JPS5846793B2 - magnetic bubble element - Google Patents

Description

[Detailed description of the invention] The present invention relates to magnetic bubble elements.

Magnetic bubbles are being put into practical use as memory devices in computer systems because they are capable of storing high-density information and consume low power.

As is well known, the magnetic bubble memory element is GGG (
By applying a predetermined magnetic field to a crystal film formed on a (gadolinium, gallium, garnet) substrate, a cylindrical magnetic domain is obtained, and the cylindrical magnetic domain is formed into a magnetic bubble.

Conventionally, such magnetic bubble memory devices have had the following problem, that is, the formation of node bubbles in the crystal film.

These hard bubbles behave differently from regular magnetic bubbles, for example, their moving direction and moving speed are different from each other.

Naturally, such hard bubbles should be removed from the magnetic bubble element, and methods to suppress them include depositing a permalloy thin film on the surface of the crystal film, or using an ion implantation layer (
A method of forming an implant layer (hereinafter abbreviated as "implantation layer") near the surface has been proposed.

Particularly recently, the latter method of forming an implant layer has become mainstream.

Generally, to drive a magnetic bubble element, a bias magnetic field is applied to form a magnetic bubble of a predetermined shape in a crystal film;
A driving magnetic field is required to move the magnetic bubble within the crystal film.

Furthermore, regarding the bias magnetic field, it is defined separately into a strip-out magnetic field where the magnetic bubble is stripped out and a collapse magnetic field where the magnetic baffle collapses.

Furthermore, the width of the collapse magnetic field and the strip-out magnetic field defines a so-called noise margin.

Generally, when using a magnetic bubble element that does not have the implantation layer described above, the value of the collapse magnetic field remains almost unchanged no matter what rotation angle the direction of the driving magnetic field is, and therefore the bias margin can be substantially larger.

However, as already mentioned, when an implant layer is formed on a crystal film to suppress no-dopuples, the collapse magnetic field increases each time the direction of the driving magnetic field reaches a certain rotation angle, and eventually the collapse magnetic field becomes It will fluctuate within a considerable range.

This variation immediately leads to a variation in the bias margin, which is accompanied by the disadvantageous problem of substantially reducing the bias margin.

However, if the implantation layer is not formed for this purpose, the above-mentioned . . . dopple that must be removed will appear again.

Therefore, the purpose of the present invention is to...
- It is an object of the present invention to propose a magnetic bubble element which is capable of suppressing dopupple and at the same time sufficiently suppressing fluctuations in bias margin to substantially increase the bias margin.

In accordance with the above object, the present invention is characterized in that the surface of a crystal film on which an implantation layer is formed is etched to a predetermined depth.

The present invention will be explained below with reference to the drawings.

Fig. 1 is a pie chart showing the relationship between the magnitude Hco of the collapse magnetic field and the magnitude Hp of the rotating driving magnetic field. The sample was observed, and the magnitude Hp of the rotational driving magnetic field at that time was 40 [Oe].

On the other hand, the circular curve 12 indicated by the dashed line in the figure was observed for the same sample, but in order to clarify the characteristics of the circular curve 11, in this case the magnitude Hp of the rotational driving magnetic field was set to 0 (
Oe).

As is clear from the figure, if the magnitude Hp of the driving magnetic field is set to 0 and the rotation of the one driving magnetic field is substantially stopped, the collapse magnetic field Hco is almost an unchanging constant value (in the example, about 1
57.5 Take C0e)).

In other words, the circular curve 12 is close to a perfect circle. However, when the rotating drive magnetic field Hp is set to 40 (Oe) and applied, the collapse magnetic field Hco changes significantly depending on the rotation angle of Hp, and the curve 11 is far from a perfect circle and becomes rather triangular.

This variation due to the rotation angle of the collapse magnetic field Hco causes the width of the bias margin to vary, thereby substantially reducing the bias margin.

Therefore, in the present invention, the surface of the crystal film on which the implantation layer is formed is etched to a predetermined depth.

Fig. 2 shows a cross section of a normal magnetic bubble element with an implant layer formed thereon, and Fig. 3 shows a magnetic bubble formed by etching according to the present invention on the normal magnetic bubble element shown in Fig. 2. FIG. 3 is a cross-sectional view of the element.

In FIGS. 2 and 3, 21 is a substrate of a magnetic bubble element, for example GGG.

A crystal film (22 in FIG. 2, 27 in FIG. 3) is formed on the upper surface of the substrate 21 by liquid phase growth.

Further, ions such as Ne or H are implanted by ion implantation or the like to form an implant layer 23 up to the region indicated by the dotted line.

In the present invention, the implant layer 23 shown in FIG. 2 is carved as shown in FIG. 3.

Assuming that the thickness of the normal implant layer 23 is 1,000 holes, it is appropriate that the amount of cutting t (FIG. 3) is about 500 or so.

In this way, by carving away the normal implant layer by an appropriate amount, the substantially triangular curve 11 shown in FIG. 1 can be made closer to a perfect circle without losing the effect of suppressing hard bubbles.

FIG. 6 is a pie chart showing the results of one experiment, and the definition of coordinates is the same as the pie chart in FIG.

As shown in FIG. 6, the circular curve 11 in FIG.
As shown in 1, it becomes quite close to a perfect circle.

Thus, the collapse magnetic field (Hco), the driving magnetic field (H
The variation with rotation of p) is significantly reduced and the bias margin is substantially increased.

In order to etch the surface of the implant layer, chemical etching, plasma etching, or ion milling using Ar ions or the like can be used.

It is believed that the bias margin improvement described above was achieved for the following reasons.

As already mentioned, the implant layer was introduced to suppress the nozzle pull, which moves differently from the normal bubble, and by introducing this implant layer, triangular closures were created within the crystal film. A yard main is formed.

This is shown in FIG. 7, which is a plan view of the magnetic bubble element shown in FIG. 2.

In FIG. 7, the triangular hatched area 71 visible on the surface of the crystal film 22 is the aforementioned closure domain.

The horizontal magnetization direction of this closure main 71 is different from the horizontal magnetization direction of the surroundings. For example, if the horizontal magnetization direction of the closure main 71 is arrow A, the surrounding horizontal magnetization direction is arrow B.

This horizontal magnetization appears particularly in the layer near the upper surface of the implant layer, resulting in a magnetic shunt effect.

In addition, in this case, the arrow A has directionality and is easily oriented 3
There are two directions.

This is generally called 3-fold symmetry.

Therefore, if a large number of closure domains exist at random, the magnetic shunt effect will have a strong influence in three directions, increasing the collapse magnetic field in these three directions.

This phenomenon clearly appears as a substantially triangular circular curve 11 in FIG.

Therefore, if the layer near the upper surface of the implant layer is etched, the magnetic shunt effect due to the closure domain will be weakened.

However, if the ionization concentration within the implant layer is reduced by this etching, the effect of suppressing bird bubbles will be lost.

Now, returning to FIG. 2 and looking at the ion concentration distribution along the dashed line 4 in the implant layer 23, it is as shown in FIG.

However, the amount of ion implantation is shown in the horizontal direction.

As described above, the ion concentration distribution within the implantation layer 23 shows an approximately normal distribution, and the central portion thereof is the region with the highest ion concentration.

Therefore, even if the surface of the implant layer 230 is etched as shown in FIG. 3, the no-heak value of the ion implantation amount is still maintained.

The ion concentration distribution along the dashed line 5 in FIG. 3 is as shown in FIG. 5, and the peak value of the ion implantation amount is ensured.

In other words, the suppressive effect of -Dopapuru has not been lost yet.

In this way, bias margin is improved.

As explained above, according to the present invention, it is possible to sufficiently suppress bird bubbles, improve bias margin deterioration due to the effect of suppressing bird bubbles, and realize a magnetic bubble element that operates stably over a long period of time. Ru.

[Brief explanation of drawings]

Figure 1 is a pie chart showing the relationship between the collapse magnetic field (Hco) and the rotating single drive magnetic field (Hp) in a magnetic baffle element with a normal implant layer formed, and Figure 2 is a pie chart showing the relationship between the collapse magnetic field (Hco) and the rotating single drive magnetic field (Hp) in a normal magnetic baffle element with an implant layer formed. Cross-sectional view of the magnetic bubble element, No. 3
The figures are based on the present invention (a cross-sectional view of a magnetic bubble element, FIG. 4 is a graph showing the concentration distribution of ions along the dashed-dot line 4 in FIG. 2, and FIG. 5 is a graph showing the concentration distribution of ions along the dashed-dot line 5 in FIG. 3). 6 is a pie chart showing the relationship between the collapse magnetic field (Hco) and the rotating 1-driving magnetic field (Hp) in the magnetic bubble element according to the present invention. FIG. In the figure, 21 is a substrate, 22' is a crystal film, and 23 is an ion implantation layer.

Claims (1)

[Claims] 1 A substrate for forming a magnetic bubble element, and a magnetic bubble crystal film formed on the substrate to generate a predetermined magnetic bubble domain by receiving a predetermined magnetic field, the surface of the magnetic bubble crystal film In a magnetic bubble element equipped with an ion implantation layer in which ions are implanted with a predetermined concentration distribution, the ion implantation layer is heated until a region corresponding to the peak value of the concentration distribution or a value in the vicinity thereof is exposed on the surface. A magnetic bubble element characterized by etching.