JPH0646502B2 - Magnetic bubble memory - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a magnetic bubble memory, and more particularly to a magnetic bubble memory having an improved transfer pattern.

[Background of the Invention]

Generally, as a magnetic bubble transfer path, a so-called field access method in which a soft ferromagnetic thin film pattern such as permalloy is magnetized by a rotating magnetic field is mainly used. As the pattern of this magnetic bubble transfer path, a pattern of the kind shown in the enlarged plan view of the main part in FIG. 1 has been mainly used so far.

1A shows a transfer path formed by using the asymmetric chevron pattern 10 as a base pattern, FIG. 1B shows a transfer path formed by using a half disk pattern 11 as a basic pattern, and FIG. 1C shows a C-shaped pattern 12 as a basic pattern. The transfer paths each configured as a pattern are shown. These transfer patterns are parallel gap patterns, for example, iE, E, Transaction magnetics,
MAG-12, No. 6, November 1976 (IEE
E Transactions on Magnetics) Pages 614-61
7 and pages 651-653.

With the recent increase in the degree of integration and density of magnetic bubble memory devices, the diameter of magnetic bubbles used has been reduced from about 1.5 μm in the past to about 1.0 μm. Similarly, assuming that the period of the basic pattern of the magnetic bubble transfer path is λ as shown in FIG. 1, this λ is 12 to 16 μm in the conventional case.
Recently, the size has been reduced to about 8 to 6 μm. Further, the inter-pattern gap g and the minimum pattern width W have been miniaturized to about 1.0 μm, which is the limit of the current photolithography technology.

With such miniaturization, the transfer characteristics of bubbles represented by a bias margin have become extremely severe, and even a slight variation or fluctuation in the manufacturing process causes a large yield reduction.

[Object of the Invention]

SUMMARY OF THE INVENTION One object of the present invention is to provide a magnetic bubble memory with improved bias margin.

Another object of the present invention is to provide a magnetic bubble memory capable of increasing the yield.

Still another object of the present invention is to provide a magnetic bubble memory capable of reducing the power consumption of peripheral circuits.

[Outline of Invention]

The present invention is directed to a permalloy transfer pattern having protrusions near the magnetic bubble outlet and the magnetic bubble inlet. These protrusions are incorporated at the stage of pattern design, and are reproduced in almost the same pattern on a photo processing mask. After the patterning of permalloy is completed, that is, when the pattern is completed, the gap g between the bubble outlet and the inlet of the two transfer patterns adjacent to each other along the bubble transfer direction is small because the projection of the design pattern is effective. It was
Therefore, the gap g and the bubble transfer bias margin of the projecting design pattern are large in the completed state as compared with the conventional design pattern. In addition, this projecting design pattern has the function of increasing the suction force of bubbles, deepening the well potential, and steepening the gradient of the well potential. Improvements are achieved.

In the present invention, as shown in FIG. 3C, the magnetic field strength distribution characteristic is measured to clarify the ease of transfer of magnetic bubbles due to the shape of the transfer pattern foot, and if the transfer margin is only the transfer pattern gap. The shape of the transfer pattern foot portion shown in FIG. 9B, in which the shape of the transfer pattern is related, is easily invented. According to the present invention, the following magnetic bubble memory is provided. It

In a magnetic bubble memory in which a plurality of permalloy transfer patterns are arranged along the transfer direction of a magnetic bubble, the transfer pattern includes an input side leg portion, an output side leg portion, and a mountain-shaped body portion that extends on both leg portions. , An input side foot portion continuous to the input side leg portion, and an output side foot portion continuous to the output side leg portion, in the one transfer pattern, the input side foot portion and the output side foot portion, Each of them has a sole portion of the foot inclined in a direction opposite to each other and an instep portion of the foot projecting from the leg portion in the opposite direction, and at a place where the two transfer patterns are adjacent to each other, the foot portion of the output side A magnetic bubble memory in which a gap (h) between the instep and the instep of the input-side foot is narrower than a gap (g) between the output-side leg and the input-side leg.

The invention, other objects of the invention and other features of the invention will be apparent from the following description with reference to the drawings.

Example of Invention

FIG. 2 shows a permalloy transfer pattern, and a pattern 10 shown by a dotted line shows a photo mask pattern.

Even if the pattern of the photomask is formed according to the design pattern as shown by the dotted line in FIG. 2A, with the current photo processing technology, the finished pattern is rounded near the inflection point of the polygonal line as shown by the solid line. Comes on. According to the analysis by the present inventors, it was found that this roundness widens the gap g between the bubble outlet OUT and the inlet IN of the transfer pattern, thereby limiting the upper limit of the bias magnetic field. FIG. 2B shows the result of observing the movement of the bubble B with a microscope.
The route from the position 1 to B12 via B5, B8 is reached. Hereinafter, this path is called a micro bubble transfer direction. As can be seen from this figure, the magnetic bubble passes from the tip portion B5 (OUT position in FIG. 2A) of the transfer pattern to the tip portion B8 (IN position in FIG. 2A) between adjacent transfer patterns. Therefore, it was found that the roundness of the leading end of the transfer pattern greatly affects the transfer characteristics.

Fig. 3 shows the magnetic field strength distribution characteristics (Well potential distribution) given to magnetic bubbles of three types of transfer patterns.
FIG. 6 is a diagram for comparing the magnetic field strength Hr of 60 [O
e], the bubble diameter is set to 1.85 [μm], and the calculation is performed under the conditions when the center of the magnetic bubble is located at the center of the gap between the adjacent transfer patterns (determined by the direction of the rotating magnetic field). Bubble entrance / exit of transfer pattern P13,
That is, the foot has a shape in which both the left and right corners are chamfered obliquely. The foot portion of the transfer pattern P14 has two sides where right and left corners intersect at a right angle. In the foot portion of the transfer pattern P15, each portion near the gap has two acute-angled sides. In the figure, the contour lines and the numbers attached thereto indicate the magnetic field strength (unit [Oe]).

The maximum well potentials of the transfer patterns P13, P14, and P15 are 36, 38, and 42 [Oe], respectively. The higher the maximum well potential, the easier the bubbles are transferred. Therefore, at this point, the patterns P15, P
14 and P13 are excellent in that order.

Regarding the transfer pattern P15, the contour line shown by the outermost crosshatch in the figure has a value of 36 [Oe]. Among these contour lines, there are three contour lines having values of 38, 40 and 42 [Oe]. Is included. The transfer pattern P14 is 36
Within the [Oe] contour, there is one 38 [Oe] contour. Since the transfer pattern P13 has the highest 36 [Oe] contour line, it does not include other contour lines. In the above-mentioned three transfer patterns, the 36 [Oe] contour lines have almost the same size as seen in the macro.
15 has dense contour lines in the center of the gap, in other words, has the steepest magnetic field gradient, and therefore bubbles are easily transferred.

If it is possible to form the transfer pattern as shown in FIG. 3 by a high-precision photographic processing technique, even though the gaps g of the transfer patterns P14 and P15 are the same, the well The pattern P15 is the pattern P due to the difference in the maximum value of the potential and the distribution density.
It can be seen that the transfer characteristics are superior to those of 14. That is, the transfer margin is related to not only the gap g of the transfer pattern but also its shape. The transfer pattern P13 has a rounded finished pattern P10 shown in FIG.
Similar to the 0 shape, this pattern not only widens the gap g, but also has a poor well-potential distribution. From the distribution chart of FIG. 3C, it is understood that the bubble entrance / exit foot portion of the transfer pattern may be provided so as to be offset toward the side close to the gap g.

FIG. 4A is a diagram showing the shapes of three types of patterns of A, B, and C, the photomask formation, and the photographic processing stage. The pattern diagrams of the latter two stages are outlines of electron micrographs. is there.

Pattern A is a conventional pattern in which the gap side ends b and c and the opposite side ends a and d are not offset (c = b, a = d) at the foot of the bubble entrance / exit of the transfer pattern. ing.

Patterns B and C are improved patterns described in Japanese Patent Application No. 59-127421 (Japanese Patent Laid-Open No. 61-8789) previously filed by one of the applicants. Patterns B and C are patterns added to the gap g side b and c at the foot of the bubble entrance / exit, and their contours are stepwise according to the minimum beam spot 25 μm square of the electron beam exposure apparatus used when making the photomask. I draw it. The pattern B has three additional spots, and the pattern C has six additional spots. The outline of each pattern becomes rounded at the photomask making stage and the photoprocessing stage, but in the finally completed permalloy pattern, the gap between the transfer patterns is the smallest in the pattern C, and the pattern A is the smallest. Is the most widespread.

FIG. 4B shows data obtained by actually measuring the inter-gap transfer characteristics of the three types of completed permalloy patterns.

In the same figure, the curves A, B and C show the characteristics of the patterns A, B and C of FIG. 4, respectively. The upper side represents the upper limit of the bias magnetic field and the lower side represents the lower limit. In addition,
The upper limit value of the rotating magnetic field strength Hr = 60 [Oe] of the curve C exceeds 260 [Oe] and is not shown.
As can be seen from this characteristic diagram, the upper limit value of the bias magnetic field in the patterns B and C is significantly improved as compared with the conventional pattern A, and the lower limit value is slightly improved. = Significant improvement in bias margin was obtained.

FIG. 5 is a diagram showing a pattern near a swap gate of a magnetic bubble memory chip to which the improved transfer pattern according to the above-mentioned prior application is applied. Transfer patterns I1 to I1
Reference numeral 6 constitutes a minor loop m for storing information, and the magnetic bubble is transferred in the counterclockwise direction indicated by PRi in the figure. J1 to J5 are write major lines W
This is a permalloy transfer pattern forming the ML, and the magnetic bubbles are transferred in the direction indicated by Rj in the figure. Pc, P
l and Pm are permalloy auxiliary bar patterns for assisting transfer. CND is a conductor layer for controlling the exchange of bubbles, and has a hairpin shape at the transfer pattern I8 portion of the minor loop m. Bubbles generated by the bubble generator are patterns J1 to J from the right side to the left side of the figure.
5 and the auxiliary bar pattern Pm inserted between them are transferred in synchronization with the movement of the rotating magnetic field Hr. The exchange of bubbles, that is, the writing of information is performed as follows. The write information is transferred to a predetermined bit position of the major line, and when the rotating magnetic field Hr has a predetermined phase, a current is passed through the conductor layer CND. At this time, the bubbles located on the left side of the pattern I8 are the auxiliary patterns Pl,
It is transferred to the entrance foot of the pattern J through Pm.
Further, the bubbles located below the auxiliary pattern Pm of the major line pass through the auxiliary pattern Pl to form the pattern I.
100, transferred to I9.

The improved transfer pattern described with reference to FIGS. 3 and 4 is shown in FIG. 5A at the bubble inlet / outlet I7 inlet and I10 outlet of each of the transfer patterns I1 to I6 and I11 to I16 of the minor loop m. Has been applied. An enlarged view of a pattern surrounded by circles 5B and 5C in the drawings is shown in FIGS. 5B and 5C. As can be seen from the enlarged view, at the foot portion of the transfer pattern where the transfer margin is severe, two isosceles right triangles having a length of 1 [μm] on the gap g side (stepwise fold lines are shaded) Prominently) is provided. In addition,
In the figure, the other shaded outlines of the transfer pattern are actually 25 [μ
Although there is a step shape according to the electron beam spot of [m] angle, the step shape is omitted here.

FIG. 6 is a plan view in the vicinity of a swap gate showing another application example of the improved pattern according to the prior application. The difference from the application example of FIG. 5 is that transfer patterns I7 to I8, I9 to I10, Pl to Pm. , J1 to J2 and J2 to I10
This means that the bubble transfer path of 0 is provided with a protrusion shown by a cross hatch in the figure.

The transfer margin of the bubble is known from the analysis of FIG. 2, but it is severe when the bubble crosses the gap g between the feet of the transfer pattern, and the gap g is only 0.1 μm.
Many of them do not work even if they are misaligned. Therefore, the large bias margin in the above-described application example is resistant to manufacturing variations and leads to an improvement in yield. This transfer margin depends not only on the gap value, the size of the transfer pattern, and the period but also on the bubble diameter. When the bubble diameter becomes 1 [μm] or less, even if the transfer margin is larger than other areas (bar pattern (Pc, Pl, Pm, major loops of J1 to J5, etc.) Protrusions may be provided on the entire surface as shown in FIG. FIG. 7 is a diagram showing a modified example of the improved pattern according to the prior application. In the figure, the transfer pattern P13 is provided with a rectangular protrusion.
The transfer pattern P14 is a half disk pattern provided with protrusions, and the transfer pattern P15 is a C-shaped pattern provided with protrusions.

FIG. 8 shows an example in which the improved pattern according to the prior application is applied to a wide gap transfer pattern. In FIG. 8A, the portion shown by the dotted line in the figure is the outline of the conventional pattern, and the portion shown by the solid line is the improved pattern. Focusing on the bubble entrance near the transfer pattern,
The conventional bottom contour e is the macro bubble transfer direction PR
Almost parallel to (direction of minor loops and major lines), the modified bottom foot contour f of the pattern is inclined to it.

As a result, the foot portion has a pattern in which the pattern is added to the gap side (h portion) and the portion on the opposite side of the gap (k portion) is cut away, and the pattern is offset to the gap side as a whole. ing.

FIG. 8B shows the result of measuring the inter-gap transfer margin of the permalloy transfer pattern manufactured based on such a design pattern. In the same figure, the curve I shows the characteristics of the transfer pattern having the improved contour f, and the curve II shows the characteristics of the transfer pattern having the conventional contour e. As can be seen from the figure, the improved pattern provided a significant improvement in bias margin.

FIG. 9A shows the design pattern (dotted line) and the finished pattern (solid line) of FIG. 7B. In the finished pattern, the part indicated by f in the figure is slightly rounded, so that the gap G is slightly wider than that of the design pattern.

FIG. 9 shows an embodiment of a transfer pattern according to the present invention, which is an improvement of the pattern of FIG. 9B, in which the gaps G1 to G2 are provided at the entrance / exit foot portions h of the adjacent transfer patterns.
It is designed to be narrower (dotted line part), and when finished, the width of the gap due to the rounding of the above-mentioned part of f is made smaller, or as shown in the figure, the tip part is better than other parts. This has the effect of reducing the gap. When the resolution in the photographic processing is not good, the protruding portion g is provided only on one foot portion of the transfer pattern as shown in FIG. 9C, which is not the subject of the present invention. FIG. 10 compares the bias magnetic field margins of the transfer patterns P14 and P17, and the transfer pattern P17 supports the effect of increasing the upper limit of the bias magnetic field.

Next, the overall structure, sectional structure, and peripheral circuit of the magnetic bubble memory chip to which the present invention is applied will be described with reference to FIGS. 11, 12, and 13, respectively.

In FIG. 11, m is a minor loop that stores information, RM
L is a read major line for transferring read information, WM
L is a write major line that transfers write information. Further, D is a bubble detector that converts a magnetic bubble into an electric signal, G is a bubble generator that generates a magnetic bubble, and R is a replicate gate circuit that copies or transfers information of the minor loop m to the read major line RML. T is a transfer gate circuit for moving the information of the write major line WML to the minor loop m, or at the same time as the transfer, sweeping out the information of the minor loop m to the major line WML.
In other words, it is a swap gate that exchanges information between the two parties. Further, a guard rail (not shown) is provided surrounding these outer peripheries to prevent the invasion of magnetic bubbles from the outer peripheries.

The gates R and T and the bubble generator G are controlled by whether or not a current in a certain direction is passed through a conductor of another layer arranged in a special relationship with the permalloy transfer pattern, and the conductor portion is shown by a thick solid line in the figure. The remaining solid lines show the permalloy transfer pattern. One end of each conductor layer of the replicate, swap and bubble generators is connected to the common terminal COM1 in the chip. One of the common terminals DET-C and C of the main and dummy magnetoresistive elements of the bubble detector on the wiring board outside the chip
OM1 is connected.

FIG. 12 is a sectional view of the vicinity of the bonding pad PAD of the magnetic bubble memory chip.

GGG is a gadolinium-gallium-garnet substrate, L
PE is a bubble magnetic film formed by a liquid phase epitaxial growth method. ION indicates an ion implantation layer formed on the surface of the LPE film for suppressing hard bubbles.
SP1 is a first spacer, and for example, SiO ₂ having a thickness of 3000 Å is formed by a vapor phase chemical reaction. CON
Reference numerals 1 and CON2 denote two conductor layers, which have a function of controlling bubble generation, copying (division) and exchange, and the lower CON1 is made of Mo and the upper CON2 is made of Au. SP2 and SP3 are interlayer insulating films (second and third spacers) made of a polyimide resin or the like for electrically insulating the conductor layer CON and the transfer pattern layer P such as Permalloy formed thereon. PAS is a passivation film made of a SiO ₂ film or the like formed by a vapor phase chemical reaction method. PAD represents a chip bonding pad, and a thin connector wire such as an Al wire is bonded thereto by a thermocompression bonding method or an ultrasonic method. The bonding pad PAD is made of Al or the like.

In this bonding pad PAD, the lower first layer PAD1 is Cr, the central second layer PAD2 is the Au layer, and the upper third layer PA.
D3 is formed of a material such as an Au plating layer, and the second layer PAD2 and the third layer PAD3 are made of Cr, Cu.
It may be formed of a material such as. Reference numeral P denotes a layer used for a bubble transfer path, bubble division, generation, exchange, and detection section, and also for a guardrail section, and the above-mentioned improvement of the foot section is performed on this layer. This pattern layer is Fe-N
permalloy layer composed of i or Fe-Si alloy and Fe-
You may make it a multilayer (P1, P2) structure of Ni.

Finally, the peripheral circuit of the element CHI will be described with reference to FIG. R
F is a circuit for generating a rotating magnetic field Hr by passing a current having a 90 ° phase difference through the X and Y coils of the element CHI. The SA senses the minute bubble detection signal from the magnetoresistive element of the element CHI by smbling in synchronization with the timing of the rotating magnetic field.
It is a sense amplifier that amplifies. The DR is a drive circuit that causes a current to flow through each functional conductor of the replicate related to the bubble generation and the swap and the read related to the writing of the MBM device at a predetermined timing. The above circuit is synchronized by the timing generation circuit TG so as to operate in synchronization with the cycle and phase angle of the rotating magnetic field Hr.

〔The invention's effect〕

According to the present invention, since the bias margin becomes large as described above, this means that a low rotating magnetic field strength Hr can be used, which reduces the power consumption of the peripheral circuit and the power supply voltage (use components Cost reduction).

[Brief description of drawings]

FIG. 1 is a plan view showing a conventional transfer pattern. FIG. 2 is a diagram showing the patterning of transfer patterns by photographic processing and the result of problem analysis. FIG. 3 is a diagram in which the influence of the potential well on the magnetic bubble due to the difference in the transfer pattern shape is analyzed.
FIG. 3C is a diagram showing an improved transfer pattern shape according to the prior application. FIG. 4 is a diagram comparing the characteristics of the three types of transfer patterns depicted in FIG. FIG. 5, FIG. 6, FIG. 7 and FIG. 8 are diagrams showing application examples of the improved pattern according to the prior application. 9A and 9B are views for explaining the present invention. FIG. 9A is a conventional pattern, FIG. 9B is a pattern showing an embodiment of the present invention, and FIG. 9C is a pattern for comparison with the present invention. Indicates. FIG. 10 is a graph for explaining the effect of the present invention in comparison with the conventional one. FIG. 11, FIG. 12 and FIG. 13 are diagrams showing the overall structure, cross-sectional structure and peripheral circuits of a magnetic bubble memory chip to which the present invention is applied, respectively. P ... Transfer pattern, B ... Bubble, PR ... Bubble transfer direction, WML ... Write major line, SWAP
... Bubble exchange control conductor, Hr ... Rotating magnetic field, DET ...
... Bubble detector, REP ... Bubble copy control conductor, GE
N ... Bubble generation control conductor, CHI ... Bubble memory chip, PAD ... Bonding pad.

Front page continuation (72) Inventor Masahiro Yanai 3300 Hayano, Mobara-shi, Chiba Hitachi Mobara factory (72) Inventor Tetsuaki Suzuki 3300 Hayano, Mobara-shi, Chiba Hitachi Ltd. Mobara factory (72) Invention Kyoda Keida 3300 Hayano, Mobara-shi, Chiba Inside the Mobara factory, Hitachi, Ltd. (56) References JP 61-8789 (JP, A)

Claims (1)

[Claims] 1. A magnetic bubble memory in which a plurality of permalloy transfer patterns are arranged along the transfer direction of magnetic bubbles, wherein the transfer pattern is an input side leg portion, an output side leg portion, and a chevron shape connecting both leg portions. Of the body, an input side foot portion that is continuous with the input side leg portion, and an output side foot portion that is continuous with the output side leg portion, in one of the transfer patterns,
The input side foot portion and the output side foot portion each have a sole portion of the foot inclined in a direction opposite to each other and an instep portion of the foot protruding from the leg portion in the opposite direction, and the two transfer patterns are A gap (h) between the instep of the output side foot and the instep of the input side foot at adjacent points
Is the gap between the output side leg and the input side leg (g)
A magnetic bubble memory characterized by being formed narrower than the magnetic bubble memory.