JPH06251579A - Magnetic memory - Google Patents

Abstract

PURPOSE:To obtain an inexpensive magnetic memory whose capacity is large, whose transfer rate is high, and whose power consumption is small. CONSTITUTION:A 1st conductive layer 4 including a 1st conductive wire 5 and a 2nd conductive layer 8 including a 2nd conductive wire 9 formed in a direction orthogonally crossed with the 1st conductive wire are laminated on a substrate 2 in a state where a main electric insulating layer 7 may intervene between them. 1st and 2nd coil parts 6 and 10 are respectively formed at a part where the 1st and the 2nd conductive wires are crossed, where a magnetic substance 11 is provided in an electrically insulated state so as to constitute a memory cell. Thus, the magnetic substance can be electrically addressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium, and more particularly to a rewritable magnetic memory that complements a conventional IC memory or magnetic memory as a recording medium having a high degree of integration.

[0002]

2. Description of the Related Art Generally, when a digital recording medium is classified into rewritable memories, IC memories such as DRAM and flash memory, magnetic tapes for digital audio,
As a peripheral memory for a computer, a floppy disk (FD), a hard disk (HD), a magneto-optical disk, or the like can be given. These recording media are
Generally, the larger the recording capacity, the lower the transfer rate, and it is used properly according to the application. For example, an IC memory having a high transfer rate is used for central information processing of a computer, and a magnetic memory having a large storage capacity but a low transfer rate is used as a peripheral memory of a computer or the like.

That is, a magnetic memory is a non-volatile, large-capacity memory that can be easily rewritten, and is widely used because it is inexpensive, but it is much inferior to an IC memory in terms of transfer rate. Further, this magnetic memory has a problem that it consumes more power than an IC memory because information in the memory is read by utilizing mechanical high speed driving.

Recently, notebook personal computers have become widespread, and FD and HD, which are magnetic memories, are gradually being replaced by IC memories due to the high density of IC memories. However, it is difficult to manufacture IC memories. In addition to going through complicated steps, the size of the silicon wafer is limited, which makes it inevitably expensive. Under such circumstances, recently, a non-volatile memory having a large capacity and a high transfer rate, such as a flash memory, has been developed, and the competition between the memories is increasing. There is a possibility that the recording medium will be replaced with a flash memory.

[0005]

However, the above-mentioned flash memory does not yet have sufficient characteristics as compared with the conventional magnetic memory when comprehensively considering the transfer rate, storage capacity, power consumption, etc., There is a strong demand for development of a recording medium, which is an advantage of a magnetic memory, is non-volatile, easy to rewrite, has a high transfer rate, and can reduce power consumption as compared with a conventional magnetic memory. The present invention focuses on the above problems, and was devised in order to effectively solve them, the purpose of which is a large capacity,
An object is to provide an inexpensive magnetic memory with a high transfer rate and low power consumption.

[0006]

In order to solve the above problems, the present invention provides a first coil which locally generates a magnetic field on a substrate or on an electrically insulating layer formed thereon. Forming a first conductive layer including a first conductive line having a portion,
A second coil portion that locally generates a magnetic field is provided on the first conductive layer with a main electrical insulating layer interposed, and the second coil portion is arranged in a direction orthogonal to the first conductive line. A second conductive layer including a conductive wire is formed so that the first coil portion and the second coil portion are located at the same position in the stacking direction, and the first coil portion and the second coil portion are provided in the first coil portion and the second coil portion. A magnetic body electrically insulated from the first conductive line and the second conductive line is formed.

[0007]

To perform recording / reproduction of the magnetic memory of the present invention, first, the magnetization directions of the respective magnetic bodies are uniformly aligned and initialized by the external magnetic field. Next, at the time of recording information, currents are simultaneously passed through the first and second conductive lines, and the currents are appropriately combined to control the magnetization direction of the magnetic material to perform writing. Further, at the time of reproducing information, one of the first and second conductive wires is supplied with a current to be used as a sensor, and the other conductive wire is supplied with a pulse current. At this time, when the magnetization reversal occurs in the magnetic material, a pulse current is generated in the sensor-side conductive wire.

[0008]

An embodiment of a magnetic memory according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a sectional view schematically showing an embodiment of a magnetic memory of the present invention, and FIG. 2 is a plan view showing an arrangement state of conductive wires and magnetic bodies in FIG. As shown in the figure, the magnetic memory 1 has a base 2 made of, for example, a non-magnetic material, on which an electrically insulating layer 3 is formed as a base layer. The insulating layer 3 is not always necessary and may be omitted. On this insulating layer 3,
When the insulating layer 3 is not provided, the first conductive layer 4 is laminated on the base 2. The first conductive layer 4 has a plurality of first conductive lines 5 arranged in parallel as shown in FIG. 2, and each conductive line has a large number of coil-shaped or semi-circular shaped first conductive lines 5. One coil portion 6 is formed with the same pitch L1.

A second conductive layer 8 is laminated on the first conductive layer 4 with a main electrical insulating layer 7 made of an oxide or the like interposed therebetween. The second conductive layer 8 has a plurality of second conductive lines 9 extending in a direction (vertical direction in FIG. 2) orthogonal to the first conductive lines 5, and each conductive line 9 is equal. A large number of second coil portions 10 which are arranged in parallel at intervals and are formed in a coil shape are formed at the same pitch L2 as the pitch L1 of the first coil portion 6 in the middle thereof.

In this case, each of the first coil portion 6 and the second coil portion 10 is located at the same position in the stacking direction (vertical direction in FIG. 1, vertical direction in the drawing) and corresponds to Inside the first and second coil portions 6 and 10, a columnar magnetic body 11 electrically insulated from the conductive wires 5 and 9 is formed so as to communicate these. The magnetic body 11 is a perpendicular magnetization film having a remanent magnetization in the perpendicular direction, and the coercive force in the perpendicular direction is 1000 Oe (Oersted) or less, preferably 700 Oe or less. Specifically, CoCr (cobalt chrome), CoO
A Co-based perpendicular magnetization film such as x or a rare earth amorphous alloy used in a magneto-optical medium is used. Furthermore, as another material, an Fe (iron) -based amorphous alloy that has a property of exhibiting a ferromagnetic phase from a certain temperature by heating and maintaining a ferromagnetic state even when the temperature returns to room temperature is used. Good.

By thus providing a large number of magnetic bodies 11, each magnetic body 11 is configured as a memory cell. A protective layer 12 is formed on the second conductive layer 8. In the illustrated example, only three or four conductive wires are shown for simplification of description, but a large number of conductive wires are actually provided. Of course, many memory cells are also formed.

Next, the operation of this embodiment will be described.
First, when the above-described magnetic memory 1 is initialized, an external magnetic field is applied to the magnetic memory 1 from above and below so that the magnetization directions of the magnetic bodies 11 are uniformly aligned in the same direction and initialized. Here, the first in the first and second conductive layers 4 and 8
And the directions of the second conductive lines 5 and 9 are the X direction and the Y direction, respectively.
Direction, and (X1, X2, ... X
n) and (Y1, Y2, ... Yn) are assigned.
Therefore, each magnetic body 11 surrounded by the first and second coil portions 6 and 10 of the first and second conductive lines 5 and 9 can be represented as a memory cell by (Xi, Yj), and the corresponding The magnetic substance 1 is generated by the magnetic fields generated in the first and second coil portions 6 and 10 by passing current through the first and second conductive lines 5 and 9.
The magnetization of unity can be reversed. At that time, current is applied to the first and second conductive wires 5 and 9 so as to satisfy the following conditions.

The currents flowing through the conductive wires are equal. The magnetization reversal does not occur even when a magnetic field is applied to the memory cell by passing a current through one conductive line. When current is applied to both conductive lines,
And the magnetization reversal of the memory cell (magnetic material) at the position where the second conductive line intersects occurs. That is, when the coercive force of the memory cell is Hc, a current flows so that the magnetic field hc generated by the conductive line satisfies the following condition. Hc / 2 <hc <Hc

(Write Operation) When writing (recording) is performed based on the above conditions, a current is passed through both conductive lines of Xi and Yj to cause a memory cell (magnetic material) corresponding to (Xi, Yj). ), The state of magnetization can be controlled, and information can be written. Specifically, the magnetization reversal can be controlled depending on the directions of the currents Xi and Yj. For example, the control is performed by a combination of current directions as shown in Table 1.

[0015]

[Table 1]

As shown in Table 1, for example, when a positive current is applied to Xi and Yj and the memory cell is magnetized upward, a negative current is applied to both Xi and Yj when negative current is applied. It will change. In the case of actual recording, a pulse current is made to flow equally through the conductive lines crossed at the memory cell position in each conductive layer. The current value to be passed must be such that the magnetization of the memory cell is reversed by the magnetic field generated by the coil at the crossed position. In this case, it is not necessary to make both conductive layers equal, and a current may be made to flow only in one conductive layer, but it is preferable to make an equal current flow in both conductive layers in order to reduce power consumption.

(Read operation) Read information (reproduction)
Sometimes, one of the first and second conductive wires, for example, Xi, is supplied with a DC bias current and is used as a sensor, and the other conductive wire, for example, Yj is supplied with a pulse current, and (Xi, Yj ), It is checked whether or not the magnetization reversal occurs in the memory cell corresponding to. For example, as shown in Table 2, a pulse current is generated in Xi on the sensor side according to the magnetization direction of the memory cell, and information can be reproduced.

[0018]

[Table 2]

By this read operation, the magnetized state of the memory cell returns to the initial state. Therefore, the write operation is performed immediately after the read. As described above, according to this embodiment, a large capacity memory can be formed without using an expensive material such as an IC memory, and moreover, it can be electrically addressed not mechanically. A high transfer rate is possible. Further, since it is not necessary to mechanically drive the magnetic head or the like for addressing, power consumption can be suppressed.

Next, a specific manufacturing process of the magnetic memory according to the present invention described above will be described in detail. First, a non-magnetic material made of ceramic was used as the base 2 of the magnetic memory 1. A conductor having a width L3 of 1.0 μm, such as Au, is formed on the base 1.
As shown in FIG. 2, a plurality of (only four in the illustrated example are shown for simplification of description only) first conductive lines 5 are formed in parallel by (gold) lines as shown in FIG. By doing so, the first conductive layer 4 is provided. This forming method is performed by a resist method using a photomask, the thickness of the first conductive wires 5 is 0.2 μm, and the diameter L4 of the first coil portions 6 formed at the equal pitch L1 is set to 2.0 μm. Was done. In this case, the first conductive line 5 is directly formed on the base 2 without providing the electrically insulating layer 3 as the base layer.

Next, a cylindrical magnetic body 11 was formed on this by a sputtering method at the position of the coil portion. This magnetic body 1
1 has a thickness of 0.5 μm, and the magnetic body 11 is prevented from coming into contact with the first coil portion 6 of the first conductive wire 5 and the second coil portion 10 of the second conductive wire 9 described later. The diameter L5 of the magnetic body 11 is set to 1.0 μm. As the material of the magnetic body 11, Fe amorphous alloy Fe
-Zr (containing 10 at% of Zr) was used. As another material, a CoCr or CoOx (cobalt oxide) -based perpendicular magnetic material can be used. However, in the case of a CoCr film, it is necessary to heat the substrate, and in the case of a CoCx-based film, storage stability is low. Inferior to.

Further, as another material, it is possible to use a rare earth amorphous alloy system for a magneto-optical medium, but this material has a problem that the preparation conditions are generally strict and the material cost is high. In that respect, Fe mentioned above
Amorphous alloys have the advantages that they are easy to produce, the material cost is low, and that the induced magnetic anisotropy can be controlled by heat treatment in a magnetic field as described later.

An Fe-based alloy can also be used as a material that can utilize the induced magnetic anisotropy, and an oxide magnetic material such as barium ferrite which is a perpendicular magnetic material can also be used as a material. In the case of this oxide magnetic material, it is advantageous because the problem of heat generation due to the induced current due to the magnetization reversal does not occur, but since the magnetic anisotropy is large, it is necessary to increase the current for the magnetization reversal, Since the magnetization is smaller than that of metals and alloys, it has a drawback that detection sensitivity is poor. The magnetic anisotropy can be controlled depending on the production conditions.

After the magnetic substance 11 is formed in this way, a main electric insulating layer 7 made of an oxide such as silicon oxide is formed to a thickness of 0.1 μm, and then the second conductive line 9 is further formed. Was laminated by a resist method in the direction orthogonal to the first conductive line 5 to form the second conductive layer 8. The thickness of the second conductive wire 9 is 0.2 μm, and the pitch L2 of the second coil portion 10 formed therein is set to be the same as the pitch L1 of the first coil portion 6. In this case, the second
Of the second coil portion 10 so that the conductive wire 9 is separated from the magnetic body 11 and the insulating state between them is maintained.
6 is set to be substantially the same as the diameter L4 of the first coil portion.

The main electrical insulation layer 7 is not limited to silicon oxide as long as it is an electrically insulative material, and not only inorganic materials but also organic materials such as synthetic resins may be used. Then, finally, an ultraviolet protective film is spin-coated on the entire upper surface of the second conductive layer 8 and is irradiated with ultraviolet rays to be cured to form a protective layer 12, thereby completing the whole.

Here, similarly to the above, the first and second conductive wires 5 and 9 are referred to as the X-ray and the Y-ray, respectively, and the magnetic bodies at the positions where the coil portions of the X-ray and the Y-line cross each other. It becomes a memory cell and is represented by (Xi, Yj). In this embodiment, the cell-to-cell spacing is set to 2.5 μm, but since this is an example for confirming the operation, the cell spacing is wide and it is easy to further narrow it. . Basically, the cell spacing depends on the integration technology that can be performed by the current photoresist method. For example, if the width of the conductive line and the diameter of the magnetic material are 0.1 μm, the cell spacing can be 0.5 μm or less. The storage memory capacity is 4 M (mega) bits / mm ² .

(Initialization) In order to initialize the storage memory, first, about 100 is perpendicular to the film surface of the memory.
The magnetic substance of the memory cell is heated to 200 ° C. while applying a magnetic field of 0 Oe (oersted), and 20 minutes per minute from the equilibrium state.
It was cooled at a rate of ° C. As a result, the magnetic substance changed to a ferromagnetic state and induced magnetic anisotropy was formed, and the magnetization was aligned perpendicular to the film surface and in the direction of the external magnetic field.

(Operation Confirmation) In order to confirm the operation, first, the current flowing in the Y-direction conductive line is increased by using the X-direction conductive line as a sensor. At this time, the pulse current generated in the conductive line in the X direction due to the magnetization reversal of the memory cell is detected. In this case, if the direction of the current is added when the magnetic field generated in the coil is opposite to the direction of magnetization of the magnetic material,
This resulted in the results shown in Table 3 below.

[0029]

[Table 3]

The same test was conducted on the remaining conductive lines of the Y line, and further, the same test was conducted by applying a current to the X line using the Y line as a sensor. By this test, 96 μA was obtained as the average value of the current values that generated the pulse current. From this result, the range of the operating current I flowing through the X-ray and the Y-line is as follows. 48 μA <I <96 μA

Here, in consideration of operational safety, the operating current I
The following operation confirmation was performed with the set value of 80 μA. First, in order to write information to any memory cell (Xi, Yj) of the magnetic memory initialized as described above, a pulse current of 80 μA is applied to each of the i-th conductive line of the X-ray and the j-th conductive line of the Y-line. Shed The pulse width in this case was set arbitrarily.

Next, for reading, the X-ray is used as a sensor, and the Y-line is set to 16 times, which is twice the pulse current at the time of writing shown at left.
A pulse current of 0 μA was sequentially applied. At this time, it is confirmed that the pulse current is generated at the i-th position of the X-ray only when the pulse current flows through the j-th conductive line of the Y-line, and the memory cell of (Xi, Yj) is in the magnetization reversal state. It was These i and j were appropriately selected from 1 to 4 and individually confirmed. Here, since the memory disappears and the memory returns to the initial state because the magnetization of the memory cell is reversed at the time of reading, the memory cell of (Xi, Yj) was written again. That is, reading must be performed in combination with rewriting.

Through a series of such tests, it was confirmed that repeated operations such as writing, reading (initialization), rewriting and reading were possible. The above embodiment is merely an example, and the Fe amorphous material, which is the material of the magnetic material, is not limited to the Fe—Zr system, and the shape of the magnetic material is not limited to the cylindrical shape. Further, the shape of the conductive wire forming each coil portion is not limited to the semicircular shape, and any shape such as a circular shape or any other shape can be used as long as the magnetic field can be efficiently applied to the magnetic body.

[0034]

As described above, according to the magnetic memory of the present invention, the following excellent operational effects can be exhibited. By using an inexpensive magnetic material such as an Fe amorphous magnetic material, it is possible to provide a large-capacity magnetic memory at low cost with a simple process. Moreover, since the address can be made electrically instead of mechanically, the transfer rate can be kept high and the power consumption can be suppressed.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing an embodiment of a magnetic memory of the present invention.

FIG. 2 is a plan view showing an arrangement state of conductive wires and magnetic bodies in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic memory, 2 ... Base | substrate, 3 ... Electrical insulating layer, 4 ... 1st conductive layer, 5 ... 1st conductive wire, 6 ... 1st coil part,
7 ... Main electrical insulating layer, 8 ... Second conductive layer, 9 ... Second conductive wire, 10 ... Second coil portion, 11 ... Magnetic body, 12 ... Protective layer, L1, L2 ... Pitch.

Claims (1)

[Claims] 1. A first conductive layer including a first conductive line having a first coil portion for locally generating a magnetic field is formed on a substrate or on an electrically insulating layer formed on the substrate. A second coil portion for locally generating a magnetic field with a main electrical insulating layer interposed on the first conductive layer and arranged in a direction orthogonal to the first conductive line. A second conductive layer including two conductive wires is formed so that the first coil portion and the second coil portion are located at the same position in the stacking direction, and the first coil portion and the second coil portion The magnetic memory is characterized in that a magnetic body electrically insulated from the first conductive line and the second conductive line is formed in the magnetic memory.