JPS6257114B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for making a Josephson junction device.

In recent years, it has been proposed to use Josefson junction devices as memory devices, for example,
It is described in No. 31156 and Japanese Patent Publication No. 53-24278. As shown in FIG. 1, these conventional Josefson junction devices are composed of a sandwich film in which an oxide film 3 of several nanometers is sandwiched as an insulating layer between a lower electrode 2 and an upper electrode 4 provided on a substrate 1. The type had a non-flat structure. In a junction element with such a cross-sectional structure, when the pattern is miniaturized, it is difficult to form a uniform junction because of the step difference, and this effect causes variations in tunnel resistance, resulting in poor operation. This was causing margins to decline.

The non-planar structure shown in Figure 1 is not necessary for the operation of the Josefson junction device, as the upper and lower electrodes 2 and 4 must be made of superconducting material, which is exposed to high temperatures. This is due to the fact that electrodes and wiring cannot be formed by vapor deposition, which is commonly used in the manufacture of semiconductor devices, because it easily oxidizes and loses its original properties.

It is therefore an object of the present invention to provide a method for producing Josephson junction elements by vapor deposition at room temperature and without time differences.

In order to achieve the above object, the method for manufacturing a Josephson junction device according to the present invention includes the steps of: depositing a first thin film made of a superconducting material, which will become a lower electrode, on one surface of a substrate; forming a first photosensitive resin pattern in the shape of a predetermined lower electrode; and using the photosensitive resin pattern as a mask, removing a portion of the first thin film that cannot be covered with the photosensitive resin. forming a lower electrode, depositing a thin film of silicon monoxide on the entire surface at room temperature to substantially the same height as the lower electrode while leaving the photosensitive resin on the lower electrode; a step of removing the silicon monoxide thin film on the lower electrode by dissolving the photosensitive resin containing the silicon monoxide; and a substantially flat surface of the lower electrode and the silicon monoxide thin film obtained by the above steps. forming a second photosensitive resin pattern having a cavity in the shape of a predetermined upper electrode thereon; and oxidizing the surface of the lower electrode using the second photosensitive resin pattern as a mask; a step of forming a second thin film made of a superconducting material to serve as an upper electrode on the entire surface of the second photosensitive resin pattern, the oxide film and the silicon monoxide thin film; The method consists of the step of dissolving the second photosensitive resin pattern, removing the second thin film portion thereon, and forming an upper electrode.

The present invention will be explained in more detail below using examples with reference to the accompanying drawings, but these are merely illustrative, and it goes without saying that various modifications and improvements may be made without going beyond the scope of the present invention. It is.

FIG. 2 is a cross-sectional view of a Josephson junction device manufactured by the method of the present invention, and FIG. 3 is a cross-sectional view showing the method of the present invention in the order of steps.

First, on one surface of the substrate 1, a first thin film 2' made of a superconducting material that will become the lower electrode, such as 2% by weight gold, 8% by weight indium, and 90% by weight lead.
is deposited on the entire surface (A). On the first thin film 2',
For example, a photosensitive resin such as photoresist (AZ1350J) is applied, and a first photosensitive resin pattern 6 in the form of a predetermined lower electrode is formed by a known method (B).
Using this first photosensitive resin pattern 6 as a mask, the first thin film 2' is formed by ion milling.
is formed on the lower electrode 2. At this time, the first photosensitive resin pattern 6 also becomes thinner, but even after the part of the first thin film 2' to be removed has completely disappeared, a part of the first photosensitive resin pattern 6 still remains. A photosensitive resin is applied to a thickness such that it remains on the lower electrode 2 (C). While leaving the photosensitive resin on the lower electrode 2, a thin film 5 of silicon monoxide SiO is deposited on the entire surface at room temperature to the same height as the film thickness of the lower electrode 2.
(D). Next, by dissolving and removing the photosensitive resin remaining on the lower electrode 2 in a solvent such as acetone, the portion of the silicon monoxide thin film 5 on the lower electrode 2 is removed (E). . A second photosensitive resin pattern 7 having a cavity in the shape of a predetermined upper electrode is formed on the substantially flat surface of the lower electrode and silicon monoxide thin film obtained by the above steps.
(F). Using this second photosensitive resin pattern as a mask, the exposed portion of the surface of the lower electrode 2 is cleaned by high frequency sputtering using argon gas, and then cleaned by high frequency plasma oxidation using oxygen gas. The portion is oxidized to form an oxide film 3 with a thickness of several nanometers, which is used as an insulating layer (G). Next, the second thin films 4' and 4 made of a superconducting material that will serve as the upper electrode, such as a few percent gold and the balance lead, are coated with a second photosensitive resin pattern 7, an oxide film 3, and a silicon monoxide thin film. Formed on the entire surface of No. 5 by vapor deposition at room temperature (H). Finally, a thin film of silicon monoxide 5
If the pattern 7 of the second photosensitive resin is dissolved and removed using a solvent in the same manner as in the formation of the upper electrode 4, only the unnecessary portion of the second thin film is removed.
is formed, and the Josephson junction element shown in FIG. 2 is obtained.

The Josephson junction device manufactured by the method of the present invention does not have the step difference that existed in the conventional Josephson junction device mentioned at the beginning, and therefore has the advantage that the variation in Donnell resistance is small. When a Josefson junction device with a pattern width of 2 μm was manufactured using the method of the present invention, the variation in tunnel resistance was almost eliminated and the operating margin was significantly improved compared to conventional devices.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a conventional Josephson junction device, FIG. 2 is a cross-sectional view of a Josephson junction device manufactured by the method of the present invention, and FIG. 3 is a cross-sectional view showing the steps of the method of the present invention. 1... Substrate, 2... Lower electrode, 3... Oxide film,
4... Upper electrode, 5... Thin film of silicon monoxide, 6...
...First photosensitive resin pattern, 7... Second photosensitive resin pattern, 2'... First thin film made of superconducting material that will become the lower electrode, 4'... Superconductor that will become the upper electrode The second thin film of the material
The part above the photopolymer pattern.

Claims (1)

[Claims] 1. A step of entirely vapor-depositing a first thin film made of a superconducting material that will become a lower electrode on one surface of the substrate, and forming a pattern of a first photosensitive resin in the shape of a predetermined lower electrode on the first thin film. a step of forming a lower electrode by removing a portion of the first thin film that cannot be covered with the photosensitive resin using the pattern of the photosensitive resin as a mask; and a step of forming a lower electrode by leaving the photosensitive resin on the lower electrode. depositing a thin film of silicon monoxide on the entire surface at room temperature to substantially the same height as the lower electrode;
a step of removing the thin film of silicon monoxide on the lower electrode by dissolving the remaining photosensitive resin; and a step of removing the thin film of silicon monoxide on the lower electrode and the thin film of silicon monoxide obtained by the above steps. forming a second photosensitive resin pattern having a cavity in the shape of a predetermined upper electrode on the upper flat surface; and using the second photosensitive resin pattern as a mask to cover the surface of the lower electrode. A step of oxidizing to form an oxide film, and forming a second thin film made of a superconducting material to serve as an upper electrode on the entire surface of the second photosensitive resin pattern, the oxide film, and the silicon monoxide thin film. and a step of removing a portion of the second thin film thereon by dissolving the second photosensitive resin pattern to form an upper electrode. Manufacturing method of bonding element.