JP2003273420A - Tunnel magneto-resistance effect element and method of manufacturing the same, and magnetic memory device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress deterioration in the rate of change in resistance due to heat treatment in a semiconductor circuit manufacturing process or the like. <P>SOLUTION: A tunnel magneto-resistance effect element includes a ferromagnetic tunnel junction 9 which is formed such that a tunnel barrier layer 6 is interposed between a pair of ferromagnetic layers 5 and 7. At least either of the ferromagnetic layers 5 and 7 includes an intermetallic compound exhibiting ferromagnetic. The intermetallic compound is expressed by a chemical formula W<SB>i</SB>X<SB>j</SB>, W<SB>i</SB>X<SB>j</SB>Y<SB>k</SB>, or W<SB>i</SB>X<SB>j</SB>Y<SB>k</SB>Z<SB>l</SB>, where W, X, Y, and Z are elements selected among a first group including Fe, Co, Ni, Cr, and Mn or among a second group including semimetal elements and groups 3B to 6B elements, with W and X being selected among the first group and the others selected among the second group, and i, j, k, and l are integers or simple ratios close to the integers. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tunnel magnetoresistive effect element having a ferromagnetic tunnel junction, a magnetic memory device, and a manufacturing method thereof.

[0002]

2. Description of the Related Art With the dramatic spread of information communication equipment, especially small personal equipment such as portable terminals, the elements such as memory and logic constituting them have high integration, high speed, low power consumption, etc. However, higher performance is required. In particular, increasing the density and capacity of non-volatile memory is becoming increasingly important as a technology for replacing hard disks and optical disks, which are essentially impossible to miniaturize due to the presence of moving parts.

The nonvolatile memory includes a flash memory using a semiconductor and an FRAM (Ferr) using a ferroelectric.
o electric Random Access Memory).
However, flash memory has a write speed of μ
It has the drawback of being slow on the order of seconds. On the other hand, it has been pointed out that the FRAM has a small number of rewritable times.

A non-volatile memory that does not have these drawbacks is drawing attention as, for example, “Wang et al., IEEE Trans.
Magn. 33 (1997), 4498 ”.
It is a magnetic memory device called a RAM (Magnetic Random Access Memory). Since this MRAM has a simple structure, it can be easily highly integrated, and since it is stored by rotation of a magnetic moment, it can be rewritten a large number of times. The access time is also expected to be extremely high, and it has already been confirmed that it can operate in the nanosecond range.

A magnetoresistive effect element used in this MRAM, especially a tunnel magnetoresistive effect (Tunnel Magnetoresist)
An ance: TMR) element is basically composed of a ferromagnetic tunnel junction of ferromagnetic layer / tunnel barrier layer / ferromagnetic layer. In this element, when an external magnetic field is applied between the ferromagnetic layers while a constant current is applied between the ferromagnetic layers, a magnetoresistive effect appears according to the relative angle of magnetization of both magnetic layers. When the magnetization directions of both ferromagnetic layers are antiparallel, the resistance value becomes maximum, and when they are parallel, the resistance value becomes minimum. The function as a memory element is provided by creating an antiparallel state and a parallel state by an external magnetic field.

The rate of change of this resistance is expressed by the following equation (1), where the spin polarizabilities of the respective magnetic layers are P1 and P2. 2P1P2 / (1-P1P2) ... Formula (1)

As described above, the larger the spin polarizability of each, the larger the resistance change rate. Regarding the relationship between the material used for the ferromagnetic layer and this resistance change rate,
There have been reports on Fe group ferromagnetic elements such as e, Co, and Ni, and alloys of these three types.

[0008]

By the way, in reading information from a TMR element, when the magnetic moments of one ferromagnetic layer sandwiching the tunnel barrier layer and the other ferromagnetic layer are antiparallel and the resistance value is high. For example, "1" is set to "0" when the respective magnetic moments are parallel to each other, and "0" is set to read out by a difference current at a constant bias voltage or a difference voltage at a constant bias current in those states. Therefore, a higher resistance change rate is more advantageous, and a memory with a lower error rate is realized.

It is known that the TMR element has a bias voltage dependency of the resistance change rate, and the resistance change rate decreases as the bias voltage increases. When reading is performed with a difference current or a difference voltage, in many cases, the voltage (V
Since it is known that the maximum value of the read signal is taken in h), it is more effective to reduce the error of the read MRAM if the bias dependence is small.

By the way, in addition to the above-mentioned TMR element, the MRAM has a semiconductor circuit as a switching element for selecting a TMR element required for reading.

When such a semiconductor circuit and a TMR element are made to coexist in the same chip, there is a step that requires heating at about 400 ° C. to manufacture the semiconductor circuit.
Similar temperature durability is required for the R element. However, it is known that the TMR element using an alloy of Fe group element such as Fe, Co, and Ni in the ferromagnetic layer has a significantly deteriorated resistance change rate at about 300 ° C. or higher, and therefore, in terms of heat resistance. I have a problem. This deterioration of the resistance change rate is
It is considered that the components of the constituent layers of the R element are interdiffused by heat and unwanted impurities enter the ferromagnetic layer or the tunnel barrier layer.

As described above, the MRA has both excellent read characteristics and high compatibility with the semiconductor circuit manufacturing process.
In order to realize M, the TMR element is required to have a high resistance change rate and heat resistance.

The present invention solves the above-mentioned conventional problems, and a tunnel magnetoresistive effect element capable of suppressing deterioration of resistance change rate due to heat treatment in a semiconductor circuit manufacturing process and a method of manufacturing the same. Another object of the present invention is to provide a magnetic memory device.

[0014]

In order to achieve the above-mentioned object, a tunnel magnetoresistive effect element according to the present invention is a magnetic element having a ferromagnetic tunnel junction in which a tunnel barrier layer is sandwiched between a pair of ferromagnetic layers. The resistance effect element is characterized in that at least one of the ferromagnetic layers contains an intermetallic compound exhibiting ferromagnetism.

Further, the magnetic memory device according to the present invention includes a tunnel magnetoresistive effect element having a ferromagnetic tunnel junction in which a tunnel barrier layer is sandwiched between a pair of ferromagnetic layers, and the tunnel magnetoresistive effect element. And a word line and a bit line sandwiched therebetween, and at least one of the ferromagnetic layers contains an intermetallic compound exhibiting ferromagnetism.

In order to form a ferromagnetic tunnel junction,
For example, it is necessary that the ferromagnetic layer containing a 3d transition metal element such as Cr, Mn, Fe, Co, and Ni be in contact with the tunnel barrier layer.

However, the tunnel barrier layer generally has an extremely thin film thickness of 6Å to 15Å, and the ferromagnetic layer contains 3 such as Cr, Mn, Fe, Co and Ni.
It is very sensitive to contamination with d-transition metal elements. Therefore, when the tunnel barrier layer is contaminated with these elements by, for example, thermal diffusion, spins of tunnel conduction electrons are scattered in the tunnel barrier layer, resulting in a disadvantage that the TMR characteristics are significantly impaired.

On the other hand, in the present invention, an intermetallic compound is used in the ferromagnetic layer using the 3d transition metal element, so that the bonding state between the 3d transition metal element and the compound element contains a covalent bond component. As a result, the thermal diffusion of the 3d transition metal element is suppressed, so that the components of the ferromagnetic layer do not contaminate the tunnel barrier layer, and high TMR characteristics can be maintained even if heat treatment is performed.

A method of manufacturing a tunnel magnetoresistive effect element according to the present invention is a method of manufacturing a tunnel magnetoresistive effect element having a ferromagnetic tunnel junction in which a tunnel barrier layer is sandwiched between a pair of ferromagnetic layers. A heat treatment is performed during or after the formation of the ferromagnetic tunnel junction to form an intermetallic compound exhibiting ferromagnetism in at least one of the ferromagnetic layers.

By performing heat treatment during or after the formation of the ferromagnetic tunnel junction, the phase of the intermetallic compound can be surely formed and a tunnel magnetoresistive effect element having high thermal stability can be obtained.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION A tunnel magnetoresistive element, a method of manufacturing the same, and a magnetic memory device to which the present invention is applied will be described below in detail with reference to the drawings.

The basic structure of the tunnel magnetoresistive effect element (hereinafter referred to as TMR element) 1 of the present invention is, for example, as shown in FIG. 1, an underlayer 3, an antiferromagnetic layer 4 and a substrate 2 on a substrate 2. The magnetization fixed layer 5 made of a ferromagnetic material, the tunnel barrier layer 6, the free layer 7 made of a ferromagnetic material, and the top coat layer 8 are laminated in this order. The TMR element 1 includes a pair of ferromagnetic layers, a magnetization fixed layer 5 and a free layer 7.
By sandwiching the tunnel barrier layer 6 with and, the ferromagnetic tunnel junction 9 is formed.

In the present invention, the ferromagnetic tunnel junction 9 is used.
Among them, at least one of the magnetization fixed layer 5 and the free layer 7, which are ferromagnetic layers, contains an intermetallic compound exhibiting ferromagnetism.

The intermetallic compound as referred to herein is a compound in which the ratio of atoms is represented by a relatively simple integer ratio, for example, the chemical formula W _i X _j , W _i X _j Y _k , or W. _i
X _j Y _k Z _l (W, X, Y and Z are Fe, Co,
It is an element selected from the first group consisting of Ni, Cr and Mn, and the second group consisting of metalloid elements and 3B to 6B group elements. In the formula, one of W and X is selected from the first group, and the other is selected from the second group. Further, in the formula, i, j, k, and l are integer values or simple ratios of values close to integers. ) Can be represented by.

From the viewpoint of exhibiting the TMR effect, the intermetallic compound is an element in which the density of states of electrons is different between the spin-up state and the spin-down state of the 3d orbit, Cr and M.
It is preferable to contain n, Fe, Co, Ni and the like.

From the viewpoint of suppressing the diffusion of atoms in the heated state, the intermetallic compound is the above-mentioned Cr, Mn, F.
It is preferable to further include a metalloid element or an element of Group 3B to Group 6B on the periodic table, which is capable of forming an intermetallic compound by covalently bonding with an element such as e, Co, or Ni. Specific examples of such metalloid elements or elements of Groups 3B to 6B on the periodic table include B, C, Ge, and A.
l, N, P, As, Sb, Bi, O, S, Se, Te,
Po etc. are mentioned.

By the way, as an intermetallic compound exhibiting ferromagnetism, a case where a metal element having different numbers of spin-ups and spin-downs, which are the main causes of manifestation of magnetism, is a ferromagnetic substance even if it is a simple substance, A metal element alone does not exhibit ferromagnetism, but is divided into compounds that exhibit ferromagnetism.

For example, as the former, for example, Co ₃ B, C
o ₂ B, Fe ₂ B, FeB, Co ₂₀ Al ₃ B ₆ , Co
Examples thereof include borides such as ₂₁ Ge ₂ B ₆ . Further, the boride may mainly contain an element selected from Cr, Mn, Fe, Co, and Ni, and for example, the magnetic element portion is composed of Fe and Co (Co _1-x Fe _x ).
₃ B, (Co _1-x Fe _x ) ₂ B, (Co _1-x F
e _x ) B or the like.

Al, C, Si, Sn, N, P, S
Fe as an intermetallic compound containing _ThreeAl, Ni_ThreeA
l, Fe_ThreeGe, Fe_ThreeC, Fe_TwoC, Fe_ThreeSi, F
e₅Si_Three, Fe_ThreeSn_Two, Fe_FourN, Fe₈N, Fe
_ThreeNiN, Fe_ThreePtN, Fe _ThreeP, Fe_2.4Co
_0.6P, NiCoSb, FeCoS_TwoEtc.
It

Further, it may be an intermetallic compound such as Fe ₃ (C _1-x B _x ), in which different metalloid elements are mixed in a portion other than the transition metal element.

Further, the intermetallic compound exhibiting ferromagnetism is not limited to the intermetallic compounds listed above, and may be partially modified such as containing a trace amount of additional element.

The latter, that is, a single element does not exhibit ferromagnetism
Examples of the intermetallic compound containing a metal element include Mn and Cr.
And the like are included. Specifically, for Heusler
Cu known as gold_TwoMnAl, Cu_TwoMnIn, N
i_TwoMnIn, Co_TwoMnSi, Cu_TwoMnSn, Ni
_TwoMnSn, Co_TwoMnSn etc. are mentioned. Also, M
nB, Mn₅SiB_TwoBorides such as MnSb, CoM
Antimony compounds such as nSb and PdMnSb are also available
is there. In addition, MnBi, Mn_FourN, Mn _Four(N
_1-xC_x), Mn_ThreeZnC, Co_TwoMn_TwoC, MnA
s_0.5Sb_{0. 5}Etc. Also, the metal of Cr
As an intercalation compound, CuCr_TwoSe_Four, HgCr_TwoS
e_Four, CdCr_ThreeSe_Four, Cr₇Te₈, Cr₅T
e₆, Cr_ThreeTe_Four, Cr_TwoTe_Three, TiCr_TwoT
e_Four, CuCr_TwoTe_FourEtc. Same as the former example
Similarly, the latter examples of intermetallic compounds are also listed above.
Not limited to the intermetallic compound
It does not matter if there is a partial change such as including.

The Curie temperature of these intermetallic compounds is preferably room temperature or higher, which makes it possible to realize a TMR element or MRAM that can operate in a normal environment. On the contrary, if the Curie temperature of the intermetallic compound is lower than room temperature, the TMR element and the MRAM do not operate at room temperature.

The tunnel barrier layer 6 sandwiched between the magnetization fixed layer 5 and the free layer 7 of the ferromagnetic tunnel junction 9 is a layer for cutting the magnetic coupling between the magnetization fixed layer 5 and the free layer 7 and passing a tunnel current. Is. Examples of the material forming the tunnel barrier layer 6 include Al, Mg, Si, Li and C.
Insulating materials such as oxides such as a, nitrides and halides can be used.

The tunnel barrier layer 6 can be obtained by oxidizing or nitriding a metal film formed by a sputtering method, an evaporation method or the like. The tunnel barrier layer 6 can also be obtained by a CVD method using an organic metal and oxygen gas, ozone gas, nitrogen gas or halogen gas.

The structure of the TMR element 1 shown in FIG. 1 other than the ferromagnetic layer forming the ferromagnetic tunnel junction 9 will be described below.

The antiferromagnetic layer 4 is antiferromagnetically coupled with the magnetization fixed layer 5, which is one of the ferromagnetic layers, so that the magnetization of the magnetization fixed layer 5 is not inverted even by the current magnetic field for writing. Is a layer for always keeping the magnetization direction of the magnetization fixed layer 5 constant. That is, in the TMR element 1 shown in FIG. 1, only the free layer 7, which is the other ferromagnetic layer, has its magnetization reversed by an external magnetic field or the like. As a material forming the antiferromagnetic layer 4, a Mn alloy containing Fe, Ni, Pt, Ir, Rh, etc., a Co oxide, a Ni oxide, or the like can be used.

The intermetallic compound exhibiting ferromagnetism as described above has a binding state having both a metallic binding component and a covalent binding component, and as a result, has both electronic conductivity and high binding energy. It will be. Among these, the electronic conductivity is a characteristic required to flow a read current when used as a memory element. On the other hand, a high covalent bond energy stabilizes the crystal structure, and thus stabilizes the crystal structure even at high temperatures. That is,
The intermetallic compound having a high covalent bond energy improves the thermal stability of the ferromagnetic layer, and suppresses the contamination of the tunnel barrier layer due to the thermal diffusion of the 3d transition metal element forming the ferromagnetic layer. .

Therefore, even if the TMR element 1 of the present invention is subjected to a heat treatment at a high temperature of, for example, over 300 ° C., it becomes a spin scattering factor of tunnel conduction electrons 3d.
Contamination of the tunnel barrier layer by the transition metal element is prevented, and high TMR characteristics can be maintained. That is, the TMR element 1 of the present invention can be subjected to heat treatment during the manufacturing process when it is used in, for example, a magnetic memory device.

The ferromagnetic layer containing the intermetallic compound exhibiting ferromagnetism as described above is formed by the vacuum vapor deposition method, the sputter vapor deposition method,
It is produced by a vapor phase growth method such as a CVD (Chemical Vapor Deposition) method, an electrolytic plating method, an electroless plating method, or the like.

By the way, depending on the composition of the ferromagnetic layer containing the intermetallic compound, the intermetallic compound structure may not grow and may have an amorphous structure or a microcrystalline structure depending on its composition. .

The TMR effect may not be immediately impaired even if the ferromagnetic layer has an amorphous structure.
When a 3d transition metal element that does not exhibit ferromagnetism by itself such as n or Cr is used, heat treatment is performed after the production of the ferromagnetic layer in order to sufficiently grow the intermetallic compound structure and obtain the desired ferromagnetism. It is preferable to employ a method of accelerating the rearrangement of atoms, a method of heating the substrate at the time of production, or the like. When heat treatment is performed during film formation, the heat treatment condition is set to 100 from the viewpoint of reliably generating a metal compound phase in the ferromagnetic layer.
C. or higher, and when heat treatment is performed after film formation, the heat treatment condition is preferably 340.degree. C. or higher.

Depending on the composition of the intermetallic compound, the TMR ratio and the magnetocrystalline anisotropy may be significantly improved when the ferromagnetic layer is made of a single crystal of the intermetallic compound.
It is also effective to epitaxially grow a single crystal film of an intermetallic compound by using a film forming method such as BE (Molecular Beam Epitaxy).

The TMR element of the present invention is shown in FIG.
It is not limited to the case where each of the magnetization fixed layer 5 and the free layer 7 as shown in (4) is composed of a single layer. For example, as shown in FIG. 2, even when the magnetization fixed layer 5 has a laminated ferri structure in which the intermediate layer 5c is sandwiched between the first magnetization fixed layer 5a and the second magnetization fixed layer 5b, The effect of the present invention can be obtained. In the TMR element 10 shown in FIG. 2, the first magnetization fixed layer 5a is in contact with the antiferromagnetic layer 4, and the exchange interaction acting between these layers causes the first magnetization fixed layer 5a to have a strong unidirectional magnetic field. Has anisotropy. The material used for the intermediate layer 5c of the laminated ferri structure is, for example, R
Examples include u, Cu, Cr, Au, Ag and the like. T in FIG.
The other layers of the MR element 10 have substantially the same structure as the TMR element 1 shown in FIG. 1, and therefore, the same reference numerals as in FIG. 1 are given and detailed description thereof is omitted.

The present invention is not limited to the case where at least one of the magnetization fixed layer 5 and the free layer 7 is made of only an intermetallic compound exhibiting ferromagnetism, and at least one of the magnetization fixed layer 5 and the free layer 7 is strong. It does not matter even if the intermetallic compound showing magnetism is partially contained. For example, a case where an intermetallic compound exhibiting ferromagnetism is partially precipitated in an amorphous structure in at least one of the magnetization fixed layer 5 and the free layer 7 is also included in the scope of the present invention.

Further, the TMR element of the present invention is not limited to the layer structure shown in FIG. 1 and FIG. 2 and can of course have various known layer structures.

The TMR element as described above is, for example, MRA.
It is suitable for use in a magnetic memory device such as M. Less than,
An MRAM using the TMR element of the present invention will be described with reference to FIGS. 3 and 4.

A cross-point type MRAM array having the TMR element of the present invention is shown in FIG. MR shown in FIG.
The AM array has a plurality of word lines WL and a plurality of bit lines BL orthogonal to these word lines WL, and the TMR element 1 of the present invention is arranged at the intersection of the word lines WL and the bit lines BL. The memory cell 11 is included. That is,
In the MRAM array shown in FIG. 3, 3 × 3 memory cells 1
1 are arranged in a matrix. Of course, the TMR element used in the MRAM array is not limited to the TMR element 1 shown in FIG. 1, but at least one of the ferromagnetic layers of the ferromagnetic tunnel junction, such as the TMR element 10 shown in FIG. 2 having a laminated ferri structure. Any structure may be used as long as it contains an intermetallic compound exhibiting ferromagnetism.

Each memory cell 11 has, as shown in FIG.
For example, a transistor 1 including a gate electrode 13, a source region 14 and a drain region 15 on a silicon substrate 12.
Have six. The gate electrode 13 constitutes a read word line WL1. A word line WL2 for writing is formed on the gate electrode 13 via an insulating layer. A contact metal 17 is connected to the drain region 15 of the transistor 16, and the contact metal 17
An underlayer 18 is connected to the underlayer. At a position corresponding to above the write word line WL2 on the base layer 18,
The TMR element 1 of the present invention is formed. A bit line BL orthogonal to the word lines WL1 and WL2 is formed on the TMR element 1.

Since the MRAM to which the present invention is applied has the TMR element having high heat resistance as described above, it maintains the high signal strength even after the heat treatment step and suppresses the increase of the error rate, which is excellent. Readout characteristics can be realized. Further, for example, the affinity with the existing CMOS process including the heat treatment at 300 ° C. or higher is improved, and the practicability can be greatly improved.

The TMR element of the present invention is not limited to the magnetic memory device described above, but also a magnetic head, an integrated circuit chip, and various electronic equipment such as personal computers, mobile terminals, and mobile phones, electric equipment, etc. Can be applied to.

[0052]

EXAMPLES Specific examples to which the present invention is applied will be described below based on experimental results. As described with reference to FIGS. 2 and 3, the MRAM has switching transistors and the like in addition to the TMR element. However, in this embodiment, as shown in FIGS. 5 and 6, in order to examine the TMR characteristics. The study was performed with a wafer on which only a strong ferromagnetic tunnel junction was formed.

<Example 1> As shown in FIGS. 5 and 6,
A characteristic evaluation element (Test Element Group) used in this example.
: TEG) is a word line WL and a bit line B on the substrate 21.
The magnetoresistive effect element 22 is formed at the intersection of the word line WL and the bit line BL. The magnetoresistive element 22 formed here is
It has an elliptical shape with a short axis of 0.5 μm and a long axis of 1.0 μm.
Further, terminal pads 23 and 24 are formed on both ends of the word line WL and the bit line BL, respectively. Further, the word line WL and the bit line BL are electrically insulated by the insulating film 25 made of Al ₂ O ₃ .

Such a TEG is manufactured as follows. First, a word line material is formed on the substrate 21,
After masking by photolithography, a portion other than the word line was selectively etched by Ar plasma to form a word line. At this time, the region other than the word line was etched to a depth of 5 nm of the substrate.

Next, a ferromagnetic tunnel junction having the following layer structure, that is, a TMR element was formed on the word line WL by a known lithography method and etching. The film thickness is shown in parentheses.

Ta (3 nm) / Cu (100 nm) / P
tMn (20 nm) / CoFe (2 nm) / Ru (0.
8nm) / Co_ThreeB (3 nm) / Al (1 nm) -O_x
/ Co _ThreeB (3 nm) / Ta (5 nm)

In the above-mentioned film structure, the tunnel barrier layer made of Al—O _x is formed by first depositing a metal Al film by DC sputtering to a thickness of 1 nm, and then setting the oxygen / argon flow rate ratio to 1: 1. Gas pressure 0.1mTorr
r under the condition that the plasma power value is 500 W
It was formed by plasma-oxidizing the 1 film.

Further, except the tunnel barrier layer made of Al—O _x, the film was formed by the magnetron sputtering method using an alloy target. Of these, when forming the magnetization fixed layer and the free layer, film formation was performed while applying a magnetic field of about 1 kOe (oersted). The composition of the layer made of CoFe was set to Co90at% -Fe10at%.

When a ferromagnetic layer (hereinafter referred to as a reference layer) which is in contact with the tunnel barrier layer of the magnetization fixed layer and which is made of Co ₃ B which is an intermetallic compound, and a free layer are produced, Co 67 at% is produced. Sputtering was performed using an alloy target of -B33 at%. After film formation, 270 ° C-
Magnetic field application heat treatment was performed in the temperature range of 450 ° C.
This magnetic field application heat treatment causes the PtMn layer, which is an antiferromagnetic layer, to be ordered and fixed in magnetization by rearrangement of atoms, adds magnetic anisotropy to the ferromagnetic layer, and produces intermetallic compounds in the free layer and the reference layer. This is a process for punishing.

After the ferromagnetic tunnel junction as described above is formed, Al ₂ O ₃ is sputtered to form a film having a thickness of 100 n.
The TEG shown in FIGS. 5 and 6 was obtained by forming the insulating layer 25 of about m in thickness and further forming the bit line BL and the terminal pad 24 by photolithography.

Example 2 A TEG was obtained in the same manner as in Example 1 except that the layer structure of the ferromagnetic tunnel junction was changed as follows. That is, in Example 2, Co was formed in the free layer.
It is used ₃ B. The composition of the magnetization fixed layer and the reference layer made of CoFe is Co90at% -Fe10at%.
Is.

Ta (3 nm) / Cu (100 nm) / P
tMn (20 nm) / CoFe (2 nm) / Ru (0.
8 nm) / CoFe (3 nm) / Al (1 nm) -O_x
/ Co _ThreeB (3 nm) / Ta (5 nm)

<Example 3> A TEG was obtained in the same manner as in Example 1 except that the layer structure of the ferromagnetic tunnel junction was changed as follows. That is, in Example 3, Fe ₃ Si is used for the reference layer and the free layer. The composition of the magnetization fixed layer made of CoFe is Co90at% -Fe10at.
%.

Ta (3 nm) / Cu (100 nm) / P
tMn (20 nm) / CoFe (2 nm) / Ru (0.
_{8nm) / Fe 3 Si (3nm} ) / Al (1nm) -O
_x / Fe ₃ Si (3 nm) / Ta (5 nm)

Example 4 A TEG was obtained in the same manner as in Example 1 except that the layer structure of the ferromagnetic tunnel junction was changed as follows. That is, in Example 4, Fe was formed in the free layer.
₃ Si is used. The composition of the magnetization fixed layer and the reference layer made of CoFe is Co90at% -Fe10at.
%.

Ta (3 nm) / Cu (100 nm) / P
tMn (20 nm) / CoFe (2 nm) / Ru (0.
8 nm) / CoFe (3 nm) / Al (1 nm) -O_x
/ Fe _ThreeSi (3 nm) / Ta (5 nm)

Example 5 A TEG was obtained in the same manner as in Example 1 except that the layer structure of the ferromagnetic tunnel junction was changed as follows. That is, in Example 5, MnSb is used for the reference layer and the free layer. The composition of the magnetization fixed layer made of CoFe is Co90at% -Fe10at%.
Is.

Ta (3 nm) / Cu (100 nm) / P
tMn (20 nm) / CoFe (2 nm) / Ru (0.
8 nm) / MnSb (5 nm) / Al (1 nm) -O _x
/ MnSb (5 nm) / Ta (5 nm)

Example 6 A TEG was obtained in the same manner as in Example 1 except that the layer structure of the ferromagnetic tunnel junction was changed as follows. That is, in Example 6, PdMnSb is used for the reference layer and the free layer. The composition of the magnetization fixed layer made of CoFe is Co90at% -Fe10a.
t%.

Ta (3 nm) / Cu (100 nm) / P
tMn (20 nm) / CoFe (2 nm) / Ru (0.
8 nm) / PdMnSb (5 nm) / Al (1 nm)-
O _x / PdMnSb (3 nm) / Ta (5 nm)

Example 7 A TEG was obtained in the same manner as in Example 1 except that the layer structure of the ferromagnetic tunnel junction was changed as follows. That is, in Example 7, Co ₂ MnSi is used for the reference layer and the free layer. The composition of the magnetization fixed layer made of CoFe is Co90at% -Fe10.
It is at%.

Ta (3 nm) / Cu (100 nm) / P
tMn (20 nm) / CoFe (2 nm) / Ru (0.
8 nm) / Co ₂ MnSi (5 nm) / Al (1 nm)
_{-O x / Co 2 MnSi (5nm} ) / Ta (5nm)

Comparative Example A TEG was obtained in the same manner as in Example 1 except that the layer structure of the ferromagnetic tunnel junction was changed as follows. The composition of the magnetization fixed layer made of CoFe is Co90at% -Fe10at%.

Ta (3 nm) / Cu (100 nm) / P
tMn (20 nm) / CoFe (2 nm) / Ru (0.
8 nm) / CoFe (2 nm) / Al (1 nm) -O _x
/ CoFe (2 nm) / Ta (5 nm)

With respect to the TEGs of Examples 1 to 7 and the comparative example produced as described above, the relationship between the heat treatment temperature and the TMR ratio and the intermetallic compound were identified as follows.

In a magnetic memory device such as an ordinary MRAM,
The information is written by reversing the magnetization of the magnetoresistive effect element by the current magnetic field, but in the present embodiment, the magnetization reversal of the magnetoresistive effect element was reversed by the external magnetic field and the TMR ratio was measured.

At this time, an external magnetic field for reversing the magnetization of the free layer of the magnetoresistive element was applied so as to be parallel to the easy axis of magnetization of the free layer. The magnitude of the external magnetic field for measurement was 500 Oe. When viewed from one of the easy magnetization axes of the free layer, −500 Oe to +500 Oe
At the same time as sweeping to e, terminal pad 2 of word line WL
The bias voltage applied to the terminal 3 and the terminal pad 24 of the bit line BL was adjusted to 100 mV, and a tunnel current was passed through the ferromagnetic tunnel junction. At this time, the resistance value to each external magnetic field was measured.

The TMR ratio is the resistance value when the magnetization of the magnetization fixed layer and the free layer is antiparallel and the resistance is high,
It is shown by taking the ratio with the resistance value in the state where the magnetization of the magnetization fixed layer and the free layer are parallel and the resistance is low.

Further, the observation of the fine structure of the reference layer and / or the free layer in each example is conducted by a transmission electron microscope (Transmission electron microscope).
Electron Microscope (TEM) and X-ray diffraction. Since the X-rays are transmitted through the film having such a thickness as to form the ferromagnetic tunnel junction, which is insufficient for obtaining a diffraction pattern, the intermetallic compound phase is identified by X-ray diffraction. In this case, the film thickness of 500 n formed under the same conditions
A monolayer film of m was separately prepared and used for the measurement.

First, when an intermetallic compound of a ferromagnetic metal element and a metalloid element is used for the reference layer and / or the free layer,
That is, the results of Examples 1 to 4 will be described.
Co ₃ B film thickness 5 used in Examples 1 and 2
After the heat treatment of the 00 nm single layer film, the phases were identified by X-ray diffraction, and as a result, it was confirmed that the phase of the intermetallic compound of Co ₃ B was obtained.

FIG. 7 shows the relationship between the heat treatment temperature and the TMR ratio in Examples 1, 2 and Comparative Example. In Example 1 using the intermetallic compound of Co ₃ B for the reference layer and the free layer, the high TMR ratio was maintained even when the heat treatment temperature was high, and the highest heat resistance was exhibited. In addition, Example 2 using Co ₃ B only in the free layer also showed higher heat resistance than the comparative example using CoFe in the free layer and the reference layer.
Although the cause of such improvement in heat resistance is not clear, Co
It is considered that this is because the binding energy of -B is higher than the binding energy of the metal bond of Co-Co or Co-Fe.

Next, the evaluation results of Example 3 and Example 4 will be described. Fe ₃ used in Examples 3 and 4
After the heat treatment of the single-layer film made of Si with a thickness of 500 nm, the phases were identified by X-ray diffraction, and as a result, it was confirmed that the phase of the intermetallic compound of Fe ₃ Si was obtained.

FIG. 8 shows the relationship between the heat treatment temperature and the TMR ratio in Examples 3, 4 and Comparative Example. Example 3 using an intermetallic compound of Fe ₃ Si for the reference layer and the free layer
In, the high TMR ratio was maintained even when the heat treatment temperature was high, and the highest heat resistance was exhibited. Further, Example 4 using Fe ₃ Si only in the free layer also showed higher heat resistance than the comparative example using CoFe in the free layer and the reference layer. Although the cause of such improvement in heat resistance is not clear,
It is considered that, as in the case of Co ₃ B, the bond energy of Fe—Si is higher than the bond energy of the metal bond of Co—Co or Co—Fe.

From the above Examples 1 to 4, the use of the intermetallic compound of the ferromagnetic metal element and the semimetal element in either one of the ferromagnetic layers of the ferromagnetic tunnel junction has the effect of improving the heat resistance. I found that I can get

From the above results, it is easily predicted that such a heat resistance improving effect can be obtained even in the system using not only Fe and Co but also Ni as the ferromagnetic metal of the intermetallic compound. To be done. Further, although B and Si were used as the semi-metal component of the intermetallic compound in Examples 1 to 4, in addition to these, an element that produces an intermetallic compound is used in the same manner as in the Co-Fe system or the Fe-Si system. It is easily expected that such a heat resistance improvement effect can be obtained even in a conventional system.

Further, the results of Examples 5 to 7 in the case of using an intermetallic compound containing a metal element that does not exhibit ferromagnetism by itself in the reference layer and / or the free layer will be described.

Thickness 5 of MnSb used in Example 5
After heat-treating a single layer film of 00 nm at 340 ° C or higher, X-ray
As a result of identifying the phase by folding, the intermetallic compound of MnSb
It was confirmed that the product phase was obtained. Similarly,
The film thickness of 500 nm made of PdMnSb used in Example 6
After heat treatment of the monolayer film at 340 ° C or higher,
Of PdMnSb as an intermetallic compound
It was confirmed that was obtained. Also used in Example 7.
Co_TwoA single layer film made of MnSi and having a thickness of 500 nm is used.
After heat treatment at 40 ° C or higher, the phase is identified by X-ray diffraction.
As a result, Co _TwoA phase of MnSi intermetallic compound is obtained
I confirmed that.

FIG. 9 shows the relationship between the heat treatment temperature and the TMR ratio in Examples 5 to 7 and Comparative Example. Examples 5 to 7 in which MnSb, PdMnSb, and Co ₂ MnSi are used for the reference layer and the free layer maintain a high TMR ratio even when the heat treatment temperature is high, and all have high heat resistance. Indicated. Although the cause of such improvement in heat resistance is not clear, as in the case of Co ₃ B and Fe ₃ Si, the covalent bond energy of Mn—Sb, Co—Si, or the like is Co—Co or Co—. It is considered that this is because it is higher than the binding energy of the metal bond of Fe.

From the above Examples 5 to 7, not only intermetallic compounds containing a metal element exhibiting ferromagnetism alone, but metals exhibiting ferromagnetism only after forming a compound which does not exhibit ferromagnetism by itself. It has been found that the intermetallic compound can also obtain the effect of improving heat resistance as in Examples 1 to 4.

From the above results, not only Mn but also C
Even with an intermetallic compound using r, it is easily expected that such an effect of improving heat resistance can be obtained. Also,
The semimetal component of the intermetallic compound is not limited to the elements used in Examples 5 to 7, and it is easily expected that such an effect of improving heat resistance can be obtained even if it is other than these. .

[0091]

As described above, according to the present invention, there is provided a tunnel magnetoresistive effect element capable of suppressing deterioration of TMR characteristics even by heat treatment at a high temperature of 300 ° C. or more and realizing excellent heat resistance. can do.

Further, by using such a tunnel magnetoresistive effect element having high heat resistance, it is possible to suppress an increase in error rate and maintain excellent read characteristics even when a heat treatment step is included in the manufacturing process. A magnetic memory device can be realized. That is, the magnetic memory device according to the present invention maintains CM with excellent read characteristics.
It is possible to significantly improve the affinity with the OS process.

According to the method of manufacturing a tunnel magnetoresistive effect element of the present invention, the phase of the intermetallic compound is surely formed in at least one of the ferromagnetic layers, and the tunnel magnetoresistive effect element having high thermal stability is obtained. be able to.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an essential part showing an example of a TMR element to which the present invention is applied.

FIG. 2 is a schematic cross-sectional view of a main part of another example of a TMR element to which the present invention is applied, showing a TMR element having a laminated ferri structure.

FIG. 3 is a schematic perspective view of a main part of a cross-point type MRAM array having a TMR element of the present invention as a memory cell.

FIG. 4 is an enlarged cross-sectional view of the memory cell shown in FIG.

FIG. 5 is a plan view of a TEG for evaluating a TMR element.

6 is a cross-sectional view taken along the line AA in FIG.

FIG. 7: TMR containing Co ₃ B as an intermetallic compound
It is a characteristic view for demonstrating the heat treatment temperature dependence of a TMR ratio of an element.

FIG. 8: TM containing Fe ₃ Si as an intermetallic compound
It is a characteristic view for explaining the heat treatment temperature dependence of the TMR ratio of the R element.

FIG. 9 is a characteristic diagram for explaining the heat treatment temperature dependence of the TMR ratio of a TMR element containing MnSb, PdMnSb or Co ₂ MnSi as an intermetallic compound.

[Explanation of symbols]

1 TMR element 2 substrates 3 Underlayer 4 Antiferromagnetic layer 5 Magnetization pinned layer 6 Tunnel barrier layer 7 free layer 8 Top coat layer 9 Ferromagnetic tunnel junction

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Claims (15)

[Claims] 1. A tunnel magnetoresistive element having a ferromagnetic tunnel junction in which a tunnel barrier layer is sandwiched between a pair of ferromagnetic layers, wherein at least one of the ferromagnetic layers is an intermetallic layer exhibiting ferromagnetism. A tunnel magnetoresistive effect element comprising a compound. 2. The intermetallic compound is Fe, Co, N.
2. The tunnel magnetoresistive effect element according to claim 1, containing at least one selected from i, Cr, and Mn. 3. The tunnel magnetoresistive effect element according to claim 2, wherein the intermetallic compound further contains a metalloid element or at least one element selected from the group of 3B to 6B elements. . 4. The intermetallic compound has the chemical formula W_iX_j,
W_iX_jY_k, Or W _iX_jY_kZ_l(W, X, Y in the formula
And Z are Fe, Co, Ni, Cr and Mn
Group 1 and metalloid elements and elements from groups 3B to 6B
It is an element selected from the second group consisting of the group. Also, the formula
One of the middle W and X is selected from the first group and the other is the second
Selected from the group of. Further, in the formula, i, j, k and l are integers.
It is a simple ratio of numbers or values close to integers. )
The tunnel magnetoresistance effect according to claim 1, characterized in that
element. 5. The intermetallic compound is boride, Heusler alloy, antimony compound, chalcogenite, MnB.
2. The tunnel magnetoresistive effect element according to claim 1, which is at least one of i and MnAl. 6. At least one of the ferromagnetic layers is
2. The tunnel magnetoresistive effect element according to claim 1, further comprising at least one layer made of a single crystal of the intermetallic compound. 7. A tunnel magnetoresistive element having a ferromagnetic tunnel junction in which a tunnel barrier layer is sandwiched between a pair of ferromagnetic layers, and a word line and a bit line sandwiching the tunnel magnetoresistive element in the thickness direction. A magnetic memory device comprising at least one of the ferromagnetic layers containing an intermetallic compound exhibiting ferromagnetism. 8. The intermetallic compound is Fe, Co, N.
8. The magnetic memory device according to claim 7, which contains at least one selected from i, Cr, and Mn. 9. The magnetic memory device according to claim 8, wherein the intermetallic compound further contains at least one element selected from the group consisting of a semi-metal element or a group of 3B to 6B elements. 10. The intermetallic compound has the chemical formula W
_i X _j , W _i X _j Y _k , or W _i X _j Y _k Z _l (W, X, Y, and Z in the formula are Fe, Co, Ni, Cr, and Mn.
A first group consisting of, and metalloid elements and 3B to 6
It is an element selected from the second group consisting of the group B elements. In the formula, one of W and X is selected from the first group, and the other is selected from the second group. Also, in the formula, i, j,
k and l are simple ratios of integer values or near integer values. 8. The magnetic memory device according to claim 7, wherein 11. The intermetallic compound is boride, Heusler alloy, antimony compound, chalcogenite, Mn.
8. The magnetic memory device according to claim 7, wherein the magnetic memory device is at least one of Bi and MnAl. 12. The magnetic memory device according to claim 7, wherein at least one of the ferromagnetic layers has at least one layer made of a single crystal of the intermetallic compound. 13. A method for manufacturing a tunnel magnetoresistive element having a ferromagnetic tunnel junction in which a tunnel barrier layer is sandwiched between a pair of ferromagnetic layers, the method comprising: forming the ferromagnetic tunnel junction or after forming the ferromagnetic tunnel junction. A method for manufacturing a tunnel magnetoresistive effect element, characterized by forming an intermetallic compound exhibiting ferromagnetism in at least one of the ferromagnetic layers by performing heat treatment. 14. The method for manufacturing a tunnel magnetoresistive effect element according to claim 13, wherein the heat treatment during the film formation is performed at 100 ° C. or higher. 15. The method for manufacturing a tunnel magnetoresistive element according to claim 13, wherein the heat treatment after the film formation is performed at 340 ° C. or higher.