JPS6059671B2 - magnetic bubble memory element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic bubble memory device, and more particularly to a transfer gate portion of a magnetic bubble memory device using an ion implantation method.

Magnetic bubble utilization devices that use magnetic bubble memory elements to store information, perform logical operations, etc. have various features such as non-volatile high storage density and low power consumption, and are solid-state devices that do not contain any mechanical elements. Therefore, it has very high reliability.

Such magnetic bubble memory devices are also required to have increased storage density due to the recent increase in the amount of information and the demand for smaller devices. However, in the elements used in conventional magnetic bubble memories, the bubble transfer pattern is formed by photo-etching permalloy deposited on a magnetic thin film, so its dimensional accuracy is limited to the accuracy of exposure to visible light, and the pattern is It is becoming difficult to increase the storage density by reducing the size of the memory. For this reason, a method of forming a transfer pattern using ion implantation has recently been developed. This method uses gadolinium as shown in the plan view in Figure 1 and the cross-sectional view in Figure 2.
A thin film 2 of magnetic garnet, which will become a bubble crystal, is formed on a gallium garnet (GGG) substrate 1 by liquid phase epitaxial growth, and a portion 4 other than the pattern 3 of the magnetic film 2 is coated with hydrogen, neon, helium, etc. It involves implanting ions.

In the device in which the pattern 3 is formed in this way, the easy magnetization axis direction of the ion-implanted portion 4 coincides with the in-plane direction as shown by the arrow a, and the easy magnetization axis direction of the pattern portion 3 coincides with the in-plane direction as shown by the unmarked mark b. It is perpendicular to the same in-plane direction. Therefore, the bubble 5 is caused by the rotating magnetic field to move along the periphery of the pattern 3 in the direction of arrow c.
It is transferred as follows. This pattern has a shape in which parts of circles and hexagons are overlapped and arranged in a continuous manner, and unlike conventional permalloy patterns, there is no need for gaps, so dimensional accuracy does not need to be loose. Therefore, the pattern can be made smaller and higher density can be achieved. is realized. Furthermore, when a rotating magnetic field is applied to the connected disk pattern 3, the bubbles move along the periphery of the disk pattern 3, as shown in FIG. 3, as shown in FIG. In addition, in such a magnetic thin film, there are axes that are easily magnetized in stripes and are spaced at intervals of 1200 mm in three directions 1, ■, and ■, and the above-mentioned connected disk pattern 3 Super track s and bad track b depending on which direction the disk patterns forming the track are aligned in a row.
Then, three bubble movement paths are created: Gutsudo Track and G. Here, super track s is a transfer path in which the K1 direction of the magnetic thin film bubble crystal and the traveling direction of the transfer path have the relationship shown in Figure 3, and it is generally said that the bias margin of the transfer path is large. This is the path through which bubbles are easily transferred. Bad track b has a bias margin due to the relationship shown in Figure 3. This is the smallest transfer path and is the path through which bubbles are difficult to transfer. Good track g is a path with an intermediate operating margin for bubble transfer. As shown in Figure 3, the path on the opposite side of the road from Super Trucks is Bad Trucks. It becomes b. In addition, all paths of the continuous disk pattern 3'' in the K1 direction of the magnetic thin film bubble crystal become good tracks g.These are caused by the magnetocrystalline anisotropy of the magnetic thin film bubble crystal. Figure 4 shows super track s and bad track b.
6-1 to 6-8 are disk patterns, 3 is a transfer path pattern, and the transfer path pattern 3 includes four disks.・Pattern 6-1 or 6-
It is assumed that the four adjacent disc patterns and the four adjacent disc patterns 6-5 to 6-8 form a continuous disc pattern arranged in a row with a gap in between.

And these disk patterns 6-1 to 6-
8 and the magnetic thin film is the disk pattern 6-1.
The lower bubble path of 6-8 is a super ● track Sj, and the upper bubble path is a bad track b. 5 is a bubble that exists in the super track s of the transfer path pattern 3 before the rotating magnetic field is applied, but as the rotating magnetic field is applied, the bubble 5
The bubble transferred as shown in ``7'' is a bubble that exists in the bad track b of the transfer path pattern 3 before applying the rotating magnetic field, but as the rotating magnetic field is applied, it becomes a super track as shown in 7''. Represents a bubble transferred to S.

Note that k1 in the figure represents the direction of the easy axis of magnetization with respect to the disk pattern of a magnetic thin film bubble crystal, such as a garnet film. As shown in FIG. 4, when the bubble 5 exists in the path below the disk pattern 6-1 of the transfer path pattern 3, that is, in the super track s, when a rotating magnetic field is applied in the counterclockwise direction, the bubble 5 is 1 per rotation of the rotating magnetic field.
Bit-by-bit adjacent disk patterns 6-2, 6-3
By repeating this process, bubble 5 is transferred up to disk pattern 6-3.

The bubble 5 transferred to the disk pattern 6-3 moves along the periphery of the disk pattern 6-4 with the rotating magnetic field of the next cycle, but the bubble 5 rotates once and moves around the disk pattern 6-4. Upper passage or bad track b
The disk pattern 6-5 is transferred across the gap to the next disk pattern 6-5 by application of the next rotating magnetic field. In this way, even if there is a gap between the disk patterns, the bubble on the super track S will cross over the gap and be transferred on the super track S. I have a tendency to go. Then, as the rotating magnetic field is applied, the bubble 5 moves and is transferred to the bubble 5''.In contrast, the disk ● pattern 6
When a counterclockwise rotating magnetic field is applied to the bubble 7 existing in the upper path of -6, that is, bad track b, the bubble 7 is transferred to the adjacent disk pattern 6-5.

When the next cycle of rotating magnetic field is applied, the bubble is unable to cross the gap and rotates along the periphery of the disk pattern 6-5 as shown by the broken line in FIG. be introduced. Then, with the application of a rotating magnetic field, the bubble 7 is transferred onto the super track s,
In this way, when there is a predetermined gap between the disk ● patterns in the transfer path pattern 3, the bubble 5 on the super track s is transferred across the gap. , the bubble 7 on the bad track b cannot cross the gap but moves along the periphery of the disk pattern and is introduced into the super track s.
Transfer gates for writing from the major loop to the minor * loop or reading from the minor * loop to the major * loop of a magnetic bubble device having a pattern transfer path can be roughly divided into the following two types.

The first is to connect the lower transfer path 8 of the medial loop, that is, the super track s, to the information bubble 5 in FIG.
Assuming that the bubble 5 is being transferred from left to right as shown in the figure, when the bubble 5 reaches a predetermined position, the transfer pattern (transfer path) of the major loop transfer path 8 and the minor loop that stores information. A hairpin-shaped conductor that transfers between pattern 9 and
The bubble 5 is pulled by the hairpin conductor pattern 10 and transferred to the minor loop transfer pattern 9. That is, information is written to the minor loop.
At this time, the bubble 5 extends across the transfer path 8 of the major loop, in other words, across the pattern of the major loop, and is transferred to the transfer path 9 of the minor loop, creating a hairpin-shaped conductor ◆ Bubble in the conductor loop of the pattern 10 This method has disadvantages in that new creation is likely to occur and the bias margin is small. The second transfer gate has the configuration shown in Figure 6, and is the transfer path 1 of the medial loop.
A striped conductor 13 is provided between 1 and the minor loop transfer pattern 12, and when the information bubble 5 reaches a predetermined position, the striped conductor 13
A pulse current is applied to the magnetic field, and the bubble 5 is transferred from the upper path of the transfer path 11 of the major loop, that is, the super track s, to the transfer pattern 12 of the minor loop for writing. In this transfer gate, the bubble 5 does not need to cross the bad track b of the transfer path 11 of the major loop;
The position of the bubble transferred from the medium to the transfer path 14 of the medium loop is read out to the lower path of the medium loop transfer path 14, that is, the bad track b, via the conductor 15, and the time series of writing and reading is There is a drawback to the reverse. In response, the following transfer gate has been proposed.

To explain this with reference to FIG. 7, 16-1 and 16-2 represent major loops, 17-1 to 17-N represent minor * loops, and 18 and 19 represent conductor patterns, respectively. The lower side of the major loop 16-1 is a super track s to which bubbles are easily transferred, and the upper side is formed as a bad track b. The lower side of the medium loop 16-2 is a super track s, and the upper side is a bad track b. And minor ● loop 17-1 or 17
-N has good tracks g on both sides. A bubble example corresponding to the address information is generated from a bubble generator (not shown), and the bubble string is a medium ◆ loop 16.
-1 super●track S with the application of a counterclockwise rotating magnetic field.

And the bubble row is a minor loop 17-1 to 17
-N, when a pulse current is passed through the conductor loop of the conductor pattern 18, the bubble train is transferred to each of the minor loops 17-1 to 17-N of the disk pattern -N. be introduced. In other words, the information bubble is from the major loop 16-1 to the minor loop 17.
11 to 17-N. In addition, when the information bubble comes to the appropriate position of the minor loops 17-1 to 17-N, a pulse current is applied to the conductor loop of the conductor pattern 19.
The bubbles in the loops 17-1 to 17-N are attracted to the disk pattern of the corresponding major loop 16-2, and a bubble train is introduced into the super track s of the major loop 16-2. These bubbles are then transferred along with the rotating magnetic field onto the super track s of the medial loop 16-2. FIG. 8 is a principle diagram for explaining the operation of this transfer gate, and is a partially enlarged view of FIG. 7 during writing. Numbers 16-1, 17- in the diagram
1 to 17-3 and 18 correspond to those in FIG. 20 is a bubble, 21 is a disk pattern, 22 and 23 are oval disk patterns which form a transfer path with a predetermined gap, and 24 is a transfer disk pattern of the minor loop 17-2. represents a pattern.

Let us now consider the case where the bubble 20 is stored in the minor loop 17-2.

When the rotating magnetic field HR is directed in the direction C, the bubble 20 we are focusing on has a major loop 16- as shown in FIG.
1 disc pattern 21 lower super track s
As the rotating magnetic field HR rotates counterclockwise, the bubble 20 also moves along the periphery of the disk ● pattern 21, and when the rotating magnetic field HR points approximately in the direction of D, the bubble 20 moves toward the 2'' direction. transferred to the location. Rotating magnetic field H
While R rotates further and its direction faces A and B, the bubble 20 does not move along the periphery of the disk pattern 21 as explained in FIG. 4, but remains at the position 2'. ing. When the rotating magnetic field HR rotates and points in the direction from B to C, the bubble 20 is transferred along the periphery of the oblong disk pattern 22 and comes to the position 2'. Furthermore, rotating magnetic field HR
starts one rotation and faces in the direction of D, as the bubble 2
0 is transferred to position 1 between oblong disk patterns 22 and 23. Oval disk patterns 22 and 23
A conductor loop of a hairpin-like conductor pattern 18 is formed between the conductor pattern 18 and
is the transfer of minor ● loop 17-2. It overlaps with the disk pattern 24 to form a transfer gate. When the bubble 20 is transferred to the position 1 in FIG. 8, the hairpin-shaped conductor ● pattern 18
When a pulse current is applied to the conductor loop and the bias magnetic field is locally weakened, the bubble 20 is striped out. The other end of the striped magnetic domain reaches the transfer disk pattern 24 of the minor loop 17-2. Eventually, when the direction of the rotating magnetic field HR changes from the direction B to the direction C, a magnetic pole is formed in the transfer disk pattern 24 that attracts the bubble 20. Even when the current pulse current is turned off, the bubble 20 is still transferred to the 1st position on the periphery of the transfer disk pattern 24. Next, as the rotating magnetic field HR rotates in the direction D, the bubble 20 transferred to the minor loop 17-2 becomes the transfer disc pattern 2.
Move to the position of 1C Jr. around 4. By configuring transfer paths at predetermined intervals in the disk pattern constituting the major loop 16-1 in this way, the major
Loop 16-1 to minor loop 17-1 to 17
-N, there is no need to cross the major loop pattern itself as in the case shown in FIG. 5, and therefore bubble nucleation at the transfer gate section is less likely to occur.

When reading, as explained in Figure 7, the minor
Since the read bubbles from loops 17-1 to 17-N proceed to the super track s below the major loop 16-2, the time series of writing and reading coincide.

In a transfer gate using such magnetocrystalline anisotropy, the conductor pattern 18 crosses the minor loops 17-1 to 17-N as shown in FIG.

Therefore, when the period of the continuous disk pattern constituting the minor loops 17-1 to 17-N is about 8 μm, the bias margin has a sufficiently large value, but when the period is about 4 μm, the bias margin is large enough. Conductor pattern 1 may not be transferred stably due to the magnetic field, or if the conductor pattern 1 is not transferred stably after transfer or when the loop goes around the minor
There is a drawback that malfunctions occur at corners due to the stress of 8. The present invention has been devised to improve this drawback. Therefore, in the present invention, an ion implantation layer is formed on the entire surface of the crystal substrate for magnetic bubbles except for a plurality of connected disk pattern areas, and the connected disk pattern areas are used as bubble transfer paths. A conductor pattern for writing these bubbles into the minor loop and a conductor pattern for writing the bubbles into the minor loop are constructed. In a magnetic bubble memory element, a conductor pattern for reading out bubbles contained in the major loop is formed in a hairpin shape on a line connecting the cusp of the major loop and the tape of the minor loop. The present invention is characterized in that at least one opening of the hairpin-shaped conductor pattern for writing and reading is provided so as not to overlap with the bubble transfer path of the minor loop.

Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings. FIG. 9 shows a first embodiment.

The figure is an enlarged view of the transfer gate portion, with reference numeral 25 indicating a major loop and 26 indicating a minor loop, both of which are shown with hunting. The major loop 25 and the minor loop 26 are connected disk patterns of connected squares or triangles, but may also be formed of connected circles. 27 is a conductor pattern, which is formed into a hairpin loop shape on a line connecting the cusp of the major loop 25 and the tape of the minor loop 26 through an insulating layer, and this conductor pattern 27 is a minor loop. It is formed so as not to overlap with 26.

The position relative to the easy magnetization axis direction K1 of the substrate crystal is as shown in the figure. FIG. 10 is an enlarged view of the transfer gate portion of the second embodiment, and the same parts as in the previous embodiment are designated by the same reference numerals. This embodiment differs from the previous embodiment in that a gap 28 is provided between the minor loop 26 and the conductor pattern 27. The size of this gap 28 is suitably 1 to 4 times the diameter of the bubble. In the first and second embodiments formed as described above, the conductor pattern 27 has a minor loop 26.
Since the bubble from the major ● loop 25 is not crossed, the bubble from the major ● loop 25 is correctly written to part a of the minor loop 26.

(Conventionally, it was sometimes written in part b) Also, malfunctions caused by bubbles extending along the edge of the conductor pattern 27, or minor loops 26 and conductors ●
Malfunctions caused by interactions with patterns are also prevented.
Therefore, phase current characteristics and phase bias margin are improved. Figure 11 shows the conventional product shown in Figure a and the first model shown in Figure b.
Figure c shows the phase current characteristics when the bias magnetic field HB is kept constant at 3380e, and figure d shows the phase bias margin when the current in the conductor pattern is kept constant. Curve A (dotted line) represents the conventional product, and curve B (solid line) represents the present example.

The test conditions were as follows: The pulse width of the current 1 of the conductor pattern was 0.2 μS The frequency of the rotating magnetic field was 50 k pressure for the conventional product, and the strength of the rotating magnetic field was 500 kHz for this example.
And so. It can be seen from Figures c and d that this embodiment is improved over the conventional product. Further, Figure e shows the current bias margin when phase 0 is fixed at 900. Figure 12 shows the gap D between the minor loop 26 and the conductor ● pattern 27 as shown in figure a, which is twice the bubble diameter (2
Figure b shows the phase current characteristics when the bias magnetic field is kept constant at 3400e, and Figure c shows the characteristics of the second embodiment when the conductor pattern current 1 is set to 100T.
The phase bias margin when r1, A is kept constant is
Figure d shows the current bias margin when the phase θ is fixed at 1620.

(However, the test conditions are the same as those of the previous example.) From this b-d diagram, it can be seen that this example has more stable characteristics than the first example. In particular, the worm-like tendency shown in figures c and d shown in the characteristics of the first embodiment is eliminated. As explained above, in the magnetic bubble memory device of the present invention, the conductor pattern of the transfer gate is formed so as not to overlap with the minor loop, so that the bubble transfer from the major loop to the minor loop can be prevented. This prevents malfunctions and contributes to improving the reliability of magnetic bubble memory devices using ion implantation.

[Brief Description of the Drawings] Figure 1 is a plan view of a magnetic bubble memory element formed by ion implantation, Figure 2 is a cross-sectional view taken along the line ■--■ in Figure 1, and Figure 3 is a magnetic thin film bubble. FIG. 4 is an explanatory diagram explaining the relationship between the crystal direction and the transfer path, and FIG. Fig. 6 is an explanatory diagram of a conventional write/read transfer gate in a concatenated disk pattern transfer path, Fig. 7 is an explanatory diagram illustrating bubble tracks of a major ● loop and a minor ● loop, and Fig. 8 is an explanatory diagram of a conventional transfer gate.・An operation principle diagram explaining the operation of the gate, FIG. 9 is a plan view of the transfer gate of the first embodiment according to the present invention, and FIG.
The figure is a plan view of the second embodiment, FIG. 11 is a diagram comparing the characteristics of the first embodiment and the conventional example, and FIG. 12 is a diagram showing the characteristics of the second embodiment. It is. 25... Major ● loop, 26... Minor ● loop, 27... Conductor pattern, 2
8. Gap.

Claims (1)

[Claims] 1. An ion implantation layer is formed on the entire surface of a crystal substrate for magnetic bubbles except for a plurality of connected disk pattern areas, and the connected disk pattern areas are used as bubble transfer paths, and the bubble transfer A major loop that transfers information bubbles by a path and a plurality of minor loops that store the bubbles are configured, and a conductor pattern for writing these bubbles into the minor loop and a conductor pattern for writing the bubbles in the minor loop. In the magnetic bubble memory element, a conductor pattern for reading out the bubbles contained in the major loop is formed in a hairpin shape on a line connecting the cusp of the major loop and the tip of the minor loop. 1. A magnetic bubble memory element, characterized in that at least one opening of the hairpin-shaped conductor pattern for writing and reading is provided so as not to overlap with the bubble transfer path of the minor loop. 2. The magnetic bubble according to claim 1, wherein the distance between the conductor pattern and the bubble transfer path of the minor loop is set to be greater than or equal to the bubble diameter of the information and less than or equal to four times the bubble diameter of the information bubble. memory element. 3 The bubble transfer path of the major loop is connected to the minor loop.
2. The magnetic bubble memory device according to claim 1, further comprising a gap in a portion of the loop facing the bubble transfer path.