JP2002246566A - Storage memory device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic memory device which enables the recording of information with a write current smaller than before, without lessening the coercive force of a storage element. SOLUTION: The magnetic memory device is equipped with a magnetoresistive effect type of storage element 10 and write lines 20 and 30 arranged close to the storage element 10, and is so constituted so to invert the direction of the magnetization of the storage element 10 by the current magnetic filed generated by the write lines 20 and 30. The write lines 20 and 30 are of composite structure consisting of nonmagnetic conductors 21 and 31 and magnetic conductors 22 and 32 having high permeability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a magnetic memory device used as a memory device for storing information.

[0002]

2. Description of the Related Art In recent years, with the rapid spread of information and communication equipment, especially small personal equipment such as a portable terminal device, devices such as memories and logics have been required to have high integration, high speed, and low power consumption. There is a demand for even higher performance, such as a higher performance. In particular, increasing the density and capacity of non-volatile memories is becoming increasingly important as a technology to replace hard disk devices and optical disk devices that are inherently difficult to miniaturize due to the existence of movable parts (for example, a head seek mechanism and a disk rotation mechanism). It is becoming.

As a nonvolatile memory, a flash memory using a semiconductor or a FeRAM (FeFe) using a ferroelectric material is used.
rro electric random access memory) is widely known. However, the flash memory has an information writing speed on the order of microseconds, and a DRAM (Dynamic Radar)
ndom Access Memory) and SRAM (Static Random Acce)
ss Memory) and the like. On the other hand, it has been pointed out that FeRAM has a problem that the number of rewritable times is small.

A non-volatile memory that does not have these disadvantages has attracted attention as an MRAM (Magnetic Random Access Memory).
Access Memory) (refer to, for example, Wang et al., IEEE Trans. Magn. 33 (1997), 4498). MRAM is based on the Giant Magnetor effect.
esistive (GMR) type or tunnel magnetoresistive effect (Tu
Information storage using a TMR (nnel Magnetoresistive) storage element has been attracting attention, particularly due to the recent improvement in characteristics of TMR materials.

More specifically, an MRAM has a magnetoresistive effect type storage element arranged in a matrix, and a word write line crossing the element group vertically and horizontally to record information in a specific element of the element group. And a bit write line, and are configured to selectively write information using only the asteroid characteristic to elements located in the intersection region thereof (for example, JP-A-10-116490). reference). MRAM with such a configuration
Has a simple structure, so that high integration is easy, and the number of rewritable times is large because information is stored by rotation of a magnetic moment in a magnetoresistive storage element. Furthermore, the access time is expected to be very fast, and it has already been confirmed that operation is possible on the order of nanoseconds.

[0006]

However, MRA
For M, the magnitude of the write current when storing information in the storage element becomes a problem. That is, when information is stored in the storage element, the magnetization direction of the storage element is reversed by a current magnetic field generated by a word write line and a bit write line. (Higher density) or lower power consumption may be hindered.

Specifically, in a conventional MRAM, a word write line and a bit write line are made of Cu (copper) or Al.
(Aluminum) or the like, it is formed only of a thin-film non-magnetic conductor generally used in semiconductors. For example, when their line width is 0.25 μm, the coercive force is 20 Oe.
In order to write data into the storage element, a large current of about 2 mA needs to flow through the write line. Further, for example, when the cross-sectional shape of the write line is substantially rectangular and the thickness is substantially the same as the line width, the current density at that time becomes 3.2 × 10 ⁶ A / cm ² , It becomes close to the disconnection limit value due to migration.

[0008] Under such circumstances, it is conceivable to reduce the write current by, for example, reducing the coercive force of the storage element. However, when the coercive force of the storage element is reduced, the magnetization direction in the storage element is reversed by external magnetic disturbance, which may cause a reduction in the reliability of the memory device.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic memory device capable of storing information with a smaller write current than before, without reducing the coercive force of the storage element.

[0010]

SUMMARY OF THE INVENTION The present invention has been devised to achieve the above object, and comprises a magnetoresistive effect type storage element and a write line arranged close to the storage element. A magnetic memory device configured to reverse a magnetization direction of the storage element by a current magnetic field generated by the write line, wherein the write line includes a nonmagnetic conductor and a magnetic conductor having high magnetic permeability. It is characterized by having a structure.

According to the magnetic memory device having the above structure, the magnetic flux penetrates through the magnetic conductor portion of the composite structure of the write lines. Therefore, when a current is applied to the write line, the magnetic force lines are distributed uniformly around the write line. Instead, magnetic field lines are generated concentrated on a portion of the non-magnetic conductor that is not a magnetic conductor. Therefore, if the direction of magnetization of the storage element is reversed by the concentrated lines of magnetic force, the direction of magnetization can be reversed with a smaller current than when the lines of magnetic force are uniformly distributed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic memory device according to the present invention will be described below with reference to the drawings.

[Outline of Magnetic Memory Device] First, a schematic configuration of the entire magnetic memory device according to the present invention will be described. FIG. 1 is a schematic diagram showing a basic configuration example of a magnetic memory device called an MRAM. MRAM is
A plurality of magnetoresistive effect type storage elements 10 arranged in a matrix are provided. Further, mutually corresponding word write lines 20 and bit write lines 30 are provided so as to cross each storage element 10 group vertically and horizontally so as to correspond to each of the rows and columns in which these storage elements 10 are arranged. ing. Each of the storage elements 10 is arranged so as to be sandwiched between the word write line 20 and the bit write line 30 from above and below, and to be located in an intersection region therebetween.

FIG. 2 is a schematic diagram showing the schematic structure of the MRAM in more detail. In the MRAM, a word write line 20 and a bit write line 30 (hereinafter collectively simply referred to as “write lines”) are arranged so as to cross the storage element group 10 vertically and horizontally.
In the intersection area of 0 and 30, in addition to the storage elements 10, the field effect transistors 40 individually connected to the storage elements 10 are provided.
Is provided. In addition, a sense line 51 and a sense amplifier 52 connected to the sense line 51 are provided corresponding to the field effect transistors 40 in each column, and the information stored in the storage element 10 is detected by these. .

Next, the configuration of each storage element portion in the MRAM having such a configuration will be described. FIG. 3 is a schematic diagram illustrating an example of a cross-sectional configuration of a single storage element portion. In each memory element portion, a field effect transistor 40 including a gate region 42, a source region 43, and a drain region 44 is disposed on a semiconductor substrate 41,
Further above, the word write line 20 and the storage element 1
0 and bit write lines 30 are arranged in order.
As is clear from this, the storage element 10 is arranged so as to be sandwiched between the write lines 20 and 30 at the intersection of the word write line 20 and the bit write line 30 from above and below.

Here, the configuration of the storage element 10 itself will be described. In the MRAM, the storage element 10 is GMR
There are two types, one using a material and the other using a TMR material. Here, the TMR type will be described as an example.

FIG. 4 is a schematic diagram showing an example of a cross-sectional configuration of a magnetoresistive film used as a TMR type storage element. In the TMR type storage element 10, for example, Ni
(Nickel), Fe (iron) or Co (cobalt),
Or an information storage layer 11 made of a magnetic material such as an alloy thereof and having a magnetization direction relatively easily rotated,
Information is written (recorded) by changing the magnetization direction of the information storage layer 11 by the current magnetic field generated by the write lines 20 and 30.

Below the information storage layer 11, for example, Al
It has a tunnel barrier layer 12 made of an insulator such as an oxide layer or a nitride layer of (aluminum), Mg (magnesium), Si (silicon) or the like, and has a magnetic property between the information storage layer 11 and a magnetization fixed layer 13 described later. In addition to breaking the static coupling, it plays the role of flowing tunnel current.

A magnetization fixed layer 13 is provided below the tunnel barrier layer 12. The magnetization fixed layer 13 is composed of two magnetic layers, a first magnetization fixed layer 13a and a second magnetization fixed layer 13b. A conductor layer 14 is provided between the two magnetic layers 13a and 13b so that the magnetic layers 13a and 13b are antiferromagnetically coupled. As a material of the conductor layer 14, for example, Ru (ruthenium), Cu
(Copper), Cr (chromium), Au (gold), Ag (silver) and the like can be used.

The second magnetization fixed layer 13b is provided so that its lower side is in contact with the antiferromagnetic material 15.
Due to the exchange interaction acting between these layers, the second magnetization fixed layer 13b has a strong unidirectional magnetic anisotropy. Examples of the material of the antiferromagnetic material 15 include Fe, N
i, Pt (platinum), Ir (iridium), Mn (manganese) alloys such as Rh (rhodium), Co and Ni oxides can be used.

Below the antiferromagnetic material 15, there is a double underlayer 16 made of, for example, Co and Si.

In the TMR type storage element 10 thus configured, information is read by detecting a change in tunnel current due to the magnetoresistance effect. However, the effect depends on the relative magnetization direction between the information storage layer 11 and the magnetization fixed layer 13.

The above-described layers (magnetic film and conductor film) 11, 13 to 16 are mainly formed by a known sputtering method, and the tunnel barrier layer 12 is formed by oxidizing or nitriding a metal film formed by sputtering. What is necessary is just to form by doing.

The TMR type storage element 10 as described above
In the MRAM provided with a memory cell, the storage element is arranged in the intersection region of the word write line 20 and the bit write line 30, and therefore, by using these two write lines 20, 30, the asteroid magnetization reversal characteristic can be improved. Is used to selectively write information to the individual storage elements 10.

At this time, the sum in the single storage element 10 is
The resultant magnetization depends on the magnetic field H applied in the easy axis direction applied thereto._EAAnd trouble
Magnetic field H in the hard axis direction_HAIs determined by vector composition with
The write current flowing through the bit write line 30 is
The magnetic field H in the easy axis direction _EAAnd write word
The current flowing through the storage line 20
Magnetic field H_HAIs applied.

FIG. 5 is an asteroid diagram showing an example of the magnetic field response of the storage element in the MRAM. The asteroid curve in the figure indicates the threshold value for reversing the magnetization direction of the information storage layer 11 due to the applied magnetic field H _EA and magnetic field H _HA . In other words, when a combined magnetic field vector corresponding to the outside of the asteroid curve is generated, the storage element 10 undergoes magnetic field reversal. However, the resultant magnetic field vector inside the asteroid does not reverse the magnetic field of the storage element 10 from one of its current bistable states. Also, a magnetic field generated by each of the write lines 20 and 30 independently is applied to the storage element 10 located at a position other than the intersection of the word write line 20 and the bit write line 30 through which a current flows,
If the magnitude of the magnetic field is equal to or larger than the one-way reversal magnetic field H _K , the magnetization direction of the storage element 10 other than the intersection region is also reversed. Only in a case corresponding to (shadow portion), information can be written to the selected storage element 10.

[First Embodiment] Next, a first embodiment of the present invention will be described.
Features of the MRAM (magnetic memory device) according to the embodiment will be described. FIG. 6 is a schematic diagram showing a configuration of a characteristic main part of an example of the magnetic memory device according to the present invention.

Generally, in a conventional MRAM, a word write line and a bit write line are formed only of a nonmagnetic conductor such as Cu or Al.

On the other hand, the MR described in the present embodiment
As shown in FIG. 6, each of the write lines 20, 30 sandwiching the storage element 10 from above and below is composed of a nonmagnetic conductor 2 made of a conductive material such as Cu, Al, or an alloy thereof.
1 and 31 and magnetic conductors 22 and 32 having high magnetic permeability.

As a material of the magnetic conductors 22, 32, for example, Ni, Fe, Co or an alloy containing these as a main component may be used. Specifically, Ni called permalloy
-It is conceivable to use an Fe alloy (iron nickel alloy).

Each of the write lines 20 and 30 has a substantially rectangular cross section. Then, the three sides except the storage element 10 side are substantially U-shaped magnetic conductors 22,
The nonmagnetic conductors 21 and 31 are exposed only on the surface on the storage element 10 side. Therefore, the exposed surfaces of the non-magnetic conductors 21 and 31 face each other between the write lines 20 and 30, and the magnetic conductors 22 and 32 are arranged so as to be symmetrical to each other. Further, in each of the write lines 20 and 30, the cross-sectional width (see A and B in the drawing) of the portion of the nonmagnetic conductors 21 and 31 exposed to the storage element 10 is determined by the element width of the storage element 10 (a and b in the drawing). (See Reference).

Each of the write lines 20, 30 as described above is
It may be formed as described below. For the bit write line 30 located above the storage element 10, for example, after forming the nonmagnetic conductor 31 as in the related art,
It is conceivable to form the magnetic conductor 32 by forming a film by plating or the like. On the other hand, the storage element 10
For example, after forming a trench (groove excavation) during the film formation process, the magnetic conductor 22 is formed on the bottom and side surfaces of the trench by a plating method, etc. It is conceivable that the trench is formed by filling the trench with the nonmagnetic conductor 21.

By using the write lines 20 and 30 having such a configuration, in the MRAM of the present embodiment, the magnetic flux passes through the magnetic conductors 22 and 32 of the composite structure. The distributed lines of magnetic force are converged by the magnetic conductors 22 and 32 having high magnetic permeability,
The nonmagnetic conductors 21 and 31 are concentrated on the exposed portion, that is, the portion of the storage element 10.

FIG. 7 is an explanatory diagram showing a specific example of a simulation result of generated magnetic force lines for one write line. As shown in FIG. 7A, when the three sides of the substantially rectangular shape are covered with the magnetic conductors 22 and 32, even when a write current is applied, the magnetic force lines are generated in a uniformly distributed state around the periphery. However, it can be seen that the magnetic flux is transmitted through the magnetic conductors 22 and 32, and the lines of magnetic force are concentrated on the non-magnetic conductors 21 and 31. Specifically, according to a numerical simulation, when the width and the thickness of the write lines 20 and 30 are each 0.25 μm, when a current of 1 mA flows, the center of the storage element 10 facing the nonmagnetic conductors 21 and 31 is turned on. The magnitude of the magnetic field generated in the portion is about 15 Oe.

On the other hand, as shown in FIG.
When the write line is composed of only the non-magnetic conductor, the magnetic field lines are uniformly distributed around the write line.
Even when a current of 1 mA flows through a write line having a width and thickness of m, only a magnetic field of about 5 Oe can be obtained in the central portion of the storage element 10.

Therefore, if the write lines 20 and 30 having the composite structure described in this embodiment are used, a write magnetic field can be generated more efficiently than in the conventional case (in the case where the magnetic field lines are uniformly distributed). The magnetization direction of the storage element 10 can be reversed with a smaller current.

In order to obtain such an effect efficiently,
It is desirable that the magnetic conductors 22 and 32 covering the write lines 20 and 30 have a magnetic permeability of about 10 or more. Also,
It has been confirmed that the effect of increasing the generated magnetic field can be obtained if the coating thickness of the magnetic conductors 22 and 32 is 0.01 μm or more.

The three sides of the substantially rectangular shape are magnetic conductors 2
2, 32, a substantially U-shaped magnetic conductor 2
2 and 32 (the nonmagnetic conductors 21 and
Many lines of magnetic force are concentrated at (31). Therefore, if the cross-sectional widths A and B of the nonmagnetic conductors 21 and 31 are formed to be equal to or larger than the element widths a and b of the storage element 10, the magnetic conductors 22 and 31 may
Since the width of the information storage layer 11 of the storage element 10 is shorter than the interval between the two end portions of the storage device 32 and the information storage layer 11 is arranged so as to be sandwiched between the two end portions, the concentration occurred. The lines of magnetic force can be efficiently applied to the information storage layer 11.

[Second Embodiment] Next, a second embodiment of the present invention will be described.
Features of the MRAM (magnetic memory device) according to the embodiment will be described. FIG. 8 is a schematic diagram showing a configuration of a characteristic main part of another example of the magnetic memory device according to the present invention.

In the MRAM described in this embodiment, as in the case of the first embodiment, each write line 2
0 and 30 are nonmagnetic conductors 21 and 31 and magnetic conductors 22 and 32
And a composite structure consisting of Each of the write lines 20 and 30 has a substantially square cross section.

However, in the MRAM of this embodiment, FIG.
As shown in FIG. 5, unlike the first embodiment, only the surfaces of the write lines 20 and 30 facing the storage element 10 side are covered with the magnetic conductors 22 and 32. Therefore, the nonmagnetic conductors 21 and 31 are exposed on both the surface on the storage element 10 side and both side surfaces connected thereto.

Each of the write lines 20 and 30 as described above is
It may be formed as described below. For the bit write line 30 located above the storage element 10, for example, a non-magnetic conductor 31 made of Cu, Al, or an alloy thereof is formed by a sputtering apparatus or a CVD (Chemical Vapor Depth).
It is conceivable that the magnetic conductor 32 made of permalloy is formed by a sputtering apparatus, and then formed into a desired pattern by ion milling or reactive ion etching. On the other hand, the word write line 20 located below the storage element 10 may be formed in the order of the magnetic conductor 22 and the nonmagnetic conductor 21, for example, opposite to the bit write line 30. However, the non-magnetic conductors 21 and 31 and the magnetic conductors 22 and 32 may be formed by a method other than the above, for example, a plating method.

By using the write lines 20 and 30 having such a configuration, the MRAM of the present embodiment can
As in the case of the first embodiment, the magnetic flux is transmitted through the magnetic conductors 22 and 32 of the composite structure. 32 and the nonmagnetic conductors 21 and 3
1 is concentrated on the exposed portion.
Therefore, when the write lines 20 and 30 having the composite structure described in the present embodiment are used, a write magnetic field can be generated more efficiently than in the conventional case (in the case where the magnetic field lines are uniformly distributed), and as a result, the write magnetic field is smaller than in the conventional case. The magnetization direction of the storage element 10 can be reversed by the current.

Further, in the MRAM of this embodiment,
Only on the surface where the magnetic conductors 22 and 32 face the storage element 10,
That is, since only one surface is covered, the degree of concentration of the lines of magnetic force is lower than in the case of the first embodiment. However, since both sides of the write lines 20 and 30 are not required to be covered, there is no need for manufacturing. Excellent easiness. That is, the conventional MRA
By simply adding the step of forming the magnetic conductors 22 and 32 twice to the manufacturing process of M, the write current can be reduced as compared with the conventional case, and it is very easy to realize.

In the first and second embodiments, both the word write line 20 and the bit write line 30 are connected to the nonmagnetic conductors 21 and 31 and the magnetic conductors 22 and 31.
Although the description has been made by taking as an example the case of having a composite structure consisting of 32, the present invention is not limited to this.
That is, it is sufficient that at least one has a composite structure, and even in that case, the write current can be reduced.

In the first and second embodiments,
The magnetic conductors 22, 32 are connected to the three sides around the write lines 20, 30.
And the case where only the surfaces of the write lines 20 and 30 facing the storage element 10 are covered with the magnetic conductors 22 and 32, respectively. However, the present invention is not limited to this. . For example, even when only the both sides of the substantially rectangular write line are covered with the magnetic conductors 22 and 32, magnetic flux penetrates the magnetic conductors 22 and 32 and concentrates on the non-magnetic conductors 21 and 31. As a result, the lines of magnetic force are generated, so that the write current can be reduced.

Further, in the first and second embodiments, the case where the storage element 10 uses the TMR material has been described. However, the same applies to the case where the storage element 10 uses the GMR material. Of course.

[0048]

As described above, the magnetic memory device of the present invention has a non-magnetic structure when a current is applied to the write line by forming the write line into a composite structure including a non-magnetic conductor and a magnetic conductor. Since the lines of magnetic force are concentrated on the conductor portion, it is possible to write information to the storage element with a smaller write current than before. Therefore,
Since the write current can be reduced without reducing the coercive force of the storage element, as a result, the magnetic memory device can be miniaturized (densified) by reducing the write line drive circuit, etc., and the power consumption of the magnetic memory device can be reduced. It becomes easy to realize improvement of reliability and the like by reducing electron migration rupture of the write line.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a basic configuration example of a magnetic memory device.

FIG. 2 is a schematic diagram illustrating an example of a schematic configuration of a magnetic memory device in detail.

FIG. 3 is a schematic diagram illustrating an example of a cross-sectional configuration of a single storage element portion forming a magnetic memory device.

FIG. 4 is a schematic diagram showing an example of a cross-sectional configuration of a magneto-resistance effect film used as a tunnel magneto-resistance effect type storage element.

FIG. 5 is an asteroid diagram showing an example of a magnetic field response of a storage element in a magnetic memory device.

FIG. 6 is a schematic diagram illustrating a configuration of a characteristic main part of an example of a magnetic memory device according to the present invention.

7A and 7B are explanatory diagrams showing a specific example of a simulation result of generated magnetic force lines for one writing line, wherein FIG. 7A is a diagram showing a simulation result according to the present invention, and FIG. 7B is a diagram showing a conventional simulation result; It is.

FIG. 8 is a schematic diagram showing a configuration of a characteristic main part of another example of the magnetic memory device according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Storage element, 20 ... Word write line, 21 ... Non-magnetic conductor, 22 ... Magnetic conductor, 30 ... Bit write line, 3
1: Non-magnetic conductor, 32: Magnetic conductor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 43/08 H01L 27/10 447 (72) Inventor Kazuhiro Bessho 6-7-35 Kita Shinagawa, Shinagawa-ku, Tokyo No. 72 within Sony Corporation (72) Naomi Yamada 6-7-35 Kita Shinagawa, Shinagawa-ku, Tokyo Sonny Corporation (72) Tetsuya Mizuguchi 6-7-35 Kita Shinagawa, Shinagawa-ku, Tokyo Soni -Inside Co., Ltd. (72) Inventor Hiroaki Narusawa 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation Inside (72) Inventor Keitaro Endo 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Soni Inside (72) Inventor Shinya Kubo 6-7-35 Kita Shinagawa, Shinagawa-ku, Tokyo Sony Corporation Inside (72) Inventor Kazuhiko Hayashi 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Formula company in the F-term (reference) 5E049 AA04 BA12 LC01 5F083 FZ10 GA05 GA09 JA32 JA36 JA37 JA38 JA39 KA01 KA05 LA12 LA16

Claims (6)

[Claims] 1. A storage device comprising: a magnetoresistive effect type storage element; and a write line disposed close to the storage element, wherein a magnetization direction of the storage element is reversed by a current magnetic field generated by the write line. In the configured magnetic memory device, the write line has a composite structure including a nonmagnetic conductor and a magnetic conductor having high magnetic permeability. 2. The magnetic memory device according to claim 1, wherein the non-magnetic conductor forming the write line is disposed facing the storage element. 3. The magnetic conductor forming the write line,
3. The magnetic memory device according to claim 2, wherein when the cross section of the write line is formed in a substantially rectangular shape, the write line is arranged so as to cover three surfaces excluding the surface on the storage element side. 4. The magnetic memory device according to claim 3, wherein a cross-sectional width of the non-magnetic conductor disposed to face the storage element is formed to be larger than an element width of the storage element. . 5. The magnetic conductor forming the write line,
3. The magnetic memory device according to claim 2, wherein when the cross section of the write line is formed in a substantially rectangular shape, the write line is arranged so as to cover only a surface facing the surface on the storage element side. 6. The magnetic conductor forming the write line,
6. The method according to claim 1, wherein the material is made of nickel, iron, cobalt, or an alloy thereof.
Item 7. A magnetic memory device according to item 1.