JPS6136697B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to bubble memory devices, and more particularly to a method for manufacturing bubble memory devices.

If a single crystal of a magnetic material with uniaxial magnetic anisotropy is cut thinly so that the easy axis of magnetization is perpendicular, or grown into a thin film by epitaxial growth, and a biased magnetic field of the required value is applied in the easy axis direction. A cylindrical magnetic domain, or magnetic bubble, is created. Since this magnetic bubble can maintain its shape and move within the plane, a propagation element is generally formed on the plane of the crystal using a thin plate of ferromagnetic material such as permalloy, and a rotating magnetic field is applied in the same plane. A method has been adopted in which a thin plate of ferromagnetic material is magnetized by generating , and the magnetic field generated by the magnetization is used to transfer magnetic bubbles. The method for manufacturing this bubble memory device involves the steps shown in FIG. Figure 1 is a diagram of the conventional bubble memory manufacturing process, where 1 is gadolinium gallium garnet (hereinafter referred to as GGG substrate), and 2
is a magnetic garnet, 3 and 6 are SiO ₂ insulating layers, and 4 is a magnetic garnet.
7 is a conductor layer such as Al or Cu, and 7 is a permalloy layer.

In step a of FIG. 1, a magnetic garnet 2 is produced on a GGG substrate 1 by liquid phase epitaxial growth, and an insulating layer 3 of SiO ₂ or the like is formed on it by a method such as sputtering _. A conductor layer 4 of Al, Cu, etc. is formed by a method such as vapor deposition. Then the first
In step b in Figure b, a photoresist 5 is applied on the conductor layer 4, exposed and etched using optical exposure technology to form a desired conductor pattern 4', and in step c, an insulator such as SiO ₂ is again applied. A layer 6 is formed, and a permalloy layer 7 is formed via the insulating layer 6 by a method such as vapor deposition. Next, in step d, a photoresist is coated on the permalloy layer 7 using the optical exposure technique again, the mask of the propagation element pattern is covered, and the propagation element 7' is formed by etching after exposure.

As described above, the conventional method uses optical exposure technology twice to fabricate a bubble memory device, but in this conventional method, the gap of the propagation element is 2 to 3 times the wavelength of the light source used during exposure. If the gap size is less than 1 .mu.m, it becomes impossible, and a gap size of 1 .mu.m is considered to be the limit in mask production. Therefore, the diameter of the transferred magnetic bubble is limited to 3/2 times the gap size, or 1.5 μm.

On the other hand, with the progress of the times, magnetic bubbles have been made smaller.
High-density, large-capacity memories are required, and propagation elements with gap dimensions of 1 μm or less are required. To meet this demand, attempts have been made to use electron beam exposure or X-ray exposure. Exposure and X-ray exposure have disadvantages in that the equipment is large, the equipment cost increases, and it takes a lot of time to create a complicated propagation element shape (pattern).

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a bubble memory device in which a propagation element having a minute gap that enables the transfer of minute magnetic bubbles is manufactured using conventional optical exposure technology.

To briefly describe the present invention, when producing a propagation element having a gap, the process of producing the gap part and the process of producing a shape other than the gap part are separated, and the gap part is produced in advance.

In a bubble memory device comprising a bubble transfer path in which a plurality of propagation elements made of magnetic material are arranged adjacent to each other through a small gap on a magnetic thin film having uniaxial anisotropy, the transfer path includes at least one
A first step of forming a first magnetic layer for molding the individual propagation elements, a second step of attaching an insulator for forming a gap between the first magnetic layers, and a second step of attaching an insulator for forming a gap between the first magnetic layers. a third step of forming a second magnetic layer for shaping the propagation element remaining in the transfer path between the first magnetic layers so as to be separated from the first magnetic layer through a slight gap; The method is characterized in that it is produced by at least a fourth step of forming the first and second magnetic layers into the shape of the propagation element.

A specific embodiment most suitable for carrying out the present invention will be described in detail with reference to the drawings.

FIG. 2 is a manufacturing process diagram of a bubble memory device according to the present invention. In FIG. 2, reference numeral 1 is a GGG substrate, 2 is a magnetic garnet layer, 3 and 6 are insulating layers such as SiO ₂ , etc., and 4 is an Al, Cu, etc. The conductor layer 7 is a permalloy layer. In step a of FIG. 2, a magnetic garnet layer 2 is grown on the GGG substrate 1 by liquid phase epitaxial growth, an insulating layer 3 is formed on the surface of the magnetic garnet layer 2, and a conductor layer 4 is formed by vapor deposition or the like via the insulating layer 3. death,
The insulating layer 6 is formed again, and the permalloy layer 7 is formed on the insulating layer 6 by a method such as vapor deposition. Next, in the step shown in FIG. 2b, after completing step a, a photoresist 8 is applied on the surface of permalloy 7, and in the dotted line area in FIG. Using an optical exposure mask, etching is performed to remove the portion above the conductor layer, including the conductor layer 4 (the permalloy 7 in FIG. 2b constitutes the first magnetic layer). The structure shown in FIG. 2b is thus obtained. The plan view of figure b is shown in figure b'.

In the next step c in FIG. 2, an insulating layer 9 made of a gap-forming insulator such as SiO ₂ is sputtered over the entire main surface from above the photoresist 8 left on the main surface in step b, and a layer of permalloy 10 is further applied on top of the insulating layer 9. is formed by a method such as vapor deposition, and step c is completed. After completion of step c, the insulating layer 9 and permalloy 10 laminated on the photoresist 8 shown in figure c are lifted off. This lift-off refers to simultaneously removing the layer above the bottom by removing the bottom layer of the stack. As a result, rows of insulating layers 6 under Permalloy 7, rows of conductor layers 4 made of Al, Cu, etc. below that, and rows of insulating layers 9 under Permalloy 10', which is the second magnetic layer, are arranged alternately. The material shown in FIG. 2d is obtained. For the material d, the thickness of the insulating layer 9 is adjusted if necessary, so that the heights of the permalloy 7 and the permalloy 10' on the main surfaces are made equal. Further, when forming the insulating layer 9, an insulating material such as SiO ₂ is also stacked on the side surface of the permalloy 7. The permalloy side surface does not adhere as much as the bottom surface of the insulating layer 9, and is less than half the thickness of the insulating layer 9.
Generally, the thickness of the insulating layer 9 is about 0.8 μm,
The insulation adhesion thickness on the permalloy side is 0.4μm
The following is true. This 0.4 μm thickness is Permalloy 7
and becomes the propagation element gap of permalloy 10'.
A photoresist was applied to the main surface of the material d with the conductor gap prepared as described above, and then exposed using a propagation element pattern mask without a gap part shown by the broken line in the figure e. ' is etched to obtain a permalloy propagation element as shown in FIG.

In this manner, a propagation element having a gap of 1 μm or less can be manufactured without the need to manufacture a fine pattern mask.

Another embodiment of the present invention will be described using FIG. 4. Each manufacturing process of this embodiment is the same as that of the first embodiment, so a description thereof will be omitted, and only the constituent parts that are different from the first embodiment will be described.

In FIG. 4, the same reference numerals as in the first embodiment are used. The feature of this embodiment is that the heights of the permalloy layer 7 and the permalloy layer 10' on the main surface are different, and there is a gap between the permalloy layer 7 and the permalloy layer 10' in the height direction. Forming the conductor layer 4 thick to provide a step difference between adjacent permalloy layers as in this embodiment is also effective in preventing electromigration. Thereafter, an insulating layer 6 of SiO ₂ or the like is formed, and a permalloy layer 7 is formed on the insulating layer 6 by vapor deposition or the like, and the process shown in FIG. 4 is obtained through the steps b, c, and d of FIG. In this embodiment, by forming the Al/Cu conductor layer 4 thickly, the distance between the permalloy layer 7 formed thereon and the magnetic garnet layer 2 increases, and the operating margin slightly decreases. This can be easily solved, for example, by making the volume of the permalloy layer 7 larger or thicker than the area of the permalloy layer 10'.

FIG. 5 shows still another embodiment of the method for manufacturing a bubble memory device according to the present invention.

The difference between this embodiment and the embodiment shown in FIG. 2 is that in the embodiment of FIG. Whereas,
In this embodiment, the conductor layer is formed into an island shape.

That is, the present embodiment shown in FIG. 5 corresponds to FIG. 3, and as can be seen by comparing the two figures, in this embodiment an island-shaped conductor layer 4' is formed at the lower end of the permalloy layer 7. In the case of this embodiment, since the conductor layer is not continuous compared to the embodiments shown in FIGS. 2 and 3,
The influence of eddy currents caused by magnetic flux from the permalloy pattern can be reduced. This can solve the problem of eddy currents caused by high-frequency drive, which is becoming increasingly common as bubble memories operate at higher and higher speeds, and it is possible to realize bubble memories that can fully support drive frequencies of several hundred kilohertz. .

According to the present invention, a propagation element having a minute gap that enables the transfer of minute magnetic bubbles can be manufactured efficiently at low cost, and has great effects on the production of large-capacity, high-density bubble memory devices.

[Brief explanation of the drawing]

FIG. 1 is a manufacturing process diagram of a conventional bubble memory device, FIG. 2 is a manufacturing process diagram of a bubble memory device according to the present invention, and FIG. 3 is a plan view of the bubble memory device.
FIG. 4 is a sectional view of a bubble memory device illustrating another embodiment of the present invention, and FIG. 5 is another embodiment of the present invention. 1... GGG substrate, 2... Magnetic garnet layer,
3, 6, 9...Insulating layer, 5, 8...Resist,
7,10... Permalloy layer.

Claims (1)

[Scope of Claims] 1. A bubble memory device comprising a bubble transfer path in which a plurality of propagation elements made of a magnetic material are arranged adjacent to each other with a small gap interposed on a magnetic thin film having uniaxial anisotropy. The transfer path includes a first step of forming a first magnetic layer for forming at least every other propagation element, a second step of attaching an insulator for gap formation between the first magnetic layers, and a second step of forming a gap forming insulator between the first magnetic layers. A third forming second magnetic layer of the remaining propagation element of the transfer path is formed between the first magnetic layer on the forming insulator so as to be separated from the first magnetic layer through a slight gap. and a fourth step of forming the first and second magnetic layers into the shape of the propagation element. 2. The bubble memory according to claim 1, wherein the adjacent first and second magnetic layers are formed at different positions in the thickness direction of the thin magnetic plate with the gap as a boundary. Method of manufacturing the device. 3. Manufacturing the bubble memory device according to claim 1 or 2, characterized in that a conductive pattern is formed on the magnetic thin plate before forming the first second magnetic layer. Law.