JP2006108316A - Memory element and memory - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a memory element capable of reducing a current value required for writing by improving spin injection efficiency. <P>SOLUTION: Magnetization fixed layers 31 and 33 are provided above and below a memory layer 32 which holds information according to magnetizing state of a magnetic body, with intermediate layers 14 and 18 in-between. Directions of magnetization M13 and M19 of ferromagnetic layers 13 and 19 of the magnetization fixed layers 31 and 33 which are the closest to the memory layer 32 are almost parallel to each other. The memory layer 32 consists of a plurality of ferromagnetic layers 15 and 17 that are laminated through non-magnetic conductor layer 16. The magnetization M17 of the ferromagnetic layer 17 which is the top layer in the memory layer 32 is not parallel to the magnetization M15 of the lowest ferromagnetic layer 15. In the memory layer 3, a current is made to flow in laminating direction to change directions of magnetization M15 and M17 of the memory layer 32, and information is recorded in the memory layer 32. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

In information devices such as computers, DRAMs with high speed and high density are widely used as random access memories.
However, since DRAM is a volatile memory in which information disappears when the power is turned off, a nonvolatile memory in which information does not disappear is desired.

  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 being developed (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.

A schematic view (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.4 and FIG.5. 4 is a perspective view, and FIG. 5 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 the figure.
The drain region 58 is formed in common with the left and right selection transistors in FIG. 4, 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.

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 a memory configured to use magnetization reversal by spin injection, in order to further suppress power consumption, it is necessary to improve spin injection efficiency and reduce input current.

In order to increase the read signal, it is necessary to secure a large magnetoresistance change rate. For this purpose, it is effective to use the intermediate layer in contact with both sides of the storage layer as a tunnel barrier layer.
In this case, since the withstand voltage of the barrier layer is limited, the current at the time of spin injection needs to be suppressed also from this point.

Therefore, as a solution to suppress the current at the time of spin injection, the storage element is a stacked structure of a fixed magnetization layer / intermediate layer / storage layer / intermediate layer / magnetization fixed layer, and a fixed magnetization layer provided above and below the storage layer. There has been proposed a configuration in which the magnetization direction of each is opposite (see Patent Document 2 and Patent Document 3).
In Patent Document 2, it is shown that the spin injection efficiency can be doubled by making the magnetization directions of the upper and lower magnetization fixed layers opposite to each other.

Nikkei Electronics 2001.1.22 (pages 164-171) JP 2003-17782 A US Patent Publication No. 2004/0027853 JP 2004-193595 A

However, in the configurations proposed in Patent Document 2 and Patent Document 3, in order to reverse the magnetization directions of the magnetization fixed layers provided above and below the storage layer, the materials and films of the respective magnetization fixed layers are used. It is necessary to make the configuration different from that adopted in a normal MTJ element.
For this reason, there exists a fault that a film | membrane structure becomes complicated or a manufacturing process becomes complicated. For example, in order to reverse the magnetization directions of the upper and lower magnetization fixed layers, annealing in a magnetic field under a plurality of different conditions is required, and the manufacturing process becomes complicated.

The direction of the magnetization rotation torque due to the current is determined by the relative angle between the direction of magnetization of the surface from which the current of the storage layer flows and the direction of magnetization of the surface of the fixed magnetization layer facing it, and the direction of the current viewed from the storage layer.
In order to improve the spin injection efficiency, it is necessary to match the direction of the magnetization rotation torque received from the magnetization fixed layer below the storage layer with the direction of the magnetization rotation torque received from the magnetization fixed layer above the storage layer.
An example will be described. When a write current is passed from the lower pinned layer to the upper pinned layer, the direction of the current seen from the storage layer flows from the upper part and flows out from the lower part. The direction of is reversed. When the magnetizations of the upper and lower surfaces of the storage layer are in the same direction and the magnetizations of the surfaces facing the storage layer of the upper and lower magnetization fixed layers are in the same direction, as seen from the storage layer at the upper and lower interfaces of the storage layer as described above Since the direction of the current is opposite, the magnetization rotation torque cancels out.
For these reasons, in order to align the direction of the magnetization rotation torque by the current, as described above, when the magnetization directions of the magnetization fixed layers provided above and below the storage layer are antiparallel, a plurality of storage layers are provided. It is necessary to make the direction of magnetization of the uppermost layer of the magnetic layer constituting the storage layer and the direction of magnetization of the lowermost layer parallel to each other.
That is, the storage layer requires two magnetic layers coupled so that the magnetization directions are parallel to each other, or an odd number of three or more magnetic layers.

In order to couple the two magnetic layers so that the magnetization directions are parallel to each other, the thickness of the intermediate layer sandwiched between the two magnetic layers is at least several nm or less, generally 0 It is necessary to suppress it to 5 nm or less. If the thickness of the intermediate layer is reduced in this way, it becomes difficult to produce the memory layer, and the spin-polarized current is retained, causing interference between the magnetic layers above and below the intermediate layer, thereby increasing the write current. Will occur.
On the other hand, when the storage layer is composed of three or more magnetic layers, the total film thickness of the entire storage layer is increased, and the write current is proportional to the volume of the storage layer, which increases the write current.

（ただし、α：記憶層のダンピング定数、Ｈ_ｋ：記憶層の一軸異方性磁界、Ｍ_ｓ：記憶層の飽和磁化、η：スピン注入係数） By the way, it has been theoretically derived that a theoretical formula for giving a threshold current for causing magnetization reversal in the spin injection phenomenon is as shown in the following formula 1. When this formula is used, an increase in the damping constant is a threshold value. The increase in current is calculated theoretically (see JZ Sun, Phys. Rev. B, Vol. 62, p. 570, 2000).

(Where α is the damping constant of the storage layer, H _{k is} the uniaxial anisotropic magnetic field of the storage layer, M _{s is} the saturation magnetization of the storage layer, η is the spin injection coefficient)

And when it is going to implement | achieve the structure proposed in the said patent document 2, etc., the intermediate | middle layer and magnetization fixed layer which are in contact with the memory | storage layer are called spin pumping with respect to the damping constant of a memory | storage layer. It is reported that the damping constant of the memory layer increases depending on the material constituting the intermediate layer and the magnetization fixed layer (for example, Yaroslav et al., Phys. Rev. B, Vol. 66, p.224403, 2002, etc.).
For this reason, even if the configuration proposed in Patent Document 2 or the like is simply manufactured, the spin injection efficiency is not improved, and depending on the film configuration, the damping constant of the memory layer is increased. On the contrary, the spin injection efficiency is lowered.

  In order to solve the above-described problems, the present invention provides a memory element that can reduce a current value required for writing by improving spin injection efficiency, and a memory including the memory element. .

  The memory element of the present invention has a memory layer that retains information by the magnetization state of a magnetic material, and a magnetization pinned layer is provided above and below the memory layer via intermediate layers, respectively, and the magnetization pinned above and below the memory layer is fixed. In each of the layers, the magnetization directions of the ferromagnetic layers closest to the storage layer are substantially parallel, and the storage layer is composed of a plurality of ferromagnetic layers stacked via a nonmagnetic conductor layer. The magnetization directions of the ferromagnetic layer and the lowermost ferromagnetic layer are antiparallel to each other, and by passing a current in the stacking direction, the magnetization direction of the storage layer changes, and information is transferred to the storage layer. Recording is performed.

According to the configuration of the above-described storage element of the present invention, the storage layer that holds information by the magnetization state of the magnetic material has a storage layer, and a fixed magnetization layer is provided above and below the storage layer via an intermediate layer, By flowing current in the stacking direction, the direction of magnetization of the storage layer changes, and information is recorded on the storage layer. Therefore, it is possible to record information by spin injection by flowing current in the stacking direction. it can.
Further, in the fixed magnetization layers above and below the storage layer, the magnetization directions of the ferromagnetic layers closest to the storage layer are approximately parallel, and the multiple layers of the storage layers are stacked via the nonmagnetic conductor layers. It consists of a magnetic layer, and the magnetization direction of the uppermost ferromagnetic layer and the lowermost ferromagnetic layer of the storage layer is antiparallel to each other. By adding the spin injection effect in the layer and the spin injection effect in the uppermost ferromagnetic layer and the upper magnetization fixed layer of the storage layer, the spin injection efficiency can be greatly increased.
Thereby, the amount of current (threshold current) required to reverse the magnetization direction of the storage layer by spin injection can be reduced.

  The memory according to 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 types of wirings that intersect each other, and the storage element is above and below the storage layer via an intermediate layer. Magnetization fixed layers are provided, and in the magnetization fixed layers above and below the storage layer, the magnetization directions of the ferromagnetic layers closest to the storage layer are substantially parallel, and the storage layers are stacked via the nonmagnetic conductor layers. Composed of a plurality of ferromagnetic layers, the uppermost ferromagnetic layer and the lowermost ferromagnetic layer of the storage layer are antiparallel to each other, and the current flows in the stacking direction by flowing current in the stacking direction. Information is recorded on the storage layer by changing the direction of magnetization. A storage element is arranged near the intersection of two types of wiring and between the two types of wiring, and is stored through the two types of wiring. A current in the stacking direction flows through the element.

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.
In addition, the amount of current (threshold current) required to reverse the magnetization direction of the storage layer of the storage element by spin injection can be reduced.

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.

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 magnetization direction of the storage layer of the storage element by the spin injection described above. The storage layer is composed of a magnetic material such as a ferromagnetic layer, and holds information by the magnetization state (magnetization direction) of the magnetic material.

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.

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.
In addition, the current magnetic field generating wiring (105 in FIG. 6) required for a normal MRAM is not necessary, and this is advantageous in terms of integration compared to a normal MRAM.

In the present invention, a storage element having a magnetic layer (storage layer) capable of retaining information according to a magnetization state and a magnetization fixed layer in which the magnetization direction is fixed is configured.
Magnetization fixed layers are provided on the upper and lower sides of the storage layer, and magnetoresistive elements are formed on the upper and lower sides. That is, a stacked structure of a magnetization fixed layer / intermediate layer / storage layer / intermediate layer / magnetization fixed layer is formed. The magnetization direction of the fixed layer is made substantially parallel.
Further, the storage layer is composed of a plurality of ferromagnetic layers stacked via a nonmagnetic conductor layer, and the uppermost ferromagnetic layer and the lowermost strong layer among the plurality of ferromagnetic layers of the storage layer. The magnetic layer has a configuration in which magnetization directions are antiparallel to each other.

  For example, when the storage layer is composed of two ferromagnetic layers stacked via a nonmagnetic conductor layer, the magnetization direction of the upper ferromagnetic layer and the magnetization direction of the lower ferromagnetic layer are different from each other. , Set to be anti-parallel to each other.

  In this way, in order to make the magnetization directions of the two ferromagnetic layers stacked via the nonmagnetic conductor layer antiparallel to each other, the two ferromagnetic layers are interposed via the nonmagnetic conductor layer. What is necessary is just to comprise so that it may couple | bond magnetically.

  As a method of magnetically coupling two ferromagnetic layers, a method using magnetostatic coupling by applying a leakage magnetic field generated from the end of each ferromagnetic layer to the opposing ferromagnetic layers, A method using interlayer exchange coupling that couples antiferromagnetically through a nonmagnetic layer can be considered.

Then, the material and film thickness of the nonmagnetic conductor layer are selected so that the ferromagnetic layers constituting the storage layer are magnetically coupled and the magnetization directions of the ferromagnetic layers are reversed at the same time.
With this configuration, each ferromagnetic layer of the storage layer is physically separated by the nonmagnetic conductor layer, but is magnetically coupled, so that the magnetization of all the ferromagnetic layers is recorded when information is recorded. Are reversed all at once.

In addition, the nonmagnetic conductor layer sandwiched between the ferromagnetic layers of the storage layer is preferably made of a material that easily causes spin diffusion in order to have a function of temporarily resetting the spin-polarized current, and has a film thickness of spin. It is desirable to make it larger than the diffusion length.
Specific materials for the nonmagnetic conductor layer include Mg, Al, Si, Ge, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Cu, Ag, Au, Ru, and Rh. A material mainly composed of one selected element or an alloy thereof can be used.

Since Cu, Al, and the like have a long spin diffusion length of 100 nm or more, if the film thickness is made larger than the spin diffusion length, the magnetic coupling between the ferromagnetic layers of the storage layer becomes weak. In addition, the thickness of the entire memory element is increased.
However, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Re, Os, Ir, Mn, Gd, etc. that can easily cause spin diffusion even with materials such as Cu, Au, Ag, Al, etc. By adding this element, the spin diffusion length is shortened, and the film thickness of the nonmagnetic conductor layer can be reduced to several nm.

  More preferably, the non-magnetic conductor layer sandwiched between the ferromagnetic layers of the storage layer is made of a material having a spin diffusion length of 50 nm or less and has a thickness equal to or larger than the spin diffusion length. To do.

Here, for example, when considering a case where a current is input from the lower layer side to the storage layer, by adopting the nonmagnetic conductor layer having the above-described configuration, the spin polarization state of the current is reset on the upper surface of the conductor layer, A combination of the lower half magnetization fixed layer and the storage layer (magnetoresistance effect element) and a combination of the upper half storage layer and the magnetization fixed layer (magnetoresistance effect element) are connected in series.
Similarly, for example, when a current is input to the storage layer from the upper layer side, the spin-polarized state of the current is reset on the lower surface of the conductor layer by adopting the nonmagnetic conductor layer having the above-described configuration. Thus, the combination of the upper half of the magnetization fixed layer and the storage layer and the combination of the lower half of the storage layer and the magnetization fixed layer are connected in series.

Therefore, in any case of the current direction described above, the spin injection effect is generated in the magnetoresistive effect elements in the lower half and the upper half, and the spin injection effect is added. Will increase.
Thereby, the write current can be reduced.

By the way, when the magnetization fixed layer is composed of an antiferromagnetic layer and a ferromagnetic layer in contact with the antiferromagnetic layer, annealing is performed in a magnetic field in order to set the magnetization of the magnetization fixed layer in a desired direction. .
In the configurations proposed in Patent Document 2 and Patent Document 3 described above, in the magnetization fixed layers provided above and below the storage layer, the magnetization directions of the ferromagnetic layers closest to the storage layer are antiparallel to each other. Therefore, it is necessary to devise such that at least one magnetization fixed layer is composed of two or more ferromagnetic layers, or annealing in a magnetic field is performed a plurality of times under different conditions. It was complicated.

On the other hand, when the magnetization direction of the ferromagnetic layer closest to the storage layer is substantially parallel in the upper and lower magnetization fixed layers of the storage layer as in the present invention, the upper and lower magnetization fixed layers are both A simple configuration including an antiferromagnetic layer and a single ferromagnetic layer can be realized.
Then, the same material is used for the antiferromagnetic layers of the upper and lower fixed magnetization layers, and after each layer of the memory element is formed, annealing in a magnetic field is performed once, so that the magnetization directions of the upper and lower fixed magnetization layers are predetermined. Can be oriented.

In addition, if the magnetization directions of the upper and lower layers of the storage layer are made anti-parallel by making the magnetization directions of the magnetization fixed layers above and below the storage layer substantially parallel, the upper and lower magnetoresistive effect elements spin. By adding the injection effect, the spin injection efficiency can be improved.
If the storage layer has a structure in which two ferromagnetic layers are magnetically coupled via a nonmagnetic conductor layer, the magnetization directions of the uppermost layer and the lowermost layer of the storage layer can be relatively easily reversed. Can be parallel.
Therefore, there is also an advantage that it is easy to configure the storage layer with two ferromagnetic layers by making the magnetization directions of the magnetization fixed layers above and below the storage layer substantially parallel.

In particular, the total thickness of the storage layer is minimized by providing the storage layer with a non-magnetic conductor layer of sufficient thickness that can reset the spin-polarized current between two ferromagnetic layers. Thus, the influence of an increase in write current due to an increase in the volume of the storage layer can be minimized.
At this time, there is an effect that the magnetization direction of these ferromagnetic layers can be easily made antiparallel using exchange interaction or magnetostatic coupling between the ferromagnetic layers.

In the present invention, the storage layer may have a configuration in which three or more ferromagnetic layers are laminated via a nonmagnetic conductor layer.
In this case, among the three or more ferromagnetic layers, if the magnetization direction of the lowermost ferromagnetic layer and the uppermost ferromagnetic layer are antiparallel, spins in the upper and lower magnetoresistive effect elements By adding the injection effect, the spin injection efficiency can be improved. That is, the magnetization direction of the intermediate ferromagnetic layer is arbitrary, and the magnetization directions of the intermediate ferromagnetic layer and the ferromagnetic layer facing each other with the nonmagnetic conductor layer interposed therebetween may be substantially parallel.

The other configuration of the storage element can be the same as a conventionally known configuration of the storage element that records information by spin injection.
The magnetization fixed layers above and below the storage layer have a configuration in which the magnetization direction is fixed only by the ferromagnetic layer or by using the antiferromagnetic coupling between the antiferromagnetic layer and the ferromagnetic layer.
In addition, the magnetization fixed layers above and below the storage layer have a structure composed of a single ferromagnetic layer or a laminated ferrimagnetic structure in which a plurality of ferromagnetic layers are stacked via a nonmagnetic layer.
When the magnetization pinned layer has a laminated ferrimagnetic structure, the sensitivity of the magnetization pinned layer to the external magnetic field can be reduced. Therefore, unnecessary magnetization fluctuations in the magnetization pinned layer due to the external magnetic field are suppressed, and the memory element operates stably. Can be made.

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

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

The storage element 3 is disposed between the source region 7 and the other address wiring (for example, bit line) 6 disposed above and extending in the left-right direction in the drawing. The storage element 3 has a storage layer composed of a ferromagnetic layer whose magnetization direction is reversed by spin injection.
The storage element 3 is arranged near the intersection of the two types of address lines 1 and 6.
The storage element 3 is connected to the bit line 6 and the source region 7 through upper and lower contact layers 4, respectively.
As a result, a current in the vertical direction 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 first magnetization fixed layer 31 in the lower layer and a second magnetization fixed layer 33 in the upper layer with respect to the storage layer 32 whose magnetization direction is reversed by spin injection. Is provided. That is, the upper and lower two magnetization fixed layers 31 and 33 are provided for the storage layer 32.
The antiferromagnetic layer 12 is provided in the first magnetization fixed layer 31, and the direction of the magnetization M <b> 13 of the ferromagnetic layer 13 of the first magnetization fixed layer 31 is fixed by the antiferromagnetic layer 12. The antiferromagnetic layer 20 is provided in the second magnetization fixed layer 33, and the direction of the magnetization M 19 of the ferromagnetic layer 19 of the second magnetization fixed layer 32 is fixed by the antiferromagnetic layer 20.
Between the storage layer 32 and the lower first magnetization fixed layer 31, the insulating layer 14 serving as a tunnel barrier layer (tunnel insulation layer) is provided. By the storage layer 32 and the first magnetization fixed layer 31, An MTJ element is configured.
A conductive nonmagnetic spacer layer 18 is provided between the storage layer 32 and the upper second magnetization fixed layer 33, and the storage layer 32 and the second magnetization fixed layer 33 constitute a GMR element. ing.

  An underlayer 11 is formed under the antiferromagnetic layer 12, and a cap layer 21 is formed over the antiferromagnetic layer 20.

The material of the ferromagnetic layers 13 and 19 of the magnetization fixed layers 31 and 33 is not particularly limited, but 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 and C can also be included.
As a material of the antiferromagnetic layers 12 and 20, an alloy of a metal element such as iron, nickel, platinum, iridium, and rhodium and manganese, cobalt oxide, nickel oxide, or the like can be used.

  In general, the value of the saturation magnetization Ms of the ferromagnetic layers 15 and 17 of the magnetization fixed layers 31 and 33 is appropriately in the range of 200 emu / cc to 2000 emu / cc.

In the present embodiment, in particular, the storage layer 32 of the storage element 3 is stacked with the nonmagnetic layer 16 sandwiched between the two ferromagnetic layers 15 and 17, and the two ferromagnetic layers 15 and 17 are formed. It is a magnetically coupled configuration.
Since the ferromagnetic layers 15 and 17 of the storage layer 32 are magnetically coupled, the magnetization M15 of the ferromagnetic layer 15 and the magnetization M17 of the ferromagnetic layer 17 are opposite to each other.

  In order to magnetically couple the two ferromagnetic layers 15 and 17 of the storage layer 32, for example, a configuration in which the two ferromagnetic layers 15 and 17 are antiferromagnetically coupled via the nonmagnetic layer 16, or The two ferromagnetic layers 15 and 17 may be configured to be magnetically coupled by exchange interaction via the nonmagnetic layer 16.

  Furthermore, in the present embodiment, the magnetization M13 of the ferromagnetic layer 13 of the first magnetization fixed layer 31 is rightward, and the magnetization M19 of the ferromagnetic layer 19 of the second magnetization fixed layer 32 is rightward. Are in a substantially parallel orientation.

As described above, the magnetization M15 of the ferromagnetic layer 15 of the storage layer 32 and the magnetization M17 of the ferromagnetic layer 17 are opposite to each other, and in the magnetization fixed layers 31 and 33 sandwiching the storage layer 32, the storage layer Since the magnetizations M13 and M19 of the ferromagnetic layers 13 and 19 facing 32 are in a substantially parallel direction, the spin injection efficiency can be increased as described above.
As a result, the amount of current necessary for reversing the directions of the magnetizations M15 and M17 of the storage layer 32 by spin injection can be reduced.

  The material of the ferromagnetic layers 15 and 17 of the memory layer 32 is not particularly limited, but 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 and C can also be contained. Alternatively, the ferromagnetic layers 15 and 17 may be configured by directly stacking a plurality of films of different materials (not via a nonmagnetic layer) such as a CoFe / NiFe / CoFe stacked film.

  As the material of the nonmagnetic layer 16 constituting the storage layer 32, ruthenium, copper, chromium, gold, silver, or the like can be used. Although the film thickness of the nonmagnetic layer 16 varies depending on the material, it is preferably used in the range of approximately 0.5 nm to 2.5 nm.

  In the memory element 3 of the present embodiment, the base layer 11 to the cap layer 21 are continuously formed in a vacuum apparatus, and then the pattern of the memory element 3 is formed by fine processing such as reactive ion etching or ion milling. By doing so, it can be manufactured.

According to the above-described embodiment, since the storage layer 32 has a configuration in which the two ferromagnetic layers 15 and 17 are magnetically coupled, the direction of the magnetization M15 of the lower ferromagnetic layer 15 and the upper layer The directions of the magnetization M17 of the ferromagnetic layer 17 are antiparallel to each other.
Also, in the magnetization fixed layers 31 and 33 sandwiching the storage layer 32, the magnetizations M13 and M19 of the ferromagnetic layers 13 and 19 closest to the storage layer 32 (ferromagnetic layers facing the storage layer 32) are substantially parallel to each other. As a result, the spin injection effect in the lower first magnetization fixed layer 31 and the lower ferromagnetic layer 15 of the storage layer 32, and the upper second ferromagnetic layer 17 and the upper second magnetization fixed in the storage layer 32 are achieved. The spin injection effect in the layer 33 is added.
Thereby, since the spin injection efficiency can be increased, the amount of current required for reversing the directions of the magnetizations M15 and M17 of the storage layer 32 by spin injection can be 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.

Next, as another embodiment of the present invention, a cross-sectional view of a memory element constituting a memory is shown in FIG.
The memory element 30 is different from the memory element 3 shown in FIG. 2 in that the first magnetization fixed layer 31 and the second magnetization fixed layer 33 both have a laminated ferrimagnetic structure.
Specifically, the first magnetization fixed layer 31 has a configuration in which two ferromagnetic layers 22 and 24 are stacked via a nonmagnetic layer 23 and are antiferromagnetically coupled. Reference numeral 33 denotes a configuration in which two ferromagnetic layers 25 and 27 are stacked via a nonmagnetic layer 26 and antiferromagnetically coupled.

Since each of the ferromagnetic layers 22 and 24 of the first pinned magnetization layer 31 has a laminated ferrimagnetic structure, the magnetization M22 of the ferromagnetic layer 22 faces right and the magnetization M24 of the ferromagnetic layer 24 faces left. Are in opposite directions.
As a result, magnetic fluxes leaking from the ferromagnetic layers 22 and 24 of the first magnetization fixed layer 31 cancel each other.

Similarly, since the ferromagnetic layers 25 and 27 of the second magnetization fixed layer 33 have a laminated ferrimagnetic structure, the magnetization M25 of the ferromagnetic layer 25 is directed leftward, and the magnetization M27 of the ferromagnetic layer 27 is directed rightward. They are in opposite directions.
As a result, magnetic fluxes leaking from the ferromagnetic layers 25 and 27 of the second magnetization fixed layer 33 cancel each other.

  The nonmagnetic layers 23 and 26 constituting the first magnetization fixed layer 31 and the second magnetization fixed layer 33 can use materials such as Ru, Cu, and Rh, and the film thickness is 0.5 nm. More than 4 nm is suitable.

  Furthermore, in the present embodiment, the magnetization M24 of the ferromagnetic layer 24 closest to the storage layer 32 in the first magnetization fixed layer 31 is facing left, and the storage layer 32 is the most in the second magnetization fixed layer 33. The magnetization M25 of the near ferromagnetic layer 25 is directed leftward, and these are substantially parallel.

Other configurations are the same as those of the memory element 3 shown in FIG.
That is, the storage layer 32 has a configuration in which the two ferromagnetic layers 15 and 17 are magnetically coupled via the nonmagnetic layer 16.

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 directions of the magnetizations M15 and M17 of 32.

  Also in the present embodiment, the storage layer 32 has a configuration in which the two ferromagnetic layers 15 and 17 are magnetically coupled, and each of the magnetization fixed layers 31 and 33 sandwiching the storage layer 32 stores data. Since the magnetizations M24 and M25 of the ferromagnetic layers 24 and 25 closest to the layer 32 (the ferromagnetic layers facing the storage layer 32) are in a substantially parallel orientation, the spin injection efficiency is the same as in the previous embodiment. Therefore, the amount of current necessary for reversing the directions of the magnetizations M15 and M17 of the storage layer 32 by spin injection can be reduced.

In other words, the amount of current necessary for recording information in the memory element 30 can be reduced, and power consumption can be reduced in a memory including the memory element 30.
Therefore, it is possible to realize a memory with low power consumption that has not been conventionally available.

(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 FIG. 1 and FIG. 4, the memory includes a semiconductor circuit for switching in addition to the memory element. Here, for the purpose of examining the magnetoresistive characteristics of the memory layer, the memory is stored. The study was performed using a wafer on which only elements were formed.

Example 1
A thermal oxide film having a thickness of 2 μm was formed on a silicon substrate having a thickness of 0.575 mm, and the memory element 3 having the configuration shown in FIG. 2 was formed thereon.
Specifically, in the memory element 3 having the configuration shown in FIG. 2, the material and thickness of each layer are as follows: the base film 11 is a Ta film with a thickness of 3 nm, and the antiferromagnetic layers 12 and 20 are PtMn films with a thickness of 20 nm. The ferromagnetic layer 13 constituting the first magnetization fixed layer 31 is a CoFe film having a thickness of 5 nm, the insulating layer 14 serving as a tunnel insulating layer is an aluminum oxide film obtained by oxidizing an Al film having a thickness of 0.5 nm, and a laminated ferri structure The ferromagnetic layers 15 and 17 constituting the storage layer 32 are 2 nm thick CoFe films, the nonmagnetic layer 16 constituting the laminated ferrimagnetic storage layer 32 is 3.6 nm thick Ru film, and the nonmagnetic spacer layer 18. Is a Cu film having a film thickness of 6 nm, the ferromagnetic layer 19 constituting the second magnetization fixed layer 33 is a CoFe film having a film thickness of 2.5 nm, and the cap layer 21 is a Ta film having a film thickness of 5 nm. And a film not shown between the antiferromagnetic layer 12 and Provided 100nm of the Cu film (that becomes a word line to be described later) to form each layer.
In the above film configuration, the composition of the PtMn film was Pt50Mn50 (atomic%), the composition of the CoFe film was Co90Fe10 (atomic%), and the composition of the NiFe film was Ni80Fe20 (atomic%).
Each layer other than the insulating layer 16 made of an aluminum oxide film was formed using a DC magnetron sputtering method.
The insulating layer 16 made of an aluminum oxide (Al—O _x ) film is formed by first depositing a metal Al film to a thickness of 0.5 nm by the DC sputtering method, and then setting the oxygen / argon flow ratio to 1: 1 and the chamber gas pressure to The metal Al layer was oxidized by a natural oxidation method at 10 Torr. The oxidation time was 10 minutes.
Further, after each layer of the memory element 3 was formed, heat treatment was performed at 10 kOe · 270 ° C. for 4 hours in a heat treatment furnace in a magnetic field, and ordered heat treatment was performed on the PtMn films of the antiferromagnetic layers 12 and 20.

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

Thereafter, a mask of the pattern of the memory element 3 was formed by an electron beam drawing apparatus, and selective etching was performed on the laminated film to form the memory element 3. Except for the memory element 3 portion, the etching was performed up to the Cu layer of the word line.
In addition, in order to generate the spin torque necessary for the magnetization reversal, it is necessary to flow a sufficient current through the storage element for the characteristic evaluation storage element, and thus it is necessary to suppress the resistance value of the tunnel insulating layer. Therefore, the pattern of the memory element 3 is an ellipse having a minor axis of 0.09 μm and a major axis of 0.18 μm, and the area resistance value (Ωμm ² ) of the memory element 3 is set to 10Ωμm ² .

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 bit line to be an upper electrode and a measurement pad were formed using photolithography.
Thus, the sample of Example 1 was produced.

(Example 2)
3, the ferromagnetic layer 22 constituting the first magnetization fixed layer 31 is a CoFe film having a thickness of 2 nm, and the ferromagnetic layer 24 constituting the first magnetization fixed layer 31 is a film. The CoFe film having a thickness of 4 nm, the ferromagnetic layers 25 and 27 constituting the second magnetization fixed layer 33 being the CoFe film having a thickness of 2.5 nm, and the nonmagnetic layers 23 and 26 constituting the magnetization fixed layers 31 and 33 being the film thickness A sample of Example 2 was prepared in the same manner as in Example 1 except that a 0.8 nm Ru film was selected.

(Comparative Example 1)
Instead of the memory layer 32 of the configuration of the memory element 30 in FIG. 3, a memory layer made of a single ferromagnetic layer is provided, this ferromagnetic layer is selected as a CoFe film having a thickness of 4 nm, and the second magnetization fixed The layer 33 is composed of a single ferromagnetic layer, and this ferromagnetic layer is selected as a CoFe film having a film thickness of 2.5 nm. The other structure is the same as that of Example 2, and the sample of Comparative Example 1 is manufactured. did.
That is, the sample of Comparative Example 1 has a laminated ferrimagnetic structure in which the magnetization fixed layer 31 below the storage layer 32 is composed of two ferromagnetic layers 22 and 24, as shown in FIG. 7A. Each of the magnetization fixed layers 33 above the layer 32 is composed of single ferromagnetic layers 32 and 19.
In addition, as shown in FIG. 7A, in the first magnetization fixed layer 31 and the second magnetization fixed layer 33, the directions of the magnetizations M24 and M19 of the ferromagnetic layers 24 and 19 closest to the storage layer 32 are antiparallel. Therefore, it can be said that it is the structure similar to the structure described in the said patent document 2 or the said patent document 3. FIG.

(Comparative Example 2)
In the configuration of the memory element 30 in FIG. 3, the ferromagnetic layer 22 constituting the first magnetization fixed layer 31 is selected as a CoFe film having a thickness of 1.5 nm, and the ferromagnetic layer 24 is selected as a CoFe film having a thickness of 3.5 nm. The second fixed layer 33 is composed of a single ferromagnetic layer, and this ferromagnetic layer is selected as a CoFe film having a thickness of 4 nm. A sample of was prepared.
That is, in the sample of Comparative Example 2, as shown in FIG. 7B, the film thicknesses of the two ferromagnetic layers 22 and 24 of the first magnetization fixed layer 31 below the storage layer 17 are different. The combined magnetization of the fixed layer 31 does not become zero (M24> M22), and the ferromagnetic layers 24 and 19 of the first magnetization fixed layer 31 and the second magnetization fixed layer 33 that are closest to the storage layer 32 respectively. In this configuration, the directions of the magnetizations M24 and M19 are antiparallel.

(Comparative Example 3)
Each layer up to the tunnel insulating layer 14 is configured in the same manner as in Example 2, and a storage layer made of a CoFe film having a thickness of 4 nm and a cap layer made of a Ta film having a thickness of 5 nm are formed thereon. A sample was prepared.
That is, the sample of Comparative Example 3 has a configuration of a normal spin injection storage element in which the magnetization fixed layer is provided only on one side of the storage layer.

The characteristics of the samples of these Examples and Comparative Examples were evaluated as follows.
Prior to the measurement, in order to control the positive and negative values of the reversal current to be symmetrical, a magnetic field can be applied to the storage element from the outside. In addition, the amount of current flowing through the memory element was set to 1 mA within a range where the insulating layer 16 was not broken.

(Reverse current value measurement)
A current was passed through the memory element, and then the resistance value of the memory element was measured. When measuring the resistance value of the memory element, the temperature was set to room temperature 25 ° C. and the bias voltage applied to the word line terminal and the bit line terminal was adjusted to 10 mV. Further, the resistance value of the memory element was measured by changing the amount of current flowing through the memory element, and a resistance-current curve was obtained from the measurement result. From this resistance-current curve, a current value at which the resistance value changes was obtained, and this was set as an inversion current value for reversing the direction of magnetization. In addition, the measurement which obtains this resistance-current curve was performed about the electric current of both polarities (a plus direction and a minus direction), and obtained the inversion current value of both polarities.

  The results obtained are summarized in Table 1.

Table 1 shows that Example 1 and Example 2 can reduce a magnetization reversal current to 0.4 mA or less.
On the other hand, in Comparative Examples 1 to 3, the magnetization reversal current is as large as 0.6 mA to 0.8 mA.
That is, as in Example 1 and Example 2, the configuration of the memory element of the present invention can reduce the inversion current value to about half that of the comparative example (which is a normal configuration). .
Therefore, by using the structure of the memory element of the present invention, information can be written to the memory layer with a current amount of 0.5 mA or less, and an unprecedented low power consumption type memory can be realized. Is possible.

  In each of the embodiments described above, the GMR element is formed by providing the nonmagnetic layer spacer layer 18 between the storage layer 32 and the upper second magnetization fixed layer 33. A tunnel insulating layer may be provided between the upper layer and the upper magnetization fixed layer to form a TMR element, and the upper and lower magnetoresistive elements may be composed of TMR elements.

  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 schematic block diagram (perspective view) of a memory using magnetization reversal by spin injection. FIG. 5 is a cross-sectional view of the memory of FIG. 4. It is the perspective view which showed the structure of the conventional MRAM typically. A is a cross-sectional view of a memory element of Comparative Example 1. FIG. B is a cross-sectional view of a memory element of Comparative Example 2. FIG.

Explanation of symbols

  3, 30 Memory element, 11 Underlayer, 12, 20 Antiferromagnetic layer, 13, 15, 17, 19, 22, 24, 25, 27 Ferromagnetic layer, 14 Tunnel insulating layer, 16, 23, 26 Nonmagnetic layer , 18 Nonmagnetic spacer layer, 21 Cap layer, 31 First magnetization fixed layer, 32 Storage layer, 33 Second 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 above and below the storage layer via an intermediate layer, respectively.
In the magnetization fixed layers above and below the storage layer, the magnetization directions of the ferromagnetic layers closest to the storage layer are substantially parallel,
The storage layer is composed of a plurality of ferromagnetic layers stacked via a nonmagnetic conductor layer,
The uppermost ferromagnetic layer and the lowermost ferromagnetic layer of the storage layer have magnetization directions antiparallel to each other,
The storage element is characterized in that 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.   The plurality of ferromagnetic layers of the storage layer are magnetically coupled to each other so that the magnetization directions of the upper and lower ferromagnetic layers are antiparallel to each other through exchange interaction acting between the ferromagnetic layers. The memory element according to claim 1.   The ferromagnetic layers of the recording layers of the storage layer are antiferromagnetically acting between the ferromagnetic layers by mutually applying a magnetic field from the magnetic poles generated at the ends of the ferromagnetic layers. 2. The memory element according to claim 1, wherein the upper and lower ferromagnetic layers are coupled so as to be antiparallel to each other via magnetostatic coupling.   The nonmagnetic conductor layer of the memory layer is selected from Mg, Al, Si, Ge, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Cu, Ag, Au, Ru, and Rh. The memory element according to claim 1, wherein the memory element is made of a material containing one or more elements as a main component or a material containing an alloy of these elements as a main component. 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 above and below the storage layer via an intermediate layer, and in the magnetization fixed layer above and below the storage layer, the magnetization of the ferromagnetic layer closest to the storage layer, respectively. The storage layer is composed of a plurality of ferromagnetic layers stacked via a nonmagnetic conductor layer, and the uppermost ferromagnetic layer and the lowermost ferromagnetic layer of the storage layer, However, the magnetization directions are antiparallel to each other, 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.
The memory is characterized in that the memory element is arranged near an intersection of the two types of wiring and between the two types of wiring, and the current in the stacking direction flows through the memory element through the two types of wiring.

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