JPS6035812B2 - Manufacturing method of magnetic bubble element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a magnetic bubble element used in a magnetic bubble memory device, and more specifically, a method for manufacturing a magnetic bubble element used in a magnetic bubble memory device.
The present invention relates to a method for forming a pattern of an element, and effectively realizes planarization of the pattern.

FIG. 1A is a sectional view of a main part of a magnetic bubble memory element manufactured by a commonly used manufacturing method.

1 is a q°C (gadolinium gallium garnet) substrate, on the surface of which a magnetic film 2 such as a rare garnet single crystal film that serves as a magnetic bubble medium is formed. A substrate layer 3 made of, for example, Si02 is formed for protection from beam irradiation.

On this base layer 3, N-Cu (aluminum-copper)
A conductor pattern 4 made of aluminum or the like is formed, and after an insulating layer 5 of Si02 or the like is deposited thereon, a permalloy pattern 6 is formed. When in use, a driving rotating magnetic field HR rotating in the in-plane direction of the substrate 1 is applied in a direction perpendicular to the substrate 1 with a bias magnetic field HB for stably existing magnetic bubbles (hereinafter referred to as "baffles"). By acting on the permalloy pattern 6, a magnetic pole is generated and bubbles in the magnetic film 2 are transferred, and a current is applied to the conductor pattern 4 to generate bubbles.
Extinguishing, controlling gates, etc. However, as shown in Figure A, the permalloy pattern 6 has a stepped shape due to the conductor pattern 4, and therefore, when the rotating magnetic field HR is directed in the direction of the arrow in the figure, a strong magnetic pole is also formed at the stepped part, and the magnetic pole is may affect the bubble and cause it to malfunction.

Also, depending on the manufacturing method, the conductor pattern 4 may be
There is also a risk that the permalloy pattern 6 may become locally thin or break due to the stepped portion. Since the step portion of the conductor pattern 4 has a negative effect on the permalloy pattern 6, attempts have been made to make the pattern a brainer, but good results have not yet been obtained.

FIG. 2 is a cross-sectional view of the main parts showing the process order of the planarization method for the subordinate structure. '11 First, a conductor layer with a thickness of about 4000A is formed on one surface of the spacer layer 3 of the substrate, and a resist is coated on the conductor layer and selectively etched. form.

(2) Next, as shown in Figure A, using the resist pattern 7 as a mask, an ion beam is irradiated from the vertical direction as shown by arrow 8 to perform ion etching.

As a result, only the lower portion of the resist pattern 7 in the conductor layer is left as shown at 4, and the other portions are etched away. However, in this process, a part of the conductor layer remains in the area of the conductor pattern 4 as shown by 4', and when etching is performed until this remaining part 4' disappears, the underlying smoother layer 3 with a thickness of about 2000 Δ is removed. becomes extremely thin due to excessive etching. [3 To prevent this, ion etching is stopped when the underlying smoother layer 3 begins to be visible, and the remaining portion 4' around the pattern is removed by chemical etching. When chemical etching is completed, the state shown in the drawing is obtained. That is, although the base is not attacked, the side portion 9 of the conductor pattern 4 is attacked by the etching solution, and an undercut portion is generated under the resist pattern 7 due to side etching. {4} As a result, as shown in Figure C, in order to form the planar layer 10, Si○
When depositing an insulating material such as, the undercut portion becomes a shadow of the resist pattern 7, and when the resist pattern 7 is removed by lift-off, the gap between the conductor pattern 4 and the planar layer 10 as shown in Fig. 2. , a groove 11 is generated.

(5} Next, as shown in FIG. 3, an insulating layer 5' such as Sj02 is deposited on the surfaces of the planarized conductor pattern 4 and the planar layer 10, and a permalloy pattern 6' is placed on top of the insulating layer 5'.
to form a pattern.

However, since the grooves 11 were formed in the steps C and D of FIG. 2, even in the completed state as shown in FIG. This results in an undesirable result.

On the other hand, if a material with a lower etching rate than the material of the conductor pattern 4 can be used as the surfacer layer 3, only the remaining portion 4' can be easily removed, and the problem can be easily solved.
There were problems such as poor adhesion between the smoother layer and the underlying bubble medium, as well as between the smoother layer and the conductor pattern and planar layer thereon, so that it could not be put to practical use.

An object of the present invention is to propose a method that can solve these problems and effectively planarize.

The technical means according to the present invention taken to achieve this objective is to apply S
An insulating layer made of i02 is formed, and AI (
When forming a conductor pattern made of aluminum) or N-Cu (aluminum-copper), the substrate holder is rotated while the surface of the insulating layer is tilted at 25 degrees to 45 degrees with respect to the direction of incidence of the ion beam. , is exploring a method characterized by including the steps of ion-etching a conductor layer on which a resist pattern is formed, then depositing a planar layer, and then removing the resist to form a planar layer. Next, examples will be used to explain how the method for manufacturing a magnetic bubble element according to the present invention is actually implemented. Fourth
The figure is a longitudinal sectional view showing the internal structure of an ion etching apparatus used in the method of the present invention. An ion gun 13 and a rotatable substrate holder 14 are built into the vacuum container 12 . During ion etching, a gas such as argon is introduced into the vacuum chamber 12 through the gas introduction hole 15, and the exhaust hole 16 is connected to a vacuum pump to create a vacuum inside the chamber. The substrate 1 to be ion-etched is mounted on the substrate holder 14, but in the case of the present invention, the axis A perpendicular to the substrate surface is not parallel to the incident direction B of the in-beam, but is tilted at an angle of 8. A motor 8 is attached to the substrate shaft 17 so that the substrate 1 can rotate in this state.
When the substrate 1 is rotated within its plane by the substrate holder 14 while being irradiated with the ion beam at an incident angle of 8 with respect to the vertical axis A of the substrate surface, the resist pattern 7 and Ion etching is hindered in the shadow area 19 on the lower side of the conductor pattern 4, but when it is rotated 180 degrees and reaches the upper position indicated by the reference numeral 20, the corner formed by the conductor pattern 4 and the surfacer layer 3 is exposed. Also, ions are irradiated smoothly. Therefore, it is surprising that by performing ion etching while rotating in a tilted state, a residual portion 4' of the conductor layer remains with no pattern as shown in Fig. 2A.
The conductor layer is etched uniformly. however,
In order to accurately form the outline of the conductor pattern 4 and to completely remove unnecessary parts of the conductor layer, it is necessary to irradiate the surface layer 3 with ions until it is slightly overetched. For example, by setting the forehead oblique angle to 0, the amount of overetching can be suppressed so as not to cause any practical problems. Figures 6 and 7 show experimental data conducted by the inventors of the present invention. Figure 6 is a graph showing the relationship between the incident angle 8 of the ion beam and etching time, and Figure 7 is the graph showing the relationship between the incident angle 8 of the ion beam and the etching time. It is a graph showing the relationship between the corner 8 and the etching amount of the spacer layer.

In FIG. 6, the horizontal axis is the ion beam incident angle, the vertical axis is the etching time of the conductor layer, and the curve C is the etching time, that is, the time from the start of etching until the underlying surfacer layer 3 starts to become visible. The axis D indicates the above-mentioned etching time+overetching time, that is, the time from the start of etching until the remaining portion 4' of the conductor layer around the pattern disappears. As is clear from FIG. 6, when the incident angle of the ion beam is about 35 to 36 degrees, both the etching time and over-etching time of the conductor layer A are the shortest. It turns out that is far away. In addition, in Fig. 7, the horizontal axis is the impingement incident angle a, and the vertical axis is the surface layer when overetched (
This is the etching amount of Si02)3. In this case, curve E
In other words, the amount of overetching of the spacer layer 3 is the minimum of about 1000△ when the ion beam incident angle 8 is about 35 degrees, and compared to the conventional ion beam from the 0 degree direction (direction perpendicular to the substrate surface). With beam irradiation, 2000A was also etched,
The bubble media layer is invaded. To summarize the above, when etching is performed until the remaining portion 4' of the conductor layer around the pattern is completely eliminated, the amount of etching of the spacer layer 3 is minimum at a point where the ion beam incident angle is about 35 degrees. Moreover, it can be seen that the etching rate of the conductor layer is slow at an incident angle of approximately 35 to 40 degrees.

This tendency is noticeable even when the incident angle 8 is in the range of about 25 to 45 degrees. Therefore, the angle of incidence 6 is 25~4
The vertical axis A of the substrate surface and the ion beam irradiation direction B within a range of 5 degrees
By setting the inclination angle with respect to the conductor layer and rotating the substrate, the amount of overetching of the substrate layer can be slightly suppressed, and unnecessary parts can be uniformly removed so that no residual part 4' of the conductor layer remains around the pattern. be able to.

As shown in FIG. 8, the thickness T of the substrate layer 3 is currently 20
00△, if the incident angle a is set to 25 to 45 degrees, the thickness t will be about half, about 1000A, but 100
If the thickness is about 0A, there is no risk that the function as a smoother layer will be impaired. Then, if Si○ is deposited as a planar layer 10 to a thickness corresponding to the overetched amount and the Si○ film 10' on the resist pattern 7 is removed by lift-off, grooves will be generated as in the secondary structure. The surface of the conductor pattern 4 and the surface of the planar layer 10 can be aligned without causing any problems, and even if a permalloy pattern is formed above it, a level of flatness can be obtained that does not cause any practical problems.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of the main part of a conventional magnetic valve element, Fig. 2 is a cross-sectional view showing the pattern forming method using the conventional planar method in the order of steps, and Fig. 3 is a magnetic bubble made planar by the method shown in Fig. 2. 4 is a longitudinal sectional view of the ion etching apparatus used in the method of the present invention; FIG. 5 is a sectional view showing the progress mechanism of etching according to the method of the present invention; FIGS. 6 and 7 is a graph showing experimental data, and FIG. 8 is a cross-sectional view of a bubble element made into a brainer by the method of the present invention. In the figure, 1 is a bubble substrate, 2 is a bubble medium layer, 3 is a substrate layer, 4 is a conductive pattern, 5 is an insulating layer, 6 is a permalloy pattern, 7 is a resist pattern, 10' is a planar layer, 14 is a substrate In the holder, 17 is a holder axis, A is an axis perpendicular to the substrate surface, and B is an ion beam irradiation direction. 1st
Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] 1 Si is placed on a substrate with a magnetic film that becomes a magnetic bubble medium.
An insulating layer made of O_2 is formed, and Al (
aluminum) or Al-Cu (aluminum-copper)
When forming a conductor pattern consisting of a resist pattern, the conductor layer on which a resist pattern is formed is exposed to ions while rotating the substrate holder with the surface of the insulating layer tilted at 25 to 45 degrees with respect to the direction of incidence of the ion beam. 1. A method of manufacturing a magnetic bubble element, comprising the steps of etching, then depositing a planar layer, and then removing the resist to make it planar.