JPS5812671B2 - How to form a multilayer structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a device, such as a magnetic bubble element, having a structure in which fine patterns are multilayered.

Conductor Fast (Con), a magnetic bubble memory element
The layer structure called "ductor first" is
As shown in the figure, a magnetic thin film 2 is epitaxially grown on a gadolinium gallium garnet (GGG) single crystal substrate 1, and silicon dioxide (SiO2
) After depositing an insulating film 3 consisting of an aluminum wiring pattern 4, an aluminum wiring pattern 4 used as control wiring for a bubble generator, gate, replicator, etc. is formed.

Next, an insulating film 5 made of silicon dioxide is deposited on the entire surface, a permalloy pattern 6 that will serve as a transfer path, a gate, a replicator, and a detector is formed on the insulating film 5, and a protective film 7 made of silicon dioxide is coated on the entire surface. It has a built-in structure.

In this structure, the shorter the distance between the permalloy pattern 6 and the magnetic thin film 2, the more effectively the magnetic flux from the permalloy pattern 6 is utilized, and the bubble operation margin can be expanded.

Therefore, it is desired to bring the permalloy pattern 6 as close to the magnetic thin film 2 as possible, but due to the normal pattern design, the aluminum wiring pattern 4 and the permalloy pattern 6 overlap, and moreover, the permalloy pattern 6 overlaps a portion of the aluminum wiring pattern 4. exists.

Therefore, it is absolutely necessary to interpose the insulating film 5 between them.

The thickness of the insulating film 5 is approximately 2300 [Å] to 2500 [Å].
] degree is necessary.

However, when the insulating film 5 of this thickness is deposited on a flat part, a break or thinning occurs on the pattern side of the aluminum wiring pattern 4, and a sufficient film thickness cannot be secured in this part.

Therefore, conventionally, at the expense of the bubble operation margin, the thickness of the insulating film 5 was set to 5000 [Å] on the flat part compared to the thickness of the aluminum wiring pattern 4 of 3000 [Å], and the thickness was made thinner on the pattern side. Even if the thickness is reduced, the required minimum thickness of 2300 Å is ensured.

The present invention is a new invention that improves the conventional drawbacks as described above, and its purpose is to minimize the distance between the permalloy pattern and the magnetic thin film while ensuring sufficient insulation between the permalloy pattern and the aluminum wiring pattern. The objective is to provide a new manufacturing method that can be approached.

For this purpose, the method for forming a multilayer structure of the present invention includes a method for forming a multilayer structure in which a second pattern is laminated on a first pattern formed on a substrate with an insulating film interposed therebetween. The method is characterized in that an insulating thin film thinner than the thickness of the first pattern is previously deposited on the parts of the substrate that are not covered by the pattern, and then an insulating film is deposited on the entire surface, and a second pattern is formed on the insulating film. Examples will be described in detail below.

The occurrence of step breakage or thinning on the side of the aluminum wiring pattern is caused by the step t1 from the surface of the aluminum wiring pattern 4 to the insulating film 3 (that is, the thickness of the aluminum wiring pattern) and the insulating film 5 deposited on the wiring pattern 4.
(t2/t1) (hereinafter, this ratio will be referred to as α
The smaller the ratio (expressed as), the greater the proportion.

By the way, the ratio α of the conventional device shown in Figure 1 is 16
7 (5000/3000).

However, when the ratio α is made larger than 1.67, there is no breakage or thinning on the side of the aluminum wiring pattern, and the thickness of this part becomes almost equal to the film thickness of the flat part.

For this reason, by reducing the step t1, the thickness of the insulating film on the side portion of the aluminum wiring pattern can be reduced as long as the above ratio of 1.67 is maintained.

Therefore, in the present invention, silicon dioxide (SiO2) is applied to the surface of the insulating film 3 in advance as shown in FIG.
An insulating film 8 such as the like is laminated to reduce the substantial step t1'.

Therefore, the thickness t2 of the insulating film 5 deposited on the entire surface can be made thinner than in the conventional case.

The table below shows the thickness of the aluminum wiring pattern at 300mm.
0 [Å], ratio α = 1.67, the thickness t4 of the insulating film 8 laminated on the surface of the insulating film 3, the step t1, the thickness t2 of the insulating film 5, and the insulation laminated on the insulating film 3. Film thickness (t2+
t4) in comparison with that of a conventional device, and FIG. 3 is a graph of these relationships.

Various methods have been considered for laminating the insulating film 8 on the insulating film 3, but one method is to deposit a resist layer on the aluminum wiring pattern 4 and then spin-coat liquid silicon dioxide. The resist layer may be removed by a lift-off method, and the silicon dioxide deposited thereon may be removed.

As explained in detail above, in the present invention, if the portion other than the aluminum wiring layer is filled with an insulating film having a thickness half that of the aluminum wiring layer, the step t1 is 15
00 [Å], and if the ratio α is set to 1.67 as in the conventional case, then the insulating film 5 deposited on the aluminum wiring pattern
The thickness of the insulating film 5 is 2500 [Å].
Thickness t2 between the permalloy layer deposited on top and the insulating film 3
+t4 is 4000 [Å] compared to the conventional 5000 [Å]
The thickness can be reduced by as much as 20% compared to the previous version.

Therefore, according to the present invention, not only can a bubble operation margin be larger than that of the conventional method, but also sufficient insulation between the wiring pattern and the permalloy deposited thereon can be ensured.

As mentioned above, when forming a multilayer structure of a control conductor pattern such as an aluminum wiring pattern of a magnetic bubble memory element and a magnetic pattern such as a permalloy pattern, it is desirable for the magnetic pattern to be close to the magnetic substrate for controlling magnetic bubbles. Although it is desirable to form the magnetic pattern on an insulating film with few steps, it is possible to apply a thin insulating film to the area where the control conductor pattern is not formed, and then apply the insulating film. However, since a magnetic pattern is formed thereon, the above-mentioned conditions required for the magnetic bubble memory element can be satisfied.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of a conventional magnetic bubble memory element, FIG. 2 is a partial sectional view showing an embodiment of the present invention, and FIG. 3 is another insulating film when the laminated thickness of the insulating film 8 is changed. FIG. In the figure, 1 is a GGG single crystal substrate, 2 is a magnetic thin film, 3, 5,
7 and 8 are insulating films, 4 is an aluminum wiring pattern, and 6 is a permalloy pattern.

Claims (1)

[Claims] 1. In a method for forming a multilayer structure in which a magnetic pattern such as a permalloy pattern is formed on a control conductor pattern formed on a magnetic substrate of a magnetic bubble memory element through an insulating film, the control conductor pattern is not formed on the magnetic substrate. Formation of a multilayer structure characterized by comprising the steps of: depositing an insulating thin film thinner than the thickness of the control conductor pattern, then depositing an insulating film over the entire surface, and forming the magnetic pattern on the insulating film 1. Method.