JPS6215951B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a non-destructive memory device composed of a large number of shift registers. More specifically, the present invention relates to the arrangement of a special-purpose shift register that is specially provided within an element and records the position of a defective shift register as information.

A typical example of a nondestructive memory device composed of a large number of shift registers is a magnetic bubble memory device. Generally, in a magnetic bubble memory device, a large number of shift registers are called a minor loop. A large-capacity magnetic bubble memory device is described in the paper “Magnetic” by PCMICHAELIS et al.
Bubble Repertory Dialer Memory” (IEEE
Trans.on magn., MAG-7, pp737-740,
As shown in Figure 1 of 1971), it has become common to consist of a large number of bubble information storage loops (minor loops) and a major loop (or major line) for reading and writing information that is commonly connected to all loops. There is.

It is well known that increasing the storage capacity can be achieved by decreasing the bubble magnetic domain diameter to increase the storage density and at the same time making the minor loops longer and more numerous. In manufacturing magnetic bubble memory devices using field access method in which bubble magnetic domains are moved using an in-plane rotating magnetic field H _R , it is important to manufacture bubble domain transfer paths such as minor loops completely defect-free from the viewpoint of device yield. It's not a good idea. Normally, the yield is improved by recognizing the existence of defective loops that are about 10% of the number of minor loops.

When using a magnetic bubble memory element having such a defective loop, it is necessary not to write bubble magnetic domains into the defective loop. For this reason, it is necessary to store the location of the defective minor loop in an external memory and mask the defective minor loop to prevent writing of bubble information. A similar operation is required for reading bubble information. A semiconductor memory is generally used as an external memory for storing the position of a defective loop. However, in semiconductor memory, there is a risk that the memory contents will be lost when the driving power source is cut off, and such a memory system cannot be said to be sufficiently reliable.

As one method to improve the reliability of storing the location of a defective loop in a bubble memory device, it has been proposed to provide an independent dedicated minor loop for storing the location of a defective loop within the bubble memory device itself, and it has been proposed to provide an independent dedicated minor loop for storing the location of the defective loop within the bubble memory device itself. Tagoto Electronics magazine, August 17, 1978 issue
It was introduced on pages 39-40. There, a dedicated minor loop for storing the location of a defective loop is called a redundancy loop (RL) and is provided in the periphery of the bubble memory element chip. Even if the memory of the defective loop position in the external TC memory is lost due to a power cut, there is an advantage that the defective loop can be successfully masked again by writing the defective loop position information in the redundant loop to the external memory again.
However, this redundant loop configuration causes a decrease in yield when assembling this chip into a one-chip memory module for the reasons described below.

Generally, in a field access type bubble memory element, the range of the bias static magnetic field H _B in which the bubble operation is normally performed depends on the in-plane magnetic field strength H _R . As shown in Figure 1, its dependence is expressed by the in-plane rotating magnetic field H _R
The upper limit value H of the operating bias magnetic field range increases with the increase of
_B (U) increases. On the other hand, the lower limit value H _B (L) remains almost unchanged. When manufacturing a bubble memory module using a bubble memory element such as the bubble memory chip 1 shown in FIG. A means for applying an in-plane rotating magnetic field to the chip is required. A good way to do this is to attach the bubble chip 1 to the chip timekeeping board 3 as shown in Figure 2B, form a coil 4 around it with a conducting wire, and generate an in-plane magnetic field by passing an alternating current through this coil. Are known. This in-plane magnetic field generating coil is normally a set of two coils arranged at right angles to each other, but only one of them is shown here for convenience.

In an in-plane rotating magnetic field applying means using such a coil, it is required to use a coil as small as possible in order to increase the operating speed of the bubble memory module. As for the distribution of the in-plane magnetic field generated by the coil, as shown in FIG. 2C, the magnetic field strength sharply decreases in the periphery of the chip region. The size of the coil is determined so that the rate of this decrease is 5 to 5% less than the magnetic field value H _R0 at the center.
An efficient coil design is to make the coil as small as possible by about 10%. 5% from central magnetic field H _{R0
The value obtained by subtracting the allowable magnetic field reduction value △H R1 =}
If H _R0 -ΔH _R is the standard in-plane rotating magnetic field value for driving the bubble element, the bias magnetic field operating range ΔH _B shown in FIG. 1 is obtained. However, when the center of the coil deviates from the center of the chip and the chip protrudes from the chip area of the magnetic field distribution, the H _R applied to the periphery of the chip rapidly decreases. As H _R decreases, as is clear from FIG. 1, the operating bias magnetic field range around the chip also decreases.

When this bubble memory chip is composed of a large number of minor loops as shown in FIG. 2A, the operating bias magnetic field range of the minor loops around the chip decreases as H _R decreases. A minor loop with a narrow operating bias magnetic field range is a defective loop, similar to a minor loop with a small operating bias magnetic field range due to a defect. Generally, in a bubble memory module manufactured by incorporating a bubble memory chip composed of a large number of minor loops into an in-plane magnetic field coil, it is unavoidable that variations occur in the alignment between the chip and the coil. Therefore, it is expected that the probability that a minor loop near the chip periphery will become a defective loop is greater than that of a minor loop in the center. In fact, as a result of manufacturing and evaluating a large number of bubble memory modules, it was found that the probability of a defective minor loop occurring is approximately five times greater in the minor loop at the periphery of the chip than at the center, as shown in Figure 2D. did.

The aforementioned redundant loop for storing information on the position of a defective minor loop is usually provided on one chip with only one or two loops, and this is a loop that cannot be replaced by any other minor loop. Therefore, the yield of redundant loops directly affects the yield of modules. When a module is manufactured using a known bubble memory in which redundant loops are present at the periphery of a chip, the defective rate of the redundant loops that cannot be replaced is extremely high, resulting in a decrease in the yield of the module. In order to avoid a drop in yield, if the size of the coil is made sufficiently large, the defect rate of minor loops around the chip will be reduced, but the disadvantage of increasing the coil size is that the peripheral circuitry will become complicated due to the bubble memory module drive. arise.

SUMMARY OF THE INVENTION An object of the present invention is to provide a memory element having a memory structure that eliminates these drawbacks and improves the assembly yield of bubble memory modules.

The principle of the present invention is that an important special-purpose minor loop that cannot be replaced by other minor loops, such as the redundant loop described above, is not provided in the periphery of the chip where the in-plane magnetic field changes rapidly. The object is to reduce the defective rate by providing it in the center of the chip where it is not affected by center deviation.

Next, embodiments of the present invention will be described using the drawings.
FIG. 3A is a diagram illustrating a first embodiment of the present invention. On the bubble material 1 capable of holding bubble magnetic domains, minor loops 22 for storing and transferring bubble magnetic domain information made of, for example, a soft magnetic pattern array are provided with major loops or major lines 21, 21' that connect the respective minor loops in common. redundant loop 2
3 is provided at the center of the minor loop group. In this embodiment, the minor loops are divided into two groups in order to increase the reading transfer speed of bubble information. Each group is led through a measure line (or loop) 21 to an independent detector section. A redundant loop 23 is provided at the boundary between these two groups, at the center of the chip. When the chip is configured in this way, the defective rate of the redundant loop becomes equal to the defective rate of the general minor loop, and the drop in module assembly yield due to variations in the alignment of the H _R coil and the chip during the bubble memory module assembly process is reduced. It can be prevented. Moreover, it becomes easy to make the size of the coil as small as possible.

FIG. 3B shows a second embodiment of the invention. In this embodiment, the grouping of the minor loops 22 is different from the previous embodiment, and two major lines or major loops 21 are provided in parallel with the minor loop group separated. The redundant loop 23 is located exactly in the center of the chip. Alternatively, a redundant loop may be provided at the position indicated by 23'. Because 23'
The position is sufficiently closer to the center than the periphery of the chip because there are a bubble magnetic domain detector connected to the major line and current terminals 24 for driving various functional parts. Therefore, the minor loop failure rate due to variations in the position of the H _R coil is sufficiently smaller than that of the general minor loop at the other end, and does not cause a decrease in the yield of module assembly.

FIG. 3C shows a third embodiment of the invention. The grouping of minor loops is the same as in the second embodiment. In this embodiment, the redundant loop 23 is provided at right angles to the longitudinal direction of the minor loop 22, that is, parallel to the major line (or major loop) 21, and along the major line near the center of the chip.

As described above, the present invention provides a small number of minor loops with special uses that cannot be replaced with many general minor loops in the center of a bubble chip, thereby reducing the failure rate of the special purpose loops.
The module assembly stage is reduced compared to known configurations. Therefore, the bubble memory module assembly yield can be improved. In the embodiments of the present invention, the redundant loop position for storing defective minor loop position information has been described as this special purpose loop. The same applies to counter loops. Furthermore, in the embodiment, the case where the number of special purpose loops is one has been explained, but if the number of special purpose loops is within 10% of the total number of minor loops, the positions to be provided are concentrated in the center of the chip. It is clear that this can also be expected to greatly improve the yield of module assembly.

In the explanation so far, the case of a field access type magnetic bubble memory element has been described as an example. However, even in non-destructive memory devices that generally consist of a large number of shift registers, there is a high probability that defects will occur around the chip due to the cutting of the chip from the wafer during the module assembly stage and the processing process for electrical connection with the outside. is greater than the probability of causing a defect in the center. Therefore, providing the important special purpose shift register in the center of the chip improves the manufacturing yield of this memory element module, as discussed above.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing general operating characteristics of a bubble memory, in which the horizontal axis H _R represents the in-plane rotating magnetic field strength, and the vertical axis H _B represents the bias magnetostatic strength. FIG. 2 is a diagram illustrating the principle of the present invention, in which A is a perspective view showing the structure of a bubble memory chip, 1 is a bubble material, 21 is a major loop or major line, 22 is a plurality of minor loops, and B is a bubble memory chip. 3 is a perspective view showing the in-plane magnetic field application part of the memory module, 3 is a chip fixing substrate, 4 is a magnetic field generating coil, and C is a diagram showing the distribution of the in-plane magnetic field applied to the bubble chip within the bubble module. , D is a diagram showing the minor loop failure rate with respect to the minor loop position in the bubble chip indicated by A. 3A to 3C are perspective views showing the structure of bubble memory chips corresponding to the first to third embodiments of the present invention, in which 1 is a bubble material;
21 and 21' represent a major loop, 22 a minor loop, and 23 and 23' a special purpose minor loop.

Claims (1)

[Claims] 1 A material chip capable of storing information around which a driving magnetic field generating coil is provided, a large number of general shift registers for storing information configured on the chip, and other information transfer paths common between the shift registers. In a nondestructive memory element having a small number of special-purpose shift registers that are used differently from general shift registers, the special-purpose shift register is located closer to the center of the chip than the register closest to the periphery of the chip among the general shift registers. A memory element characterized in that the register is arranged near the center of the magnetic field generating coil.