Nb to Co and Fe is set so that the content of these added elements in the entire ferromagnetic material is 5 atomic percent or more and 20 atomic percent or less.
By setting the content to 5 atomic% or more, as shown in FIG. 4, the saturation magnetization is reduced, so that the magnetization reversal current can be reduced. Further, as shown in FIG. 5, the rate of resistance change can be increased by increasing the electronic density of states of up-spin s orbital electrons and p orbital electrons.
On the other hand, if the content is too large, it may exist as a magnetic layer, but the saturation magnetization necessary for constituting the memory element cannot be obtained. Therefore, the content is set to 20 atomic% or less.

  As described above, according to the present invention, at least one of the ferromagnetic layers constituting the storage layer or the magnetization fixed layer is composed mainly of at least one selected from Co and Fe, and V, Cr, Nb. By adding at least one selected from the above, the MR ratio and the spin injection efficiency can be improved, and the current density required to reverse the magnetization direction of the storage layer can be reduced.

In order to pass a sufficient write current to the memory element, it is necessary to reduce the area resistance value of the tunnel insulating layer (tunnel barrier layer).
The sheet resistance value of the tunnel insulating layer needs to be controlled to about several tens of Ωμm ² or less from the viewpoint of obtaining a current density necessary for reversing the magnetization direction of the storage layer by spin injection.
In the tunnel insulating layer made of the MgO film, it is necessary to set the film thickness of the MgO film to 1 nm or less in order to make the sheet resistance value in the above range.

In addition, it is desirable to make the memory element small so that the magnetization direction of the memory layer can be easily reversed with a small current.
Accordingly, the area of the memory element is preferably 0.04 μm ² or less.

In the present invention, at least one of the ferromagnetic layers constituting the storage layer or the magnetization fixed layer is configured by adding V, Cr, Nb to the main component composed of Co, Fe having the composition range described above.
That is, one or all of the ferromagnetic layers constituting the storage layer have the composition having the above-described composition range, and one or all of the ferromagnetic layers constituting the magnetization fixed layer have the above-described composition. A configuration having a composition range described above includes one or all of the ferromagnetic layers constituting the storage layer and one or all of the ferromagnetic layers constituting the magnetization fixed layer. It is done.

  It is also possible to directly laminate a ferromagnetic layer having the composition range described above and another ferromagnetic layer having a different material or composition range, and even when laminated in this way, the effect of the present invention is achieved. Is obtained.

  In addition, the film configuration of the storage element has no problem whether the storage layer is disposed above the magnetization fixed layer or the lower 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. Reading may be performed by a tunnel current or may be performed 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 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 16 serving as a tunnel barrier layer (tunnel insulating layer) is provided between the storage layer 17 and the magnetization fixed layer 31, and the storage layer 17 and the magnetization fixed layer 31 constitute an MTJ element.

  A base layer 11 is formed below the antiferromagnetic layer 12, and a cap layer 18 is formed on the storage layer 17.

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.

  In the present embodiment, in particular, at least one of the ferromagnetic layers constituting the storage layer 17 and the magnetization fixed layer 31, that is, the storage layer 17 and the ferromagnetic layers 13 and 15 of the magnetization fixed layer 31, At least one selected from Co and Fe is used as a main component, and at least one selected from V, Cr and Nb is contained in an amount of 5 atomic% to 20 atomic%.

The ferromagnetic layer mainly composed of Co and Fe having the composition range described above may contain other elements such as transition metals such as Gd, Mo, Mn, Cu and Zr, and light elements such as boron and carbon. Good.
For example, boron (B) is contained in a Co—Fe alloy, and CoFeB is the main component, and at least one selected from V, Cr, and Nb is contained in an amount of 5 atomic% to 20 atomic%. Is also possible.

In the case where the memory layer 17 is not composed of the above-described Co and Fe as main components, the constituent material of the memory layer 17 is not particularly limited.
In this case, for example, an alloy material composed of one or more of Co, Fe, Ni, and Gd can be used. Further, transition metal elements such as Mo, Mn, Cu, and Zr, and light elements such as B can be included.
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.

The constituent materials of the ferromagnetic layers 13 and 15 of the magnetization fixed layer 31 are not particularly limited when the ferromagnetic layers 13 and 15 are not composed of the above-described Co and Fe as main components.
In this case, for example, an alloy material composed of one or more of Fe, Ni, Co, and Gd can be used. Furthermore, transition metal elements such as Nb and Zr, and light elements such as B and C can also be included.

Ru, Cu, Cr, Au, Ag, or the like can be used as the material of the nonmagnetic layer 14 constituting the laminated ferrimagnetic pinned layer 31. Although the film thickness of the nonmagnetic layer 14 varies depending on the material, it is preferably used in the range of approximately 0.5 nm to 2.5 nm.
As a material of the antiferromagnetic layer 12, an alloy of a metal element such as Fe, Ni, Pt, Ir, Rh, and Mn, an oxide of Co or Ni, or the like can be used.

  The film thickness of the ferromagnetic layers 13 and 15 of the magnetization fixed layer 31 is suitably 1 nm or more and 4 nm or less.

  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.

Then, after each layer of the memory element 3 is formed by the above-described film forming method, for example, heat treatment is performed at 10 kOe · 270 ° C. · 4 hours in a heat treatment furnace in a magnetic field. A regularized heat treatment of the magnetic layer 12 is performed.
Thereafter, a mask of the pattern of the memory element 3 is formed using, for example, an electron beam drawing apparatus, and the memory element 3 is patterned into a predetermined pattern by performing selective etching on the laminated film of each layer of the memory element 3. To do.
It should be noted that portions other than the memory element 3 are insulated by an insulating layer. For example, Al ₂ O ₃ having a thickness of about 100 nm is formed by sputtering.
In this way, the memory element 3 can be manufactured.

  According to the above-described embodiment, at least one of the ferromagnetic layers 17, 13, and 15 constituting the storage layer 17 or the magnetization fixed layer 31 of the storage element 3 is made of at least one selected from Co and Fe. As a main component, at least one content selected from V, Cr, and Nb is 5 atomic% or more and 20 atomic% or less, so that a high MR ratio can be ensured and spin injection efficiency is achieved. Thus, the current density required for reversing the direction of the magnetization M1 of the storage layer 17 by spin injection can be significantly reduced.

Furthermore, according to the present embodiment, the magnetoresistive change rate (MR ratio) can be increased by using the insulating layer 16 as the intermediate layer as the magnesium oxide layer.
By increasing the MR ratio in this way, it is possible to improve the efficiency of spin injection and reduce the current density required to reverse the direction of the magnetization M1 of the storage layer 17.

  Accordingly, a highly reliable memory that operates stably can be realized, and power consumption can be reduced in the memory including the memory element 3.

Next, as another embodiment of the present invention, a cross-sectional view of a memory element constituting a memory is shown in FIG.
In this storage element 30, a magnetization fixed layer 31 is provided in the lower layer and a magnetization fixed layer 32 is provided in the upper layer with respect to the storage layer 17 in which the direction of the magnetization M1 is reversed by spin injection. In other words, the upper and lower two magnetization fixed layers 31 and 32 are provided for the storage layer 17.

The upper magnetization pinned layer 32 has only a single ferromagnetic layer 20.
An insulating layer 19 serving as a tunnel barrier layer (tunnel insulating layer) is provided between the storage layer 17 and the upper magnetization fixed layer 32. The storage layer 17 and the magnetization fixed layer 32 constitute an MTJ element. Yes.
The antiferromagnetic layer 21 is provided on the magnetization fixed layer 32, and the direction of the magnetization M <b> 20 of the ferromagnetic layer 20 of the magnetization fixed layer 32 is fixed by the antiferromagnetic layer 21.
A cap layer 18 is formed on the antiferromagnetic layer 21.

In the present embodiment, in particular, the ferromagnetic layers constituting the storage layer 17 and the magnetization fixed layers 31 and 32, that is, the storage layer 17, the ferromagnetic layers 13 and 15 of the magnetization fixed layer 31, and the magnetization fixed layer 32. And at least one layer of the ferromagnetic layer 20 having at least one of Co and Fe as a main component and at least one content selected from V, Cr, and Nb is 5 atomic% or more and 20 atomic% or less. To do.
Furthermore, the insulating layers 16 and 19 that are intermediate layers are MgO layers.

  In the ferromagnetic layer having at least one of Co and Fe in the above composition range as a main component and at least one content selected from V, Cr, and Nb being 5 atomic% to 20 atomic%, other elements In addition to iron, cobalt, and gadolin, transition elements such as molybdenum, manganese, copper, niobium, and zirconium, and light elements such as boron and carbon may be included.

  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. Information can be recorded in the storage element 30 by reversing the direction of the magnetization M <b> 1 of 17.

  According to the above-described embodiment, at least one of the ferromagnetic layers 17, 13, 15, and 20 constituting the storage layer 17 or the magnetization fixed layer 31 of the storage element 30 is mainly made of at least one of Co and Fe. The composition is such that at least one content selected from V, Cr, and Nb is 5 atomic% or more and 20 atomic% or less, so that a high MR ratio can be secured and the spin injection efficiency is improved. Thus, the current density required to reverse the direction of the magnetization M1 of the storage layer 17 by spin injection can be significantly reduced.

Furthermore, according to the present embodiment, the magnetoresistive change rate (MR ratio) can be increased by using the insulating layers 16 and 19 as intermediate layers as magnesium oxide layers.
By increasing the MR ratio in this way, it is possible to improve the efficiency of spin injection and reduce the current density required to reverse the direction of the magnetization M1 of the storage layer 17.

  Furthermore, in the present embodiment, the magnetization fixed layers 31 and 32 are provided on the lower layer side and the upper layer side via the insulating layers 16 and 19 with respect to the memory layer 17, respectively. However, the current required to reverse the direction of the magnetization M1 of the storage layer 17 can be reduced.

  Therefore, a highly reliable memory that operates stably can be realized, and power consumption can be reduced in the memory including the memory element 30.

In each of the above embodiments, the present invention is applied to a memory element that records information by spin injection. However, the present invention can be applied to a memory layer by applying a magnetic field (such as a current magnetic field). The present invention can also be applied to a normal MRAM that reverses the direction of magnetization.
Even when the present invention is applied to a normal MRAM, the magnetoresistance change rate (MR ratio) can be increased, so that the read signal intensity is increased, the operation margin of the memory element is increased, and read errors are reduced. Is obtained.

  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 relationship between the addition amount (atomic%) of V or Cr, and a saturation magnetization amount. It is a figure which shows the electronic state density of ACoFe. It is a figure which shows an electronic state density when adding V to BCoFe. It is a figure which shows an electronic state density when adding Cr to CCoFe. It is a schematic block diagram (perspective view) of the memory using the magnetization reversal by spin injection. It is sectional drawing of the memory of FIG. It is the perspective view which showed the structure of the conventional MRAM typically.

Explanation of symbols

  3,30 Memory element, 11 Underlayer, 12, 21 Antiferromagnetic layer, 13, 15, 20 Ferromagnetic layer, 14 Nonmagnetic layer, 16, 19 Insulating layer, 17 Memory layer, 18 Cap layer, 31, 32 Magnetization Fixed layer

Claims (5)

It has a storage layer that holds information according to the magnetization state of the magnetic material,
A magnetization fixed layer is provided via an intermediate layer for the storage layer,
The intermediate layer comprises magnesium oxide;
At least one of the ferromagnetic layers constituting the storage layer or the magnetization fixed layer is composed mainly of at least one selected from Co and Fe, and at least one selected from V, Cr and Nb is 5 atoms. % Or more and 20 atomic% or less. A memory element, comprising:   The memory element according to claim 1, wherein information is recorded by changing a magnetization direction of the memory layer by passing a current in a stacking direction.   At least one of the ferromagnetic layers constituting the storage layer or the magnetization fixed layer is mainly composed of CoFeB and contains at least one selected from V, Cr, and Nb in a range of 5 atomic% to 20 atomic%. The memory element according to claim 1, wherein: 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 magnetization fixed layer is provided via an intermediate layer with respect to the storage layer, the intermediate layer is made of magnesium oxide, and the storage layer or the ferromagnetic layer constituting the magnetization fixed layer At least one layer is composed of at least one selected from Co and Fe as a main component and contains at least one selected from V, Cr and Nb in an amount of 5 atomic% to 20 atomic%.
The memory, wherein the storage element is disposed near an intersection of the two types of wiring and between the two types of wiring.   5. The storage element according to claim 4, wherein the storage element is configured to record information on the storage layer by changing a magnetization direction of the storage layer by passing a current in a stacking direction. The listed memory.

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