JPS6341158B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnetic bubble transfer path used in a magnetic bubble memory element used as a storage device for electronic computing devices, etc. In particular, it relates to a permalloy bubble transfer path with a period of 4 μm or less and a method for forming the same.

(Prior art) A magnetic bubble memory device is made by forming a thin film of magnetic garnet (magnetic bubble crystal) on a single-crystal substrate of gadolinium, gallium, or garnet by liquid phase epitaxial growth, and then depositing a film of permalloy or the like on top of the thin film of magnetic garnet (magnetic bubble crystal). A bubble transfer path is formed using a soft magnetic thin film in which patterns such as a half-disk type or an asymmetrical chevron type are lined up.Bubbles generated by a bubble generator according to information are guided to the transfer path, and the bubbles are transferred to the pattern. Information is stored as "1" if there is a bubble, and "0" if there is no bubble.

In such magnetic bubble memory devices, higher storage density is required due to recent increases in the amount of information and miniaturization of devices.

The storage capacity of currently manufactured magnetic bubble storage devices is 4 Mb or less. Generally, the period of a permalloy pattern for transferring magnetic bubbles is determined by the storage capacity, and the permalloy pattern of a 4Mb magnetic bubble storage device has a period of 4 μm. The storage capacity of future magnetic bubble storage devices
16Mb is the industry's goal, but such storage devices require permalloy patterns.
It is said that it is necessary to reduce the period to 2 μm or less.

The wide gap pattern method, which is one of the currently used permalloy transfer patterns with a period of 4 μm, has become difficult to form in detail due to patterns with a period of less than 4 μm and the limitations of optical lithography. There was a problem that sufficient characteristics could not be obtained with the permalloy transfer path.

Focusing on the fact that the limitation of optical lithography is the long wavelength of the light used, proposals have been made to use X-ray lithography;
Line lithography has had the problem of being inferior to optical lithography in terms of mass production.

In view of the above-mentioned conventional problems, the present applicant aims to provide a magnetic bubble memory element having a high-density bubble transfer path. A pattern 2 is formed on the magnetic bubble crystal 1, a soft magnetic thin film pattern 3 that is equal to or thinner than the nonmagnetic pattern 2 is partially overlapped with the nonmagnetic pattern 2, and the soft magnetic thin film pattern 3 is We have proposed a magnetic bubble transfer path formed so as to be magnetically discontinuous by the edge portion 4 of the non-magnetic material pattern 2 (Japanese Patent Application No. 59-20753 (Japanese Unexamined Patent Publication No. 1988-1999)).
Publication No. 167189)). According to this proposal, because of the magnetic discontinuity that occurs in the portion corresponding to the edge portion 4, the soft magnetic thin film pattern 3, which has a simple shape, becomes like a half-disk type pattern, and bubbles can be transferred. Furthermore, since the soft magnetic thin film pattern can have a simple shape as described above, bubble transfer paths with a small period can be formed even with the current optical lithography technology, and high density can be realized. The present inventors further studied the characteristics of the bubble transfer path proposed above, and found that lines of magnetic force flow between the upper central part 2a and the lower peripheral part 2b of the pattern, via the periphery of the edge part 4 of the non-magnetic pattern 2. It was found that this had an undesired effect on bubble transfer, and that bubble transfer sometimes did not occur.

(Problems to be Solved by the Invention) An object of the present invention is to provide a permalloy transfer path with excellent characteristics in which the details of the shape of a soft magnetic material transfer pattern such as permalloy are controlled by a pattern of a non-magnetic conductor, and a method for manufacturing the same. Our goal is to provide the following.

(Means for Solving the Problems) The magnetic bubble transfer path according to the present invention forms a pattern of a non-magnetic conductor or a non-conductor on a magnetic bubble crystal, and a soft magnetic material that is equal to or thinner than the non-magnetic material pattern. A thin film pattern is formed in contact with a side wall surface of the nonmagnetic pattern, and the soft magnetic thin film pattern is configured not to overlap the top surface of the nonmagnetic pattern.

A method for forming a magnetic bubble transfer path according to the present invention includes forming a pattern of a non-magnetic material on a magnetic bubble material,
After forming a soft magnetic thin film pattern that is equal to or thinner than the nonmagnetic pattern so that it partially overlaps with the nonmagnetic pattern, and further that the soft magnetic thin film pattern is magnetically discontinuous at the edge portion of the nonmagnetic pattern, The method is characterized in that the soft magnetic thin film overlapping the non-magnetic pattern is removed.

(Function) FIG. 1 is a graph showing the transfer characteristics of a 2 μm period permalloy transfer pattern according to an embodiment of the present invention, in which the horizontal axis is the rotating magnetic field (H _D ), and the vertical axis is perpendicular to the magnetic bubble crystal. Applied bias magnetic field (H _B )
where the solid line represents the present invention and the dotted line represents the patent application filed in 1983-
20753 (Japanese Unexamined Patent Publication No. 60-167189). In both cases, magnetic bubbles are not transferred to the left side of the line. From FIG. 1, it can be seen that the present invention, in which permalloy is removed from a non-magnetic material, expands the range of _HD and _HB in which magnetic bubbles can be transferred.

(Embodiment) According to an embodiment of the present invention, as shown in FIGS. 3 and 4, Al--Cu,
A non-magnetic conductor or non-conductor material such as Ti or Au is deposited and patterned using photolithography and ion milling so that the period (t) is 2 to 4 microns to form a non-magnetic pattern. Form 20. Next, permalloy or the like is deposited on the entire surface of the magnetic bubble crystal 40 to a thickness equal to or less than that of the nonmagnetic pattern 20. Subsequently, 30 in Fig. 4 was formed by photolithography and ion milling.
Then, as shown at 10 in FIGS. 3 and 4, a pattern that partially overlaps with the nonmagnetic pattern 20 is formed. In this state, the patterns 10 and 30 become magnetically discontinuous at a portion 15 corresponding to the shoulder of the non-magnetic pattern 20. After that, when a viscous substance such as resin is applied on the patterns 10 and 30,
Pattern 30 is selectively exposed as the material flows such that only pattern 10 is covered with this material. When this is removed by appropriate etching, a half-disc permalloy pattern 10 that is in contact with the side wall surface 20a of the non-magnetic pattern 20 and does not overlap the upper surface 20b is obtained.

FIG. 5 is a diagram showing three further examples of embodiments. In the figure, 1 indicates a magnetic bubble crystal, 2 a non-magnetic material pattern, 3 a soft magnetic thin film pattern, and the diagonal lines indicate a removed portion.

The embodiment shown in Fig. 5a is the one in which the shape of the soft magnetic thin film pattern of the first embodiment is enlarged, and Fig. 5b
The embodiment shown in Fig. 5 is the embodiment shown in Figure A, with the semicircular portion of the non-magnetic material pattern 2 having a triangular shape, and the embodiment shown in Fig. 5C is the embodiment shown in Figure B placed back to back. The soft magnetic thin film pattern is shared between the forward path A and the backward path B, and the effect is the same as that of the first embodiment.

(Effects) According to the present invention, a fine transfer path pattern with a period of 4 μm or less is formed by optical lithography, and the transfer path has excellent transfer characteristics.

[Brief explanation of the drawing]

Fig. 1 is a graph explaining the transfer characteristics depending on the structure of the transfer path, Fig. 2 a and b are a plan view and a cross-sectional view of a conventional transfer path, respectively, and Fig. 3 shows an embodiment of the transfer path of the present invention. A plan view, FIG. 4 is a sectional view taken along the line -- in FIG. 3, and FIGS. 5a-5c are plan views showing another embodiment. In the drawing, 1 is a magnetic bubble crystal, 2 is a non-magnetic material pattern, 3 is a soft magnetic thin film pattern, and 4 is an edge portion of the non-magnetic pattern.

Claims (1)

[Claims] 1. A non-magnetic conductor or non-conductor pattern is formed on a magnetic bubble crystal, and a soft magnetic thin film pattern that is equal to or thinner than the non-magnetic material pattern is in contact with the side wall surface of the non-magnetic material pattern. 1. A magnetic bubble transfer path, characterized in that the soft magnetic thin film pattern is formed so as not to overlap the upper surface of the non-magnetic pattern. 2 A pattern of a nonmagnetic material is formed on a magnetic bubble material, a soft magnetic thin film pattern that is equal to or thinner than the nonmagnetic pattern is partially overlapped with the nonmagnetic pattern, and the soft magnetic thin film pattern is formed on the edge of the nonmagnetic pattern. 1. A method for forming a magnetic bubble transfer path, which comprises forming a soft magnetic thin film so as to be magnetically discontinuous in some areas, and then removing a soft magnetic thin film overlapping the nonmagnetic pattern.