JP4281285B2 - Tunnel magnetoresistive element and magnetic memory device - Google Patents

Description

[0001]
BACKGROUND 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]
[Prior art]
With the rapid spread of information communication devices, especially small personal devices such as portable terminals, the elements such as memory and logic that compose this device have higher performance such as higher integration, higher speed, lower power consumption, etc. 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 discs that are essentially impossible to downsize due to the presence of moving parts.
[0003]
Examples of the nonvolatile memory include a flash memory using a semiconductor and an FRAM (Ferro electric Random Access Memory) using a ferroelectric. However, the flash memory has a drawback that the writing speed is as slow as microsecond order. On the other hand, in FRAM, a problem that the number of rewritable times is small has been pointed out.
[0004]
Non-volatile memories that do not have these drawbacks are attracting attention as MRAM (Magnetic Random Access Memory) as described in, for example, “Wang et al., IEEE Trans Magn. 33 (1997), 4498”. This is a so-called magnetic memory device. Since this MRAM has a simple structure, it can be easily integrated and has a large number of rewritable times in order to store data by rotating a magnetic moment. The access time is also expected to be very high, and it has already been confirmed that it can operate in the nanosecond range.
[0005]
The magnetoresistive effect element used in this MRAM, in particular, the tunnel magnetoresistive effect (Tunnel Magnetoresistance: TMR) element, is basically composed of a ferromagnetic tunnel junction of a ferromagnetic layer / tunnel barrier layer / ferromagnetic layer. In this element, when an external magnetic field is applied between the ferromagnetic layers with a constant current flowing 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 is maximized, and when they are parallel, the resistance value is minimized. The function as a memory element is brought about by creating an antiparallel and parallel state by an external magnetic field.
[0006]
The rate of change in resistance is expressed by the following formula (1), where the spin polarizabilities of the respective magnetic layers are P1 and P2.
2P1P2 / (1-P1P2) ... Formula (1)
[0007]
Thus, the resistance change rate increases as the respective spin polarizabilities increase. Regarding the relationship between the material used for the ferromagnetic layer and the rate of change in resistance, there have been reports on Fe group ferromagnetic elements such as Fe, Co, and Ni, and alloys of these three types.
[0008]
[Problems to be solved by the invention]
By the way, information reading of the TMR element is performed when the magnetic moment between one ferromagnetic layer and the other ferromagnetic layer sandwiching the tunnel barrier layer is antiparallel and the resistance value is high, for example, “1”, and vice versa. When the magnetic moments are parallel, “0” is set, and reading is performed based on the difference current at a constant bias voltage or the difference voltage at a constant bias current in those states. Therefore, a higher resistance change rate is advantageous, and a memory with a low error rate is realized.
[0009]
Further, it is known that the resistance change rate depends on the bias voltage in the TMR element, and the resistance change rate decreases as the bias voltage increases. When reading is performed with a difference current or voltage, it is known that in many cases the maximum value of the read signal is obtained at a voltage (Vh) at which the resistance change rate is halved by the bias voltage dependency. The smaller one is effective in reducing errors in the read MRAM.
[0010]
Incidentally, the MRAM includes a semiconductor circuit as a switching element for selecting a TMR element necessary for reading in addition to the above-described TMR element.
[0011]
When such a semiconductor circuit and a TMR element coexist in the same chip, there is a process that requires heating at about 400 ° C. for the production of the semiconductor circuit, and therefore the TMR element must have the same temperature durability. It is said. However, the TMR element using an alloy of Fe group elements such as Fe, Co, Ni, etc. for the ferromagnetic layer is known to have a remarkably deteriorated resistance change rate at about 300 ° C. or more. Have a problem. This deterioration in resistance change rate is considered to be due to the fact that components of the constituent layers of the TMR element are mutually diffused by heat, and unwanted impurities enter the ferromagnetic layer or the tunnel barrier layer.
[0012]
As described above, in order to realize an MRAM that achieves both excellent read characteristics and high compatibility with a semiconductor circuit manufacturing process, a high resistance change rate and heat resistance are required for a TMR element.
[0013]
The present invention solves such a conventional problem, a tunnel magnetoresistive effect element capable of suppressing deterioration in resistance change rate due to heat treatment such as a semiconductor circuit manufacturing process, a manufacturing method thereof, and a magnetic memory An object is to provide an apparatus.
[0014]
[Means for Solving the Problems]
  To achieve the above object, a tunnel magnetoresistive element according to the present invention is a tunnel magnetoresistive element having a ferromagnetic tunnel junction with a tunnel barrier layer sandwiched between a pair of ferromagnetic layers, At least one of the ferromagnetic layers isCovalently bonded to a 3d transition metal element;Intermetallic compounds exhibiting ferromagnetismCobalt boride (Co ₃ B)It is characterized by containing.
[0015]
  Further, the magnetic memory device according to the present invention includes:Formed on a semiconductor substrate and the semiconductor substrate;A tunnel magnetoresistive element having a ferromagnetic tunnel junction with a tunnel barrier layer 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 circuit formed on the semiconductor substrate and connected to the word line or the bit line;
And at least one of the ferromagnetic layers isCovalently bonded to a 3d transition metal element;Intermetallic compounds exhibiting ferromagnetismCobalt boride (Co ₃ B)It is characterized by containing.
[0016]
  The tunnel magnetoresistive effect element according to the present invention is 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 at least one of the above ferromagnetic layers Is an iron silicide (Fe) as an intermetallic compound that is covalently bonded to a 3d transition metal element and exhibits ferromagnetism. ₃ Si) is contained.
[0017]
  A magnetic memory device according to the present invention includes a semiconductor substrate, a tunnel magnetoresistive effect element formed on the semiconductor substrate and having a ferromagnetic tunnel junction with a tunnel barrier layer sandwiched between a pair of ferromagnetic layers, A word line and a bit line sandwiching a tunnel magnetoresistive effect element in a thickness direction; a circuit formed on the semiconductor substrate and connected to the word line or the bit line;
And at least one of the ferromagnetic layers is covalently coupled to a 3d transition metal element, and iron silicide (Fe) as an intermetallic compound exhibiting ferromagnetism. ₃ Si) is contained.
[0018]
  In order to form a ferromagnetic tunnel junction, for example,Fe, CoIt is necessary that a ferromagnetic layer containing a 3d transition metal element such as a tunnel barrier layer is in contact.
[0019]
  However, the tunnel barrier layer is generally extremely thin with a thickness of 6 to 15 mm, and includes a ferromagnetic layer.Fe, CoIt is very sensitive to contamination of 3d transition metal elements such as Therefore, when the tunnel barrier layer is contaminated with these elements, for example, by thermal diffusion, the spin of tunnel conduction electrons is scattered in the tunnel barrier layer, which causes a disadvantage that the TMR characteristic is significantly impaired.
[0020]
  In contrast, the present inventionFe, CoIntermetallic compound in ferromagnetic layer using 3d transition metal elementFe ₃ Si, Co ₃ BBy usingFe, Co3d transition metal elements and compound elementsSi, BA covalent component is included in the binding state. ThisFe, CoSince the thermal diffusion of the 3d transition metal element is suppressed, high TMR characteristics can be maintained even if heat treatment is performed without the components of the ferromagnetic layer contaminating the tunnel barrier layer.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a tunnel magnetoresistive effect element, a manufacturing method thereof, and a magnetic memory device to which the present invention is applied will be described in detail with reference to the drawings.
[0022]
The basic structure of a tunnel magnetoresistive effect element (hereinafter referred to as a TMR element) 1 of the present invention is as shown in FIG. 1, for example, on a substrate 2, an underlayer 3, an antiferromagnetic layer 4, and a ferromagnetic structure. A magnetization fixed layer 5 made of a body, a tunnel barrier layer 6, a free layer 7 made of a ferromagnetic material, and a top coat layer 8 are laminated in this order. The TMR element 1 forms a ferromagnetic tunnel junction 9 by sandwiching a tunnel barrier layer 6 between a magnetization fixed layer 5 and a free layer 7 which are a pair of ferromagnetic layers.
[0023]
In the present invention, at least one of the magnetization fixed layer 5 and the free layer 7 which are ferromagnetic layers in the ferromagnetic tunnel junction 9 contains an intermetallic compound exhibiting ferromagnetism.
[0024]
The intermetallic compound here is a compound whose atomic ratio is represented by a relatively simple integer ratio._iX_j, W_iX_jY_kOr W_iX_jY_kZ_lWherein W, X, Y and Z are selected from the first group consisting of Fe, Co, Ni, Cr and Mn, and the second group consisting of metalloid elements and group elements from group 3B to group 6B. In the formula, one of W and X is selected from the first group, and the other is selected from the second group, and i, j, k, and l are integer values or integers. It is a simple ratio with a value close to.
[0025]
The intermetallic compound preferably contains Cr, Mn, Fe, Co, Ni, and the like, which are elements having different electron state densities in the spin-up state and the spin-down state of the 3d orbital, from the viewpoint of expressing the TMR effect.
[0026]
Further, from the viewpoint of suppressing the diffusion of atoms in the heated state, the intermetallic compound is covalently bonded to the elements such as Cr, Mn, Fe, Co, and Ni described above to generate an intermetallic compound. It is preferable to further include a metalloid element or a group 3B to 6B element on the periodic table. Specific examples of such metalloid elements or elements from Group 3B to 6B on the periodic table include B, C, Ge, Al, N, P, As, Sb, Bi, O, S, Se, Te, Po, etc. are mentioned.
[0027]
By the way, as an intermetallic compound exhibiting ferromagnetism, there are cases where a metal element having a different number of spin-ups and spin-downs, which is the main cause of magnetism, is a ferromagnet, and a metal element alone In the case of, it is divided into compounds that do not exhibit ferromagnetism but exhibit ferromagnetism in compounds.
[0028]
For example, as the former, for example, Co₃B, Co₂B, Fe₂B, FeB, Co₂0Al₃B₆, Co₂₁Ge₂B₆And borides such as The boride only needs to contain an element selected from Cr, Mn, Fe, Co, and Ni. For example, the magnetic element portion is composed of Fe and Co (Co_1-xFe_x)₃B, (Co_1-xFe_x)₂B, (Co_1-xFe_x) B or the like.
[0029]
Further, as intermetallic compounds containing Al, C, Si, Sn, N, P, and S, Fe₃Al, Ni₃Al, Fe₃Ge, Fe₃C, Fe₂C, Fe₃Si, Fe₅Si₃, Fe₃Sn₂, Fe₄N, Fe₈N, Fe₃NiN, Fe₃PtN, Fe₃P, Fe_2.4Co_0.6P, NiCoSb, FeCoS₂Etc.
[0030]
For example, Fe₃(C_1-xB_x) And the like, it may be an intermetallic compound in which different metalloid elements or the like are mixed in a portion other than the transition metal element.
[0031]
Further, the intermetallic compounds exhibiting ferromagnetism are not limited to the intermetallic compounds listed above, and there may be a partial change such as containing a small amount of additive elements.
[0032]
Examples of the latter, that is, intermetallic compounds containing a metal element that does not exhibit ferromagnetism alone include those containing Mn, Cr, and the like. Specifically, Cu known as Heusler alloy₂MnAl, Cu₂MnIn, Ni₂MnIn, Co₂MnSi, Cu₂MnSn, Ni₂MnSn, Co₂MnSn etc. are mentioned. MnB, Mn₅SiB₂Borides such as MnSb, CoMnSb, and antimony compounds such as PdMnSb are also possible. In addition, MnBi, Mn₄N, Mn₄(N_1-xC_x), Mn₃ZnC, Co₂Mn₂C, MnAs_0.5Sb_0.5Etc. As an intermetallic compound of Cr, CuCr₂Se₄, HgCr₂Se₄, CdCr₃Se₄, Cr₇Te₈, Cr₅Te₆, Cr₃Te₄, Cr₂Te₃TiCr₂Te₄, CuCr₂Te₄Etc. Similarly to the former example, the intermetallic compound of the latter example is not limited to the above-described intermetallic compounds, and there may be a partial change such as containing a trace amount of additive elements.
[0033]
The Curie temperature of these intermetallic compounds is preferably room temperature or higher, whereby a TMR element or MRAM that can operate in a normal environment can be realized. Conversely, when the Curie temperature of the intermetallic compound is lower than room temperature, the TMR element or MRAM does not operate at room temperature.
[0034]
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 flowing a tunnel current. As a material constituting the tunnel barrier layer 6, for example, an insulating material such as an oxide such as Al, Mg, Si, Li, or Ca, a nitride, or a halide can be used.
[0035]
The tunnel barrier layer 6 can be obtained by oxidizing or nitriding a metal film formed by sputtering or vapor deposition. 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.
[0036]
Further, the configuration of the TMR element 1 shown in FIG. 1 other than the ferromagnetic layer constituting the ferromagnetic tunnel junction 9 will be described below.
[0037]
The antiferromagnetic layer 4 is antiferromagnetically coupled to the magnetization fixed layer 5 that is one of the ferromagnetic layers, so that the magnetization of the magnetization fixed layer 5 is not reversed even by a current magnetic field for writing, and the magnetization is fixed. This is a layer for always keeping the magnetization direction of the layer 5 constant. That is, in the TMR element 1 shown in FIG. 1, the magnetization of only the free layer 7 which is the other ferromagnetic layer is reversed by an external magnetic field or the like. As a material constituting the antiferromagnetic layer 4, an Mn alloy containing Fe, Ni, Pt, Ir, Rh, Co oxide, Ni oxide, or the like can be used.
[0038]
Since the intermetallic compound exhibiting ferromagnetism as described above has both a metal-bonding component and a covalent component in its bonding state, as a result, it has both electron conductivity and high binding energy. . Among these, electronic conductivity is a characteristic necessary for flowing a read current when used as a memory element. On the other hand, the high covalent bond energy stabilizes the crystal structure, so that the crystal structure is stable even at high temperatures. That is, the thermal stability of the ferromagnetic layer is improved by an intermetallic compound having a high covalent bond energy, and contamination of the tunnel barrier layer due to thermal diffusion of the 3d transition metal element constituting the ferromagnetic layer is prevented. Suppress.
[0039]
Therefore, even if the TMR element 1 of the present invention is subjected to a heat treatment at a high temperature exceeding 300 ° C., for example, the tunnel barrier layer is prevented from being contaminated by the 3d transition metal element that causes the spin scattering of the tunnel conduction electrons, 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 applied to, for example, a magnetic memory device.
[0040]
As described above, a ferromagnetic layer containing an intermetallic compound exhibiting ferromagnetism is formed by vapor deposition methods such as vacuum deposition, sputter deposition, and CVD (Chemical Vapor Deposition), electroplating, and electroless plating. Etc. are produced.
[0041]
By the way, depending on the composition of the ferromagnetic layer containing an intermetallic compound, the intermetallic compound structure may not grow and may become an amorphous structure or a microcrystalline structure when produced at room temperature.
[0042]
The expression of the TMR effect may not be immediately impaired even if the ferromagnetic layer has an amorphous structure, but in particular, when a 3d transition metal element that does not exhibit ferromagnetism such as Mn and Cr is used, In order to obtain the desired ferromagnetism by sufficiently growing the intermetallic compound structure, a method of promoting the rearrangement of atoms by performing a heat treatment after the preparation of the ferromagnetic layer, a method of heating the substrate at the time of preparation, etc. preferable. From the viewpoint of reliably generating a metal compound phase in the ferromagnetic layer, when heat treatment is performed during film formation, the heat treatment condition is preferably 100 ° C. or higher, and when heat treatment is performed after film formation, The heat treatment condition is preferably 340 ° C. or higher.
[0043]
In addition, depending on the composition of the intermetallic compound, the TMR ratio and magnetocrystalline anisotropy may be significantly improved when the ferromagnetic layer is made of a single crystal of the intermetallic compound. Therefore, the composition of MBE (Molecular Beam Epitaxy) or the like may be increased. It is also effective to epitaxially grow a single crystal film of an intermetallic compound using a film method.
[0044]
The TMR element of the present invention is not limited to the case where each of the magnetization fixed layer 5 and the free layer 7 as shown in FIG. For example, as shown in FIG. 2, even if the magnetization fixed layer 5 has a laminated ferrimagnetic structure in which the intermediate layer 5c is sandwiched between the first magnetization fixed layer 5a and the second magnetization fixed layer 5b, The effects of the present invention can be obtained. In the TMR element 10 shown in FIG. 2, the first magnetization fixed layer 5 a is in contact with the antiferromagnetic layer 4, and the first magnetization fixed layer 5 a has a strong unidirectional magnetic force due to the exchange interaction acting between these layers. Has anisotropy. Examples of the material used for the intermediate layer 5c having the laminated ferri structure include Ru, Cu, Cr, Au, and Ag. The other layers of the TMR element 10 in FIG. 2 have substantially the same configuration as that of the TMR element 1 shown in FIG. 1, and therefore, the same reference numerals as those in FIG.
[0045]
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 exhibits ferromagnetism. It may be a case where an intermetallic compound is partially contained. For example, the case where an intermetallic compound exhibiting ferromagnetism partially precipitates 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.
[0046]
Further, the TMR element of the present invention is not limited to the layer configuration shown in FIGS. 1 and 2, and it is needless to say that various known layer configurations can be adopted.
[0047]
The TMR element as described above is suitable for use in a magnetic memory device such as an MRAM. The MRAM using the TMR element of the present invention will be described below with reference to FIGS.
[0048]
FIG. 3 shows a cross-point type MRAM array having the TMR element of the present invention. The MRAM array shown in FIG. 3 has a plurality of word lines WL and a plurality of bit lines BL orthogonal to the word lines WL, and the TMR element 1 of the present invention is located at the intersection of the word lines WL and the bit lines BL. The memory cell 11 is arranged. That is, in the MRAM array shown in FIG. 3, 3 × 3 memory cells 11 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. Any structure may be used as long as it contains an intermetallic compound exhibiting ferromagnetism.
[0049]
As shown in FIG. 4, each memory cell 11 includes a transistor 16 including a gate electrode 13, a source region 14, and a drain region 15 on, for example, a silicon substrate 12. The gate electrode 13 constitutes a read word line WL1. A write word line WL2 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 a base layer 18 is connected to the contact metal 17. The TMR element 1 of the present invention is formed on the base layer 18 at a position corresponding to the upper side of the write word line WL2. On the TMR element 1, bit lines BL orthogonal to the word lines WL1 and WL2 are formed.
[0050]
Since the MRAM to which the present invention is applied has a TMR element with high heat resistance as described above, it maintains a high signal intensity even after the heat treatment process, suppresses an increase in error rate, and has excellent read characteristics. Can be realized. Further, for example, the affinity with an existing CMOS process including heat treatment at 300 ° C. or higher is improved, and the practicality can be greatly improved.
[0051]
The TMR element of the present invention is applied not only to the magnetic memory device described above, but also to magnetic heads, integrated circuit chips, various electronic devices such as personal computers, mobile terminals, mobile phones, and electric devices. It is possible.
[0052]
【Example】
Hereinafter, specific examples to which the present invention is applied will be described based on experimental results. As described with reference to FIGS. 2 and 3, the MRAM includes a switching transistor in addition to the TMR element. In this embodiment, as shown in FIGS. A wafer with only a ferromagnetic tunnel junction was investigated.
[0053]
<Example 1>
As shown in FIG. 5 and FIG. 6, the element for characteristic evaluation (Test Element Group: TEG) used in this embodiment has a word line WL and a bit line BL arranged on a substrate 21 at right angles. A magnetoresistive element 22 is formed at the intersection of the line WL and the bit line BL. The magnetoresistive effect element 22 formed here has an elliptical shape with a minor axis of 0.5 μm and a major axis of 1.0 μm. Terminal pads 23 and 24 are formed at both ends of the word line WL and the bit line BL, respectively. The word line WL and the bit line BL are made of Al.₂O₃It is electrically insulated by an insulating film 25 made of
[0054]
Such a TEG is manufactured as follows. First, a word line material was formed on the substrate 21, masked by photolithography, and portions other than the word lines were selectively etched with Ar plasma to form word lines. At this time, regions other than the word line were etched to a depth of 5 nm of the substrate.
[0055]
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 thickness in parentheses indicates the film thickness.
[0056]
Ta (3 nm) / Cu (100 nm) / PtMn (20 nm) / CoFe (2 nm) / Ru (0.8 nm) / Co₃B (3 nm) / Al (1 nm) -O_x/ Co₃B (3 nm) / Ta (5 nm)
[0057]
Among the above film configurations, Al-O_xFirst, a metal Al film is deposited with a thickness of 1 nm by DC sputtering, and then a flow ratio of oxygen / argon is 1: 1, a chamber gas pressure is 0.1 mTorr, and a plasma power value is 500 W. The metal Al film was formed by plasma oxidation under the above conditions.
[0058]
Al-O_xExcept for the tunnel barrier layer made of, the film was formed by magnetron sputtering using an alloy target. Among these, when producing the magnetization fixed layer and the free layer, the film was formed while applying a magnetic field of about 1 kOe (Oersted). The composition of the CoFe layer was Co90 at% -Fe10 at%.
[0059]
Co, which is an intermetallic compound₃Sputtering using a Co67 at% -B33 at% alloy target is performed when a ferromagnetic layer (hereinafter referred to as a reference layer) and a free layer, which are made of B and are in contact with the tunnel barrier layer, of the magnetization fixed layer. It was. After film formation, magnetic field application heat treatment was performed under the temperature range of 270 ° C. to 450 ° C. This heat treatment by applying a magnetic field produces ordering and magnetization of the PtMn layer, which is an antiferromagnetic layer, by atomic rearrangement, addition of magnetic anisotropy to the ferromagnetic layer, and intermetallic compounds in the free layer and the reference layer. It is a process for damaging.
[0060]
After fabrication of the ferromagnetic tunnel junction as described above, Al₂O₃The insulating layer 25 having a thickness of about 100 nm was formed by sputtering, and the bit line BL and the terminal pad 24 were formed by photolithography, whereby the TEG shown in FIGS. 5 and 6 was obtained.
[0061]
<Example 2>
A TEG was obtained in the same manner as in Example 1 except that the layer configuration of the ferromagnetic tunnel junction was as follows. That is, in Example 2, Co is formed in the free layer.₃B is used. The composition of the magnetization fixed layer and the reference layer made of CoFe is Co90 at% -Fe10 at%.
[0062]
Ta (3 nm) / Cu (100 nm) / PtMn (20 nm) / CoFe (2 nm) / Ru (0.8 nm) / CoFe (3 nm) / Al (1 nm) -O_x/ Co₃B (3 nm) / Ta (5 nm)
[0063]
<Example 3>
A TEG was obtained in the same manner as in Example 1 except that the layer configuration of the ferromagnetic tunnel junction was as follows. That is, in Example 3, the reference layer and the free layer are Fe layers.₃Si is used. The composition of the magnetization fixed layer made of CoFe is Co 90 at% -Fe 10 at%.
[0064]
Ta (3 nm) / Cu (100 nm) / PtMn (20 nm) / CoFe (2 nm) / Ru (0.8 nm) / Fe₃Si (3 nm) / Al (1 nm) -O_x/ Fe₃Si (3 nm) / Ta (5 nm)
[0065]
<Example 4>
A TEG was obtained in the same manner as in Example 1 except that the layer configuration of the ferromagnetic tunnel junction was as follows. That is, in Example 4, the free layer has Fe₃Si is used. The composition of the magnetization fixed layer and the reference layer made of CoFe is Co90 at% -Fe10 at%.
[0066]
Ta (3 nm) / Cu (100 nm) / PtMn (20 nm) / CoFe (2 nm) / Ru (0.8 nm) / CoFe (3 nm) / Al (1 nm) -O_x/ Fe₃Si (3 nm) / Ta (5 nm)
[0067]
<Example 5>
A TEG was obtained in the same manner as in Example 1 except that the layer configuration of the ferromagnetic tunnel junction was 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 Co 90 at% -Fe 10 at%.
[0068]
Ta (3 nm) / Cu (100 nm) / PtMn (20 nm) / CoFe (2 nm) / Ru (0.8 nm) / MnSb (5 nm) / Al (1 nm) -O_x/ MnSb (5 nm) / Ta (5 nm)
[0069]
<Example 6>
A TEG was obtained in the same manner as in Example 1 except that the layer configuration of the ferromagnetic tunnel junction was 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 Co 90 at% -Fe 10 at%.
[0070]
Ta (3 nm) / Cu (100 nm) / PtMn (20 nm) / CoFe (2 nm) / Ru (0.8 nm) / PdMnSb (5 nm) / Al (1 nm) -O_x/ PdMnSb (3 nm) / Ta (5 nm)
[0071]
<Example 7>
A TEG was obtained in the same manner as in Example 1 except that the layer configuration of the ferromagnetic tunnel junction was as follows. That is, in Example 7, the reference layer and the free layer are made of Co.₂MnSi is used. The composition of the magnetization fixed layer made of CoFe is Co 90 at% -Fe 10 at%.
[0072]
Ta (3 nm) / Cu (100 nm) / PtMn (20 nm) / CoFe (2 nm) / Ru (0.8 nm) / Co₂MnSi (5 nm) / Al (1 nm) -O_x/ Co₂MnSi (5 nm) / Ta (5 nm)
[0073]
<Comparative example>
A TEG was obtained in the same manner as in Example 1 except that the layer configuration of the ferromagnetic tunnel junction was as follows. The composition of the magnetization fixed layer made of CoFe is Co 90 at% -Fe 10 at%.
[0074]
Ta (3 nm) / Cu (100 nm) / PtMn (20 nm) / CoFe (2 nm) / Ru (0.8 nm) / CoFe (2 nm) / Al (1 nm) -O_x/ CoFe (2 nm) / Ta (5 nm)
[0075]
Regarding the TEGs of Examples 1 to 7 and Comparative Example produced as described above, the relationship between the heat treatment temperature and the TMR ratio and the identification of intermetallic compounds were performed as follows.
[0076]
In a normal magnetic memory device such as an MRAM, information is written by reversing the magnetization of the magnetoresistive effect element using a current magnetic field. In this embodiment, the TMR ratio was measured by reversing the magnetization of the magnetoresistive effect element using an external magnetic field. .
[0077]
At this time, an external magnetic field for reversing the magnetization of the free layer of the magnetoresistive effect 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. Then, when viewed from one of the easy axes of the free layer, the sweep is performed from −500 Oe to +500 Oe, and at the same time, the bias voltage applied to the terminal pad 23 of the word line WL and the terminal pad 24 of the bit line BL is adjusted to 100 mV. Then, a tunnel current was passed through the ferromagnetic tunnel junction. The resistance value with respect to each external magnetic field at this time was measured.
[0078]
The TMR ratio is such that the resistance value when the magnetization of the magnetization fixed layer and the free layer is antiparallel and the resistance is high, and the magnetization of the magnetization fixed layer and the free layer are parallel and the resistance is low. It is shown by taking the ratio with the resistance value in the state.
[0079]
Moreover, observation of the fine structure of the reference layer and / or free layer of each example was performed by a transmission electron microscope (TEM) and X-ray diffraction. In addition, since the film thickness that constitutes the ferromagnetic tunnel junction as described above transmits X-rays and is insufficient for obtaining a diffraction pattern, the intermetallic compound phase is identified by X-ray diffraction. At that time, a single-layer film having a thickness of 500 nm formed under the same conditions was separately prepared and used for measurement.
[0080]
First, the case where 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 used in Example 1 and Example 2₃As a result of identifying the phase by X-ray diffraction after heat-treating the single layer film made of B having a thickness of 500 nm, Co₃It was confirmed that a phase of B intermetallic compound was obtained.
[0081]
Moreover, the relationship between the heat processing temperature of Example 1, Example 2, and a comparative example and TMR ratio is shown in FIG. Co in reference layer and free layer₃In Example 1 using the intermetallic compound of B, a high TMR ratio was maintained even when the heat treatment temperature was high, and the highest heat resistance was exhibited. Also, only the free layer₃Example 2 using B also showed higher heat resistance than the comparative example using CoFe for the free layer and the reference layer. Although the cause of such an improvement in heat resistance is not clear, it is considered that the bond energy of Co—B is higher than the bond energy of the metal bond of Co—Co or Co—Fe.
[0082]
Next, the evaluation results of Example 3 and Example 4 will be described. Fe used in Example 3 and Example 4₃As a result of performing phase identification by X-ray diffraction after heat-treating a single layer film made of Si having a thickness of 500 nm, Fe₃It was confirmed that a phase of Si intermetallic compound was obtained.
[0083]
Moreover, the relationship between the heat processing temperature of Example 3, Example 4, and a comparative example and TMR ratio is shown in FIG. Fe in the reference and free layers₃In Example 3 using an Si intermetallic compound, a high TMR ratio was maintained even when the heat treatment temperature was high, and the highest heat resistance was exhibited. Also, only the free layer has Fe₃Example 4 using Si also showed higher heat resistance than the comparative example using CoFe for the free layer and the reference layer. The cause of this improvement in heat resistance is not clear, but Co₃As in the case of B, it is considered that the bond energy of Fe—Si is higher than the bond energy of the metal bond of Co—Co or Co—Fe.
[0084]
From Examples 1 to 4 described above, an effect of improving heat resistance can be obtained by using an intermetallic compound of a ferromagnetic metal element and a metalloid element for any one of the ferromagnetic layers of the ferromagnetic tunnel junction. I understood it.
[0085]
From the above results, it is easily expected that such a heat resistance improvement effect can be obtained even in a system using not only Fe and Co but also Ni as the ferromagnetic metal of the intermetallic compound. In addition, B and Si were used as the metalloid component of the intermetallic compound in Examples 1 to 4. However, in addition to these, elements that generate an intermetallic compound are used in the same manner as in the Co—Fe and Fe—Si systems. It is easily expected that such a heat resistance improving effect can be obtained even with a conventional system.
[0086]
Further, the case where an intermetallic compound containing a metal element that does not exhibit ferromagnetism alone is used for the reference layer and / or the free layer, that is, the results of Examples 5 to 7 will be described.
[0087]
As a result of identifying the phase by X-ray diffraction after heat-treating the 500 nm-thick single layer film made of MnSb used in Example 5 at 340 ° C. or higher, the phase of the MnSb intermetallic compound is obtained. It was confirmed. Similarly, a single layer film of PdMnSb made of PdMnSb used in Example 6 was heat-treated at 340 ° C. or higher, and the phase was identified by X-ray diffraction. As a result, an intermetallic compound phase of PdMnSb was obtained. It was confirmed that In addition, the Co used in Example 7₂As a result of identifying a phase by X-ray diffraction after heat-treating a 500 nm-thick single layer film made of MnSi at 340 ° C. or higher, Co₂It was confirmed that an intermetallic compound phase of MnSi was obtained.
[0088]
Moreover, the relationship between the heat processing temperature of Examples 5-7 and a comparative example and TMR ratio is shown in FIG. MnSb, PdMnSb, Co in reference layer and free layer₂In Examples 5 to 7 using MnSi, a high TMR ratio was maintained even when the heat treatment temperature was high, and all exhibited high heat resistance. The cause of this improvement in heat resistance is not clear, but Co₃B and Fe₃As in the case of Si, it is considered that the covalent bond energy of Mn—Sb, Co—Si or the like is higher than the bond energy of the metal bond of Co—Co or Co—Fe.
[0089]
From Examples 5 to 7 above, not only intermetallic compounds containing a metal element that exhibits ferromagnetism alone, but also intermetallic compounds that do not exhibit ferromagnetism alone but exhibit ferromagnetism only after forming a compound. It was found that the effect of improving heat resistance was obtained as in Examples 1 to 4.
[0090]
From the above results, it is easily expected that such an effect of improving heat resistance can be obtained even with an intermetallic compound using Cr as well as Mn. Further, the metalloid component of the intermetallic compound is not limited to the elements used in Examples 5 to 7, and it is easily expected that such heat resistance improvement effect can be obtained even if it is other than these elements. Is done.
[0091]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a tunnel magnetoresistive effect element that realizes excellent heat resistance, which can suppress deterioration of TMR characteristics even by a high-temperature heat treatment of, for example, 300 ° C. or higher.
[0092]
In addition, by using such a tunnel magnetoresistive effect element having high heat resistance, even when the manufacturing process includes a heat treatment step, it is possible to suppress an increase in error rate and maintain excellent read characteristics. A device can be realized. That is, the magnetic memory device according to the present invention can greatly improve the affinity with the CMOS process while maintaining excellent read characteristics.
[0093]
In addition, according to the method for manufacturing a tunnel magnetoresistive element of the present invention, a tunnel magnetoresistive element having high thermal stability can be obtained by reliably forming an intermetallic compound phase on at least one of the ferromagnetic layers. .
[Brief description of the drawings]
FIG. 1 is a schematic cross-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 showing another example of a TMR element to which the present invention is applied, and showing a TMR element having a laminated ferrimagnetic structure.
FIG. 3 is a schematic perspective view of a main part of a cross-point type MRAM array having the TMR element of the present invention as a memory cell.
4 is an enlarged cross-sectional view of the memory cell shown in FIG. 3;
FIG. 5 is a plan view of a TEG for evaluating a TMR element.
6 is a cross-sectional view taken along line AA in FIG.
FIG. 7 shows Co as an intermetallic compound.₃It is a characteristic view for demonstrating the heat processing temperature dependence of the TMR ratio of the TMR element containing B.
FIG. 8 shows Fe as an intermetallic compound.₃It is a characteristic view for demonstrating the heat processing temperature dependence of the TMR ratio of the TMR element containing Si.
FIG. 9 shows MnSb, PdMnSb or Co as an intermetallic compound.₂It is a characteristic view for demonstrating the heat processing temperature dependence of the TMR ratio of the TMR element containing MnSi.
[Explanation of symbols]
1 TMR element
2 Substrate
3 Underlayer
4 Antiferromagnetic layer
5 Magnetization fixed layer
6 Tunnel barrier layer
7 Free layer
8 Topcoat layer
9 Ferromagnetic tunnel junction

Claims (8)

A tunnel magnetoresistive element having a ferromagnetic tunnel junction with a tunnel barrier layer sandwiched between a pair of ferromagnetic layers,
At least one of the ferromagnetic layers is covalently bonded to a 3d transition metal element and contains cobalt boride (Co ₃ B) as an intermetallic compound exhibiting ferromagnetism. element.   2. The tunnel magnetoresistive element according to claim 1, wherein at least one of the ferromagnetic layers has at least one layer made of a single crystal of the intermetallic compound. A semiconductor substrate;
A tunnel magnetoresistive element formed on the semiconductor substrate and having a ferromagnetic tunnel junction with a tunnel barrier layer sandwiched between a pair of ferromagnetic layers;
A word line and a bit line sandwiching the tunnel magnetoresistive element in the thickness direction ;
A circuit formed on the semiconductor substrate and connected to the word line or the bit line;
With
At least one of the ferromagnetic layers is covalently bonded to a 3d transition metal element and contains cobalt boride (Co ₃ B) as an intermetallic compound exhibiting ferromagnetism. 4. The magnetic memory device according to claim 3 , wherein at least one of the ferromagnetic layers has at least one layer made of a single crystal of the intermetallic compound. A tunnel magnetoresistive element having a ferromagnetic tunnel junction with a tunnel barrier layer sandwiched between a pair of ferromagnetic layers,
At least one of the ferromagnetic layers is covalently bonded to a 3d transition metal element and contains iron silicide (Fe ₃ Si) as an intermetallic compound exhibiting ferromagnetism, wherein the tunnel magnetoresistive element is characterized in that .   6. The tunnel magnetoresistive element according to claim 5, wherein at least one of the ferromagnetic layers has at least one layer made of a single crystal of the intermetallic compound. A semiconductor substrate;
A tunnel magnetoresistive element formed on the semiconductor substrate and having a ferromagnetic tunnel junction with a tunnel barrier layer sandwiched between a pair of ferromagnetic layers;
A word line and a bit line sandwiching the tunnel magnetoresistive element in the thickness direction ;
A circuit formed on the semiconductor substrate and connected to the word line or the bit line;
With
At least one of the ferromagnetic layers contains iron silicide (Fe ₃ Si) as an intermetallic compound that is covalently bonded to a 3d transition metal element and exhibits ferromagnetism. 8. 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.

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