JPS6095787A - Production of magnetic bubble memory - Google Patents

Abstract

PURPOSE:To produce an ion-implanted magnetic bubble memory without damaging the surface of a magnetic garnet by using a double film mask of a prescribed material. CONSTITUTION:An organic resin film 8 of the 1st film of an ion-implanting mask is coated on a magnetic garnet 2 put on a substrate 1, and the 2nd film of a metallic thin film 3 is vapor-deposited on the film 8. Then a photoresist pattern 4 is laminated to the 2nd film of the film 3. The pattern 4 is used as a mask to etch the film 3 with an argon ion beam, etc. Thus a mask pattern is obtained for the film 3'. In this case, the rugged parts of the film 3 are removed completely by overetching. The film 8 having a low etching speed remains on the garnet 2. Thus the damages are prevented on the surface of the garnet 2. Then the film 3' is used as a mask to etch the film 8 with use of an oxygen ion. In the same way, the rugged parts which give evil effects to the surface characteristics of the garnet 2 are not transcribed despite the overetching. Thus it is possible to obtain an ion-implanted magnetic bubble memory of high accuracy by an ion implanting process using a smooth and accurate mask pattern.

Description

[Detailed Description of the Invention] [Technical field to which the invention pertains] The present invention relates to a method for manufacturing a magnetic bubble memory, and more specifically, a contiguous method for forming a transfer pattern of magnetic bubbles by partially implanting ions into a magnetic garnet thin film. This invention relates to a method for forming a continuous disk pattern in a magnetic bubble memory using an as-disk drive method.

[Prior art]

In recent years, the density of magnetic bubble memories has increased, and in contrast to the conventional permalloy transfer method Vζ, a continuous disk (hereinafter referred to as CD) drive method using an ion implantation method, which is more suitable for manufacturing high-performance devices, has been used. Magnetic bubble memory is now being put into practical use. CI by ion implantation
) One of the conventional techniques for forming the entire pattern is to apply photoresist on magnetic garnet, expose it to light, and develop it.
There is a method of forming an ion implantation pattern on the surface of magnetic garnet by forming an ion implantation mask pattern and implanting ions. In this method, the photoresist film must be thick enough to prevent ions from being implanted into the magnetic garnet immediately below the photoresist film, and in the manufacture of ordinary CD devices, a thickness of μm is required. However, if the thickness of the photoresist film is thick, it is difficult to control the shape of the sidewalls of the mask pattern when forming the pattern that will serve as a mask for ion implantation, and there is also a risk of deformation during ion implantation. Although simple, it is not suitable for high-density devices using microbubbles, which require precision in pattern shape.

To compensate for these drawbacks, a method has been proposed in which a metal film such as gold is formed on magnetic garnet, this metal film is covered with photoresist, the photoresist film is patterned, and this pattern is used as a mask for ion implantation. There is.

To explain this using FIGS. 1(a) to (e), the first
As shown in Figure (Fl), a magnetic garnet 2 is formed on a garnet substrate l by the LPE method. Next, a metal film 3 made of a thin gold film is formed thereon by vapor deposition, and then a photoresist film is applied! A photoresist pattern 4 having a CD pattern is formed.

Next, as shown in FIG. 1(b), a metal film 3 such as a thin gold film is etched by ion beam etching using argon ions.
ft etching to form a metal film mask pattern 3'. In this etching, since the etching speed of gold is faster between gold and magnetic garnet, the unevenness of the gold thin film is reduced and transferred to the magnetic garnet. However, if a large convex portion exists in the gold thin film, a metal residue 6 as shown in the figure is generated.

However, if the number of overetching stages is increased in order to reduce the number of metal beams, a step 9 will occur in the magnetic garnet 2 at the edge of the mask pattern. The degree of this step differs depending on the degree of non-uniformity of the gold thin film and the non-uniformity of the etching rate, and causes variations in device characteristics.

Next, as shown in FIG. 1(C), the golden pigeon mask pattern 3 is
Ion implantation of helium, argon, neon, etc. is performed using mask 1 as a mask to form the entire ion implantation region 7. The ion implantation depth in the ion implantation region 7 is uniform, but the magnetic Gurney
) Since the surface remains uneven, the thickness of the ion-implanted region where bubbles exist substantially varies, resulting in deterioration of device characteristics. Still under the metal residue 6, the metal residue is smeared, and the ion implantation region becomes shallow, creating a defect for bubble transfer.

Considering the above, when a thin gold film or the like is used as a mask, the masking effect is better than that of photoresist, and the required thickness can be 1 μm or less, so that a mask pattern with high dimensional accuracy can be formed. Since CD devices require pattern accuracy of 1 μm or less, pattern etching is usually performed by dry etching e11 such as ion beam milling or reactive ion etching. However, when forming the mask, dry etching is used to etch the metal film.Since the underlying magnetic garnet does not have sufficient etching resistance against the ion beam energy and beam energy required to etch the metal film, it is difficult to etch only the metal film. or difficult. Therefore, the ion-implanted region, which is the unmasked region of the underlying magnetic garnet, is overetched, resulting in non-uniform CD device characteristics. At the same time, minute irregularities that occur in the metal film formed on the base are transferred to the base magnetic garnet, and sometimes metal grains become metal bars during etching, impeding ion implantation, resulting in deterioration of device characteristics and increase in defect loops. Therefore, in the conventional method, the mask itself has drawbacks such as accuracy and deformation, or the magnetic garnet is damaged during mask formation, and it is difficult to use magnetic bubble memory that waits for a favorable transfer pattern. The drawback was that it was difficult to manufacture.

[Purpose of the invention]

The purpose of the present invention is to eliminate the above-mentioned drawbacks, to form an excellent mask with excellent ion implantation mask effect, to ensure pattern accuracy, and to do so without compromising the magnetic garnet surface km during mask formation. An object of the present invention is to provide a method for manufacturing a magnetic bubble memory with excellent transfer characteristics by ion implantation.

[Structure of the invention]

The method for manufacturing a magnetic bubble memory of the present invention includes the steps of forming a first film made of an organic resin film with a predetermined thickness or more in contact with magnetic garnet, and a second film made of a metal film overlying the first film. A step of depositing the second film to form a 2N film, a step of patterning the double film to form a mask for ion implantation, and a step of implanting ions into the magnetic garnet with the mask fully closed to form a transfer pattern. It consists of:

[Explanation of Examples]

An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 2(a) to 2(C) are cross-sectional views showing an embodiment of the present invention in the order of steps for which a complete explanation will not be given.

This example can be implemented through the following steps.

First, as shown in FIG. 2(a), an organic resin film 8 such as photoresist is applied as a first film of an ion implantation mask onto the magnetic garnet 2 formed on the garnet substrate l, and then baked. As the film 2 described later, a metal film 3 such as a thin gold film is formed by vapor deposition. A photoresist for forming an ion implantation mask pattern is applied thereon to form a photoresist pattern 4.

Next, as shown in FIG. 2(b), using the photoresist pattern 4 as a mask, the metal film 3 made of a thin gold film formed as the second film is etched by argon ion beam etching to form the second film. Metal film mask pattern 3'
form. Incidentally, sufficient overetching was performed to completely remove the unevenness of the gold thin film. At this time, since the etching speed of the organic resin film 8 made of photoresist is several times the etching speed of the gold thin film, the unevenness of the gold thin film is reduced and the photoresist film of the first film, that is, the organic resin film is etched. It is transferred to 8. At this time, it is important that the thickness of the resist film, which is the organic resin film 8, be set to such a thickness that the surface of the magnetic garnet 20 will not be exposed even by this over-etching. That is, the organic resin film 8 of the first film
The thickness of the first film is t%, the size of the unevenness of the second film is h1, the etching rate of the first film is fc8Es
, if the etching rate of the second film is SF3, then EI t)hX-- SF2.

As described above, by determining the thickness of the organic resin film 8 of the first film, even if the metal film 3 of the second film is completely patterned, the organic resin film 8 of the first film is It can be left as shown in Figure (b).

Next, as shown in FIG. 2 (CJ), the metal film 3 of the second film is
The all-pole mask pattern 3' formed by the above is used as a mask,
Reactive ion etching (RI) using oxygen ions
(denoted as E), the first film is etched with the resin film 8 of the first film. Since the etching ratio of the organic resin film 8 made of magnetic garnet and photoresist film to oxygen ions is sufficiently large, the surface of the magnetic garnet 2 will remain intact even if sufficient overetching is performed until the unevenness of the photoresist film is completely etched away. Any unevenness that may adversely affect device characteristics is not transferred.

Therefore, a magnetic garnet having an accurate double film mask pattern and a smooth exposed surface as shown in FIG. 3(C) can be obtained. Therefore, when ion implantation is performed using the ion implantation mask pattern formed as described above as a mask, an ion implantation region with precision due to the accurate pattern and uniformity of depth due to the smooth surface can be obtained. As a result, a magnetic bubble memory with excellent transfer characteristics can be manufactured.

Note that during RIE processing of the +T machine resin film of the first film, the photoresist pattern 4ij on the mask pattern is etched and removed at the same time as the first film, so a resist stripping step is not necessary.

In addition, since the mask effect for ion implantation is due to the metal film of the second film, the thickness of the 81!2 film can be the same as the conventional gold single layer mask, and the mask pattern accuracy is Since the magnetic garnet film is not collected during etching of the resin film, the first film can be etched sufficiently until it matches the pattern of the second film, so that the pattern formation radius is the same as that of the second film. Therefore, the 2M film pattern accuracy of this example is comparable to that of the prior art.

As described above, according to this embodiment, it is possible to manufacture a CD device with few defects without causing unevenness on the surface of the magnetic garnet.

Next, as another example, a 2M film having the structure shown in FIGS. An example in which a film is used as a mask will be explained.

As in the first embodiment, a polyimide resin is applied onto the magnetic garnet 2 formed on the garnet substrate 1 and k and baked to form the organic resin film 8 of the first film. The second metal film 3 was formed by depositing molybdenum by sputtering.

Etching of the second metal film 3 made of molybdenum was performed by RIE using chlorine ions using a photoresist film patterned by exposure and development as a mask.

At this time, since the polyimide resin is hardly etched apart from the etching of molybdenum, the molybdenum film of the second film can be buttered without etching the polyimide resin film of the first film.

That is, since sufficient overetching can be performed, the unevenness of the molybdenum film of the second film can be completely removed. Furthermore, since the first film has high etching resistance, it can be made much thinner than in the first embodiment.

Next, using the metal film mask pattern 3' made of the molybdenum film of the second film as a mask, the organic resin film 8 made of the polyimide resin film of the first film is etched by oxygen RIE. A mask pattern similar to the metal mask pattern 3' made of a molybdenum film can be formed.

In this case as well, for the same reason as in the first embodiment, a mask pattern for ion implantation can be formed while keeping the surface of the magnetic garnet smooth.

In the above embodiments, examples of a double film of photoresist and gold and a double film of polyimide resin and molybdenum have been explained, but the present invention is not limited to these. Of course, the same effect as described above can be obtained if the organic resin film is an organic resin film that can be etched by oxygen R11 (with a small etchant) and the second film is a metal film that has a large masking effect against ion implantation.

〔Effect of the invention〕

As explained above, according to the present invention, the first film is an organic resin film, and the second film is a metal film (21) (because a film ion implantation mask is used, the first film is etched with oxygen). R.I.
By using E, a mask pattern can be formed without damaging the surface of the magnetic garnet, and since the masking effect for ion implantation is mainly due to the second metal film, it is better to use the resist alone as an ion implantation mask. , it is possible to make the mask thinner, forming a minute CD pattern,
That is, there is an excellent effect on manufacturing high-density CD devices.

[Brief explanation of drawings]

FIGS. 1(a) to (C) are cross-sectional views showing a conventional method for manufacturing a magnetic bubble memory in the order of steps, and FIGS. 2(a) to (C) are sectional views showing an embodiment of the present invention. 1 is a cross-sectional view in the order of steps. 1...Garnet substrate, 2...Magnetic garnet, 3...Gold film, 3'... Metal film mask pattern, 4... Photoresist pattern, 5... Metal protrusion, 6... Metal remainder, 7... Ion implantation region, 8...・・・・Organic resin film% 9・・・・Magnetic garnet step.

Claims (2)

[Claims] (1) Forming a first film made of an organic resin film with a predetermined thickness or more in contact with the magnetic garnet, and attaching a second film made of a metal film to overlap the first film. A step of forming a double layer film, a step of patterning the 2M film to form a mask for ion implantation, and a step of implanting ions into the magnetic garnet through the mask to form a transfer pattern. A manufacturing method for magnetic bubble memory. (2) Thickness of the first film + ct% 1% Size of unevenness of the film 't-11% When the etching rate of the first film is S:1 and the etching rate of the second film is ft5E2. 8w1t)hX□The method for manufacturing a magnetic bubble memory according to claim 13 (E2).