JPH01149285A - Magnetic thin film storage element - Google Patents

Abstract

PURPOSE:To improve storing density by causing the magnetizing condition of a magnetic thin film element to be single domain structure not to have magnetic wall structure. CONSTITUTION:A thin film core 3, which is one cell (= one bit corresponding) of a thin film core memory is caused to be the single domain structure. Thus, since this thin film core 3 does not have magnetic block structure in the core 3, the conventional close arrangement of the memory cell or a creep phenomenon, which is a problem in the general thin film core memory as malfunction in a memory condition due to high speed operation, does not completely appear. Accordingly, the memory cell can be closed. Thus, the storing density is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a memory element, and particularly to a magnetic thin film memory element having an element structure suitable for high-density storage and reproduction.

[Conventional technology]

A magnetic thin film memory element has been proposed in which a large number of closed magnetic circuit structures are formed on a substrate using a thin film formation technique.

Conventional magnetic thin film memory elements of this type (hereinafter referred to as thin film core memories) include those in which a magnetic thin film is continuously formed on the digit lines as described in Japanese Patent Publication No. 47-31854, As described in Japanese Patent No. B-28811, a structure in which memory elements are separated for each bit is known.

[Problem that the invention seeks to solve]

In the above-mentioned conventional technology, in order to prevent the reliability of the memory from decreasing due to erroneous reversal of the memory contents due to the creep phenomenon, etc.
The size of a memory cell corresponding to a bit is several 100 micrometers to several square meters, and there is a problem in that it cannot cope with higher density storage elements.

Furthermore, reliability against erroneous reversal and the like was not perfect.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic thin film memory element that eliminates the erroneous reversal of stored contents in a memory in the prior art and enables higher density by bringing memory cells closer together.

[Means for solving problems]

The above object is achieved by making the thin film core, which is one cell (=corresponding to one bit) of the thin film core memory, have a so-called single domain structure without a domain wall.

[Effect]

A single domain thin film core has no magnetic domain structure within the core. Therefore, there is no erroneous reversal of stored contents due to creep phenomena or the like.

This can greatly improve the reliability of thin film core memory. Furthermore, since it becomes possible to arrange the memory cells close to each other, it becomes possible to significantly improve the storage density.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram of one cell (one bit) explaining one embodiment of a thin film core memory according to the present invention, in which 1 is a non-magnetic glass substrate, 2.4 is a patterned CUG film. In this example, 3 is a word line (
(drive line), 4 is used as a digit line (output line). 3 is a thin film core formed by patterning a permalloy vapor deposited film,
It has an axis of easy magnetization parallel to the conductive line 2 (word line).

In addition, the thin film core has a so-called single domain structure with no magnetic domain inside it, and its shape is as follows:
It has a circular shape that makes it difficult to form magnetic domains.

Next, the operation of the core memory of this embodiment will be explained.

First, the thin film core 3 has n 1 tt parallel to the axis of easy magnetization.
It is stable in a magnetized state facing either +t Ott, and corresponds to the information storage state (in the figure, upward, °'0'
"situation).

Now, there is an induced current ■ in word line 2. , the magnetic field Hw generated by (8) acts on the memory element 3 on the word line, and the magnetization of the memory element 3 rotates toward the difficult magnetization direction.

At this time, depending on whether the magnetization rotates from the tt 1 tt state or from the n On state, the digit &'j1
4, a pulse voltage P4 of a different polarity is induced. This becomes the read voltage.

In the case of writing, with the magnetization directed toward the difficult axis, a pulse current Id with a polarity corresponding to the information signal is applied to the digit line 4.
flow to. Then, due to the action of the magnetic field H4 with the polarity corresponding to the pulse, the rotational direction of magnetization is determined, and the magnetization state is stabilized in the easy axis direction of u 1 tt or O゛', and writing is completed (in the figure, fl I It becomes).

FIG. 2 is a schematic diagram showing an example of a configuration in which the memory cells shown in FIG. 1 are integrated, and the same parts as in FIG. 1 are given the same reference numerals, and 5 is a signal processing circuit.

As shown in the figure, an actual thin-film core memory is constructed by integrating a large number of memory cells to achieve a large capacity. At this time, signal processing of the conductive line arrays (word lines, digit lines) drawn out corresponding to the large capacity cells is performed by a signal processing circuit 5 such as an LSI. At this time, as shown in Figure 11, by making the thin-film core a single-domain structure, problems that have arisen in general thin-film core memories such as memory cell placement in close proximity and memory state malfunction due to high-speed operation have been solved. The creep phenomenon does not occur at all, and the reliability of the memory can be greatly improved.

In addition, since the size of the thin film core can be reduced to several micrometers as a core with a single domain structure, it is possible to achieve a density approximately 500 times higher than that of a conventional core memory.

In the embodiments described above, both the conductivity and the thin film core were formed by patterning the vapor deposited film, but the film formation may be performed by sputtering, CVD, etc., and the patterning may also be performed by dry etching such as ion milling, or wet etching. .

Furthermore, as a means to obtain conductive wires and thin film core patterns,
A pattern may also be printed. In this case, there is an advantage that mass productivity is greatly improved.

In the embodiment shown in FIG. 1 above, the memory cell is constructed in the order of conductive line (word line) 2 - thin film core 3 - conductive line (digit line) 4. may be reversed.

FIG. 3 is a block diagram of a memory cell explaining another embodiment of the present invention, and the same reference numerals as in FIG. 1 correspond to the same parts.

In the figure, as shown in (a), the structure of the memory cell is shown as follows: thin film core 3 - conductive line (word line) 2 - conductive line (digit line)
4 are formed on the substrate 1 in this order.

Further, in FIG. 2B, conductive lines (word lines) 2 -> conductive lines (digit lines) 4 - thin film cores 3 are formed on the substrate 1 in this order.

FIG. 4 is a configuration diagram of a memory cell explaining still another embodiment of the present invention, which has a circular shape with different major and minor axis lengths, and is the same as FIGS. 1 and 3. The symbols correspond to the same parts.

In the same figure (a), the shape of the thin film core 3 is an elliptical shape, whereas it is a disk shape in the above embodiment, and in the same figure (b), it is an elliptical shape. be.

By doing so, shape anisotropy with an easy axis occurs in the longitudinal direction (long axis direction) of the thin film core 3, which has the advantage of being less susceptible to the influence of external magnetic fields.

In each of the above embodiments, permalloy is used as the material for the thin film core, but other magnetic materials such as metal materials such as CO-based alloys may be used.

Note that the axis of easy magnetization parallel to the word line may be imparted by applying a magnetic field during film formation or by heat treatment in a magnetic field after film formation.

〔Effect of the invention〕

As described above, according to the present invention, there is no erroneous reversal of the contents stored in the thin film core memory, so reliability is greatly improved. In addition, it is possible to arrange memory cells close to each other, increasing the storage density by more than 500 times compared to conventional technology.
It is possible to provide a magnetic thin film memory element with excellent functionality by eliminating the drawbacks of the prior art.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a memory cell showing an embodiment of the present invention;
2 is a schematic diagram showing a configuration example in which the memory cells shown in FIG. 1 are integrated; FIGS. 3(a) and 3(b) are configuration diagrams of memory cells showing another embodiment of the present invention; (a) and (b) are configuration diagrams of a memory cell showing still another embodiment of the present invention. 1... Board, 2... Conductive wire (word ta)
, 3... Thin film core, 4... Conductive wire (digit line), 5... Signal processing circuit. Figure 1 Figure 2 Figure 3 (a) (b)

Claims (1)

[Scope of Claims] 1. A magnetic thin film memory element comprising a pair of conductive line arrays formed in two layers orthogonally on a substrate and a magnetic thin film element disposed at the intersection thereof; A magnetic thin film memory element characterized in that the magnetization state of is a single domain structure having no domain wall structure. 2. A magnetic thin film memory element according to claim 1, wherein the magnetic thin film element has a circular shape with a long axis length and a short axis length different from each other.