JPS58123711A - Preparation of magnetic bubble memory element - Google Patents

Abstract

PURPOSE:To improve the accuracy of a pattern formed on a film to be etched by tilting the angle of ion incidence and rotating a specimen in the ion milling process. CONSTITUTION:An insulating film 2, a conductor film 3, an insulating film 4, a permalloy film 5, a mask film 6, and a resist film are provided on a substrate 1 and the film 6 is etched with patterns 7, 8 provided on the resist film as a mask. Subsequently, ion milling is conducted to etch the exposed portion on the film 5. At this time, the angle of ion incidence is tilted by 5-30 degrees against the perpendicular direction to the surface of the substrate and the substrate is kept turning. The exposed portion of the film 6 is again etched. Subsequently, the exposed portions of the films 5, 4 and the film 3 under them are removed by the ion milling as in the case of the above process. Finally, the resist 7, 8 and the film 6 are removed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a magnetic bubble memory device, and more particularly to a method for manufacturing a magnetic bubble memory device that can be manufactured through simple steps.

As is well known, a magnetic bubble memory forms a conductor pattern and a permalloy pattern on a bubble magnetic film.

These patterns are usually formed by performing photoetching twice, but a new method has been proposed in which these patterns are formed by photoetching once (this method is called the one-mask method) (for example, in 50-62'881). In this method, one photomask having patterns corresponding to the conductor and permalloy patterns on the same surface is used, and resist patterns (turns) of both are formed with different thicknesses by one exposure.Then, these resist patterns are The laminated film on the substrate is etched using a mask to form conductors and turns at the same time.

Conventionally, in the above-mentioned one-mask method, a contour lid (a turn formed of a conductive film for generating a droplet and a gate operation) and a permalloy pattern (for full transfer) are used. With ion milling 1□1 in the etching process for forming conductor turns, there is a tendency for pattern dimensions to decrease during nigration (ion etching). Problems remained.

The present invention eliminates the causes of the above-mentioned problems, further improves the one-mask method, and provides a method for manufacturing a magnetic bubble memory element in which a conductor pattern and a permalloy pattern can be formed with high precision.

First, the cause of the conventional problem of deterioration in pattern precision and the means of the present invention for preventing it will be explained.

FIGS. 1A to 1C are schematic diagrams showing how milling of a resist and a material to be etched progresses by ion milling. In the figure, 10 is a resist pattern, 20 (rl film to be etched), 30 is an ion (Ar) beam, and the broken line indicates the progress of milling.

In ion milling, the milling speed varies depending on the incident angle of the ions, so as milling progresses, a surface in a particular direction with a high milling speed appears. When ions are incident perpendicularly, this particular surface has an inclination of about 45 degrees, and as milling progresses, it takes on the shape shown by the broken line K in FIG. 1(a).

By the way, since the resist patterns with different film thicknesses used in the one-mask method are formed using semi-transparent photomask patterns, there is a limit in resolution compared to the generally used opaque photomask patterns, and as shown in Fig. 1(b). As shown in FIG. 2, the sides of the resist pattern 10 are tapered. When ions are incident perpendicularly to this resist pattern (prior art), this inclined side surface becomes a surface with a high milling speed. Therefore, as the milling progresses, the pattern 40 formed on the film to be etched rapidly becomes thinner. It has been found that this is the cause of the problems in the prior art.

On the other hand, as shown in Fig. 1 (C), ion beam 1
When the incident angle of the sample is tilted and the sample is rotated, the maximum milling surface changes from time to time. Therefore, it has been found that the erosion of the resist by milling progresses almost uniformly, and the reduction in size of the pattern 40 formed on the film to be etched is also small.

The present invention is based on this, and in the ion milling process,
By tilting the ion incidence angle and rotating the sample, the accuracy of the pattern formed on the film to be etched is improved.

As a result of various experiments, it has been found that the effect can be obtained by tilting the ion incident angle by 5 degrees or more. On the other hand, if this inclination angle is made larger than 60 degrees, the progress of milling at micro-interval areas (pattern spacing of approximately 1 μm) will be extremely slowed down due to the oblique shadow of the K-cyst pattern (approximately 1.2 μm thick). Etching of the part becomes impossible. Therefore, the inclination of the ion incidence angle must be between 5 and 30 degrees.

I understand that.

Hereinafter, the present invention will be explained in detail with reference to examples. FIGS. 2(a) to 2(e) are process diagrams showing one embodiment of the present invention. The manufacturing process will be explained in accordance with the order of the drawings.

(a): A magnetic garnet film (thickness: 1.5 m) epitaxially grown on a non-magnetic garnet (approximately 0.4 m thick).
0 to 1.5 μm) on the surface of the substrate 10 having a first insulating film (e.g. M3o film, thickness 1000A) 252, a conductor film forming a conductor pattern (e.g. M
Three-layer film of o/Au/Mo, thickness @3500A, M.

are adhesive layers for the upper and lower membranes)6. Second insulating film (
For example, M2O3 film (thickness 1000A) 4, permalloy film (thickness e.g. 3500A) 5, mask film (e.g. Ti
An O2 film, a thickness of 10'0 Oi) 6, and a resist film are sequentially deposited, and the resist film is irradiated with light of partially different intensities through a mask with partially different light transmittances. After that, it is developed to form a resist pattern 7.8 having partially different thicknesses.

(b): Using the above resist pattern 7.8 as a mask,
The mask film 6 is etched using Freon gas plasma to remove the exposed portion.

(C) Second, ion milling is performed to etch the exposed portion of the permalloy film 5.

Here, the ion incident angle during ion milling is tilted from 5 degrees to 50 degrees from the direction perpendicular to the substrate surface, and the substrate is rotated several times (for example, 5 to 6 rotations/min). (d): Again, the Freon The exposed portions of the mask film 6 are etched away by gas plasma treatment.

(e) Second, the exposed portion of the permalloy film 5, the exposed portion of the second insulating film 4, and the conductive film 3 thereunder.
is removed by ion milling.

In this step as well, the ion incidence angle is tilted from 5 degrees to 30 degrees from the direction perpendicular to the substrate surface, similar to the ion milling described above.
And keep the board rotating.

Finally, the remaining resist pattern 7.8 is removed by, for example, oxygen plasma, and the mask film 6 is removed by Freon gas plasma.

Through the above-described steps, a magnetic bubble memory element having a highly accurate conductor pattern and a Hermalloy pattern can be manufactured.

As explained above, 1.1 In the manufacturing method of the present invention, the one-mask method is improved by taking into account the dependence of the ion milling rate on the ion incidence angle. can be formed with high precision.

[Brief explanation of drawings]

FIGS. 1(a) to (C) are schematic diagrams for explaining the progress of milling of resist and material to be etched by ion milling, and FIGS. 2(a) to (e) show an embodiment of the present invention. It is a process diagram. 1... Substrate 2... First insulating film 3...
Conductor film 4...Second insulating film 5...Permalloy film 6...Mask film 7.8...Resist pattern attorney Junnosuke Nakamura-6' 1F1 Figure ^- 1'2 Figure ( Q) (b) (C) (d) (e)

Claims (1)

[Claims] A method for manufacturing a magnetic bubble memory element including the following steps. (1) U2O5 on a substrate with a magnetic garnet film
, Cr2O3, SiO2 and T+02, a conductive film, and A-1320, 0r.
20. . Step of sequentially laminating and depositing a second insulating film selected from 5102 and T r 02, a permalloy film, a mask film, and a photoresist film. (2) A step of irradiating the photoresist film with light having partially different intensities to form resist patterns with partially different thicknesses. (6) A step of removing the exposed portion of the mask film by plasma etching after using the resist pattern. (4) Above? (-Step of removing the exposed portion of the Malloy film by ion milling with the ion incident angle tilted by 5 degrees to 30 degrees from the direction perpendicular to the substrate surface and the substrate being rotated. A step of removing the exposed portions by plasma etching. (6) The exposed portions of the second insulating film and the exposed portions of the conductive film and the permalloy film thereunder are removed at the ion incidence angle as described above. 5 degrees or more from the vertical direction of the board surface
A step of removing the substrate by ion milling while tilting the substrate at 60 degrees and rotating the substrate. (7) Step of removing the remaining resist pattern.