JP3282943B2 - Memory element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a memory device utilizing a magnetoresistance effect.

[0002]

2. Description of the Related Art Conventionally, as a memory element using a magnetoresistive effect, a conventional MR (magnetoresistive effect) material such as Ni-Fe or Ni-Fe-Co as shown in FIG. Memory devices using conductors (sense lines) made of Ni-Fe (-Co) / TaN / Ni-Fe (-Co) have been proposed (USP
4,754,431 and IEEE Trans.Mag.Vol.27, No.6,1991,
pp5520-5522). Since these materials use a conventional material as the MR material, the MR change rate is 2 to 3%, the output at the time of reading information is small, and essentially nondestructive reading is difficult. Also, since recording and reading are performed using only word lines, a large current is required.

[0003]

Since a conventional material is used as the MR material, the MR change rate is 2 to 3%, the output at the time of reading information is small, and it is essentially difficult to perform nondestructive reading. Also, at the time of recording, a very large current is required because a magnetic field is generated using only the word lines to perform recording on the element.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to realize a larger resistance change rate ΔR at a practically low magnetic field.
An object of the present invention is to provide a high-density memory element which is capable of non-destructive reading and has high recording / reproducing efficiency using a magnetoresistive effect element exhibiting / R.

[0005]

A memory device according to the present invention comprises a first magnetic film, a second magnetic film, a non-magnetic metal film separating the first magnetic film and the second magnetic film, and a sense element. And a word line for generating a magnetic field for performing recording / reading in the element portion, wherein the sense line and the word line are located mainly in parallel. Thereby, the above object is achieved.
The axis of easy magnetization of the magnetic film having a large coercive force among the first magnetic film and the second magnetic film may be mainly orthogonal to the sense line and the word line.

A memory element according to the present invention comprises a first magnetic film,
An element portion including a second magnetic film, a non-magnetic metal film separating the first magnetic film and the second magnetic film, and a sense line; and a magnetic field for recording and reading is applied to the element portion. A generated word line, wherein the sense line is mainly orthogonal to the word line, thereby achieving the above object.

The axis of easy magnetization of the magnetic film having a large coercive force among the first magnetic film and the second magnetic film may be a direction of a composite magnetic field of a magnetic field mainly generated by a current flowing through a sense line and a word line. .

The semiconductor device may further include a soft magnetic film provided to guide a magnetic field generated from a current flowing through the word line to the element portion.

[0009]

The memory element of the present invention uses an artificial lattice film having a different coercive force in the element part, and has the element part, a sense line associated with the element part, and a word line thereover via an insulating layer. When a current is applied to an element using an artificial lattice film, a self-bias is generated in the element. Therefore, the recording / reading efficiency is improved by utilizing the composite magnetic field of the magnetic field generated from the current flowing through the element section and the word line. In addition, the axis of easy magnetization of the artificial lattice film is oriented in the direction of the combined magnetic field between the element section and the word line, and the yoke of the soft magnetic film is provided so that the combined magnetic field is effectively guided to the element section. An efficient memory element that can be recorded and read with a small current by applying a magnetic field well is realized. When a current is applied to the element portion which is an artificial lattice film, a self-bias is induced in the element portion in a direction substantially orthogonal to the direction in which the current flows. Therefore, when the element section is orthogonal to the word line, the direction of the magnetic field induced in the element section is the strongest in the direction of the combined magnetic field of the self-bias generated from the element section and the magnetic field generated from the word line. Therefore, when "1" is recorded in this memory element, a current is applied to the element section and the word line so that the combined magnetic field is maximized, and when "0" is recorded, the combined magnetic field is "1".
Is applied so that the combined magnetic field is maximized in the direction opposite to the case where was recorded. Further, even when the element section is located at a position parallel to the word line, the magnetic field induced in the element section has the strongest combined magnetic field direction of the self-bias generated from the element section and the magnetic field generated from the word line. On the other hand, the effect of the demagnetizing field increases as the shape of the element portion decreases, and the effect increases as the pattern becomes smaller. Therefore, when performing recording / reading on the element, it is difficult to saturate the element under the influence of the demagnetizing field. That is, it is difficult to record and read. Therefore, in order to improve the recording / reading efficiency even a little, the direction of the magnetic field generated in the element portion for recording / reading the easy axis direction of the artificial lattice film as the element portion (synthetic magnetic field direction). To In addition, record
As means for efficiently reading, a soft magnetic film for inducing a magnetic field generated from a word line is used as a yoke of the element portion.

In order to more efficiently generate a magnetic field generated from a word line, a laminated film or an artificial lattice film using a soft magnetic film and a non-magnetic film is used. By these actions, an efficient memory element is realized.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A memory element according to the present invention has an element portion and a word line for generating a magnetic field for performing recording and reading in the element portion. The element section has a first magnetic film, a second magnetic film, a non-magnetic metal film separating the first magnetic film and the second magnetic film, and a sense line. The first magnetic film and the second magnetic film have different coercive forces. That is, one is
It is a hard magnetic film, and the other is a soft magnetic film. In the element portion, a magnetic multilayer film (artificial lattice film) excluding the sense line is referred to as a magnetoresistance change portion.

In this specification, a magnetic film having a coercive force of 20 Oe or more is called a "hard magnetic film", and a magnetic film having a coercive force of less than 20 Oe is called a "soft magnetic film". A hard magnetic film having a coercive force of less than 100 Oe is particularly called a “semi-hard magnetic film”. Further, the value of the coercive force used in this specification is a value measured at a low-frequency alternating current (typically, 60 Hz). When the element portion and the sense line associated therewith are parallel to the word line, the direction of the self-bias applied to the element portion and the direction of the magnetic field generated from the word line are the same, that is, the combined magnetic field is also the same direction. Therefore, the maximum magnetic field can be applied to the element section. The magnitude of the self-bias depends on the shape of the element, the thickness of the element, and the current density of the current flowing through the element. This is because the smaller the element shape, the greater the effect of the demagnetizing field. In order to minimize the effect of the demagnetizing field, the shape in which the direction in which the self-bias is applied (the direction orthogonal to the current direction) is lengthened. It is desirable to do. It is also desirable that the number of laminations be as small as possible in order to obtain sensitivity with a small current. Although the resistance change rate of the magnetoresistance effect is larger than that of the conventional one by about 5% even in the sandwich type as shown in FIG. 1A, the non-magnetic metal film 14 as shown in FIG. When several layers are stacked through the intermediary, the resistance change rate of the magnetoresistance effect is about 3 times higher than that of the sandwich type.
%. Therefore, in consideration of both the sensitivity and the rate of change in resistance, it is desirable that the film thickness of the number of layer laminations be 0.1 μm or less.

It is desirable that the direction of the easy axis of magnetization of the artificial lattice film is set to the self-bias direction in order to efficiently perform recording / reading.

When the element section and the word line are perpendicular to each other (when the self-bias and the magnetic field generated from the word line are perpendicular to each other), the magnetic field applied to the element section by the combined magnetic field direction becomes maximum. Therefore, in order to reduce the influence of the demagnetizing field, it is desirable to make the element shape such that the direction in which the combined magnetic field becomes almost maximum is lengthened. In order to obtain sensitivity, it is desirable that the number of laminations be as small as possible. Although the resistance change rate of the magnetoresistance effect is larger than that of the conventional one by about 5% even in the sandwich type as shown in FIG. 1A, the non-magnetic metal film 14 as shown in FIG. When several layers are stacked, the resistance change rate of the magnetoresistive effect is about 3% larger than that of the sandwich type. Therefore, in consideration of both the sensitivity and the rate of change in resistance, it is desirable that the film thickness of the number of layer laminations be 0.1 μm or less.

It is desirable that the direction of the axis of easy magnetization of the artificial lattice film is set to the direction of the synthetic magnetic field in order to efficiently perform recording and reading.

The word line is formed as a laminated film of a soft magnetic film and a non-magnetic film, so that the word line itself is self-biased, so that the self-bias of the word line and the magnetic field generated by the word line are shifted in the same direction. For example, a large magnetic field can be generated.

The soft magnetic film used as a yoke for efficiently guiding the magnetic field generated by the word line to the element portion preferably has a high magnetic permeability and a large saturation magnetic flux density.
CoNbZr, FeTaN or the like is desirable.

Hereinafter, the effects of the present invention will be described with reference to specific examples.

[0019] (Example 1) target Co (semi-hard magnetic film _{11), Ni 80 Fe 10 Co} 10 ( soft magnetic film 13), C
The semi-hard magnetic film 11, the non-magnetic metal film 12, and the soft magnetic film 13 are sequentially laminated using u (non-magnetic metal film 12), and a sandwich type [Co (30) / Cu (20) / NiFeCo (30)] (the value in parentheses indicates the film thickness nm) was formed, and after etching the element shape, Au / Cr was deposited to form the sense line 26. An insulating film SiO ₂ 25 was sputtered thereon by about 1 μm, and Au / Cr of the word line 24 was further formed thereon.
A memory element in which an element portion and a word line were positioned in parallel as shown in FIG. The magnitude of the self-bias was examined by changing the shape of the element portion. Table 1 shows the results.

[0020]

[Table 1]

This result indicates that the current density of the device was 12 mA / μ.
This is the self-bias for m ² . From the above Table 2, it was confirmed that the self-bias of the magnetoresistive effect element portion of this example increases as the element width decreases. Therefore, it is clear that the shape of the element portion can increase the self-bias by reducing the width in the direction (self-bias direction) orthogonal to the direction in which the current flows.

Example 2 As in Example 1, Co (semi-hard magnetic film 11) and Ni ₈₀ Fe ₁₀ Co were used as targets.
₁₀ (Soft magnetic film 13), semi-hard magnetic film 11, non-magnetic metal film 12, soft magnetic film 13 using Cu (non-magnetic metal film 12).
Are sequentially laminated to form a sandwich type [Co (30) / Cu (20) / NiFeCo (30)] magnetoresistive change portion as shown in FIG. 1 (a), and after etching the element shape, , Au / Cr was deposited to form the sense line 26. An insulating film SiO ₂ 25 was sputtered thereon by about 1 μm, and Au / Cr of the word line 24 was further formed thereon.
A memory element as shown in FIG. The combined magnetic field of the self-bias and the magnetic field generated from the word line was examined by changing the shape of the element portion. Table 2 shows the results.

[0023]

[Table 2]

This result indicates that the current density of the device was 12 mA /
This is a composite magnetic field in the case where the self-bias in the case of μm ² and the cross-sectional area of the word line are constant and the current density is 8.3 mA / μm ² . From the results in Table 2, if the word line is constant,
It was found that the magnetic field applied to the element by the word line was constant, and a combined magnetic field with the self-bias of the element shape was applied to the element. Therefore, it is apparent that a magnetic field can be efficiently applied to the element portion by arranging the elements such that the self-bias direction of the element and the direction of the magnetic field generated by the word line are parallel to each other. (Example 3) Co (semi-hard magnetic film 11) as a target,
Semi-hard magnetic film 11 and non-magnetic metal film 1 using Ni ₈₀ Fe ₁₅ Co ₅ (soft magnetic film 13) and Cu (non-magnetic metal film 12)
2. A soft magnetic film 13 is sequentially laminated to form a sandwich type [Co (30) / Cu (20) / NiFeCo (30)] magnetoresistance change portion as shown in FIG. Then, Au / Cr was deposited to form the sense line 36. An insulating film SiO ₂ 35 is sputtered thereon by about 1 μm, and Au / Cr of the word line 34 is formed thereon.
As shown in FIG. 5, a memory element in which an element portion and a word line were orthogonal to each other was manufactured. At this time, the current flowing through the element portion was set to a constant current density of 12 mA / μm ^2, and the current flowing through the word line was changed to 20, 40, 60, 80, and 100 mA, and the direction of the combined magnetic field and the magnitude of the combined magnetic field were determined. It is shown in FIG. Thus, as shown in FIG. 3, when the element section and the word line are orthogonal (when the self-bias and the magnetic field generated from the word line are orthogonal), the magnetic field applied to the element section by the direction of the combined magnetic field becomes maximum. Therefore, the magnetic field applied to the element by the direction of the combined magnetic field is maximized, and efficient recording / reading can be performed by directing the easy axis direction of the element (in particular, the easy axis direction of the film having a large coercive force) to the direction. Is clear.

Example 4 As in Example 1, Co (semi-hard magnetic film 11) and Ni ₆₈ Fe ₂₀ Co were used as targets.
₁₂ (soft magnetic film 13), semi-hard magnetic film 11, non-magnetic metal film 12, soft magnetic film 13 using Cu (non-magnetic metal film 12).
Are sequentially laminated to form a sandwich type [Co (30) / Cu (20) / NiFeCo (30)] magnetoresistive change portion as shown in FIG. 1 (a), and after etching the element shape, , Au / Cr was deposited to form a sense line 56. An insulating film SiO ₂ 55 was sputtered thereon by about 1 μm, and Au / Cr was deposited and etched to form a word line 54. In order to form a yoke 57 for guiding a magnetic field generated from the word line to the element portion, CoTaZr, which is a soft magnetic film, was sputtered and etched to form the yoke 57 as shown in FIG. At the same time, a memory device without a yoke was also prepared, and the magnitude of a magnetic field applied to the device was compared.
The element shape at this time was 40 μm × 20, 10, 5 μm, the word line width was constant at 40 μm, and the layer thickness was 0.12 μm.
m. Table 3 shows the results. However, the current flowing in the element section is 12 mA / μm ² , and the current density flowing in the word line is 8.3 mA / μm ² .

[0026]

[Table 3]

From the results shown in Table 3, it was confirmed that the magnetic field applied to the element portion was larger when the yoke was provided than when the yoke was not provided. Therefore, it is clear that a magnetic field can be efficiently applied to the element portion by providing the yoke, and an efficient memory element can be realized.

(Embodiment 5) Using a high vacuum evaporation apparatus,
(100) Si / Cu (50) [Co (10) / NiFe (100) / Cu (24) / Ag (2) / Cu (24) / Co with the structure shown below on the substrate
(50) / Cu (24) / Ag (2) / Cu (24) / Co (10) / NiFe (100)], and after etching the element shape, Au / Cr The sense line 56 was formed by vapor deposition. An insulating film SiO ₂ 55 was sputtered thereon by about 1 μm, and Au / Cr was deposited and etched to form a word line 54. In order to form a yoke 57 for guiding a magnetic field generated from the word line to the element portion, CoTaZr, which is a soft magnetic film, was sputtered and etched to form the yoke 57 as shown in FIG. At this time, the element shape was 40 μm × 5 μm, the film thickness was 0.043 μm, the width of the word line was constant at 40 μm, and the film thickness was 0.2 μm. FIG. 6 shows an MR curve of the element portion used at this time. From this, it was found that the magnetization direction of the soft magnetic film (NiFe) having a small coercive force was reversed at 3 Oe, and the magnetization direction of the semi-hard magnetic film (Co) having a large coercive force was reversed at 39 Oe. In order to confirm the operation of this memory element, 12 mA / μ is applied to the sense line during recording.
m ² , and a current of 8.3 mA / μm ² is applied to the word line ”
1 ”is recorded, and when reading, 6 mA is applied to the sense line.
/ [Mu] m ^2, shows the readout output waveform at a current of ± 4mA / μm ² to the word line in Figure 7 (a). Next, FIG.
When recording in the opposite direction to (a), 12 mA is applied to the sense line.
/ Μm ^2, make a record of the word line in passing a current of 8.3mA / μm ² "0", in the sense line when reading 6
mA / μm ^2, shows the readout output waveform at a current of ± 4mA / μm ² to the word line in FIG. 7 (b). From these, recording / reading of “1” and “0” was confirmed.
From the above, the operation of the 1-bit memory cell indicating 1 bit of the memory was confirmed.

(Embodiment 6) In order to confirm a 3-bit memory operation by forming a matrix as shown in FIGS. 8A and 8B using the memory cell of Embodiment 5, (a) (B) Recording and reading were performed respectively. At this time, the direction of the axis of easy magnetization of the element portion is configured to be the direction of the synthetic magnetic field generated from the sense line and the word line.
In the case of (a), 30 mA is applied to the sense line 81 and 10 A is applied to the word line 8a in order to perform recording / reading of 3 bits.
“1” was recorded by applying a current of 0 mA. Next, -30 mA is applied to the sense line 81 and -100 m is applied to the word line 8b.
A current was applied and "0" was recorded. Then, a current of 30 mA was applied to the sense line 81 and a current of 100 mA was applied to the word line 8c to record "1". In order to perform reading, 15 mA is applied to the sense line 81, and ± 50 is applied to the word line 8a.
When a current of mA was applied and the voltage change appearing at both ends of the sense line was measured, an output waveform as shown in FIG. 9 was obtained.
1 "," 0 ", and" 1 "were confirmed, and the same recording / reading operation was also confirmed for the sense lines 82 and 83. In the case of (b), three bits were used as in (a). 30m to sense line 81 to record / read
A, apply a current of 100 mA to the word line 8a. "
1 "was recorded. Next, -30 mA was applied to the sense line 81.
A current of -100 mA was applied to the word line 8b, and "0" was recorded. Then, a current of 30 mA was applied to the sense line 81 and a current of 100 mA was applied to the word line 8c to record "1". In order to read, 15m
A, when a current of ± 50 mA flows through the word line 8a and the voltage change appearing at both ends of the sense line is measured, an output waveform as shown in FIG. 9 is obtained, and "1", "0", and "1" can be confirmed. Was. In the case of the sense line 82, the current direction of the word line is in the opposite direction.
0 mA and a current of 100 mA were applied to the word line 8a to record "1". Next, 30m to the sense line 82
A, apply a current of -100 mA to the word line 8b. "
0 "was recorded.
A, a current of 100 mA is applied to the word line 8c, "1"
Was recorded. In order to perform reading, the sense line 82
When a current of -15 mA is supplied to the word line 8a and a voltage change appearing at both ends of the sense line is measured, an output waveform as shown in FIG. 9 is obtained.
0 "and" 1 "were confirmed. In the case of the sense line 83, the operation was confirmed by the same recording / reading method as in the case of the sense line 81. From the above, FIGS. It is clear that recording and reading can be performed as a memory using either of the above matrices, but it has been found that the area (b) can be made smaller in terms of area. 10 was recorded and read in order to confirm a 3-bit memory operation by using a matrix as shown in FIG. A current of 40 mA is applied to the sense line 101 and a current of 150 mA is applied to the word line 10 a to perform “1” in order to perform 3-bit recording / reading. Then, -4 is applied to the sense line 101.
At 0 mA, a current of -150 mA was applied to the word line 10b to record "0". Then, 4
A current of 0 mA and a current of 150 mA were applied to the word line 10c, and "1" was recorded. In order to perform reading, 20 mA is applied to the sense line 101 and ± 75 m is applied to the word line 10a.
When the current of A is applied and the voltage change appearing at both ends of the sense line is measured, an output waveform as shown in FIG. 9 is obtained.
1 "," 0 ", and" 1 "were confirmed, and the same recording / reading operation was also confirmed for the sense lines 102 and 103.

From the above, it is clear that recording and reading can be performed as a memory even by using this type of matrix.

[0031]

According to the present invention, it is possible to efficiently apply a magnetic field to the element portion by utilizing a combined magnetic field of a self-bias applied by flowing a current through the element portion and a magnetic field generated from the word line. By making the axis of easy magnetization of the element in the direction of the resultant magnetic field, a memory element with higher recording / reading efficiency can be realized. Further, by providing a yoke for guiding the magnetic field generated from the word line to the element portion, the current flowing through the word line can be reduced.

[Brief description of the drawings]

FIG. 1A is a perspective view of a sandwich type magnetoresistive element showing a first embodiment of the present invention. FIG. 1B is a configuration diagram of a laminated type magnetoresistive element.

FIG. 2 is a perspective view of a memory device according to a second embodiment of the present invention.

FIG. 3 is a perspective view of a memory element showing a third embodiment of the present invention.

FIG. 4 is a diagram showing a combined magnetic field direction and a magnitude of a magnetic field generated from an element portion (sense line) and a word line of a memory element according to a third embodiment of the present invention;

FIG. 5 is a perspective view of a memory element showing a fourth embodiment of the present invention.

FIG. 6 is an MR curve diagram of an element portion of a memory element showing Example 5 of the present invention.

FIG. 7 shows an input waveform and an output waveform of a memory device according to a fifth embodiment of the present invention.

8A is a parallel type matrix diagram of a memory device according to a sixth embodiment of the present invention. FIG. 8B is an orthogonal matrix diagram of a memory device according to a sixth embodiment of the present invention.

FIG. 9 illustrates a third example of the memory device according to the sixth and seventh embodiments of the present invention.
Waveform diagram showing bit output

FIG. 10 is a matrix diagram of a memory element showing a seventh embodiment of the present invention.

FIG. 11 is a perspective view of a conventional memory element.

[Explanation of symbols]

Reference Signs List 11 semi-hard magnetic film 12 non-magnetic metal film 13 soft magnetic film 14 non-magnetic metal film 24 word line 25 insulating layer 26 sense line 34 word line 35 insulating layer 36 sense line 54 word line 55 insulating layer 56 sense line 57 yoke (soft) magnetic film) 81, 82, 83 sense lines 8a, 8b, 8c word line 101, 102, 103 sense lines 10a, 10b, 10c word line 11a NiFeCo superlattice 11b sense lines 11c SiO ₂ 11d wordlines

──────────────────────────────────────────────────続 き Continuation of the front page (72) Mitsuo Satomi, Inventor 1006 Kadoma, Kazuma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-7-66033 (JP, A) 195888 (JP, A) JP-A-59-195887 (JP, A) JP-A-10-294507 (JP, A) JP-A-63-167276 (JP, U) International publication 95/10112 (WO, A1) IEEE Transactions on Magnetics, Vol. 6 (1991), p. 5520-5522, IEEE Transactions on Magnetics, Vol. 5 (1990), p. 2532-2534 IEEE Transactions on Magnetics, Vol. 5 (1992), p. 2359-2361 Jpn. J. Appl. Phys. , Vol. 34 (1995), p. L415-L417 Summary of 19th Annual Meeting of the Japan Society of Applied Magnetics, (1995), p. 346 Proceedings of the 19th Annual Meeting of the Japan Society of Applied Magnetics, (1995), p. 485 Jpn. J. Appl. Phys. , Vol. 33 (1994), p. L1668-L1669 Journal of the Japan Society of Applied Magnetics, Vol. 20, No. 1 (1996), p. 22-26 (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 27/105 G11C 11/14 G11C 11/15 H01L 43/08 JICST file (JOIS)

Claims (5)

(57) [Claims] 1. A a first magnetic layer, a second magnetic layer, said first
A non-magnetic metal film for separating the said magnetic layer second magnetic layer,
A memory device having an element portion including a sense line, and a word line generated in the element unit a magnetic field for recording and reading, memory device the sense line and the word line is positioned parallel . 2. An easy axis of magnetization of a magnetic film having a large coercive force among the first magnetic film and the second magnetic film has a sense line.
2. The memory element according to claim 1, wherein the memory element is orthogonal to the word line and the word line. 3. A first magnetic film, a second magnetic layer, said first
A non-magnetic metal film for separating the said magnetic layer second magnetic layer,
A memory device having an element portion including a sense line, and a word line generated in the element unit a magnetic field for recording and reading, large coercive of the first magnetic layer and the second magnetic layer With magnetic force
The easy axis of magnetization of the magnetic film
In the direction of the composite magnetic field generated by the current flowing through the
A memory element characterized by the following . 4. The memory device according to claim 3, wherein said sense line is orthogonal to a word line. 5. The memory device according to claim 1, further comprising a soft magnetic film provided to guide a magnetic field generated from a current flowing through the word line to the device portion.