JPS63131392A - Magnetic bubble memory element - Google Patents

Abstract

PURPOSE:To obtain excellent bubble transfer characteristic in a high density element using a bubble whose diameter is 1.2mu or below by using polymer resin having a thermal fluidity to a 2nd insulation film in the process of curing. CONSTITUTION:The magnetic film 1 holding magnetic bubbles coated on a nonmagnetic substrate with lamination, a 1st insulation film 2, a conductor pattern 3, a 2nd insulation film 4 and a soft magnetic pattern 5 are provided at least and the bubble diameter is 1.2mum or below. The resin having a fluid property by heat treatment at least parity in the 2nd insulation film 4 is used and not only the fluidity at the coating of the resin solution but also the molten fluidity by heat treatment are utilized together to decrease the title angle at the edge of the conductor pattern. Thus, the 2nd insulation film 4 is formed with high accuracy and the element with excellent characteristic is manufactured with high reproducibility.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic bubble memory element that forms a soft magnetic material pattern on a conductor pattern via a glabellar insulating film, and particularly relates to a magnetic bubble memory element with a micro diameter of 12 μm or less. This invention relates to an interlayer insulating film for obtaining good bubble transfer characteristics in high-density devices using puzzles.

[Conventional technology]

A magnetic bubble memory element generates a magnetic field at the edge of the pattern by forming a soft magnetic pattern on the top of a bubble-net film and applying a rotating magnetic field in one in-plane direction. Bubble transfer is performed using these magnetic poles. On the other hand, this soft magnetic pattern is formed on the conductor pattern with a glabella insulating film interposed therebetween.

Therefore, if the step of the conductive pattern is transferred as is to the soft magnetic material pattern, a step will be generated in the soft magnetic material pattern, and a magnetic pole will be generated in the step portion by one rotation magnetic field or a vertical bias magnetic field. The magnetic poles at this stepped portion have an adverse effect on bubble transfer, causing deterioration of transfer characteristics.

Conventionally, this problem has been solved by, for example, Japanese Patent Application Laid-Open No. 55-22295.
As disclosed in the above publication, a method has been proposed in which a conductive pattern is formed between a soft magnetic material and a thermosetting resin as an interlayer insulating film. In this method, a thermosetting resin solution is applied and then thermally cured to form a resin insulating film.The fluidity of the thermosetting resin solution is used to flatten the steps of the conductor pattern. It can be said that this is an extremely simple and highly reproducible flattening method.

However, this method was used to form a transfer path for microbubbles with a bubble diameter of 12 μm or less.

Its transfer characteristics were unsatisfactory. That is, in this case, it has become clear that the transfer characteristics are degraded at the step portion of the conductor pattern.

FIG. 2 shows the relationship between the transfer characteristics at this stepped portion and the bubble diameter. The sample for which the relationship in the same figure was obtained is
A first insulating film, a conductor pattern, a second insulating film, and a soft magnetic material pattern are formed on a magnetic film of each puzzle diameter. Rokinazolinedione was used. In the figure, when the bubble diameter is 1.2 μm or more, the transfer margin (the range of bias magnetic field necessary for good bubble transfer) is more than a factor of 10, whereas when the bubble diameter is 1.2 μm or more,
It can be seen that when the value becomes less than m, the transfer margin rapidly decreases. Note that in order to perform good memory operation, a transfer margin of 10% or more is required.

[Problem that the invention seeks to solve]

It has become clear that as the bubble diameter becomes smaller, the flattening effect of the conventional flattening method becomes insufficient.

This is because when the bubble diameter becomes smaller, the bias magnetic field required to cause the bubble to exist increases, even for a slight step difference between the two soft magnetic patterns.

This is thought to be caused by the generation of large unnecessary magnetic poles. Note that the inclination angle (θ) at the end of the conductor pattern shown in FIG. 3 is more important than the difference in height itself, which is the cause of the generation of unnecessary magnetic poles.

That is, inside a soft magnetic material, magnetization tends to have a parallel and continuous distribution as much as possible due to exchange interaction.

Therefore, in the stepped portion, the magnetization inside the soft magnetic material is almost oriented in the direction of the inclination angle, and it is thought that the larger the inclination angle (θ) is, the greater the number of unnecessary magnetic poles is. The effect of the bias magnetic field is to direct the direction of magnetization in the step part more perpendicularly, and as the bias magnetic field increases,
The perpendicular component of magnetization increases, and the unnecessary magnetic poles also increase.

FIG. 4 is a diagram showing the relationship between the slope (θ) and the bubble diameter for ensuring a transfer margin of 10 inches.

The sample was the same as the sample used in FIG. 3, but a second insulating film was formed. From the figure, it can be seen that in order to secure a transfer margin of 10 inches, when the bubble diameter is as small as t2 μm or less, the inclination angle needs to be 20 to 0°.

An object of the present invention is to obtain good transfer characteristics in an element using microscopic bubbles with a diameter of 12 μm or less.

[Means for solving problems]

The above object is achieved by setting the inclination angle of the second insulating film having a predetermined thickness at the end of the conductor pattern to 20 to o0.

For this reason, in the present invention, a resin having a property of flowing by heat treatment is used for at least a portion of the second insulating film.

That is, the inclination angle at the end of the conductor pattern is significantly reduced by utilizing not only the fluidity of the resin solution during application but also the melting fluidity due to heat treatment. Therefore, in the present invention, the above object is achieved by using a polyimide precursor represented by the following general formula (1) or (II), heating and melting it, and then curing it.

-Ar' is at least one group selected from the following formula: 1 to 1;
It is 00.

is at least one type of group selected from Norichi, and m is 1
It is 0-500.

Further, the polyimide precursor represented by the above formula (1) (III) has high solubility in a solvent and forms a homogeneous and highly concentrated polyamic acid film, so that various film thicknesses can be easily formed. As a solvent.

N-methyl-2-pyrrolidone, benzylpyrrolidone, N
, N-dimethylacetamide, dimethylformamide,
Polar solvents such as dimethyl sulfoxide are preferred, especially when performing spin coating as described later, N-methyl-2
-pyrrolidone, N.

N-dimethylacetamide is preferred. These solvents may be used simply or in combination of two or more.

For the glabellar insulating film of the magnetic bubble memory element, a polyimide resin film is formed by applying the above-mentioned polyamic acid film onto a substrate with an uneven surface provided with a conductor pattern, and then heat-curing the film. Coating methods include spin coating, roll coating, dipping, and printing, but spin coating is most preferred in order to form a coating uniformly over the entire surface of the substrate with good productivity.

The temperature of the heat curing treatment is 140 to 400°C, preferably 250 to 400°C.
400°C 1 hour 10-180 minutes, preferably 250-4
The 00°C time is preferably 10 to 180 minutes, preferably 30 to 120 minutes.

The atmosphere is an inert gas such as Ar or N2, or a pressure of 0.
The pressure is reduced below I Pa.

The above polyimide precursors (1) and (n) have arrow-like properties in common.

(11) Melts and flows at a suitable temperature below the curing temperature of the polymer.

(2) The inclination angle θ at the end of the conductor pattern can be significantly reduced by the melt flow.

(3) It is cured by heat treatment at a temperature higher than the temperature at which it melts and flows, and becomes a polymer with a high molecular weight.

A method of flattening the surface of a substrate using a resin that melts and flows when heated is disclosed in JP-A-57-1210611. However, the purpose of this method is to reduce the absolute value of the difference in height with respect to the unevenness on the substrate surface, and it is difficult to apply it generally to the problems specific to the magnetic bubble element, which is the object of the present invention.

That is, the first feature of the present invention is to obtain a second insulating film having a predetermined film thickness with an inclination angle of 0 to 20 degrees at the end of the conductor pattern. Here, the predetermined film thickness is 100 mm for bubbles with a submicron diameter of 1.28 m or less.
~500 nm, preferably in the range of 200-500 nm. Although these values depend on the pattern shape of the soft magnetic material pattern, the above film thickness range is desirable for the soft magnetic material transfer path that crosses the conductive material pattern.

FIG. 4 shows the inclination angle required for the transfer margin to be 10 inches or more with respect to the bubble diameter. As can be seen from this figure, when the bubble diameter is 1.2 μm or less, the inclination angle needs to be 20° or less.

FIG. 5 shows the relationship between the thickness of the second insulating film formed on the conductor pattern and the angle of inclination at the edge of the pattern, comparing the conventional resin insulating film and the resin insulating film of the present invention. It is something. From FIG. 6, the film thickness required to make the inclination angle less than or equal to this angle is found to be 500 nm or more for the conventional resin insulating film, and 150 nm or more for the resin insulating film of the present invention. On the other hand, the thickness of the second insulating film is 200 mm for the reason mentioned above.
~300 nm is desirable. Therefore, it can be seen that in order to obtain good transfer characteristics, it is necessary to use the resin insulating film of the present invention as the second insulating film.

A second feature of the present invention is that the second insulating film has the above general formula (1
) or the polyimide precursor of (n), which is cured after being heated and melted, is used to reduce the inclination angle of the end of the conductor pattern, and has a glass transition temperature of 250°C or higher, preferably 500°C or higher to 400°C. By being a film, it is possible to increase the temperature margin for forming the soft magnetic material to be formed later on the second insulating film. In other words, the substrate temperature is
Even in the soft magnetic material formation process using a vapor deposition method that exceeds 300 degrees Celsius, the underlying second insulating film does not soften, so there is no risk of wrinkles or other deformation occurring in the formed soft magnetic material film. becomes smaller.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1 As shown in Fig. 1, a bubble garnet film (bubble diameter 0.9
μm) SIO! as the first insulating film on the t! A conductor pattern 5 is formed using the film 2 and A1L/Aio (FIG. 1 (α)), where SiO2+ Au/M
The film thickness of M6 is +00 nm and 550° C.m, respectively, and M6 is used as an adhesive layer between 5iO1 and AtL, and the film thickness is 20 nrn. Next, the following formula (corresponding to general formula (1))
A solution of a polyimide precursor represented by N,N-dimethylacetamide (resin concentration 15% by weight) was spin-coated,
After heating and melting in a nitrogen atmosphere, it was cured to form an insulating film 4-11 (FIG. 1 (At, (c)).

Margin below (However, the heat treatment was performed at 200°C for 30 minutes and 650°C for 30 minutes. At this time, solvent evaporation, melting flow, and imidization were performed at 200°C.
This occurs before heating to 550°C, and crosslinking and curing occurs before heating to 550°C. The glass transition temperature of the cured film at this time was measured using a differential scanning calorimeter DSC-150 of Shinku Riko Co., Ltd.
When measured at 0, the temperature was 505°C.

Next, a soft magnetic material film (thickness: 550 nm) was formed on this insulating film 4 by high frequency sputtering, and after forming a resist pattern, the soft magnetic material was etched by ion milling to form a soft magnetic material pattern ( Figure 1 (1
Figure 1).

In the magnetic bubble memory element formed in this manner, the inclination angle at the end of the conductor pattern was about 10 DEG C., and the transfer margin was improved from the conventional 4 to 5 inches to 10 to 12 inches.

Example 2 An insulating film 4 was prepared using a polyimide precursor (corresponding to general formula (1)) with a resin concentration of 15% by weight as shown in columns 1 to Nn8 of Table 1.
A magnetic bubble memory element was manufactured in the same manner as in Example 1 except that the magnetic bubble memory element was formed, and the transfer margin was examined. The transfer margin has improved from the conventional 4 to 5 inches to 10 to 121, as shown in columns 1 to 8 of Table 1.

Example 3 An insulating film 4 was prepared using a polyimide precursor (corresponding to general formula (n)) with a resin concentration of 15% by weight as indicated by numbers 1 to Nh7 in Table 2.
An LA bubble memory was manufactured in the same manner as in Example 1, except that a 100% oxide layer was formed, and the transfer margin was examined. The transfer margin has improved from the conventional 4 to 5% to 8 to 10% as shown in numbers 1 to 7 of Table 2.

Example 4 All examples were the same except that the insulating film 4 was formed using a polyimide precursor obtained by mixing the polyimide precursor used in Example 1 and the polyimide precursor shown in Table 2, column 4 at 1/1% by weight. A magnetic bubble memory element was manufactured in the same manner as in Example 1, and the transfer margin was examined.

The transfer margin has improved from the conventional 4 to 5 inches to 10 to 12 inches. In addition, the glass transition temperature of the insulating film 4 at this time is 61
The temperature was 5°C.

Margin below [Effects of the Invention] According to the present invention, the inclination angle at the end of the conductor pattern is significantly reduced to 1%, resulting in minute bubbles (diameter of 12 μm or less).
A significant characteristic improvement effect was observed in the magnetic bubble element having the following properties. Figure 7 shows the relationship between the transfer margin and the rotating magnetic field in a soft magnetic material transfer path that crosses the conductor pattern for a magnetic film with a bubble diameter of 0.9 μm.
Comparison results between a conventional resin insulating film and a resin insulating film of the present invention are shown. Note that the thickness of each of these resin insulating films was 500 nm. From the same figure, the transfer margin when using a conventional resin insulating film is 4% in a rotating magnetic field of 6004.
On the other hand, it can be seen that the resin insulating film of the present invention has a three-fold improvement of 12 inches.

As described above, according to the present invention, the second insulating film can be formed with high precision using an extremely simple method of coating and heat treatment, and elements with excellent characteristics can be manufactured with high reproducibility. be.

[Brief explanation of the drawing]

FIG. 1 is a manufacturing process diagram of a magnetic bubble memory device according to an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between bubble diameter and transfer margin in a conventional magnetic bubble memory device using a resin insulating film, and FIG. Figure 3 is a cross-sectional view of a magnetic bubble memory element.
Fig. 4 is a diagram showing the relationship between the bubble diameter and inclination angle θ necessary to secure a transfer margin of 10 inches or more, Fig. 5 is a diagram showing the relationship between resin film thickness (A) and inclination angle ( The figure is a diagram showing the relationship between the rotating magnetic field and the bias magnetic field. 1. Bubble garnet film 2.
・・・・・・・・・・・・5iO1 film 5・・・・・・・・・
...Conductor pattern 4...Insulating film 5...Soft magnetic pattern/pattern
, 6'1, A'-・, 〆Representative Patent Attorney Katsuo Ogawa 1 Figure 2 Mouth) (0) 1 Shil'? tζ), A Chikutsusu 3rd year, 2015, 2000, 0 200 400 GOO room audience exposure crisis (α)

Claims (1)

[Claims] 1. A magnetic film capable of holding magnetic bubbles laminated and deposited on a non-magnetic substrate, a first insulating film, a conductor pattern, a second
In a magnetic bubble memory element comprising at least an insulating film and a soft magnetic material pattern and having a bubble diameter of 1.2 μm or less, the second insulating film is made of a polymer resin that has thermal fluidity during the curing process. Features a bubble memory element.