JPS6160502B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a method for manufacturing an ion implantation bubble device, particularly to a method for manufacturing a substrate that allows a large induced anisotropic magnetic field ΔHk to be obtained.

Background of the technology In a magnetic bubble device, the first
A permalloy pattern 10 as shown in Figure a is arranged, and an in-plane rotating magnetic field is applied to magnetize the pattern to create a magnetic pole that moves along the periphery of the pattern.
2 is moved together with the magnetic pole. The arrow indicates an example of a bubble propagation trajectory. Initially, the bubble diameter was about 6 μm, but as improvements were made, the bubble diameter was reduced to 3 μm, 1 μm, etc., and higher integration and larger capacity were achieved. When the bubble becomes minute, such as 1 μm in diameter, the method shown in Figure A, in which a large number of patterns 10 are arranged with a gap g, is difficult to manufacture because the gap g also needs to be made small according to the bubble diameter. Problems arise such as bubble propagation being inhibited in the gap. Ion-implanted bubble devices can deal with such problems, and form bubble propagation paths by changing the axis of easy magnetization on the surface of a magnetic substrate through ion implantation.

That is, as shown in FIGS. 1b and 1c (the former is a plan view and the latter is a cross-sectional view), a garnet magnetic layer 16 for bubbles is grown by liquid phase epitaxial growth on a nonmagnetic substrate 14 made of, for example, GGG, and then gold is deposited thereon. After depositing an (Au) film, it is patterned to form a film 18 with triangular wave-like side edges, and ions are implanted 20 over the entire surface.
In areas where the gold film 18 exists, the ions are blocked by the gold film and do not reach the magnetic substrate 16, but in areas where there is no gold film, they enter the magnetic substrate to form the ion implantation layer 16a.
The axis of easy magnetization of the liquid phase epitaxial layer 16 lies in its thickness direction, and bubbles can be generated and maintained by applying a bias magnetic field perpendicular to the substrate. However, in the ion implantation layer 16a, the implanted ions enter the crystal and try to expand the crystal, but this is blocked by the surrounding liquid phase epitaxial layer, so it becomes a force that causes the crystal to bulge toward the open surface side. ,
Such strain causes the axis of easy magnetization of layer 16a to be oriented parallel to the plane. In other words, induced magnetic anisotropy occurs. When such a magnetic substrate 16 is magnetized by an in-plane magnetic field, magnetization occurs in the direction of the magnetic field, but magnetization occurs along the periphery of the gold film 18, so that the periphery is not treated as an ion-implanted layer. Similar to the propagation pattern 10, the layer boundaries have the function of propagating bubbles as the rotating magnetic field rotates. Gold film 18 may be removed after ion implantation. In addition, bubbles are formed in the liquid phase epitaxial layer 16 in which the axis of easy magnetization is oriented in the thickness direction.
limited within. The above is an overview of the ion implantation type bubble device. In this type of device, the gap g
Since there are no gaps and the pattern is continuous, it is easy to manufacture even fine patterns, and of course there is no problem such as bubbles getting caught in the gap g and not propagating.

Conventional technology and problems The ions to be implanted are generally Ne ⁺ ions and H ⁺ ions.
It is an ion. The induced anisotropic magnetic field increases as the amount of implanted ions increases, but it does not increase indefinitely, but with Ne ⁺ ions, etc., it saturates at a certain point, and even at that saturation value, it becomes large enough to form a bubble propagation path. value is not met. A larger induced anisotropic magnetic field ΔHk can be obtained for H ⁺ ions than for Ne ⁺ ions. but
Since H ⁺ ions have a small particle size, a larger amount of ions must be implanted than Ne ⁺ ions, and the implantation time becomes very long. Furthermore, since H ⁺ ions are minute, they move after implantation, resulting in poor stability. Therefore, a multiple ion implantation method in which both of these are implanted is generally adopted, and the amount of H ⁺ ions implanted is controlled to obtain the necessary anisotropic magnetic field ΔHk. However, the time required is quite long.

OBJECTS OF THE INVENTION The present invention seeks to provide a method for manufacturing a bubble device in which the required induced anisotropic magnetic field can be obtained with a relatively short ion implantation time.

Structure of the Invention The present invention involves selectively implanting ions into the surface of a magnetic substrate for bubbles to form a bubble propagation pattern, then depositing an insulating spacer on the substrate, and forming a bubble detection pattern etc. thereon with ions. The method for manufacturing an implanted bubble device is characterized in that after the ion implantation, the substrate is heated to 250 to 450°C and sputtered to deposit the insulating spacer. will be explained in detail.

Embodiments of the Invention FIG. 2 shows the main parts of a bubble device according to the present invention. 16 is a YSm Lu Ca Ge IG layer grown by liquid phase epitaxial growth on a GGG substrate, and its upper surface 16a ₁ is coated with Ne ⁺ ions at 50 KeV and at a dose of 1×10 ¹⁴ /cm ² over the entire surface of layer 16. This is the layer that is created by typing. 16a ₂ below this layer contains Ne ⁺ ions.
_16a3 is a layer formed by implanting H ⁺ ions at 50 ^KeV and a dose of x x 10 ¹⁶ /cm ^{2 ;}
These are made by applying a gold mask 18 shown by dotted lines and then implanting ions to form the bubble propagation path described above. The above x is 2 to 6. Layer 16a ₁ ,
16a ₂ and 16a ₃ are implanted ions Ne ⁺ , Ne ⁺ , H ⁺
It shows the concentration peak and its surroundings, and the depth of each layer is about 0.1 μm, 0.3 μm, and 0.5 μm. The depth of this layer, specifically the ion acceleration voltage, can be changed as appropriate. After the ion implantation, the gold mask 18 is removed, and then a first spacer 20 of silicon dioxide (SiO ₂ ) is formed by RF (radio frequency) sputtering. Then 350℃ to stabilize the ion-implanted layer.
After heat treatment was performed for 30 minutes to form a bubble detection permalloy pattern 22 and a chromium oxide (Cr ₂ O ₃ ) film 24 on the first spacer 20, a second spacer 26 of SiO ₂ was similarly formed by the RF sputtering method to detect bubbles. After opening windows for the detection patterns 22 and 24, metal (Ti-Au) is vapor deposited and patterned to form a conductive pattern 28, and then again.
A protective film 30 is formed by depositing SiO ₂ .

In the present invention, when forming the first spacer 20 by RF sputtering, the substrate temperature is increased. Generally, it is said that it is desirable to perform this sputtering at a low temperature, and the substrate is kept at a low temperature by forced cooling.
Increase the substrate temperature as shown in the figure. In FIG. 3, the horizontal axis is the sputtering time, the vertical axis is the substrate temperature, and time 0 indicates the time when the substrate is loaded into the RF sputtering device. When sputtering is performed, the equipment temperature rises, so after the substrate is loaded, it will start to rise from room temperature due to the rising temperature of the equipment, but until 10 minutes have passed, the temperature between the SiO ₂ target of the sputtering equipment and the substrate is Keep the shutters in between closed and do not sputter. After 10 minutes, open the shutter and start sputtering. As a result, the substrate temperature rises rapidly and settles down to a constant value of 335° C. in this example. Open the shutter after 30 minutes and finish the sputtering.

FIG. 4 shows the relationship between the substrate temperature Ts during sputtering and the induced anisotropic magnetic field ΔHk. Spatuta temperature 400℃
increases the induced anisotropic magnetic field △Hk the most. This graph was obtained under the above-mentioned implantation conditions (x=2) and after the first spacer was formed, heat treatment was performed at 350° C. for 30 minutes. The measurement point on the far left is data at room temperature, which means the temperature rise has been suppressed. Looking at this graph, the ΔHk of 400℃ sputtering is improved by about 25% compared to room temperature sputtering, which clearly shows the advantage of high-temperature sputtering. This graph does not depend on the ion species; therefore, the H ⁺ ion may be He ⁺ or the like. In the conventional method, it is recommended to keep the substrate temperature below 200℃, but one of the reasons for keeping the substrate temperature low is that when the temperature is high, the implanted ions, especially the H ⁺ ions, become more active and can flow out of the substrate. This is because there is a fear that it may dissipate. Even in the present invention, there is a problem of dissipation of H ⁺ ions, and therefore it is not preferable to heat the substrate to a high temperature and then suddenly start sputtering. It is desirable to take it. It is thought that by doing this, the SiO ₂ film that begins to adhere at the start of sputtering prevents the dissipation of H ⁺ ions. Note that if the spatter temperature is too high,
As shown in the graph in the figure, ΔHk begins to decrease, which is thought to be due to the dissipation of H ⁺ ions. Therefore, the sputtering temperature is preferably 250° C. to 450° C. To maintain this temperature range, forced cooling of the substrate may be adjusted, but it is convenient to appropriately set the RF power.

After depositing the first spacer 20 with high-temperature RF sputtering, heat treatment (350
℃ for 30 minutes), but if the spacer 20 is attached, ΔHk will not decrease even during this heat treatment. If heat treatment is performed without attaching the spacer 20, △
Hk will decrease. Film thickness of first spacer 20
The thickness should be approximately 2000Å.

As an ion-implanted bubble device, △Hk=
3000 Oe is where you want it. Therefore, in the case of conventional low temperature sputtering, it is necessary to further increase the dose and therefore increase the H ⁺ ion implantation time. In this regard, according to the present invention, △Hk=
Since the number of ions is more than 3000, the amount of ion implantation and time required are smaller than that of the conventional method.

FIG. 5 shows the relationship between the induced anisotropic magnetic field ΔHk and the dose of H ⁺ ions. The dotted line indicates the temperature when the substrate temperature Ts during SiO ₂ first spacer sputtering is 50℃.
The solid line is when it is 350°C. As is clear from the figure, when the substrate temperature is high, ΔHk is always large for the same dose amount.

Effects of the Invention As described above, according to the present invention, the substrate temperature during sputtering for forming the first spacer of silicon dioxide is maintained at a high temperature (250° to 450°C), so even if the ion dose is small, A large △Hk can be obtained, which has the advantage of shortening the required time.
Also, even if the spatsuta temperature is changed and the dose is the same, △
A means for adjusting ΔHk, such as setting Hk to a desired value, can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of essential parts of a bubble device, FIG. 2 is a sectional view showing an embodiment of the present invention, and FIGS. 3 to 5 are various characteristic curve diagrams. In the drawing, 16 is a magnetic substrate for bubbles, 16a ₂ , 1
6a ₃ is an ion implantation layer forming a propagation pattern; 2
0 is an insulating spacer, and 22 is a bubble detection pattern.

Claims (1)

[Claims] 1. Fabrication of an ion-implanted bubble device by selectively implanting ions onto the surface of a bubble magnetic substrate to form a bubble propagation pattern, then depositing an insulating spacer on the substrate, and forming a bubble detection pattern, etc. thereon. In the method, after the ion implantation, the substrate is
A method of manufacturing an ion-implanted bubble device, characterized in that the insulating spacer is deposited by sputtering at a temperature of 250 to 450°C.