JP2002204006A - Magnetoresistance element and magnetoresistance effect type storage element - Google Patents

Abstract

(57) Abstract: Provided are a magnetoresistive element and a magnetoresistive storage element having improved selectivity and an output signal by controlling an applied bias. SOLUTION: Two resistance elements 70 and 71 are connected in series, and a magnetoresistance element is used for at least one of them. When using a magnetoresistive element for both, the magnetoresistance can be controlled independently of each other, the nonmagnetic material of the first magnetoresistive element is an electrical insulator, and the nonmagnetic material of the second magnetoresistive element is a conductor. Then, the second magnetoresistive element is operated as a bias control element, the characteristics of the first magnetoresistive element are controlled, and the voltage applied to the storage element is controlled. When the other is configured as a varistor-type element, bias from an unselected storage element is suppressed, and selectivity of the storage element is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a storage element utilizing a magnetoresistance effect (hereinafter, referred to as MR),
The present invention relates to a high-sensitivity and high-density magnetoresistive element and a magnetoresistive storage element.

[0002]

2. Description of the Related Art A solid-state storage device using an MR film is known from LJSchwee, Proceedings of Intermag Conference, IEE Transaction on Magnetics Kyoto (Proc. IN).
TERMAG Conf. IEEE Trance. OnMagn. Kyoto) (1972) 40
5. Various types of MRAMs (magnetic random-access memos) proposed by (5) and comprising a word line as a current line for generating a recording magnetic field and a sense line for reading using an MR film.
ry has been proposed (AVPohm et al., IEE Transactions on Magnetics (I
EEE Trance. On Magn.) 28. (1992) 2356.). For these storage devices, a NiFe film or the like exhibiting an anisotropic MR effect (AMR) having an MR change rate of about 2% is used, and there has been a problem in improving the output.

It has been discovered that an artificial lattice film made of a magnetic film exchange-coupled via a non-magnetic film exhibits a giant magnetoresistance effect (GMR) (AVBaibich et al., Physical Review Letter (Phys. Rev. Lett.)). .) 61 (1988) 247
2) An MRAM using a GMR film was proposed (KTRanmuthu et al., IEEE Trance. Magnetics).
n Magn.) 29. (1993) 2593.). However, although the GMR film made of the magnetic film having the antiferromagnetic exchange coupling shows a large MR change rate, it requires a larger applied magnetic field than the AMR film and has a problem that a large information recording and reading current is required. is there.

[0004] In contrast to the above exchange-coupled GMR film, there is a spin-valve film as a non-coupled GMR film, which uses an antiferromagnetic film (B. Dieny et al., Journal of Magnetic Materials 93). (1991) 101.), and those using (semi) hard magnetic film (H. Sakakima et al.,
Japanese Journal of Applied Physics (Jpn. J. Appl. Phys.) 33. (1994) L1668), which has a low magnetic field similar to that of the AMR film and shows a larger MR ratio than the AMR film. This proposal proposes an MRAM using a spin valve type using an antiferromagnetic film or a hard magnetic film.
This storage element has a nondestructive readout characteristic (NDR).
O: Non-destructive Read-Out) (Y.Irie et al., Japanese Journal
Of Applied Physics (Jpn. J. Appl. Phys.) 3
4. (1995) L415).

[0005] The non-magnetic layer of the above-mentioned GMR film is a conductor film of Cu or the like. However, studies have been made on a tunnel type GMR film (TMR: tunnel magneto resistance) using an insulating film of Al ₂ O ₃ or the like as the non-magnetic layer. MRAM using this TMR film has been proposed. In particular, a TMR film is expected to have a higher output because of its high impedance.

When an MRAM is operated by arranging magneto-resistive elements, a memory cell which is a magneto-resistive element is selected by selecting a bit line and a word line that are orthogonal to each other. Even when a TMR film having excellent element selectivity is used, there is a path that passes through unselected elements, which is equivalent to connecting resistors in parallel, and the MR of one element is output as an output. There was a problem that it could not be fully utilized. In addition, this problem causes a decrease in output S / N with an increase in storage capacity.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetoresistive element and a magnetoresistive storage element having improved selectivity and an output signal in order to solve the above-mentioned conventional problems.

[0008]

To achieve the above object, a magnetoresistive element according to the present invention comprises a first resistive element and a second resistive element.
Are connected in series, and at least one of the first and second resistance elements is a magnetoresistive element.

Further, the magnetoresistance effect type storage element of the present invention comprises:
A first resistance element and a second resistance element are connected in series, at least one of the first and second resistance elements is a magnetoresistance element, and the magnetoresistance element is A plurality of two-dimensional or three-dimensional storage elements are arranged as a single storage element.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, at least one of two resistive elements is a magnetoresistive element, and the other is formed using a magnetoresistive element or a resistive element having a non-linear current-voltage characteristic. They are connected in series to add bias controllability to the magnetoresistive element. Examples of the resistance element having such a non-linear current-voltage characteristic include a varistor-type element and at least one element using an inter-band tunnel effect, a resonance tunnel effect, a single electron tunnel effect, and a Josephson effect as an operation principle. It is preferable to use When using a magnetoresistive element for the two resistive elements,
According to the magnetization direction of the ferromagnetic material constituting the magnetoresistive element,
By allowing the magnetoresistance to be controlled independently of each other, one can operate as a storage element and the other can operate as a bias control element. In such a configuration, one of the magnetoresistive elements has a nonmagnetic material made of a conductor, a semiconductor, or an electrical insulator, and the other magnetoresistive element has a nonmagnetic material made of a conductor or a semiconductor. Preferably, the latter magnetoresistive element is operated as a bias control element, and the characteristics of the former magnetoresistive element are controlled, thereby improving the selectivity of the configured magnetic memory element.

When one is configured as a magneto-resistive element and the other is configured as a resistive element having a non-linear current-voltage characteristic, the varistor voltage of a varistor-type element is optimized, and in the case of a tunnel effect element, the gap voltage is optimized. By designing and manufacturing, it is possible to improve the selectivity of the configured magnetic memory element. Here, the varistor voltage and the gap voltage indicate the voltage point at which the dynamic resistance of the non-linear characteristic has the highest rate of change, and this voltage point is used as a threshold value even when using a resistive element having another non-linear current-voltage characteristic. Use.

Further, another magnetoresistive element is connected in parallel to a resistive element having a non-linear current-voltage characteristic disposed at a subsequent stage, so that the bias voltage of the magnetoresistive element with respect to the varistor voltage and the gap voltage is reduced. The desired selective read operation can be improved also by raising and lowering by the magnetoresistance effect. In this case, the non-magnetic material of the magnetoresistive element is preferably made of a conductor, a semiconductor, or an electric insulator. Further, a non-magnetic material having an electric insulator has a large magnetoresistance effect, and is more preferable.

Hereinafter, description will be made with reference to the drawings.

FIG. 1 is a schematic diagram showing a configuration of a spin-valve type memory element using an antiferromagnetic film (or a magnetization rotation suppressing film). The ferromagnetic film (M) 19 in the MR element portion is an antiferromagnetic film (A
F) exchange-coupled with 18
The ferromagnetic film (M) 19 forms a fixed layer. The current of the word line 17 and / or the sense line or bit line (1
Due to the magnetic field generated by the currents 4 and 15), the free layer 13 mainly using a soft magnetic film rotates the magnetization, and maintains the memory state depending on the magnetization direction with respect to the ferromagnetic film (M) 19 (fixed layer). In FIG. 1, reference numeral 12 denotes a non-magnetic layer electrical insulating film (NM), reference numerals 14 and 15 denote conductive films forming sense lines or bit lines, and reference numeral 16 denotes an interlayer insulating film (I).

If these MR elements are arranged in a matrix as shown in FIG. 2A, an MRAM device can be obtained. That is, the magnetoresistance effect type storage elements 21 are arranged in a matrix,
The conductive films 14 and 15 form a lattice connection. Here, the conductive film (word line) 17 is arranged side by side so as to overlap the conductive film 14, but is omitted in FIG. 2A.

FIG. 2B is a perspective view of FIG. 2A. The conductive film (word line) 17 is arranged so as to run in parallel with the conductive film 14 while being electrically insulated.

The magnetoresistive effect type storage element 21 is composed of the conductive film 1
The conductive film (word line) 17 is positioned at a lattice point by 4 and 15 and is vertically contacted by conductive films 14 and 15 so that a magnetic field can be applied to the magnetoresistive effect type storage element 21 most effectively. To place. In the case of the drawing, a case is shown in which the memory element is disposed immediately above the magnetoresistive storage element 21.

As shown in FIG. 2, the magnetoresistive storage element 21
In order to effectively apply a magnetic field to the free layer 13, which is a storage cell of the magnetoresistive storage element 21, using the conductive film (word line) 17, The distance between the conductive film 13 and the conductive film (word line) 17 is approximately
It is preferably at most 500 nm. Conductive film (word line)
In the case where the current density applied to 17 is set to 1 × 10 ⁷ A / cm ² or less, the distance between free layer 13 and conductive film (word line) 17 is more preferably about 300 nm or less.

Reading of the stored contents of the magnetoresistive effect type storage element 21 is performed by using the conductive films 14, 1 serving as sense lines and bit lines.
5, the change of the resistance value of the magnetoresistive storage element 21 is monitored. At this time, there are a case where the resistance change is monitored as a voltage change under the application of a constant current and a case where the resistance change is monitored as a current change under the application of a low voltage. Use both.

However, simply connecting the elements in parallel requires
The selectivity of the storage element is inevitably reduced, resulting in deterioration of S / N. A thick solid line 43 shown in FIG. 3 indicates a bias line passing through a selected element, and a thick broken line 44 indicates an example of a bias line passing through an unselected element.
By connecting the non-selected bias lines in parallel as described above, the decrease in the S / N of the MRAM device becomes more remarkable as the storage capacity increases.

In the present invention, this problem is solved by forming two magneto-resistive elements which are formed of a ferromagnetic substance and a non-magnetic substance in series, and controlling the magneto-resistance of the elements independently of each other. Was. In other words, the first magnetoresistive element, which is one of the magnetoresistive elements, has a nonmagnetic material as an electrical insulator, and the other second magnetoresistive element has a nonmagnetic material as a conductive material. By operating the resistance element as a bias control element and controlling the characteristics of the first magnetoresistive element, the S / N of the MRAM device can be improved.

Further, a magnetoresistive element and a resistance element having a non-linear current-voltage characteristic are connected in series, and a bias applied to a selected storage element is applied to the surroundings by utilizing the strong non-linearity of the non-linear resistance element. By setting higher than the bias, the S / N of the MRAM device can be improved.

Further, an element constituted by combining a second magnetoresistive element and a non-linear resistance element in parallel is arranged at a stage subsequent to the first magneto-resistance element as a storage cell, and the non-linear element has strong nonlinearity. By using the generated switching characteristic and setting the characteristic voltage within the magnetoresistance change range obtained by the second magnetoresistance element, the second magnetoresistance element operates as a bias control element,
By controlling the characteristics of the magnetoresistive element, the S / N of the MRAM device can be improved.

FIG. 4A shows the operation principle of the AF spin-valve type memory element. The ferromagnetic film (M) 19, which is a fixed layer, is AF
It is formed to be exchange coupled with layer 18, the magnetization of which is pinned in one direction. The direction of the current flowing through the word line (W) 17 is changed to reverse the magnetization of the free layer 13 in a different direction, thereby recording "1" and "0".

In reading out the selected memory, the resistance difference between the reference resistance element and the appropriate reference resistance element is measured to determine whether it is "1" or "0".
Identify. That is, in the case of FIG. 4B, since the resistance difference is 0, it is identified as “0”, and in the case of FIG.
Therefore, it is identified as "1". Here, for convenience,
Although the states of “1” and “0” are specified, it is needless to say that the states may be reversed. In this case, it is preferable to use the same resistance as that of the magnetoresistive element serving as the storage element, as shown in FIGS. 4B and 4C. As described above, the magnetoresistive element itself may be used as the reference resistor.

In this embodiment, an example is shown in which the ferromagnetic film 19 is used as the fixed layer in the AF layer 18, but the coercive force difference between the ferromagnetic film 19 and the soft magnetic film layer 13 is used without using the AF layer 18. In the magnetoresistive element constituted by using the ferromagnetic film 19, the ferromagnetic film 19 may be used as a storage layer. In the case of such an element, the coercive force (H _C2 ) of the ferromagnetic film 19 is made larger than the coercive force (H _C1 ) of the soft magnetic film layer 13, and H> H _C2 at the time of memory writing.
(Or H <-H _C2) be made in, at the time of reading H _C2
>H> H _C1 (or −H _C1 >H> −H _C2 ). At this time, H _C2 >H> H _C1 , −H _C1
>H> -H _C2 ), by applying a magnetic field in the positive and negative directions to invert the magnetization direction of the soft magnetic film 13 and monitoring the value of the change in magnetoresistance with respect to the ferromagnetic film 19, the memory state is non-destructive. , And the present invention may be configured using this configuration.

The above is a description of the operation principle of a 1-bit element.
It is necessary to arrange these elements in a matrix as shown in FIG. In this case, for each element, for example, two word lines orthogonal to each other near the element at the address (N, M), or a sense line (or bit line) and a word line which are also arranged orthogonally, Alternatively, a synthetic magnetic field is generated using the sense lines and the bit lines to write data, thereby improving write selectivity.

For reading, the magnetoresistive element and the magnetoresistive control element of the present invention are arranged in parallel at the intersection of the sense line group and the bit line group that intersect each other. , And the memory cell at the address (N, M) can be selected. At this time, in order to transmit the signal pulse efficiently,
In particular, the element for controlling the reluctance of the present invention is useful for preventing the inflow of a signal pulse via another path and the return of a harmonic component due to the speeding up of the signal pulse.

In general, a Ni—Co—Fe alloy is suitable for the free layer 13 of the magnetoresistive element shown in FIG. The atomic composition ratio of the Ni-Co-Fe film is Ni _x Co _y Fe _z , where 0.6 ≦ x ≦
0.9, 0 ≦ y ≦ 0.4, Ni-rich soft magnetic film of 0 ≦ z ≦ 0.3, or Ni _{x ′} Co _{y ′} Fe _{z ′} , where 0 ≦ x ′ ≦ 0.4, 0.2 ≦ y ′ ≦
It is desirable to use a Co-rich film of 0.95, 0 ≦ z ′ ≦ 0.5.

The films having these compositions have low magnetostriction characteristics (1 × 10 ⁻⁵ or more) required for sensors and MR heads.

The thickness of the free layer is 1 nm or more and 10 nm or more.
The following is good. When the film thickness is large, the MR ratio is reduced by the shunt effect, but when too thin, the soft magnetic characteristics are deteriorated. More preferably, it is 2 nm or more and 7 nm or less.

MRAM in which magnetoresistive elements are arranged in a matrix
5A, the first magnetoresistive element 70 and the second magnetoresistive element or the non-linear resistive element or the element 50 combining the both are connected in series as shown in FIG. 5A. Is preferred. More specifically, conductive film 1
4, a first magnetoresistive element 70, a second magnetoresistive element, a non-linear resistive element, or an element 5 combining both
0 and the conductive film 15 are connected in series. Further, the resistance value of the first magnetoresistive element 70 is variable.

As described above, in order to obtain the selectivity of the memory cell, the second resistance element (NL) 71 for controlling the characteristics of the element is connected in series with the first resistance element 70 as shown in FIG. 5B. It is desirable to arrange. In FIG. 5B, the TMR element 70
In contrast, the NL 71 is arranged at the lower part, but may be arranged at the upper part.

According to the present invention, the resistance element (NL) for controlling the characteristics of the element is a magnetoresistive element composed of a ferromagnetic material (fixed layer and free layer) sandwiching a nonmagnetic conductor (or semiconductor). desirable. At this time, 71 which is a magnetoresistive element is a non-tunnel type giant magneto resistance (GMR) element. An appropriate load element (for example, load resistance) LR73 is connected to the non-magnetic conductor to form an element as shown in FIG. 5C. In this case, if the magnetization directions of the two ferromagnetic bodies 71 constituting the NL are parallel, the applied bias current flows to the sense line, and if the magnetization directions are antiparallel, a part of the bias current is diverted in the LR direction. . This shunt occurs due to a magnetic field switching operation that generates an impedance difference between the NL magnetoresistive element and the LR element, and the resulting bias drop to the sense section is reduced by the parallel resistance through the unselected magnetoresistive element. And the use of the magnetoresistive magnetic storage element constituted by the magnetoresistive element of the present invention makes it possible to improve the S / N of the MRAM device.

Further, as shown in FIG. 6A, the selectivity of the memory cell can be improved also in the MRAM device including the magnetoresistive element formed by connecting the magnetoresistive element 70 and the non-linear resistance element 60 in series.

FIG. 6B is a schematic sectional view of an example of the equivalent circuit of FIG. 6A. That is, a conductive film (word line) 1
7, a conductive film 14, a conductive film (contact electrode) 61, a magnetoresistive element 70 between the conductive film (contact electrode) 61, a non-linear resistance element 60 and the conductive film 1.
5 are stacked in series.

As the resistance element having a non-linear current-voltage characteristic, an element having a varistor type characteristic,
It is preferable to use at least one of an interband tunnel effect element, a resonance tunnel effect element, a single electron tunnel effect element, and a Josephson effect element.

That is, as shown in FIG. 3, the voltage applied to the selected storage cell section via the non-selected storage cell (see the broken line section 44) is set to a value lower than the varistor voltage or the tunnel gap voltage. By fabricating a nonlinear resistance element so that the applied voltage is equal to or higher than the varistor voltage or the tunnel gap voltage, the selectivity of the memory cell is improved,
It is possible to improve the S / N of the RAM device.

FIG. 7 is a diagram showing the configuration of an MRAM device comprising the magnetoresistive element of the present invention, and FIG. 10 shows an example of the electrical characteristics of the magnetoresistive element of the present invention. As shown in FIG. 7, when the N-th row sense line 14 and the M-th bit line 15 are selected and the selected element is biased to the S point, the element group other than the M-th column connected to the N-th row sense line is connected to the U point. , M rows are biased to the V point, and the other elements are biased to the O point. At this time, Vs> Vb, Vb
> Vu, Vv, Vo, and the characteristic voltage becomes lower than the characteristic voltage except for the point S, so that it is possible to retrieve the storage information of only the selected element, which is such a problem.

Setting the bias level to three values as in the timing chart of pulse bias application shown in FIG. 8 is effective in stabilizing the device operation. The sense line when not selected is biased at L-level, the bit line when not selected is biased at M-level, the sense line when selected is H-level, and the bit line when selected is Ll.
I will bias it with evel. This operation enables a read operation of the element to be selected. In addition, H-
By setting the bias difference between level and M-level larger than the bias difference between M-level and L-level, operation stability is improved. According to the example shown in FIG. 8, Vs> Vb >>Vu> Vo >>
Vv, and the selected memory cell can be read.

Further, as shown in FIG. 11, an element constituted by combining a second magneto-resistance element 71 and a non-linear resistance element 111 in parallel is arranged after the first magneto-resistance element 70 and stored. The device was constructed. In this case, by using the switching characteristic generated by the strong nonlinearity of the nonlinear element and setting the characteristic voltage within the magnetoresistance change range obtained by the second magnetoresistance element, the second magnetoresistance element can be used. Operates as a bias control element, and shunts the output from the first magnetoresistive element, thereby turning on and off the storage and reading. FIG.
2 shows a characteristic diagram of the resistor element arranged at the subsequent stage. When the bias voltage point when the second magnetoresistive element is in the low resistance state is point P and the bias voltage point when the second magnetoresistive element is in the high resistance state is point Q under a constant current application, the bias is applied to point P. Since the non-linear elements connected in parallel have a much larger resistance than the second magneto-resistive element, the current is
5 is output. In the state biased to the point Q, since the nonlinear element has a smaller resistance than the second magnetoresistive element, the current flows through the nonlinear element, is terminated, and the output to the sense line is greatly reduced. it can. At this time, the current shunt rate directly depends on the change rate of the dynamic resistance Rd of the nonlinear element. When the Rd of the nonlinear element changes about 10 times at the points P and Q, the shunt ratio is 1
It can be 0 times. As described above, the larger the change rate of the dynamic resistance Rd is, the more steep the output can be turned on and off, and the read selectivity of the storage element can be improved.

As the metal magnetic film of the fixed layer, materials such as Co, Fe, Co-Fe, Ni-Fe, and Ni-Fe-Co alloy are excellent. In particular, Co, Fe or a Co—Fe alloy is good for obtaining a large MR ratio, and therefore it is desirable to use them at the interface with the nonmagnetic layer.

Further, XMnSb (where X represents Ni, Pt, Pd, Cu) has a high magnetic polarizability, so that a large MR ratio can be obtained when an MR element is constructed.

As the oxide magnetic film of the fixed layer, MFe ₂ O
₄ (M is one or more elements selected from Fe, Co, and Ni) is desirable. These are ferromagnetic up to relatively high temperatures, and Co and Ni-rich have extremely high resistance compared to Fe-rich. Also C
Since o-rich has a feature of great magnetic anisotropy, desired characteristics can be obtained by adjusting these composition ratios.

As the AF layer (or the magnetization rotation suppressing layer) in contact with the fixed layer, the metal film is made of Ir-Mn,
There are Rh-Mn, Ru-Mn, Cr-Pt-Mn, etc., which have an advantage that the film can be exchange-coupled to the magnetic film by forming the film in a magnetic field, and the process can be simplified. On the other hand, ordered alloys such as Ni-Mn and Pt- (Pd) -Mn require heat treatment for ordering, but are excellent in thermal stability, and Pt-Mn is particularly preferred.

As the oxide film, α-Fe ₂ O ₃ , NiO,
Or LTO ₃ (L is a rare earth element excluding Ce, T is Fe, C
r, Mn, and Co are shown. ) Is preferred.

In general, a Ni—Co—Fe alloy is suitable for the free layer. The atomic composition ratio of the Ni-Co-Fe film is NixC
oyFez, where 0.6 ≦ x ≦ 0.9, 0 ≦ y ≦ 0.4, 0 ≦ z ≦ 0.3
Ni-rich soft magnetic film, or Nix'Coy'Fez ', where 0 ≦ x ′ ≦ 0.4, 0.2 ≦ y ′ ≦ 0.95, 0 ≦ z ′ ≦ 0.5 Co-rich
It is desirable to use a membrane.

Non-magnetic layer 1 between free layer 13 and fixed layer 19
When an electrical insulator is used as oxide 2, oxide, carbide, or nitride such as Al ₂ O ₃ or MgO is excellent. In particular, in the case of nitride, MN (O) (where M
Is selected from at least one of Al, B, and In.
(O) indicates mixing of oxygen. Is preferred. Alternatively, a wide gap semiconductor having an energy gap value of 2 to 6 eV is also preferable.

The resistance of the magnetoresistive element depends on the thickness of the non-magnetic material which is an electrical insulator. In order to operate as a magnetoresistive element, it is necessary to configure it in a range of about 0.5 nm to 5 nm. That is, a desired value of the resistance of the magnetoresistive element can be realized by controlling the thickness of the nonmagnetic material.

When a metal is used for the nonmagnetic layer 12 between the free layer 13 and the pinned layer 19, there are Cu, Ag, Au, Ru and the like, but Cu is particularly excellent. The thickness of the non-magnetic layer should be at least as small as possible to weaken the interaction between the magnetic layers.
0.9 nm or more is required. When the nonmagnetic layer becomes thicker, M
Since the R ratio decreases, the film thickness is preferably 10 nm or less, preferably
Should be 3 nm or less. When the thickness of the nonmagnetic layer is 3 nm or less, the flatness of each layer is important, and if the flatness is poor, the two magnetic layers 13 and 11 which should be magnetically separated by the nonmagnetic layer. Or, a magnetic coupling occurs between them and 19, resulting in deterioration of the MR ratio and reduction in sensitivity. Therefore,
The unevenness at the interface between the magnetic layer and the non-magnetic layer is desirably 0.5 nm or less.

[0051]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, more specific examples will be described.

Example 1 A multi-sputtering apparatus, a photolithography technique, a dry etching technique, and a polishing flattening technique were used on a substrate provided with a conductive portion used as a contact portion for a bit line in advance, as shown in FIG. A magnetoresistive storage element having a cross-sectional structure as shown was manufactured.

The memory element portion is formed on the substrate 90,
One of which is composed of a magneto-resistive element 70 and 71, the one of the magnetoresistive element _{71, Ni 0 .68 Co 0.2 Fe} 0.12 as soft magnetic film 71C used for the free layer, the hard magnetic film 7 is used as a fixed layer
Use Co _0.75 Pt _0.25 as 1a and C as nonmagnetic conductive film 71b.
u. The Cu of the nonmagnetic conductive film 71b is also drawn out as the electrode 91, and is connected to the contact layer 61 or the resistor 73 that is produced simultaneously with the word electrode body 17 for the other magnetoresistive element. In addition, Pt, Au, Cu, or Al, Au
Using Cr, Ti / Au, Ta / Pt, Cr / Cu / Pt / Ta, etc., Al or AuCr, Ti / Au, Ta / Pt, Cr / Cu
/ Pt / Ta or the like was used. Al ₂ O ₃ or C
and measure the electrical insulation with such aF ₂ or SiO ₂ or Si ₃ N _4.

The other magneto-resistive element 70 is provided with a TMR element, and is formed by sputtering from a target material of Co _0.9 Fe _0.1 , Al, Co _0.5 Fe _0.5 , IrMn, and Ni _0.8 Fe _0.2 (all compositions are atomic). Ratio), NiFe (20) / CoFe (4) / Al ₂ O ₃ (1.2) / CoFe (4) / IrMn (2
0) (The value in parentheses indicates the thickness (nm)).

Here, Al ₂ O ₃ of the nonmagnetic insulating layer 70b was prepared by forming an Al film and then performing an oxidation process. The oxidation step was performed by natural oxidation in a vacuum tank, by natural oxidation under heating in a vacuum tank, or by oxidation in plasma in a vacuum tank. It was confirmed that a good non-magnetic insulating film was obtained in any of the steps.

In the case of the present embodiment, a method of natural oxidation under heating in a vacuum chamber was used. In addition, the thickness of the non-magnetic insulating layer (12a, 70b) at this time is 0.3 nm to secure insulation.
The above is necessary. If the thickness of the non-magnetic insulating layer (12a, 70b) is too large, the tunnel current will not flow, so the thickness is desirably 3 nm or less. Non-magnetic insulating layer at this time
Since the thickness of (12a, 70b) is directly related to the resistance of the element,
It is preferable to adjust the film thickness in accordance with the desired element resistance. However, even in this case, the flatness of each layer is important, and when the flatness is reduced, the nonmagnetic insulating layers (12a, 70b) are broken, and tunnel leakage occurs or two ferromagnetic films (13, 19, 70a and 70c), a magnetic coupling occurs,
The MR ratio of the MR element section (21, 70) is degraded and the sensitivity is lowered.
Therefore, the unevenness of the interface between each ferromagnetic film and the non-magnetic insulating film is 0.
The thickness is preferably 5 nm or less, more preferably 0.3 nm or less.

When the MR characteristics of the TMR element alone were measured at room temperature under an applied magnetic field of 40 Oe, the MR ratio was about 36%. The bonding area at this time is about 0.5 μm vertically and about 1.5 μm horizontally
It was prepared in.

When a bias current was applied from the sense line 14 to the sense line 15 by constant current driving and measurement was performed, when the magnetization directions of the two ferromagnetic materials of the second magnetoresistive element 71 were parallel, A change in resistance according to the parallel / antiparallel magnetization direction of the first magnetoresistive element 70 was detected. In other words, it can be seen that the memory could be read by associating the parallel and antiparallel with “0” and “1”. First, a current is applied to the word line 17 to magnetize the SM film of the first magnetoresistive element in one direction, and then a current pulse is also applied to the word line 17 to measure a voltage change of the storage element measured through the sense line. Monitored. A change in the output of information stored in the first magnetoresistive element 70 in accordance with the polarity of the current pulse applied to the word line was detected, and it was confirmed that the arranged magnetoresistive element 70 operates as a storage element.

Next, when a current is applied to the word line 72 to make the magnetization directions of the two magnetic films of the second magnetoresistive element 71 antiparallel, the detected output is lower than in the parallel case. . This means that the applied current is
This indicates that the flow was diverted in the direction. In this embodiment, a load resistance of 1 to 10Ω is used for the LR section.

That is, according to the operation result, when the magnetization direction of the subsequent stage magnetoresistive element is in the parallel state, reading of the preceding storage element is possible, and when the magnetization direction of the subsequent stage of the magnetoresistive element is in the antiparallel state, It was possible to create a state where reading of the storage element in the preceding stage was difficult, and the magnetoresistance effect type storage element of the present invention was realized.

As a result, the output of the storage element by the preceding magnetoresistive element can be distributed to the output path by the resistance change to the subsequent magnetoresistive element, and the information can be selectively read from the storage element. It became.

(Example 2) Al ₂ O ₃ or SiO ₂ was formed on a substrate provided with a conductive portion used as a lower electrode contact in advance.
_A contact hole was provided in the interlayer insulating layer formed by depositing _2, and a SiC polycrystalline film layer was formed thereon by direct sputtering of SiC in an Ar atmosphere. The substrate is 200-750
C., and the sputtering power was 400 to 500 W. This SiC layer can also be formed by Si thermal evaporation in a C ₂ H ₂ atmosphere. After an insulating layer was further provided thereon and a contact portion was provided at a desired position, a contact portion was formed using copper plating, and a planarization process was performed to form a varistor element portion. The characteristics of the varistor-type element portion were adjusted by controlling the grain growth and the state of grain boundary bonding of the polycrystalline film.

Further, a magnetoresistive element portion was manufactured using a multi-source sputtering apparatus. The magnetoresistive element is a TMR type element, and C
o From a target material of _0.9 Fe _0.1 , Al, Co _0.5 Fe _0.5 , IrMn, Ni _0.8 Fe _0.2 using a sputtering method (all compositions are atomic ratios), NiFe (20) / CoFe (4) / Al ₂ O ₃ ( 1.2) / CoFe (4) / IrMn (20)
(The thickness in the parentheses indicates the thickness (nm)).

Al ₂ O ₃ of the nonmagnetic insulating layer was prepared by forming an Al film and then performing an oxidation process. The oxidation step was performed by natural oxidation in a vacuum tank, by natural oxidation under heating in a vacuum tank, or by oxidation in plasma in a vacuum tank. It was confirmed that a good non-magnetic insulating film was obtained in any of the steps. In the present example, it was manufactured by a method based on natural oxidation in a vacuum chamber.

When the MR characteristics of the device were measured at room temperature and an applied magnetic field of 40 Oe, the MR ratio was about 36%, and the junction area at this time was about 0.5 μm × about 1.5 μm.

The magnetoresistive element fabricated using such a film was constructed and fabricated as a single memory cell as shown in the schematic diagram of FIG. 6, and the operation was confirmed by voltage driving. The storage element portion is configured by connecting a magnetoresistive element and a varistor-type element in series. Pt or
Use Cu, Au, Al or Cu, AuC for word line conductive film
r, Ti / Au, Ta / Pt, Cr / Cu / Pt / Ta, etc. were used. Al ₂ O ₃ or CaF ₂ , SiO ₂ , Si ₃ N ₄ for insulation between storage element and word line
And so on.

FIG. 10 shows a state in which a voltage bias is applied to the manufactured memory cell. The selected storage cell, S
In the case of the type, since the bias is applied to the S point higher than the varistor voltage, a desired output voltage can be secured.

Other unselected storage cells (see FIG. 7)
U type, V type and O type are
The bias was applied to the point, the V point, and the O point, and none of them was biased to a voltage higher than the varistor voltage at which the resistance rapidly decreased, so that the output from the memory cell was not affected.

Thus, by configuring an MRAM device using the magnetoresistive storage element of the present invention, it is possible to improve the selectivity of the memory cell and to improve the S / N of the MRAM device.

(Embodiment 3) A multi-sputtering apparatus, a photolithography technique, a dry etching technique, a polishing flattening technique, and the like are used on a substrate provided in advance with a conductive part used as a contact part for a bit line, as shown in FIG. The magnetoresistive storage element represented by the equivalent circuit shown in FIG.

The storage element portion is composed of two magnetoresistive elements, and one of the lower magnetoresistive elements is a TMR.
Co _0.9 Fe _0.1 , Al, Co _0.5 Fe _0.5 , IrMn, Ni _0.8 F
e Using a sputtering method from a target material of _0.2 (all compositions are atomic ratios), NiFe (20) / CoFe (4) / Al ₂ O ₃ (1.2) / CoFe (4) /
IrMn (20) (in parentheses indicates thickness (nm)).

Further, a varistor type resistance element is connected in parallel with the magnetoresistance element. A varistor voltage is raised near the varistor voltage by arranging a load resistor after the magnetoresistive element, and a bias point is applied to the varistor type element according to the magnetoresistance value.

Here, Pt, Cu, Au or the like is used for the contact electrode or the sense line conductive film, and Al or Cu, AuCr, Ti / Au, Ta / Pt, Cr / Cu / Pt / Ta or the like was used. Al ₂ O ₃ or CaF ₂ or SiO for each interlayer insulating layer
₂ or Si ₃ N ₄ for insulation.

The magnetoresistive element disposed on the other upper part is also TM
R type element, Co _0.9 Fe _0.1 , Al, Co _0.5 Fe _0.5 , IrMn, Ni _0.8
NiFe (20) / CoFe (4) / Al ₂ O ₃ (1.2) / CoFe by sputtering from a target material of Fe _0.2 (all compositions are atomic ratios)
(4) / IrMn (20) (the value in parentheses indicates the thickness (nm)).

Here, Al ₂ O ₃ of the non-magnetic insulating layer was prepared by forming an Al film and then performing an oxidation process.
The oxidation step was performed by natural oxidation in a vacuum tank, by natural oxidation under heating in a vacuum tank, or by oxidation in plasma in a vacuum tank. It was confirmed that a good non-magnetic insulating film was obtained in any of the steps.

When the MR characteristics of the TMR element alone were measured at room temperature and Oe with an applied magnetic field of 40, the MR ratio was about 36%. The bonding area at this time is about 0.5 μm vertically and about 1.5 μm horizontally
It was prepared in.

In this device, the operation was confirmed by applying a bias current from the sense line 14 to the sense line 15 by constant current bias drive. When the operation was measured, when the magnetization directions of the two ferromagnetic materials of the lower magnetoresistance element 71 were parallel, a change in resistance according to the parallel / antiparallel magnetization directions of the upper magnetoresistance element 70 was detected. .

Next, a current is supplied to the word line 72 to
It was confirmed that when the magnetization directions of the two magnetic films of the magnetoresistive element 71 were set to be antiparallel, the current was largely diverted to the varistor type element side. Thus, it was confirmed that the bias applied to the storage cell was controlled by the magnetoresistive storage element of the present invention.

(Example 4) As a resistance element exhibiting strong nonlinearity (see 60 in FIG. 6A), a tunnel element (MIM) is used to construct and manufacture a single storage cell as shown in FIG. The operation was confirmed with. The magnetoresistive element was formed with the configuration shown in Example 2. Here, Al-Al ₂ O ₃ -Au was used for the MIM element.

FIG. 13 shows a state of a change in magnetoresistance under application of a voltage bias to the manufactured memory cell. First
A state is shown in which the magnetoresistance difference generated according to the magnetizations of the fixed layer and the free layer of the magnetoresistance element 70 being parallel (P) and antiparallel (AP) is obtained as an output. FIG. 13 shows that not only the magnetoresistance effect can be obtained as a current change in the case of voltage driving, but also that the magnetoresistance effect can be obtained as a voltage change in the case of current driving.

Thus, by configuring an MRAM device using the magnetoresistive effect type storage element of the present invention, it is possible to improve the selectivity of the memory cell and to realize an improvement in the S / N of the MRAM device.

The magnetoresistive element used in the embodiment is not limited to the TMR element, but can be used for a GMR element.

Further, by configuring an MRAM device using the magnetoresistive effect type storage element of the present invention shown in the above embodiments, an MRAM device having excellent cell selectivity can be constructed.

[0084]

As described above, according to the present invention,
The bias applied to the magnetoresistive element can be controlled, and even when an MRAM is configured, the selectivity of the magnetic storage cells when arranged in a matrix is excellent, and the S / N is deteriorated even when the storage capacity is increased. An effective magnetoresistive storage device can be realized.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of a storage element according to an embodiment of the present invention.

FIG. 2 is a basic configuration diagram of a storage element according to an embodiment of the present invention.

FIG. 3 is a diagram showing the operation principle of the magnetoresistive storage element according to one embodiment of the present invention;

FIG. 4 is a diagram showing the operation principle of a storage element according to one embodiment of the present invention;

FIG. 5 is a schematic configuration diagram of a storage element according to an embodiment of the present invention.

FIG. 6 is a schematic configuration diagram and an equivalent circuit diagram of a storage element according to an embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of a storage element according to an embodiment of the present invention.

FIG. 8 is a diagram showing the operation principle of a storage element according to one embodiment of the present invention.

FIG. 9 is a schematic configuration diagram of a storage element according to an embodiment of the present invention.

FIG. 10 is a basic characteristic diagram of a storage element according to an embodiment of the present invention.

FIG. 11 is an equivalent circuit diagram of a storage element according to an embodiment of the present invention.

FIG. 12 is a basic characteristic diagram of a storage element according to an embodiment of the present invention.

FIG. 13 is a basic characteristic diagram of a storage element according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Nonmagnetic insulating film 13 Soft magnetic film (free layer) 14 Conductive film 15 Conductive film 16 Interlayer insulating film 17 Conductive film (word line) 18 Antiferromagnetic film or magnetization rotation suppression layer 19 Ferromagnetic film 21 Magnetoresistance effect type memory Element 41 Selected storage cell 42 Unselected storage cell 43 Sense pulse path passing through selected storage cell 44 Sense pulse path passing through unselected storage cell 50 Resistive element (magnetic resistance element or non-linear resistance element) 60 Nonlinear resistance element (varistor type resistance element) 61 Conductive film (contact electrode) 70 First magnetoresistance element 71 Second magnetoresistance element 72 Conductive film (word line of second magnetoresistance element) 73 Load resistance (LR) 74 inter-layer insulating film 90 base 91 non-magnetic conductive film 110 load resistance 111 non-linear resistance element (varistor type resistance element)

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H01L 27/105 H01L 29/66 Z 29/66 27/10 447 (72) Inventor Kiyoyuki Morita Kadoma, Kadoma-shi, Osaka 1006 Matsushita Electric Industrial Co., Ltd. F term (reference) 5E049 AA04 AA07 AC00 AC05 BA12 CB02 GC01 5F083 FZ10 GA30 JA36 JA37 JA38 JA39 JA56 JA60 PR22

Claims (27)

[Claims] A first resistance element and a second resistance element are connected in series, and one of the first and second resistance elements is a magnetoresistive element; Magnetic resistance element. 2. The magnetoresistive element according to claim 1, wherein said magnetoresistive element has a laminated structure of at least two magnetic layers and a nonmagnetic layer therebetween. 3. The magnetoresistive element according to claim 1, wherein said first resistive element and second resistive element are connected in series, and both said first and second resistive elements are magnetoresistive elements. element. 4. The magnetoresistive element according to claim 3, wherein the magnetoresistive elements of the first and second resistive elements can control the magnetoresistance independently of each other. 5. A method according to claim 1, wherein each of said first and second resistive elements has a plurality of magneto-resistive elements. 4. The magnetoresistive element according to claim 3, wherein the element can be controlled. 6. The non-magnetic layer of one of the first and second resistance elements is an electrical insulator acting as a spin tunnel barrier between the non-magnetic layers, and the other resistance element is a non-magnetic layer. 4. The non-magnetic layer according to claim 3, wherein the non-magnetic layer is a conductor.
3. The magnetoresistive element according to claim 1. 7. The device according to claim 1, wherein one of the first and second resistance elements is a magnetoresistance effect element, and the other resistance element is a resistance element having a non-linear current-voltage characteristic. Magnetoresistive element. 8. The magnetoresistive element according to claim 7, wherein the resistance element having the non-linear current-voltage characteristic is a varistor type element. 9. The magnetoresistive element according to claim 8, wherein the varistor element is a SiC polycrystalline varistor element. 10. The resistance element having the non-linear current-voltage characteristic is at least one element selected from an interband tunnel effect element, a resonance tunnel effect element, a single electron tunnel effect element, and a Josephson effect element. 3. The magnetoresistive element according to claim 1. 11. One of the first and second resistance elements is a magnetoresistive element,
2. The magnetoresistive element according to claim 1, wherein the other resistive element is an element in which a resistive element having a non-linear current-voltage characteristic and a magnetoresistive element are connected in parallel. 12. The magnetoresistive element according to claim 11, wherein said resistive element having a non-linear current-voltage characteristic is a varistor element. 13. The magnetoresistive element according to claim 12, wherein said varistor element is a SiC polycrystalline varistor element. 14. The resistance element having the non-linear current-voltage characteristic is at least one element selected from an interband tunnel effect element, a resonance tunnel effect element, a single electron tunnel effect element and a Josephson effect element.
3. The magnetoresistive element according to claim 1. 15. A first resistance element and a second resistance element are connected in series, and one of said first and second resistance elements is a magneto-resistance element. A magnetoresistive effect type storage element, wherein a plurality of magnetoresistance elements are arranged two-dimensionally or three-dimensionally as a single storage element. 16. The magnetoresistive element according to claim 1, wherein said magnetoresistive element has a laminated structure of at least two magnetic layers and a nonmagnetic layer therebetween.
6. The magnetoresistive storage element according to 5. 17. The magnetoresistive storage element according to claim 15, wherein both the first and second resistance elements are magnetoresistance elements. 18. The magnetoresistive storage element according to claim 17, wherein the magnetoresistive elements of the first and second resistive elements can control the magnetoresistance independently of each other. 19. The first and second resistive elements have a laminated structure of at least two magnetic layers and a non-magnetic layer between them, and the first and second resistive elements have a laminated structure. The non-magnetic material of any one of the resistance elements is an electrical insulator acting as a spin tunnel barrier between the non-magnetic layers, and the non-magnetic substance of the other resistance element is a conductor. A magnetoresistive storage element. 20. One of the first and second resistance elements is a magnetoresistive element,
16. The magnetoresistive storage element according to claim 15, wherein the other resistance element has a non-linear current-voltage characteristic. 21. The magnetoresistive storage element according to claim 20, wherein said resistance element having a non-linear current-voltage characteristic is a varistor element. 22. The magnetoresistive storage element according to claim 21, wherein the varistor element is an SiC polycrystalline varistor element. 23. The resistance element having the non-linear current-voltage characteristic is at least one element selected from the group consisting of an interband tunnel effect element, a resonance tunnel effect element, a single electron tunnel effect element and a Josephson effect element.
0. A magnetoresistive storage element according to item 0. 24. One of the first and second resistance elements is a magnetoresistive element,
The other resistance element is an element in which a resistance element having a non-linear current-voltage characteristic and a magnetoresistance element are connected in parallel, and a plurality of the elements are arranged two-dimensionally or three-dimensionally as a single storage element. Magneto-resistance effect type storage element. 25. The magnetoresistive storage element according to claim 24, wherein the resistance element having the non-linear current-voltage characteristics is a varistor element. 26. The magnetoresistive storage element according to claim 25, wherein said varistor element is an SiC polycrystalline varistor element. 27. A resistance element having a non-linear current-voltage characteristic,
25. The magnetoresistive storage element according to claim 24, which is at least one element selected from an interband tunnel effect element, a resonant tunnel effect element, a single electron tunnel effect element, and a Josephson effect element.