JPS6048072B2 - Thin film conductor pattern - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thin film conductor pattern used in a bubble control circuit designed to prevent electromigration.

There are transfer gates, block replicators, anilators, generators, replicators, etc. that control the transfer of magnetic bubble domains (hereinafter referred to as bubble control), but most of these are equipped with conductive patterns and Bubble control is performed by passing current through the conductor pattern to create a local magnetic field.

For example, FIG. 1A shows a transfer gate section of a bubble memory, which consists of a conductor section 10 and a large number of permalloy magnetic patterns 5, 6, 7, . . . for transfer.

These are a conductor pattern 10, transfer magnetic patterns 5, 6, 7, etc. on a uniaxial magnetic anisotropic bubble magnetic substrate.
It is formed with a two-layer structure. To briefly explain an example of the operation, when the rotating driving magnetic field HR faces in the magnetic field direction HR as shown in FIG. . Next, the driving magnetic field is in the direction HR. , H.R. , H.R. When facing, the magnetic poles are 2, 3, and 4, and the bubble moves to the corresponding positions one after another. Next, when the driving magnetic field is directed in the direction HR, the bubble moves to the bubble attracting magnetic pole 1' generated in the magnetic pattern 7, and thereafter the driving magnetic field is directed in the direction HR. , HR3, etc., the bubble moves to positions 2', 3', and so on. When the bubble is at position 1'' of the magnetic pattern 8, when a pulse current is passed through the conductor pattern 1 with a polarity that creates a bubble anti-propagating magnetic field inside the hairpin-shaped portion and a bubble attracting magnetic field outside, the driving magnetic field HR Even if it faces direction HR2, it cannot go to position a and remains in the vicinity.Then, the driving magnetic field is directed in direction HR., HR.
When facing . . . , the bubble moves to positions c, d . . . , 5 . Bubble generators, replicators, etc. are similar in that they generate and split bubbles by passing current through a hairpin-shaped conductor pattern.
This current value, especially the current density, is quite high because the conductor pattern is made of a thin film. And when used for a long time, there is a tendency for disconnection accidents to occur. A detailed study of this disconnection accident revealed that the disconnection section had certain characteristics. This will be explained below with reference to FIG. FIG. 2 shows a part of a thin film conductor pattern in a conventional transfer gate or the like.

As shown in the figure, the conductor pattern 10 consists of a substantially U-shaped narrow hairpin portion 10a and wide base portions 10b and 10c which are connected to both ends of the hairpin portion and are orthogonal to the hairpin portion, and are symmetrical. When a voltage is applied to this conductor pattern 10 and a current 1 is caused to flow, the above-mentioned bubble control magnetic field is generated in the hairpin-shaped part.
There is a tendency for wire breakage 20 to occur in Bl, especially in portion A. This can be thought of as follows. That is, when current 1 flows, electrons move in the opposite direction to the current, but the kinetic energy of this electron flow is transmitted to the metal atoms of the conductor pattern 10, and the metal atoms become active, breaking atomic bonds and moving. Begin to. This phenomenon is generally called electromigration. This phenomenon causes gaps in the conductor pattern 10, which reduces the cross-sectional area of the portion, increases current density, and further activates electromigration, eventually leading to disconnection. There is a high probability that the disconnection occurs in the shaded areas A and B, and especially in the shaded area A, the probability is 2/
3. In the shaded area B, the former has a high probability of occurring at a rate of 1/3. In this way, although it differs depending on the type of metal that makes up the conductor pattern, the disconnection is generally on the negative side (portion B is also on the negative side when viewed from one current path of 10a with the bending point as both ends). There is a tendency for it to occur frequently. This is considered to be because the kinetic energy of electrons on the negative side is large and electromigration is actively performed. The present invention has been devised with attention to the above point, and has a substantially U-shaped narrow hairpin portion and four wide base portions that are connected to both ends of the hairpin portion and extend in a direction that intersects the hairpin portion. A thin film conductor pattern for magnetic bubble domain control, in which the current density of the conductor pattern on the negative side viewed from the direction of current flow in the narrow hairpin-shaped portion is made smaller than that on the positive side by means such as widening the width. It is characterized by this.

Next, the present invention will be described in detail with reference to Examples. FIG. 3 shows a first embodiment of the invention.

This figure shows a portion of the conductor pattern 10 as in FIG. 2, but as shown in this figure, the minus side 10a1 of the hairpin-shaped portion 10a of the conductor pattern 10 is made wider than the plus side 10a2. When the width of the conductor pattern 10 is made uniformly wide on the negative side 10a1 in this way, the density of the current flowing there becomes smaller. Therefore, the density of electrons flowing there is also reduced, making electromigration less likely to occur. Furthermore, since the width is wide, even if a few holes or missing portions are formed due to electromigration, it is unlikely to cause wire breakage, and thus the conductor pattern will not be broken even after long-term use. Note that instead of increasing the width of the conductor pattern, the thickness of the conductor pattern may be increased, and it is also possible to use these in combination. By increasing the width of the negative side of the conductor pattern 10 in this way, it is possible to prevent the occurrence of a disconnection at point A (7) shown in Figure 2, but this time a disconnection will occur at point B. Therefore, the embodiment shown in Fig. 4 is an embodiment in which both of these parts are widened. Fig. 4 shows a second embodiment of the present invention.

In this example, the location A where the probability of wire breakage occurring is high as shown in Figure 2,
In both B, the width of the relevant part is widened. In this way, the current density at both locations A and B is reduced, and the occurrence of wire breakage can be prevented for the same reason as described above, and the life of the conductive pattern 10 can be extended. However, in actual use, in the method shown in Figure 4, the strength of the generated magnetic field or its distribution changes at locations A < 5B, so
In some cases, the conductor pattern shown in FIG. 4 may not be preferable, and the pattern shown in FIG. 3 may be preferable. Of course, this conductor pattern can be applied not only to the transfer gate but also to the conductor pattern of the aforementioned block replicator and the like.

As explained in detail above, according to the present invention, it is possible to effectively prevent the occurrence of disconnection due to the electromigration phenomenon occurring in the conductor pattern in the bubble control circuit, and as a result, the effective life of the conductor pattern can be extended. Yes, it is extremely useful.

[Brief explanation of the drawing]

FIG. 1A is a partial plan view showing an example of a conductive pattern and a permalloy magnetic pattern for transfer in a conventional bubble memory;
FIG. 2 is a plan view showing the shape of a conductor pattern of a conventional transfer gate, and FIGS. 3 and 4 are plan views showing an embodiment of the present invention. be.

Claims (1)

[Scope of Claims] 1. A thin film conductor pattern for controlling a magnetic bubble domain, which has a substantially U-shaped narrow hairpin portion and a wide base portion that is connected to both leg ends of the hairpin portion and intersects the hairpin portion, comprising:
A thin film conductor pattern characterized in that the current density of the conductor pattern on the negative side in the narrow hairpin-shaped portion when viewed in the current direction is made smaller than that on the positive side by means such as increasing the width. 2. The thin film conductor pattern according to claim 1, wherein one entire leg on the negative side of the narrow hairpin-shaped portion is made wider than the entire other leg on the positive side. 3. Claim 1, characterized in that the vicinity of the connecting part between the narrow hairpin-shaped part and the wide base on the negative side, and the positive side of the folded part of the narrow hairpin-shaped part are locally widened. Thin film conductor pattern described.