JPS60187992A - Magnetic bubble device - Google Patents

Abstract

PURPOSE:To extend an overall transfer margin by removing continuously an ion- implanted layer of an ion-implanted transfer path near the connection part to another transfer path. CONSTITUTION:A tapering photoresist having a prescribed taper angle is used as a mask to subject an ion-implanted layer 8 of the ion-implanted transfer path to ion milling near the connection part to a Permalloy 12 of a Permalloy transfer path. In this case, the photoresist is not flowed in a thermoelectric current on a flat wafer, and the ion-implanted layer 8 near the connection part is removed continuously, and a smooth tapering ion milling part 13 is formed. The potential barrier on boundaries of ion implantation in the connection part is reduced to extend the transfer margin. Further, when the thickness of a magnetic garnet 6 in a part other than the layer 8 is reduced to equalize the thickness of the layer 6, heights of magnetic bubbles 4 are equalized, and a common range of operating bias magnetic fields of the ion-implanted transfer path and the Permalloy transfer path is extended. Thus, the overall transfer margin is extended.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a composite magnetic bubble element having two or more types of bubble transfer means, particularly an ion implantation transfer path and a permalloy transfer path. The present invention relates to an element structure suitable for a case where bias magnetic fields are different from each other.

[Background of the invention]

In order for composite magnetic bubble memory to be put into practical use (
Two points must be satisfied: 1) Bubbles can be transferred without any problem at the connection between different types of transfer paths, and (2) The common area of the bias magnetic field range in which bubbles operate is sufficiently large between different types of transfer paths. .

FIG. 1(a), (bl shows an example of the connection part of a composite memory with a bit period of 4 μm and a schematic diagram of the element cross section. Bubble 4 is transferred from ion implantation transfer path 1 to permalloy transfer path 2. When the ion is implanted, it passes through the connection part 3.At this time, there is a problem in that the bubble tends to disappear due to the barrier (potential barrier) that occurs at the ion implantation boundary.Therefore, a taper as shown in Fig. 1(b) Ion implantation has been devised, and the transfer characteristics have become relatively good.However, in reality, the ion implantation pattern mask (film thickness 15
µm polyimide resin) photoresist'k
Since a method is used to taper the boundary by overlapping heat flow, (11) If the heating temperature is raised to create a sufficiently smooth taper, the photoresist will flow along the resin pattern. (2) To prevent the flow, the photoresist will be heated When the temperature is lowered, the problem arises that the taper angle cannot be made sufficiently small, and there is a drawback that the reproducibility of the transfer characteristics is poor.

In addition, in the conventional composite element (bit period 4 μm), by adjusting the ion implantation conditions, the operation bias magnet IM of the bubble, '! il- was changed to make it common to the magnetic field range of the permalloy transfer path. However, if a thinner magnetic garnet (thickness in the submicron region) is used in an element with a bit period of 3 μm or less, the ion implantation conditions alone cannot be adjusted, and the overall operating margin of both transfer paths is significantly reduced. there were.

[Purpose of the invention]

It is an object of the present invention to provide a means for significantly improving the bubble transfer characteristics at the connection part in a composite transfer path, and furthermore, to provide a means for significantly improving the bubble transfer characteristics at the connection part in a composite transfer path, and furthermore, to provide a means for significantly improving the bubble transfer characteristics at the connection part in a composite transfer path, and further, to provide a common operating bias magnetic field between the ion implantation transfer path and the second transfer path. The objective is to provide a means for increasing range and overall transfer margin.

[Summary of the invention]

At the connection between the transfer paths of a composite magnetic bubble element, by performing ion milling using the tapered resist above the ion implantation layer as a mask, (1) heat flow is caused above the flatway, so no flow is caused; (2)
Since the milling speed of garnet is lower than that of resist, it was possible to form a smoother taper in garnet than in resist, and as a result, the transfer margin of the connection area could be expanded. Furthermore, by etching the film thickness of the permalloy region in the same process, it was possible to adjust the bias magnetic field to any desired magnitude.

[Embodiments of the invention]

The present invention will be explained in detail below.

Example 1) In Fig. 2 (al), the ion implantation layer 8 is subjected to ion milling in a tapered shape at the connection part as shown in 13 in the figure. As a result, the potential of the bubble at the connection part as in Fig. 1 (bl) is The barrier was reduced and the transfer characteristics were improved.In a device using garnet material for a 4Mb device with a bit period of 4μm, this structure was able to expand the total transfer margin to more than 10%. Unlike the conventional method, it was found that the structure can be manufactured using a stable device process without problems such as the flow of the taper resist or difficulty in forming the taper angle.

Example 2) In a 4 μm periodic element, a transfer margin of over 10% was obtained with the structure of Example 1, but with this structure, a transfer margin of 3 μm was obtained.
As a result of experiments conducted by fabricating all high-density devices with a period of m or less, the operating magnetic field range of the ion implantation transfer path and that of the permalloy transfer path differ as shown in Figure 2 (15 and 16 in BL), and the common operating range is significantly different. It was found that the deviation of the operating bias magnetic field was completely corrected using almost the same process as in Example 1). We devised a structure in which the desired amount of garnet film thickness in the permalloy region is etched.

An example of a method for forming this structure will be explained with reference to FIG.

First, as shown in FIG. 3 (al), a magnetic garnet 6 in which magnetic bubbles are present is formed on one part of the non-magnetic garnet substrate 5 by a normal liquid phase epitaxial growth method.
Mask pattern for forming ion implantation transfer path]
7 is formed by normal photoetching, and ions 18 (i7) such as H2+ are implanted.

Here, polyimide resin with a film thickness of 1.5 μm is used for the mask pattern, and H2+ is made of 4XI at an acceleration voltage of 60 kV.
0 1/am typed. Next, this resin is treated with plasma
It is removed with an asher, and the photoresist AZ-1350J is formed into a tapered shape as shown in 19 of the figure (bl). The taper angle in this example is approximately 30°.
Met. Here, it is important that the tapered lower surface of the resist is in the ion implantation region. Next, in this state, ion milling 20i was performed to etch the flat portion 850A of the magnetic garnet 6. The milling conditions are
Ar+ acceleration voltage 600V, current density 350 mA/c
m, milling time is 6 minutes. As a result, it was possible to form a taper angle 21' with a gentle slope 13 in the ion implantation region. This is equivalent to one resist milling speed (~2
This is because the threshold (00 people/m1n) is about 30% larger than that of garnet, and it is convenient for changing the film thickness continuously and smoothly.

Next, the resist is removed using a plasma asher, and ion implantation (25
KeV,' l Bubble transfer is carried out without any problem at the connection part of both transfer paths,
This is also important because the operating bias magnetic fields in both transfer paths are of the same magnitude. The following process (dl
, (e) is similar to normal bubble element formation. That is, in (d), after depositing 5iO29eO1]μm,
The ion-implanted layer was stabilized by annealing at 400°C x 1/2 hour, and the following Au conductor lO, PIQ layer 11. A permalloy transfer path 12 is formed (the subsequent process of forming a protective film and a bonding pad is omitted). What is important here is that the permalloy pattern y12 overlaps the upper layer of the tapered part 13 of the ion-implanted layer at the transfer path connection part, so that the bubble can reciprocate through the connection part without any problem.

〔Effect of the invention〕

In the high-density composite device with pit synchronization of 3 μm or less produced according to the present invention, good transfer characteristics with a common operating margin of more than 10 times can be obtained.

In the case of the above example, the operating bias magnetic field H8 of the element with bit synchronization of 2 μm in the rotating magnetic field H, = 600e is 60
8 00e (125%) from 00e to 6800e
The ion implantation transfer path, connection section, and permalloy transfer path all worked together. When taper milling was not performed on the same sample, the operating range of the Permalloy transfer path was the bias magnetic field range from 6500e to 7200e, and the common operating region was only 45 inches from 6500e to 6800e.

In an example in which a material with a bubble diameter of 0.8 μm is used in a 3 μm periodic element, the operating bias magnetic field can be lowered by approximately 200 e by reducing the film thickness by 1000 J, and an effect similar to that of the above embodiment was obtained.

Naturally, this method can also be used for a composite device using a current drive method as the second transfer means.

[Brief explanation of drawings]

FIG. 1 shows an example of the transfer connection part (al) and its cross-sectional schematic diagram (bl
, FIG. 2 (al is a schematic sectional view for explaining the first embodiment, FIG. 2 is a schematic cross-sectional diagram for explaining the first embodiment, bl is a schematic diagram of the operating bias magnetic field for explaining the present invention in detail, and FIG. 3 is a schematic cross-sectional diagram for explaining the first embodiment of the present invention. Explanation of the device manufacturing process used to obtain the structure 1. Explanation of symbols] ion implantation transfer path, 2 permalloy transfer path, 3 transfer connection, 4 magnetic bubble, 5...Non-abrasive carnet board, 6...Magnetic garnet, 7...8-dopple suppression layer, 8...Transfer guard ion implantation layer, 9
...SiO□, ]0...Au conductor, 11...
・Polyimide resin layer, 12... Permalloy (Ni-F
e), 13... Taper on milling, 14... 1 O/implant transfer path operating range, 15... Permalloy transfer path operating range before milling, 16... Operating range after IJing, 17...・Ion implantation mask, 18... H2+ ion implantation, 19... Taper resist, 19'...
Resist after milling, 20... Ion milling, 2
1...Ion implantation ○ A 3 concave Continuation of page 1 ■Inventor Toshikatsu Sahara Rio Kuni ω 0 Inventor Rio Sugi 1) Rio Kuni ω iTera City Higashi Koigakubo 1-28 Hata Hitachi, Ltd. [Inside the Institute Hitachi, Ltd. Middle F Institute, 1-28 Higashi Koigakubo, Tera City

Claims (1)

[Claims] ■. In a composite magnetic bubble memory element comprising a magnetic medium in which magnetic bubbles exist and two or more types of means for transferring the magnetic bubbles, at least one type of transfer means is an ion implantation transfer path, and the other transfer path is 1. A magnetic bubble element having a structure in which an ion implantation layer is continuously removed in the vicinity of a connection part with a magnetic bubble element. 2. The magnetic bubble element according to claim 1, wherein a part of the film thickness of the magnetic medium in the transfer path other than the ion implantation transfer path is smaller than the film thickness of the ion implantation transfer path.